Largest Prehistoric Animals

The largest prehistoric animals include both vertebrate and invertebrate species. Many of them are described below, along with their typical range of size (for the general dates of extinction, see the link to each). Many species mentioned might not actually be the largest representative of their clade due to the incompleteness of the fossil record and many of the sizes given are merely estimates since no complete specimen have been found. Their body mass, especially, is largely conjecture because soft tissue was rarely fossilized. Generally, the size of extinct species was subject to energetic and biomechanical constraints.

Non-mammalian synapsids (Synapsida)

Caseasaurs (Caseasauria)

The herbivorous ''Alierasaurus'' was the largest caseid and the largest amniote to have lived at the time, with an estimated length around . '' Cotylorhynchus hancocki'' is also large, with an estimated length and weight of at least and more than .

Edaphosaurids (Edaphosauridae)

The largest edaphosaurids were '' Lupeosaurus'' at long and ''Edaphosaurus'', which could reach even more than in length.

Sphenacodontids (Sphenacodontidae)

The biggest carnivorous synapsid of Early Permian was ''Dimetrodon'', which could reach and . The largest members of the genus ''Dimetrodon'' were also the world's first fully terrestrial apex predators.

Tappenosauridae

The Middle Permian '' Tappenosaurus'' was estimated at in length, nearly as large as the largest dinocephalians.

Therapsids (Therapsida)

Anomodonts (Anomodontia)

The plant-eating dicynodont '' Lisowicia bojani'' is the largest-known of all non-mammalian synapsids, at about long, tall, and in body mass. However, in 2019 its weight was later more reliably estimated by modelling its mass from the estimated total volume of its body. These estimates varied depending on the girth of its rib cage and the amount of soft tissue modelled around the skeleton, with an overall average weight of 5.9 metric tons (6.5 short tons), and a lowermost estimate with minimal body fat and other tissues at 4.9 metric tons (5.4 short tons) and a maximum of 7 metric tons (7.7 short tons) at its bulkiest.

Biarmosuchians (Biarmosuchia)

The Late Permian ''Eotitanosuchus'' (a possible synonym to '' Biarmosuchus'') may have been over in length, possibly up to and more than in weight for adult specimens.

Dinocephalians (Dinocephalia)

* Perhaps the largest known dinocephalian was the titanosuchid '' Jonkeria truculenta'', with volumetric models suggesting it could have weighed . '' Tapinocaninus pamelae'' was slightly smaller, volumetric models suggesting it weighed .
* The largest carnivorous non-mammalian synapsids was the anteosaurid ''Anteosaurus'', which was long, and weighed . Fully grown ''Titanophoneus'' from the same family Anteosauridae likely had a skull of long.

Gorgonopsians (Gorgonopsia)

'' Inostrancevia latifrons'' is the largest known gorgonopsian, with a skull length of more than , a total length approaching and a mass of . ''Rubidgea atrox'' is the largest African gorgonopsian, with skull of nearly long. Other large gorgonopsians include '' Dinogorgon'' with skull of ~ long, '' Leontosaurus'' with skull of almost long, and ''Sycosaurus'' with skull of ~ long.

Therocephalians (Therocephalia)

The largest of therocephalians is ''Scymnosaurus'', which reached a size of the modern hyena.

Non-mammalian cynodonts (Cynodontia)

* The largest known non-mammalian cynodont, as well as the largest member of Cynognathia, is '' Scalenodontoides'', a traversodontid, which had a maximum skull length of approximately based on a fragmentary specimen.
* '' Paceyodon davidi'' was the largest of morganucodontans, cynodonts close to mammals. It is known by a right lower molariform in length, which is bigger than molariforms of all other morganucodontans.
* The largest known docodont was ''Castorocauda'', almost in length.

Mammals (Mammalia)

Non-therian mammals

Gobiconodonts (Gobiconodonta)

The largest gobiconodont and the largest well-known Mesozoic mammal was ''Repenomamus''. The known adult of ''Repenomamus giganticus'' reached a total length of around and an estimated mass of . With such parameters it surpassed in size several small theropod dinosaurs of the Early Cretaceous. ''Gobiconodon'' was also a large mammal, it weighed , had a skull of in length, and had in presacral body length.

Multituberculates (Multituberculata)

The largest multituberculate, ''Taeniolabis taoensis'' is the largest non-therian mammal known, at a weight possibly exceeding .

Monotremes (Monotremata)

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* The largest known monotreme (egg-laying mammal) ever was the extinct long-beaked echidna species known as '' Murrayglossus hacketti'', known from a couple of bones found in Western Australia. It was the size of a sheep, weighing probably up to .
* The largest known ornithorhynchid is '' Obdurodon tharalkooschild'', it was even larger than -long '' Monotrematum sudamericanum''.
* '' Kollikodon ritchiei'' was likely the largest monotreme in the Mesozoic. Its body length could be up to a .

Metatherians (Metatheria)

* The largest non-marsupial metatherian, as well as the largest carnivorous metatherian, was '' Proborhyaena gigantea'' which is estimated to have weighed weigh . Another large metatherian was '' Thylacosmilus atrox'', weighing , one estimate suggesting even . ''Australohyaena'' is another large metatherian, weighing up to .
* Stagodontid mammal '' Didelphodon'' was one of the largest Mesozoic metatherians and all Cretaceous mammals. Its skull could reach over in length and a weight of complete animal was .

Marsupials (Marsupialia)

* The largest known marsupial, and the largest metatherian, is the extinct ''Diprotodon'', about long, standing tall and weighing up to . Fellow vombatiform '' Palorchestes azael'' was similar in length being around , with body mass estimates indicating it could exceed .
* The largest known carnivorous marsupial was ''Thylacoleo carnifex''. Measurements taken from a number of specimens show they averaged in weight. are the largest Giant koala (''Phascolarctos stitorni'') are modern Koala (''Phascolarctos cinerus'') and has an estimated weight of , which is the same weight as a large contemporary male koala. the largest ever ''Sarcophilus laniarius'' which were around 15% larger and 50% heavier than modern devils.Owen and Pemberton, p. 35.
* The largest known kangaroo was an as yet unnamed species of ''Macropus'', estimated to weigh , larger than the largest known specimen of '' Procoptodon'', which could grow up to and weigh . Some species from the genus '' Sthenurus'' were similar in size or a bit larger than the extant grey kangaroo (''Macropus giganteus''). The largest ever tree kangaroo ''Bohra'' were much larger than any tree-kangaroo, with estimated body masses of .
* The largest potoroid ever recorded was ''Borungaboodie'', which was nearly 30% bigger than the largest living species and weighed up to .
* The largest member of the Thylacinidae is '' Thylacinus megiriani'', which is somewhat reasonably larger than the Tasmanian wolf (''Thylacinus cynocephalus''), and bigger than its fellow Miocene relative ''Thylacinus potens'', usually being 57.3 kilograms in weight.

Non-placental eutherians

Cimolestans (Cimolesta)

The largest known cimolestan is ''Coryphodon'', high at the shoulder, long and up to of mass. ''Barylambda'' was also a huge mammal, at . ''Wortmania'' and ''Psittacotherium'' from the group Taeniodonta were among the largest mammals of the Early Paleocene. Lived as soon as half a million years after K–Pg boundary, ''Wortmania'' reached in body mass. ''Psittacotherium'', which appeared two million years later, reached .

Leptictids (Leptictida)

The largest leptictid ever discovered is '' Leptictidium tobieni'' from the Middle Eocene of Germany. It had a skull long, head with trunk long, and tail long. Close European relatives from the same family Pseudorhyncocyonidae had skulls of in length.

Tenrecs and allies (Afroscida)

The larger of the two species of bibymalagasy (''Plesiorycteropus madagascariensis''), extinct tenrec relatives from Madagascar, is estimated to have weighed from 10 to 18 kilograms (21 to 40 lb).

Even-toed ungulates (Artiodactyla)

* The largest known land-dwelling artiodactyl was ''Hippopotamus gorgops'' estimated to have weighed over , with its closely related European descendant, ''Hippopotamus antiquus'', possibly rivaling it, estimated to be 14.1 ft (4.3 m) in length and in weight. However, volumetric models suggests it was slightly smaller, weighing .
* ''Daeodon'' and similar in size and morphology ''Paraentelodon''
were the largest-known entelodonts that ever lived, at long and high at the shoulder. The huge ''Andrewsarchus'' from the Eocene of Inner Mongolia had a skull about long though the taxonomy of this genus is disputed.

* The largest of Bovinae as well as the largest bovid was ''Bison latifrons''. It reached a weight from to , in length, shoulder height of , and had horns that spanned . The North American ''Bison antiquus'' reached up to long, tall, weight of , and horn span of . The African '' Pelorovis'' reached in weight and had bony cores of the horns about long. Another enormous bovid, the african giant buffalo (''Syncerus antiquus'') reached in length from muzzle to the end of the tail, in height at the withers, in height at the hindquarters, and the distance between the tips of its horns was as large as . Aside from local populations and subspecies of extant species, such as the gaur population in Sri Lanka, European bison in British Isles, Caucasian wisent and Carpathian wisent, the largest modern extinct bovid is aurochs (''Bos primigenius'') with an average height at the shoulders of in bulls and in cows, while aurochs populations in Hungary had bulls reaching . The kouprey ('' Bos sauveli''), reaching in shoulder height, has existed since the Middle Pleistocene and is also considered to be possibly extinct.
* The long-legged ''Megalotragus'' is possibly the largest known alcelaphine bovid, bigger than the extant wildebeest. The tips of horns of ''M. priscus'' were located at a distance of about from each other.

* The extinct cervid Irish elk (''Megaloceros giganteus'') reached over in height, in mass and could have antlers spanning up to across, about twice the maximum span for a moose's antlers. The giant moose (''Cervalces latifrons'') reached high and was twice as heavy as the Irish elk but its antler span at was smaller than that of ''Megaloceros''. North American stag-moose (''Cervalces scotti'') reached in length and a weight of .
* The largest known giraffid, aside from the extant giraffe, is ''Sivatherium'', with a body weight of .
* The largest protoceratid was '' Synthetoceras'', it reached long and in mass.
* The largest known wild suid to ever exist was '' Kubanochoerus gigas'', having measured up to and stood around tall at the shoulder. '' Megalochoerus'' could be similar in size, possibly weighing or .
* The largest tayassuid extinct ''Platygonus'' species were similar in size to modern peccaries especially giant peccary, at around in body length, and had long legs, allowing them to run well. They also had a pig-like snout and long tusks which were probably used to fend off predators.
* The largest camelid was ''Titanotylopus'' from the Miocene of North America. It possibly reached and a shoulder height of over . The Syrian camel ('' Camelus moreli'') was twice as big as the modern camels. It was at the shoulder and tall. ''Camelops'' had legs 20% longer than that of the dromedary and was about tall at the shoulder, weighing about .
* The anoplotheriid ''Anoplotherium'' is thought to have been capable of reaching up to in the case of ''A. commune'' and in the case of ''A. latipes''. ''A. latipes'' in particular could have measured more than in length and in shoulder height. Because it was probably capable of facultative bipedalism, it could have been capable of standing over tall.

Cetaceans (Cetacea)

* The heaviest archeocete was ''Perucetus'', with weight estimated at , while length is estimated at . However, Motani and Pyenson in 2024 argued that it is extremely difficult for Perucetus to rival or exceed the blue whale in weight. They discussed that since Perucetus is much shorter than the blue whale in length, it should be at least 3.375 times denser or 1.83 times fatter to weigh heavier, which is impossible for vertebrates whose whole-body density range from 0.75 to 1.2. Motani and Pyenson tested the hypotheses of Bianucci and colleagues by performing various body mass estimation methods: the regression-based and volumetric mass estimation resulted in for a length range of , though the likely body mass range would fall within . They also claimed that the previous estimation is inflated by assumed isometry, and that the effect from pachyostosis on the estimation of body mass is not negligible as it resulted in underestimation. The longest of known Eocene archeocete whales was ''Basilosaurus'' at in length.
* The largest squalodelphinid was '' Macrosqualodelphis'' at in length.
* Some Neogene rorquals were comparable in size to modern huge relatives. ''Parabalaenoptera'' was estimated to be about the size of the modern gray whale, about long. Some balaenopterids perhaps rivaled the blue whale in terms of size, though other studies disagree that any baleen whale grew that large in the Miocene.
* The largest macroraptorial sperm whale is ''Livyatan'', with an estimated length of 44–57 ft (13.5–17.5 m) and an estimated weight of 62.8 short tons (57 tonnes).
* The largest dolphin is '' Orcinus paleorca'', a Pleistocene relative of the modern Orca (''Orcinus orca''). The tooth is conical and belonged to the upper right or lower left jaw of an adult individual. The tooth fragment is in height–though the actual height may have been double that– longitudinally–from the side facing the tongue to the side facing the lip–and transversely–from the left side of the tooth to the right. In comparison, the modern killer whale has teeth around in height and in diameter. Like the modern killer whale, the tooth lacks a coat of cementum. However, unlike the modern killer whale, ''O. paleorca'' had a circular tooth root as opposed to an oval, and the pulp extended more towards the back than the front.

Odd-toed ungulates (Perissodactyla)

* One of the largest known perissodactyls, and the second largest land mammal (see ''Palaeoloxodon namadicus'') of all time was the hornless rhino ''Paraceratherium''. The largest individual known was estimated at tall at the shoulders, in length from nose to rump, and in weight. A large specimen of an unnamed species of the related Dzungariotherium has been estimated to be around 20.6 metric tonnes.
* Some prehistoric horned rhinos also grew to large sizes. The biggest ''Elasmotherium'' reached up to long, high and weighed . Such parameters make it the largest rhino of the Quaternary. Woolly rhinoceros (''Coelodonta antiquitatis'') of the same time reached or , at the shoulder height and in length.
* ''Metamynodon'', an amynodontid, reached in length, comparable to ''Hippopotamus'' in measurement and shape.
* The giant tapir (''Tapirus augustus'') was the largest tapir ever, at about and tall at the shoulders. Earlier, this mammal was estimated even bigger, at tall, and assigned to the separate genus ''Megatapirus''.
* The largest known lophiodont is ''Lophiodon'', with ''L. lautricense'' being estimated to reach more than in weight.
* One of the biggest chalicotheres was ''Moropus''. It stood about tall at the shoulder.
* Late Eocene perissodactyls from the family Brontotheriidae attained huge sizes. The North American ''Megacerops'' (also known as ''Brontotherium'') reached tall at the shoulders, in length, and in weight.''Embolotherium'' from Asia was equal in size.
* The largest prehistoric horse was '' Equus giganteus'' of North America. It was estimated to grow to more than and at the shoulders. The largest anchitherine equid was ''Hypohippus'' at , comparable to large modern domestic horses. '' Megahippus'' is another large anchitheriine. With the body mass of it was much heavier than most of its close relatives.
* Among the largest-sized genera of palaeotheres, close relatives of horses, is ''Palaeotherium'', with ''P. giganteum'' being estimated to reach weights of more than . Previously until the naming of ''P. giganteum'' in 1994, ''P. magnum'' was considered the largest species of ''Palaeotherium'', potentially reaching in shoulder height and in length. Another palaeothere '' Cantabrotherium'' is estimated to have weighed about .

Phenacodontids (Phenacodontidae)

The largest known phenacodontid is '' Phenacodus''. It was long and weighed up to .

Dinoceratans (Dinocerata)

The largest known dinoceratan was ''Eobasileus'' with skull length of , tall at the back and tall at the shoulder. Another huge animal of this group was ''Uintatherium'', with skull length of , tall at the shoulder, in length and , the size of a rhinoceros. Despite their large size, ''Eobasileus'' as well as ''Uintatherium'' had a very small brain.

Carnivores (Carnivora)

Caniformia

* The largest terrestrial mammalian predator, as well the largest known bear and terrestrial carnivoran of all time was '' Arctotherium angustidens'', the South American short-faced bear. A humerus of ''A. angustidens'' from Buenos Aires indicates that the males of the species could have weighed and stood at least tall on their hind-limbs. Another huge bear was the giant short-faced bear (''Arctodus simus''), with the average weight of and the maximum estimated at . There is a guess that the largest individuals of this species could reached even larger mass, up to . The extinct cave bear ('' Ursus spelaeus'') was also heavier than many recent bears. Largest males weighed as much as . The largest males of the possibly disrupted subspecies of brown bear (''Ursus arctos''), steppe brown bear (''Ursus arctos priscus''), is also estimated to have weighed .Marciszak, A., Schouwenburg, C., Lipecki, G., Talamo, S., Shpansky, A., Malikov, D., & Gornig, W. (2019). Steppe brown bear Ursus arctos “priscus” from the Late Pleistocene of Europe. Quaternary International, 534, 158–170. https://doi.org/10.1016/j.quaint.2019.02.042 Another large bear was '' Agriotherium africanum'', this species was estimated to have initially estimated to have weighed , but more recent estimates suggest it could’ve weighed . '' Ailuropoda baconi'' from the Pleistocene was larger than the modern giant panda ('' Ailuropoda melanoleuca'').
* The biggest odobenid and one of the biggest pinnipeds to have ever existed is ''Pontolis magnus'', with a skull length of (twice as large as the skulls of modern male walruses) and having a total body length of more than . Only the modern male elephant seals (''Mirounga'') reach similar sizes.
The second largest prehistoric pinniped is ''Gomphotaria pugnax'' with a skull length of nearly .

* One of the largest of prehistoric otariids is '' Thalassoleon'', comparable in size to the biggest extant fur seals. An estimated weight of ''T. mexicanus'' is no less than .

* The biggest known mustelid to ever exist was likely the giant otter, '' Enhydriodon omoensis''. It exceeded in length, and would have weighed in at around , much larger than any other known mustelid, living or extinct. There were other giant otters, like ''Siamogale'', at around and ''Megalenhydris'', which was larger than a modern-day giant river otter. '' Megalictis'' was the largest purely terrestrial mustelid (although ''Enhydriodon'' had recently been mentioned as the largest mustelid that also happens to be a terrestrial predator). Similar in size to the jaguar, ''Megalictis ferox'' had even wider skull, almost as wide as of the black bear. Another large-bodied mustelid was the superficially cat-like '' Ekorus'' from the Miocene of Africa. At almost , the long-legged ''Ekorus'' was about the size of a wolf. Other huge mustelids include '' Perunium'' and hypercarnivorous '' Eomellivora'', both from the Late Miocene.
* The heaviest procyonid was possibly the South American '' Chapalmalania''. It reached in body length with a short tail and , comparable in size to an American black bear (''Ursus americanus''). Another huge procyonid was ''Cyonasua'', which weighted about , about the same size as a medium-sized dog.
* The largest canid of all time was ''Epicyon haydeni'', which stood tall at the shoulder, had a body length of and weighed , with the heaviest known specimen weighing up to . The extinct dire wolf (''Aenocyon dirus'') reached in length and weighed between . The largest wolf (''Canis lupus'') subspecies ever existed in Europe is the '' Canis lupus maximus'' from the Late Pleistocene of France. Its long bones are 10% larger than those of extant Subspecies of Canis lupus, European wolves and 20% longer than those of ''C. l. lunellensis''. The Late Pleistocene Pleistocene wolf#Italian wolves, Italian wolf was morphometrically close to ''C. l. maximus''.
* The largest Amphicyonidae, amphicyonid (bear-dogs) was a species of ''Pseudocyon'' weighing around , representing a very large individual.

Feliformia

* The largest definitive Nimravidae, nimravid was ''Quercylurus, Quercylurus major'' as its fossils suggest it weighed similar in size to the modern-day lion and was scansorial. The closely related ''Dinailurictis, Dinailurictis bondali'' was slightly smaller weighing , making it as large as a lioness. ''Eusmilus, Eusmilus adelos'' was the largest of the Hoplophoninae, hoplophonine nimravid, reaching a weight of , comparable to a small African lion. While it was assumed that ''Hoplophoneus, Hoplophoneus occidentalis'' could’ve weighed , other experts suggested it was smaller, being about the size of a leopard. A 2012 study suggested this species could’ve weighed .
* The largest barbourofelidae, barbourofelid was ''Barbourofelis fricki'', with the shoulder height of and could’ve weighed . If recent phylogeny is accurate, then this would make ''B. fricki'' the largest known nimravid.
* The largest Machairodontinae, machairodont (saber-toothed cats) Felidae, felid was ''Amphimachairodus, Amphimachairodus kabir'', with the males possibly reaching . ''Smilodon, Smilodon populator'' was a close contender, with males weighing . Another large member of the ''Amphimachairodus'' genus, ''A. horribilis'', is estimated to weigh . Another contender is ''Nimravides, Nimravides catocopis'' with the largest specimen weighing up to . An unnamed species of ''Xenosmilus'' thought to have weighed between .
* The heaviest known Pantherinae, pantherine Felidae, felids were the extinct leonines ''Panthera fossilis,'' which has been estimated to have maximum weight of , the American lion (''Panthera atrox''), weighing up to ,John Campbell Merriam, Merriam, J. C. & Stock, C. 1932: The Felidae of Rancho La Brea. Carnegie Institution of Washington Publications 442, 1–231. and the Natodomeri lion of eastern Africa, which was comparable in size to large members of ''P. atrox''. The Panthera tigris soloensis, Ngangdong tiger (''Panthera tigris soloensis''), was estimated to have weighed up to , however this has been contested with some estimates suggesting the largest individuals weighed .
* The largest Felinae, feline felid was ''Acinonyx pleistocaenicus'', with the largest specimen weighing . Its close relative, giant cheetah (''Acinonyx pardinensis''), reached , approximately twice as large as the modern cheetah. The North American ''Pratifelis'' was larger than the extant cougar.

* The largest viverrid known to have existed is ''Viverra leakeyi'', which was around the size of a wolf or Amur leopard, small leopard at .
* The largest known extinct hyena was the Percrocutidae, percrocutid hyena'', Dinocrocuta, Dinocrocuta gigantea''. It was originally estimated to have weighed . However, recent weight estimates may suggest it may have weighed less. An individual with a skull length of , is estimated to have weighed . One specimen is reported to have a skull length of . ''Pachycrocuta, Pachycrocuta brevirostris'' was another large extinct hyena. It’s estimated at at the shoulder and weight. However, other experts leaned towards representing the upper end of the species. ''Crocuta'' hyenas have also been known large sizes, even larger than the extant spotted hyena, most notably the extinct spotted hyena subspecies, the cave hyena, with average individuals weighing . ''Crocuta eturno'' was another large ''Crocuta'' species with estimates suggesting this species could’ve weighed .
* The extinct giant fossa (''Cryptoprocta spelea'') had a body mass in range from to , much larger than the modern Fossa (animal), fossa weighs (up to for adult males).

Hyaenodonts (Hyaenodonta)

* The largest Hyainailouridae, hyainailourid, as well as the largest Hyaenodonta, hyaenodont was ''Megistotherium, Megistotherium osteothlastes'' at . While it’s close relative, ''Simbakubwa, Simbakubwa kutokaafrika'', was estimated to reach , the same regression suggested ''Megistotherium'' was larger than ''Simbakubwa''. ''Hyainailouros'' was another large hyainailourid. The largest species in the genus, ''H. bugtiensis'', which could’ve weighed between .
* The largest Hyaenodontidae, hyaenodontid was ''Hyaenodon gigas'', weighing in at around .

Oxyaenids (Oxyaenidae)

The largest known Oxyaenidae, oxyaenid was ''Sarkastodon'' weighing in at .

Mesonychians (Mesonychia)

Some mesonychians reached a size of a bear. Such large were ''Mongolonyx'' from Asia and ''Ankalagon'' from North America. Another large mesonychian is ''Harpagolestes'' with a skull length of a half a meter in some species.

Bats (Chiroptera)

Found in Quaternary deposits of South and Central Americas, ''Desmodus draculae'' had a wingspan of and a body mass of up to . Such proportions make it the largest vampire bat that ever evolved.

Hedgehogs, gymnures, shrews, and moles (Eulipotyphla)

The largest known animal of the group Eulipotyphla was ''Deinogalerix'', measuring up to in total length, with a skull up to long.

Rodents (Rodentia)

* Several of the extinct South American Dinomyidae, dinomyids were much bigger than modern rodents. ''Josephoartigasia monesi'' was the largest-known rodent of all time, approximately weighing an estimated . ''Phoberomys pattersoni'' weighed . Both ''Josephoartigasia'' and ''Phoberomys'' reached about tall at the shoulder. Another huge dinomyid, ''Telicomys, Telicomys gigantissimus'' had a minimal weight of .
* ''Amblyrhiza inundata'' from the family Heptaxodontidae was a massive animal, it weighed .
* The largest beaver was the Castoroides, giant beaver (''Castoroides'') of North America. It grew over 2 m in length and weighed roughly , also making it one of the largest rodents to ever exist.
* The largest old world porcupine are the ''Hystrix refossa'' was larger than living porcupines. It was approximately 20% larger than its closest relative, the living Indian porcupine (''H. indica''), reaching lengths of over .

Rabbits, hares, and pikas (Lagomorpha)

The biggest known prehistoric lagomorph is Menorca, Minorcan giant lagomorph ''Nuralagus rex'' at .

Pangolins (Pholidota)

The largest pangolin was the extinct ''Manis palaeojavanica'' Its total length is measured up to .

Primates (Primates)

* The largest known non-hominid primate is ''Gigantopithecus blacki''. Studies estimate heights around tall, weighing . Some suggested that it would not exceed tall with a bipedal posture. Another giant ape-like hominid was ''Meganthropus palaeojavanicus'' at in body height, although it is known from very poor remains.
* During the Pleistocene, some archaic humans were close in sizes or even larger than early modern humans. Neanderthals (''Homo neanderthalensis'') reached and in average weight for males and females, respectively, larger than the parameters of modern humans (''Homo sapiens'') ( and for males and females, respectively). A tibia from Kabwe (Zambia) indicates an indeterminate ''Homo'' individual of possibly in height. It was one of the tallest humans of the Middle Pleistocene and noticeably large even compared to recent humans. The tallest ''Homo sapiens'' individuals from the Middle Pleistocene of Spain reached and for males and females, respectively. Some ''Homo erectus'' could be as large as tall and in weight.
* The heaviest known Old World monkey is the prehistoric baboon is ''Theropithecus oswaldi'' which have weighed , some even suggested to reach . A male specimen of ''Dinopithecus'' projected to weigh an average of and up to , exceeds the maximum weight record of the chacma baboon, the largest extant baboon.
* The largest known New World monkey was ''Cartelles'', which is studied as specimen of ''Protopithecus'', weighing up to . ''Caipora bambuiorum'' is another large species, weighing up to .
* The largest Omomyidae, omomyids were ''Macrotarsius'' and ''Ourayia'' from the Middle Eocene. Both reached in weight.
* Some prehistoric Lemuriformes, lemuriform primates grew to huge sizes as well. ''Archaeoindris'' was a sloth lemur that lived in Madagascar and weighed , as large as an adult male gorilla. ''Palaeopropithecus'' from the same family was also heavier than most modern lemurs, at . ''Megaladapis'' is another large extinct lemur at in length and an average body mass of around . Other estimates suggest but its still much larger than any extant lemur.

Elephants, mammoths, and mastodons (Proboscidea)

* The elephant ''Palaeoloxodon namadicus'' has been suggested to have been the largest land mammal ever, based on a particularly large partial femur which was estimated to have belonged to an individual in weight and about tall at the shoulder, though the author of the estimate said that this was speculative and should be treated with caution. In 2023, a publication by Gregory S. Paul and Larramendi estimated that another specimen identified as cf. P. namadicus, also only known from a partial femur, would have weighed 18–19 tonnes (40,000–42,000 lb). Other authors have noted that weight estimates for proboscideans based on single bones can lead to estimates that are "highly improbable" compared to accurate estimates from complete skeletons. In 2024, Biswas, Chang and Tsai estimated a maximum shoulder height of over 4.5 metres (15 ft) and suggested that the body mass for 5 measured specimens ranged from 13.2 to 18.5 tonnes (29,000 to 41,000 lb) from specimens from Taiwan. The largest individual reported individual of the steppe mammoth of Eurasia (''Mammuthus trogontherii'') was estimated to reach at the shoulders and in weight. ''Stegodon zdanskyi'', the biggest species of ''Stegodon'', was in body mass. Another enormous proboscidean is ''Stegotetrabelodon, Stegotetrabelodon syrticus'', over in height and in weight. The Columbian mammoth (''Mammuthus columbi'') was about tall at the shoulder but didn't weigh as much as other huge proboscideans. Its average mass was with one unusually large specimen about .
* The Mammutidae, mammutid ''"Mammut" borsoni'' is one of the largest known proboscideans and land mammals. The average fully-grown male is estimated to have been tall and weighed about , with very large males possibly rivalling the estimated size of the largest ''Palaeoloxodon namadicus''. This species also had the longest tusks of any animals with the largest recorded specimen being long from basis to tip along the curve.
* ''Deinotherium'' was the largest proboscidean in Deinotheriidae family. Bones retrieved in Crete confirm the existence of specimen tall at the shoulders and more than in weight.

Sea cows (Sirenia)

According to reports, Steller's sea cows have grown to long as adults, much larger than any extant species, extant sirenians. The weight of Steller's sea cows is estimated to be .

With its direct ancestor, the Cuesta sea cow being around 9 m (30 ft) long and possibly 10 tonnes (11 short tonnes) in weight.

Arsinoitheres (Arsinoitheriidae)

The largest known Arsinoitheriidae, arsinoitheriid was ''Arsinoitherium''. ''A. zitteli'' would have been tall at the shoulders, and long. ''A. giganteum'' reached even larger size than ''A. zitteli''.

Hyraxes (Hyracoidea)

Some of the prehistoric hyraxes were extremely large compared to modern small relatives. The largest hyracoid ever evolved is ''Titanohyrax, Titanohyrax ultimus''. With the mass estimation in rage of to over it was close in size to Sumatran rhinoceros. Another enormous hyrax is ''Megalohyrax'' which had skull of in length and reached the size of tapir. More recent ''Gigantohyrax'' was three times as large as the extant relative ''Procavia capensis'', although it is noticeably smaller than earlier ''Megalohyrax'' and ''Titanohyrax''.

Desmostylians (Desmostylia)

The largest known desmostylian was a species of ''Desmostylus'', with skull length of and comparable in size to the Steller's sea cow.

''Paleoparadoxia'' is also known as one of the largest desmostylians, with body length of .

Glyptodonts, armadillos and pampatheres (Cingulata)

The largest Cingulata, cingulate known is ''Doedicurus'', at long, high and reaching a mass of approximately . The largest species of ''Glyptodon'', ''Glyptodon clavipes'', reached in length and in weight.

Anteaters and sloths (Pilosa)

The largest known pilosan was the megatheriinae ''Eremotherium, Eremotherium laurillardi'', a ground sloth that was initially estimated to weigh up to and a length of up to , which is as big as a bull African bush elephant. However, many studies have gotten lower estimates, with one study suggesting that was the most accurate size estimate for an adult. The closely related ground sloth, ''Megatherium, Megatherium americanum'', was slightly smaller with volumetric models suggesting it could’ve weighed .

Astrapotherians (Astrapotheria)

Some of the largest known astrapotherians weighed about , including the genus ''Granastrapotherium'' and some species of ''Parastrapotherium'' (''P. martiale''). The skeleton remains suggest that the species ''Hilarcotherium, Hilarcotherium miyou'' was even larger, with a weight of .

Litopterns (Litopterna)

The largest known Litopterna, litoptern was ''Macrauchenia'', which had three hoofs per foot. It was a relatively large animal, with a body length of around .

Notoungulates (Notoungulata)

The largest Notoungulata, notoungulate known of complete remains is ''Toxodon''. It was about in body length, and about high at the shoulder and resembled a heavy rhinoceros. Although incomplete, the preserved fossils suggest that ''Mixotoxodon'' were the most massive member of the group, with a weight about .

Pyrotherians (Pyrotheria)

The largest mammal of the South American order Pyrotheria was ''Pyrotherium'' at in length and in weight.

Reptiles (Reptilia)

Lizards and snakes (Squamata)

* Mosasaurs are the largest-known Squamata, squamates. The largest-known mosasaur is likely ''Mosasaurus, Mosasaurus hoffmanni'', estimated at more than in length, however these estimations are based on heads and total body length ratio 1:10, which is unlikely for ''Mosasaurus'', and probably that ratio is about 1:7. Another giant mosasaur is ''Tylosaurus'', estimated at in length. Another mosasaur, ''Prognathodon'' reached similar sizes.
* The largest known prehistoric snake is ''Titanoboa, Titanoboa cerrejonensis'', estimated at or even in length and .The madtsoiid ''Vasuki indicus'' may have rivaled or surpassed ''Titanoboa'' in length, however had smaller vertebral dimensions compared to it. A close rival in size to those snakes is Palaeophiidae, palaeophiid marine snake ''Palaeophis, Palaeophis colossaeus'', which may have been around in length or even up to . Another known very large fossil snake is ''Gigantophis, Gigantophis garstini'', estimated at in length, although later study shows smaller estimation about . The largest fossil Pythonidae, python is ''Liasis dubudingala'' with length roughly . The largest viper as well as the largest venomous snake ever recorded is ''Laophis, Laophis crotaloides'' from the Early Pliocene of Greece. This snake reached over in length and in weight. Another huge fossil viper is indeterminate species of ''Vipera''. With a length of around it was one of the biggest predators of Mallorca during the Early Pliocene. The largest known Scolecophidia, blind snake is ''Boipeba tayasuensis'' with estimated total length of .
* The largest known land lizard is probably megalania (''Varanus priscus'') at in length. As extant relatives, megalania could have been venomous and in that case this lizard was also the largest venomous vertebrate ever evolved. However, maximum size of this animal is subject to debate. Recent studies have estimated it at long.

Turtles, tortoises and close relatives (Pantestudines)

Cryptodira

* The largest known turtle ever was ''Archelon ischyros'' at long and . Possible second-largest sea turtle was ''Protostega'' at in total body length. There is even a larger specimen of this genus from Texas estimated at in total length. Partially known ''Cratochelone'' is estimated to reach in total length. Another huge prehistoric sea turtle is the Late Cretaceous ''Gigantatypus'', estimated at over in length. ''Psephophorus terrypratchetti'' from the Eocene attained in body length.
* The largest tortoise was ''Megalochelys, Megalochelys atlas'' at up to in shell length and weighing . ''M. margae'' had carapace of long; an unnamed species from Java reached at least in carapace length. The Cenozoic ''Titanochelon'' were also larger than extant giant tortoises, with a shell length of up to . Other giant tortoises include ''Centrochelys, Centrochelys marocana'' at in carapace length and Mesoamerican ''Hesperotestudo sp.'' at in carapace length.
* The largest trionychidae, trionychid ever recorded is indeterminate specimen GSP-UM 3019 from the Middle Eocene of Pakistan. Bony carapace of GSP-UM 3019 is long and wide indicates the total carapace diameter (with soft margin) about . ''Drazinderetes, Drazinderetes tethyensis'' from the same formation had a bony carapace long and wide. Another huge trionychid is North American ''Axestemys, Axestemys byssinus'' at over in total length.

Side-necked turtles (Pleurodira)

The largest freshwater turtle of all time was the Miocene Podocnemididae, podocnemid ''Stupendemys'', with an estimated parasagittal carapace length of and weight of up to . ''Carbonemys cofrinii'' from the same family had a shell that measured about , complete shell was estimated at .

Macrobaenids (Macrobaenidae)

The largest Macrobaenidae, macrobaenids were the Early Cretaceous ''Yakemys'', Late Cretaceous ''Anatolemys'', and Paleocene ''Judithemys''. All reached in carapace length.

Meiolaniformes

The largest Meiolaniidae, meiolaniid was ''Meiolania''. ''Meiolania platyceps'' had a carapace long and probably reached over in total body length. An unnamed Late Pleistocene species from Queensland was even larger, up to in carapace length. ''Ninjemys, Ninjemys oweni'' reached in carapace length and in weight.

Sauropterygians (Sauropterygia)

Placodonts and close relatives (Placodontiformes)

''Placodus'' was among the largest placodonts, with a length of up to .

Nothosaurs and close relatives (Nothosauroidea)

The largest nothosaur as well as the largest Triassic sauropterygian was ''Nothosaurus giganteus'' at in length.

Plesiosaurs (Plesiosauria)

* The largest known Plesiosauroidea, plesiosauroid was an indeterminate specimen possibly belonging to ''Aristonectes'' (identified as cf. ''Aristonectes'' sp.), with a body length of and body mass of . Another long plesiosauroid was ''Albertonectes'' at . ''Thalassomedon'' rivaled it in size, with its length at . Other large plesiosauroids are ''Styxosaurus'' and ''Elasmosaurus''. Both reached some more than in length. ''Hydralmosaurus'' (previously synonymized with ''Elasmosaurus'' and ''Styxosaurus'') reached in total body length. In past, ''Mauisaurus'' was considered to be more than in length, but later it was determined as ''nomen dubium''.

* There is much controversy over the largest-known of the Pliosauroidea. ''Pliosaurus, Pliosaurus funkei'' (also known as "Predator X") is a species of large pliosaur, known from remains discovered in Norway in 2008. This pliosaur has been estimated at in length. However, in 2002, a team of paleontologists in Mexico discovered the remains of a pliosaur nicknamed as "Monster of Aramberri", which is also estimated at in length, with shorter estimation about . This species is, however, claimed to be a juvenile and has been attacked by a larger pliosaur. Some media sources claimed that Monster of Aramberri was a ''Liopleurodon'' but its species is unconfirmed thus far. Another very large pliosaur was ''Pliosaurus, Pliosaurus macromerus'', known from a single incomplete mandible. The Early Cretaceous ''Kronosaurus queenslandicus'' is estimated at in length and in weight. The Late Jurassic ''Megalneusaurus rex'' could reach lengths of . Close contender in size was the Late Cretaceous ''Megacephalosaurus eulerti'' with a length in range of .

Proterosuchids (Proterosuchidae)

''Proterosuchus fergusi'' is the largest known Proterosuchidae, proterosuchid with a skull length of and a possible body length of .

Erythrosuchids (Erythrosuchidae)

The largest Erythrosuchidae, erythrosuchid was ''Erythrosuchus africanus'' with a maximum length of .

Phytosaurs (Phytosauria)

Some of the largest known Phytosauria, phytosaurs include ''Redondasaurus'' with a length of and ''Smilosuchus'' with a length of more than .

Non-crocodylomorph pseudosuchians (Pseudosuchia)

* The largest Shuvosauridae, shuvosaurid and one of the largest pseudosuchian from the Triassic period was ''Sillosuchus''. Biggest specimens could have reached in length.
* The largest known carnivorous pseudosuchian of the Triassic is loricatan ''Fasolasuchus, Fasolasuchus tenax'', which measured an estimated of . It is both the largest "rauisuchian" known to science, and the largest non-dinosaurian terrestrial predator ever discovered. Biggest individuals of ''Postosuchus'' and ''Saurosuchus'' had a body length of around . A specimen of ''Prestosuchus'' discovered in 2010 suggest that this animal also reached lengths of nearly making it one of the largest Triassic pseudosuchians.
* ''Desmatosuchus'' was likely one of the largest known aetosaurs, about in length and in weight.

Crocodiles and close relatives (Crocodylomorpha)

Aegyptosuchids (Aegyptosuchidae)

The Late Cretaceous ''Aegisuchus'' was originally estimated to reach in length by the lower estimate and as much as by the upper estimate although a length of over 15 m is likely a significant overestimate. However, this estimation is likely to be a result of miscalculation, and its length would be only around .

Crocodylians (Crocodylia)

* The largest caiman and likely one of the largest crocodylians was ''Purussaurus, Purussaurus brasiliensis'' estimated at . According to another information, maximum estimate measure and almost in length and in weight respectively. However, a 2022 study estimated a length of 7.6–9.2 metres (25–30 ft) and a mass of 2–6.2 metric tons (2.2–6.8 short tons) using a phylogenetic approach; and a length of 9.2–10 metres (30–33 ft) and mass of 3.9–4.9 metric tons (4.3–5.4 short tons) using a non-phylogenetic approach.
* Another giant caiman was ''Mourasuchus''. Various estimates suggest the biggest specimens reached in length and in weight. but more recent estimates suggest in body length.
* The largest Alligatoroidea, alligatoroid is likely ''Deinosuchus, Deinosuchus riograndensis'' at long and weighing .
* The largest extinct species of the genus ''Alligator'' was the Haile alligator (''Alligator hailensis''), which had a skull long and was similar in size to the extant American alligator (''Alligator mississippiensis'').
* The largest Gavialidae, gavialids were Asian ''Rhamphosuchus'' at and South American ''Gryposuchus'' at in length.
* The basal crocodyloidean ''Astorgosuchus bugtiensis'' from the Oligocene was large. It estimated at in length.
* The largest known Crocodylidae, true crocodile was ''Euthecodon'' which estimated to have reached or even long. The largest species of the modern ''Crocodylus'' were Kenyan ''Crocodylus thorbjarnarsoni'' at in length, Tanzanian ''Crocodylus anthropophagus'' at in length and indeterminate species from Kali Gedeh (Java) at in length.
* The largest known Mekosuchinae, mekosuchian is ''Paludirex, Paludirex vincenti'', which is estimated to reach up to . Partial jaw specimen from Pliocene that is attributed to ''Quinkana'' suggest an individual about in length, although other species (known from Oligocene to Pleistocene) are smaller with length around .

Paralligatorids (Paralligatoridae)

The largest Paralligatoridae, paralligatorid was likely ''Kansajsuchus,'' estimated at up to long.

Tethysuchians (Tethysuchia)

* Some extinct Pholidosauridae, pholidosaurids reached giant sizes. In the past, ''Sarcosuchus imperator'' was believed to be the largest crocodylomorph, with initial estimates proposing a length of and a weight of . However, recent estimates have now shrunk to a length of and a weight of . Related to ''Sarcosuchus'', ''Chalawan thailandicus'' could have reached more than in length, although other estimates suggest .
* The largest Dyrosauridae, dyrosaurid was ''Phosphatosaurus gavialoides,'' estimated at in length.

Stomatosuchids (Stomatosuchidae)

''Stomatosuchus'', a Stomatosuchidae, stomatosuchid, was estimated at in length.

Notosuchians (Notosuchia)

* Some of largest terrestrial notosuchian crocodylomorphs were the Miocene Sebecidae, sebecid ''Barinasuchus'', with a skull of long, and Eocene sebecid ''Dentaneosuchus'' with estimated mandible length of . Various estimates suggest a possible length of these animals between . Using proportion of ''Stratiotosuchus'' which is also large to have long skull, ''Barinasuchus'' is estimated to have length at least .
* Other huge notosuchian, although only known from fragmentary material, is an early member ''Razanandrongobe'', which skull size may exceeded that of ''Barinasuchus'' and overall length may be around .

Thalattosuchians (Thalattosuchia)

* The largest thalattosuchian as well as the largest Teleosauroidea, teleosauroid was unnamed fossil remain from Paja Formation, which may belongs to animal with length of , which is as large as outdated length estimate of the Early Cretaceous ''Machimosaurus rex'', more recently estimated at in length. ''Neosteneosaurus edwardsi'' (previously known as ''Steneosaurus edwardsi'') was the biggest Middle Jurassic crocodylomorph, it reached long.
* ''Plesiosuchus'' was very large Metriorhynchidae, metriorhynchid. With the length of it exceeded even some pliosaurids of the same time and locality such as ''Liopleurodon''. Other huge metriorhynchids include ''Tyrannoneustes'' at in length and ''Torvoneustes'' at in length.

Basal crocodylomorphs

''Redondavenator'' was the largest Triassic crocodylomorph ever recorded, with a skull of at least in length. Another huge basal crocodylomorph was ''Carnufex'' at long even through that is immature.

Pterosaurs (Pterosauria)

* The largest known pterosaur was ''Quetzalcoatlus northropi'', at and with a wingspan of . Another close contender is ''Hatzegopteryx'', also with a wingspan of or more. This estimate is based on a skull long. Yet another possible contender for the title is ''Cryodrakon'' which had a wingspan. An unnamed Pterodactyloidea, pterodactyloid pterosaur from the Nemegt Formation could reach a wingspan of nearly . According to various assumptions, the wingspan of ''Arambourgiania philadelphiae'' reached from to more than . South American ''Tropeognathus'' reached the maximum wingspan of .
* The largest of non-Pterodactyloidea, pterodactyloid pterosaurs as well as the largest Jurassic pterosaur was ''Dearc'', with an estimated wingspan between and . Only a fragmentary Rhamphorhynchidae, rhamphorhynchid specimen from Germany could be larger (184% the size of the biggest ''Rhamphorhynchus''). Other large non-pterodactyloid pterosaurs were ''Sericipterus'', ''Campylognathoides'' and ''Harpactognathus'', with the wingspan of , , and , respectively.

Choristoderes (Choristodera)

The largest known choristoderan, ''Kosmodraco, Kosmodraco dakotensis'' (previously known as ''Simoedosaurus dakotensis'') is estimated to have had a total length of around .

Tanystropheids (Tanystropheidae)

''Tanystropheus'', the largest of all Tanystropheidae, tanystropheids, reached up to in length.

Thalattosaurs (Thalattosauria)

The largest species of Thalattosauria, thalattosaur, ''Miodentosaurus, Miodentosaurus brevis'' grew to more than in length. The second largest member of this group is ''Concavispina'' with a length of .

Ichthyosaurs (Ichthyosauria)

* The largest known Shastasauridae, shastasaur, Ichthyosauria, ichthyosaur and marine reptile was ''Ichthyotitan'', which is estimated to have measured . In addition to the Aust specimen, which has been attributed to ''Ichthyotitan'', could’ve measured over . Another large shastasaur ''Shastasaurus sikanniensis'' at in length and in weight. ''Shonisaurus popularis'' was another large Ichthyosaur, measuring in length and weighing .
* The largest cymbospondylidae ichthyosaur as well as the largest animal of the Middle Triassic was ''Cymbospondylus youngorum'' at in length and in weight.

Pareiasaurs (Pareiasauria)

Largest Pareiasauridae, pareiasaurs reached up to in length. Such sizes had Middle Permian ''Bradysaurus'', ''Embrithosaurus'', and ''Nochelesaurus'' from South Africa, and the Late Permian ''Scutosaurus'' from Russia. The most robust ''Scutosaurus'' had in body mass.

Captorhinids (Captorhinidae)

The heavy built ''Moradisaurus, Moradisaurus grandis'', with a length of , is the largest known Captorhinidae, captorhinid. The second largest captorhinid was ''Labidosaurikos'' with the largest adult skull specimen long.

Non-avian dinosaurs (Dinosauria)

Sauropodomorphs (Sauropodomorpha)

The largest of non-sauropod Sauropodomorpha, sauropodomorphs ("prosauropod") was ''Euskelosaurus''. It reached in length and in weight. Another huge sauropodomorph ''Yunnanosaurus youngi'' reached long.

Sauropods (Sauropoda)

* A mega-sauropoda, sauropod, ''Maraapunisaurus, Maraapunisaurus fragillimus'' (previously known as ''Amphicoelias fragillimus''), is a contender for the largest-known dinosaur in history. It has been estimated at in maximum length and in weight. Unfortunately, the fossil remains of this dinosaur have been lost. More recently, it was estimated at in length and in weight.
* Known from the incomplete and now disintegrated remains, the Late Cretaceous ''Bruhathkayosaurus matleyi'' was an anomalously large sauropod. Informal estimations suggested as huge parameters as in length and in weight. Some estimates, however, suggest and but it's still much heavier than most other sauropods. More recent estimations by Gregory Paul in 2023 has placed its weight range around to a . If true, it would make ''Bruhathkayosaurus'' the single largest terrestrial animal to have walked the earth and would have rivalled the largest blue whale recorded.
* BYU 9024, a massive cervical vertebra found in Utah, may belong to a ''Barosaurus, Barosaurus lentus'' or ''Supersaurus, Supersaurus vivianae'' of a huge size, possibly in length and in body mass. ''Supersaurus vivianae'' itself may have been the longest dinosaur yet discovered as a study of 3 specimens suggested length of or over .

* ''Mamenchisaurus sinocanadorum'' was likely the largest Mamenchisauridae, mamenchisaurid, reaching nearly in length and in weight. ''Xinjiangtitan shanshanesis'' from the same family had -long neck, about 55% of its total length that could be at least .
* The Middle Jurassic ''Breviparopus, Breviparopus taghbaloutensis'' was mentioned in ''The Guinness Book of Records'' as the longest dinosaur at although this animal is known only from fossil tracks. Originally thought to be a brachiosauridae, brachiosaurid, it was later identified as a huge Diplodocoidea, diplodocoid, possibly in length and in weight.
* The tallest sauropod was ''Sauroposeidon proteles'' with estimated height at . ''Asiatosaurus'' could potentially reach in height, but this animal is known only from teeth. ''Giraffatitan'' was estimated at in height.

Other huge sauropods include ''Argentinosaurus'', ''Alamosaurus'', and ''Puertasaurus'' with estimated lengths of and weights of .Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press. ''Patagotitan'' was estimated at in length and in average weight, and was similar in size to ''Argentinosaurus'' and ''Puertasaurus''. Giant sauropods like ''Supersaurus'', ''Sauroposeidon'', and ''Diplodocus'' probably rivaled them in length but not in weight. ''Dreadnoughtus'' was estimated at in weight and in length, but the most complete individual was immature when it died. ''Turiasaurus'' is considered the largest dinosaur from Europe, with an estimated length of and a weight of . However, lower estimates at and would make it smaller than the Portuguese ''Lusotitan'', which reached in length and in weight.

Many large sauropods are still unnamed and may rival the current record holders:
* The "List of informally named dinosaurs#Archbishop, Archbishop", a large brachiosaur that was discovered in 1930. , a scientific paper on the specimen is still in progress.
* ''Brachiosaurus nougaredi'' is yet another large brachiosaur from Early Cretaceous North Africa. The remains have been lost, but the sacrum drawing remains. It suggests a sacrum of almost long, making it the largest dinosaur sacrum discovered so far, except those of ''Argentinosaurus'' and ''Apatosaurus''.
* In 2010, the femur of a large sauropod was discovered in France. The femur suggests an animal that grew to immense sizes.

Non-avian theropods (Theropoda)

* The largest Theropoda, theropod as well as the largest terrestrial predator yet known is ''Tyrannosaurus, Tyrannosaurus rex'', with the largest specimen known nicknamed Scotty (RSM P2523.8), located at the Royal Saskatchewan Museum, is reported to measure 13 m (43 ft) in length. Using a mass estimation technique that extrapolates from the circumference of the femur, Scotty was estimated as the largest known specimen at 8.87 metric tons (9.78 short tons) in body mass
* Other large theropods were ''Giganotosaurus carolinii'', and ''Spinosaurus aegyptiacus'', whose largest specimens known estimated at and in length, and weigh between and 14m(46 ft) in length and 7.4 metric tonnes (8.2 short tons) respectively (which makes ''Spinosaurus ''the longest terrestrial carnivore). Some other notable giant theropods (e.g. ''Carcharodontosaurus'','' Acrocanthosaurus'', and ''Mapusaurus'') may also have rivaled them in size.
* ''Macroelongatoolithus'', ranging from in length, is the largest known type of egg fossil, dinosaur egg. It is assigned to Oviraptorosauria, oviraptorosaurs like ''Beibeilong''.

Armoured dinosaurs (Thyreophora)

The largest-known thyreophoran was ''Ankylosaurus'' at in length and in weight.Vickaryous, M.K., Teresa Maryańska, Maryanska, T., & Weishampel, D.B. 2004. Ankylosauria. In: Weishampel, D.B., Dodson, P., & Osmólska, H. (Eds.). ''The Dinosauria'' (2nd edition). Berkeley: University of California Press. Pp. 363–392. ''Stegosaurus'' was also long but around tonnes in weight.

Marginocephalians (Marginocephalia)

Pachycephalosaurs (Pachycephalosauria)

The largest pachycephalosaur was the eponymous ''Pachycephalosaurus''. Previously claimed to be at in length, it was later estimated about long and a weight of about .

Ceratopsians (Ceratopsia)

The largest ceratopsian known is ''Triceratops, Triceratops horridus'', along with the closely related ''Eotriceratops, Eotriceratops xerinsularis'' both with estimated lengths of . ''Pentaceratops'' and several other ceratopsians rival them in size. ''Titanoceratops'' had one of the longest skull of any land animal, at long. A recently discovered ''Torosaurus'' (nicknamed "Adam") may exceed this size with a skull length of meters.

Ornithopods (Ornithopoda)

* The very largest known ornithopods, like ''Shantungosaurus'' were as heavy as medium-sized sauropods at up to , and in length. ''Magnapaulia'' reached in length, or, according to original description, even . The Mongolian ''Saurolophus'', ''S. angustirostris'', reached long and possibly more.Paul, Greg (2010). "The Princeton Field Guide to Dinosaurs". New Jersey: Princeton University Press. p. 335. Such animal could weighed up to . The largest ''Edmontosaurus'' reached in length and around in body mass. An estimated maximum length of ''Brachylophosaurus'' is resulting in weight of . PASAC-1, informally named ''"List of informally named dinosaurs#Sabinosaurus, Sabinosaurus"'', is the largest well-known North American saurolophine, around long, that is about 20% larger than other known specimens. ''Hypsibema missouriensis'' was up to long. The Late Cretaceous ''Charonosaurus'' was estimated around in length and in weight.
* The largest ornithopod outside of Hadrosauroidea was likely the ''Iguanodon''. Biggest specimens reached in length and weighed around . Another large ornithopod is ''Iguanacolossus'', with in length and in weight.
* The largest Rhabdodontidae, rhabdodontid was ''Matheronodon'', estimated at in length. ''Rhabdodon'' reached approximately and according to 2016 estimates.

Birds (Aves)

The largest bird in the fossil record may be the extinct Aepyornis, elephant bird species ''Aepyornis maximus'' of Madagascar, whose closest living relative is the Kiwi (bird), kiwi. Giant elephant birds exceeded in height, and average a mass of

The largest fowl was the Dromornithidae, mihirung ''Dromornis, Dromornis stirtoni''
of Australia. It exceeded in height, and average a mass of

Another contender is ''Brontornis, Brontornis burmeisteri'', an extinct flightless bird from South America which reached a weight of and a height of approximately .Degrange, F. J., Noriega, J. I., & Areta, J. I. (2012). Diversity and paleobiology of the Santacrucian birds. ''Early Miocene paleobiology in Patagonia: high-latitude paleocommunities of the Santa Cruz Formation'', 138–155.

The tallest recorded bird was ''Pachystruthio, Pachystruthio dmanisensis,'' a relative of the ostrich. This particular species of bird stood at tall and average a mass of

The largest known flightless Neoaves, neoave was the Phorusrhacidae, terror bird ''Paraphysornis, Paraphysornis brasiliensis'' of South America, the Brazilian terror bird exceeded in mass,

Table of heaviest extinct bird species

Enantiornitheans (Enantiornithes)

One of the largest Enantiornithes, enantiornitheans was ''Enantiornis'', with a length in life of around , hip height of , weight of , and wingspan comparable to some of the modern gulls, around . ''Gurilynia'' was the largest Mesozoic bird from Mongolia, with a length of , hip height of , and weight of .

Avisauridae

The Late Cretaceous ''Avisaurus'' was almost as large as ''Enantiornis''. It had a wingspan around , a length of , hip height of , and weight of . Even larger could be the ''Soroavisaurus''. One tibiotarsus (PVL-4033) indicates an animal with a length of , hip height of , and weight of . However, according to Walker and Dyke (2009) which considered PVL-4033 as ''Martinavis'' sp., its tibiotarsus length is , much shorter than that of ''Lectavis'' ( tibiotarsus) which the same book estimated a length of , hip height of , and weight of ''. Mirarce'' was comparable in size to a Turkey (bird), turkey, much larger than most of other enantiornitheans.

Pengornithidae

One of the biggest Early Cretaceous enantiornithine bird was ''Pengornis'' at in length and skull length of .

Gargantuaviidae

''Gargantuavis'' is the largest known bird of the Mesozoic, a size ranging between the cassowary and the Common ostrich, ostrich, and a mass of like modern ostriches. In 2019 specimens MDE A-08 and IVPP-V12325 were measured at in length, in hip height, and in weight.

Dromornithiformes

The largest Dromornithidae, dromornithid was ''Dromornis stirtoni'' over tall and in mass for males.

Gastornid (Gastornithiformes)

Large individuals of ''Gastornis'' reached up to in height. Weight of ''Gastornis'' ranges from to and sometimes to for European specimens and from to for North American.

Waterfowl (Anseriformes)

Possibly flightless, the Miocene ''Garganornis ballmanni'' was larger than any extant members of Anseriformes, with in body mass. Another huge anseriform was the flightless New Zealand goose (''Cnemiornis''). It reached , approaching in size to small species of moa.

Swans (Cygnini)

The largest known swan was the Pleistocene giant swan (''Cygnus falconeri''), which reached a bill-to-tail length of about , a weight of around , and a wingspan of . The New Zealand swan (''Cygnus sumnerensis'') weighed up to , compared to the related extant black swan at only . The large marine swan ''Annakacygna, Annakacygna yoshiiensis'' from the Miocene of Japan far exceeded the extant mute swan in both size and weight.

Anatinae

Finsch's duck (''Chenonetta finschi'') reached in weight, surpassing related modern Australian wood duck ().

Pelicans, ibises and allies (Pelecaniformes)

*The Early Pliocene ''Pelecanus schreiberi'' was larger than most extant pelicans. ''Pelecanus odessanus'' from the Late Miocene was probably the same size as ''P. schreiberi'', its tarsometatarsus is long.
*The largest heron was the Bennu heron (''Ardea bennuides''). Based on remains discovered, it was approximately tall and had a wingspan up to , thus surpassing the size of the largest living species in the heron family, the goliath heron.
*The Jamaican ibis (''Xenicibis xympithecus'') was a large ibis, weighing about 2 kg (70 oz).

Storks and allies (Ciconiiformes)

The largest known of Ciconiiformes was ''Leptoptilos robustus'', standing tall and weighing an estimated . ''Ciconia maltha'' is a relatively large species of ''Ciconia'', with a height of over and a wingspan up to across.

Cranes (Gruiformes)

A large true crane (Gruinae) from the late Miocene (Tortonian) of Germany was equal in size to the biggest extant cranes and resembled the long-beaked Siberian crane (''Leucogeranus leucogeranus'').

Shorebirds (Charadriiformes)

''Mancallinae, Miomancalla howardi'' was the largest known charadriiform of all time, weighing approximately 0.6 kg (1.3 lb) more than the second-largest member, the great auk (''Pinguinus impennis'').

Hesperornithines (Hesperornithes)

The largest known of the Hesperornithes, hesperornithines was ''Canadaga arctica'' at long.

New World vultures (Cathartiformes)

One of the heaviest flying birds of all time was ''Argentavis'', a Miocene Teratornithidae, teratornithid. The immense bird had a wingspan estimated up to and a weight up to . ''Argentavis'' humerus was only slightly shorter than an entire human arm. Another huge teratorn was ''Aiolornis'', with a wingspan of around . The Pleistocene ''Teratornis, Teratornis merriami'' reached and in wingspan, with lower size estimates still exceeding the largest specimens of California condor (''Gymnogyps californianus'').

Seriemas and allies (Cariamiformes)

The largest known-ever Cariamiformes, Cariamiforme and largest Phorusrhacidae, phorusrhacid or "terror bird" (highly predatory, flightless birds of America) was ''Brontornis'', which was about tall at the shoulder, could raise its head above the ground and could have weighed as much as . The immense phorusrhacid ''Kelenken'' stood tall with a skull long ( of which was beak), had the largest head of any known bird. South American ''Phorusrhacos'' stood 2.4-2.7 m (7.9-8.8 ft) tall, and weighed nearly , as much as a male ostrich. The largest North American phorusrhacid was ''Titanis'', which reached a height of approximately 2.5 m (8.2 ft), slightly taller than an African forest elephant.

Accipitriforms (Accipitriformes)

The largest known Accipitriformes, bird of prey ever was the enormous Haast's eagle (''Hieraaetus moorei''), with a wingspan of , relatively short for their size. Total length was probably up to in female and they weighed about . Another giant extinct hawk was ''Titanohierax'' about that lived in the Antilles and The Bahamas, where it was among the top predators. An unnamed late Quaternary eagle from Hispaniola could be 15–30% larger than the modern golden eagle (''Aquila chrysaetos''). Some extinct species of ''Buteogallus'' surpassed their extant relatives in size. ''Buteogallus borrasi'' was about 33% larger than the modern great black hawk (''Buteogallus urubitinga, B. urubitinga''). ''Buteogallus daggetti, B. daggetti'', also known as "walking eagle", was around 40% larger than the savanna hawk (''Buteogallus meridionalis, B. meridionalis''). Eyles's harrier (''Circus eylesi'') from the Pleistocene-Holocene of New Zealand was more than twice heavier than the extant ''Circus approximans, C. approximans''.

Moa (Dinornithiformes)

The tallest known bird was the South Island giant moa (''Dinornis robustus''), part of the moa family of New Zealand that went extinct about 500 years ago. It stood up to tall, and weighed approximately half as much as a large elephant bird due to its comparatively slender frame.

Tinamous (Tinamiformes)

MPLK-03, a tinamou specimen that existed during the Late Pleistocene in Argentina, possibly belongs to the modern genus ''Eudromia'' and surpacces extant ''Eudromia elegans, E. elegans'' and ''Eudromia formosa, E. formosa'' in size by 2.2–8% and 6–14%, respectively.

Elephant birds (Aepyornithiformes)

The largest bird in the fossil record may be the extinct elephant birds (''Vorombe'', ''Aepyornis'') of Madagascar, which were related to the ostrich. They exceeded in height and in weight.Wood, Gerald ''The Guinness Book of Animal Facts and Feats'' (1983)

Ostriches (Struthioniformes)

With in body mass, ''Pachystruthio dmanisensis'' from the lower Pleistocene of Crimea was the largest bird ever recorded in Europe. Despite its giant size, it was a good runner. A possible specimen of ''Pachystruthio'' from the lower Pleistocene of Hebei Province (China) was about in weight, twice heavier than the common ostrich (''Struthio camelus''). Remains of the massive Asian ostrich (''Struthio asiaticus'') from the Pliocene indicate a size 20% bigger than adult male of the extant ''Struthio camelus''.

Pigeons and doves (Columbiformes)

The largest pigeon relative known was the dodo (''Raphus cucullatus''), possibly exceeding in height and weighing as much as , although recent estimates have indicated that an average wild dodo weighed much less at approximately .

Pheasants, turkeys, gamebirds and allies (Galliformes)

The largest known of the Galliformes was likely the giant malleefowl, which could reach in weight.

Songbirds (Passeriformes)

The largest known Passeriformes, songbird is the extinct giant grosbeak (''Chloridops regiskongi'') at long.

Cormorants and allies (Suliformes)

* The largest known cormorant was the spectacled cormorant of the North Pacific (''Phalacrocorax perspicillatus''), which became extinct around 1850 and averaged around and .
* The largest known darter was ''Giganhinga'' with estimated weight about , earlier study even claims .
* The largest known Plotopteridae, plotopterid, penguin-like flightless bird was ''Copepteryx, Copepteryx titan'' that is known from long femur, almost twice as long as that of emperor penguin.

Grebes (Podicipediformes)

The largest known grebe, the Atitlán grebe (''Podylimbus gigas''), reached a length of about .

Bony-toothed birds (Odontopterygiformes)

The largest known of the Odontopterygiformes— a group which has been variously allied with Procellariiformes, Pelecaniformes and Anseriformes and the largest flying birds of all time other than ''Argentavis'' were the huge ''Pelagornis'', ''Cyphornis'', ''Dasornis'', ''Gigantornis'' and ''Osteodontornis''. They had a wingspan of and stood about tall. Exact size estimates and judging which one was largest are not yet possible for these birds, as their bones were extremely thin-walled, light and fragile, and thus most are only known from very incomplete remains.

Woodpeckers and allies (Piciformes)

The largest known Piciformes, woodpecker is the possibly extinct imperial woodpecker (''Campephilus imperialis'') with a total length of about .

Parrots (Psittaciformes)

The largest known Psittaciformes, parrot is the extinct ''Heracles inexpectatus'' with a length of about 1 meter (3.3 feet).

Penguins (Sphenisciformes)

One of the heaviest penguins ever known is ''Kumimanu fordycei'', with a body mass estimate of , derived from humerus measurements. Another example is ''Palaeeudyptes klekowskii'' of Antarctica, with a bill-to-tail length estimated at and an estimated body weight of , slightly smaller than previous estimates. The Eocene ''Anthropornis nordenskjoeldi'' is comparable in size, and was once estimated to reach lengths of and a weight of . However, recent estimation from humerus measurements put ''A. nordenskjoeldi'' more in the range of in weight. Other large penguins include the New Zealand giant penguin (''Pachydyptes pondeorsus'') weighing around , and ''Icadyptes salasi'' at .

Owls (Strigiformes)

The largest known Strigiformes, owl of all time was the Cuban ''Ornimegalonyx'' at tall probably exceeding .

Amphibians (Amphibia)

The largest known amphibian of all time was the long temnospondyli, temnospondyl ''Prionosuchus''.

Lissamphibians (Lissamphibia)

Frogs and toads (Anura)

The largest known frog ever was an as yet unnamed Eocene species that was about . The Late Cretaceous ''Beelzebufo'' grew to at least (snout-vent length), which is around the size of a modern African bullfrog.

Salamanders, newts and allies (Urodela)

* ''Andrias matthewi'' was the largest lissamphibian ever known, with total length up to .
* ''Habrosaurus'' was the largest Sirenidae, sirenid. It reached long.

Diadectomorphs (Diadectomorpha)

The largest known diacectid, herbivorous ''Diadectes'', was a heavily built animal, up to long, with thick vertebrae and ribs.

Anthracosauria

The largest known anthracosaur was ''Anthracosaurus'', with skull about in length.

Embolomeri

The longest member of this group was ''Eogyrinus attheyi'', species sometimes placed under genus ''Pholiderpeton''. Its skull had length about .

Temnospondyls (Temnospondyli)

The largest known temnospondyl amphibian is ''Prionosuchus'', which grew to lengths of . Another huge temnospondyl was ''Mastodonsaurus, Mastodonsaurus giganteus'' at long. Unnamed species of temnospondyl from Lesotho is partial, but possible body length estimation is .

Fishes (Pisces)

Fishes are a paraphyletic group of non-tetrapod vertebrates.

Jawless fish (Agnatha)

Conodonts (Conodonta)

''Iowagnathus, Iowagnathus grandis'' is estimated to have length over .

Heterostracans (Heterostraci)

Some members of Psammosteidae such as ''Obruchevia'' and ''Tartuosteus'' are estimated to reached up to .

Thelodonts (Thelodonti)

Although known from partial materials, ''Thelodus, Thelodus parvidens'' (=''T. macintoshi'') is estimated to reached up to .

Cephalaspidomorphs (Cephalaspidomorphi)

A species of ''Parameteoraspis'' reached up to .

Spiny sharks (Acanthodii)

The largest of the now-extinct Acanthodii was ''Xylacanthus (fish), Xylacanthus grandis'', an Ischnacanthiformes, ischnacanthiform based on a ~ long jaw bone. Based on the proportions of its relative ''Ischnacanthus'', ''X. grandis'' had an estimated total length of .

Placoderms (Placodermi)

The largest known placoderm was the giant predatory ''Dunkleosteus''. The largest and most well known species was ''D. terrelli'', was initially estimated to be in length and in weight. However, more recent reconstructions suggest estimates over is poorly supported. Instead the largest ''D. terrelli'' probably measured in length and weighed . Another large placoderm, ''Titanichthys, Titanichthys clarki'', may have rivaled it in size. Recent reconstructions suggest ''T. clarki'' was estimated to have a length around .

Cartilaginous fish (Chondrichthyes)

Mackerel sharks (Lamniformes)

* Species in the extinct genus ''Otodus'' were huge. A giant shark, ''Megalodon, Otodus megalodon'' is by far the biggest Lamniformes, mackerel shark as well as Fish, non-tetropod fish ever known. Most estimates of megalodon's size extrapolate from teeth, with maximum length estimates up to with a 2025 study estimating a maximum length estimate of and Mode (statistics), modal length estimates based on individuals from all Ontogeny, ontogenetic stages (life stages) of . Due to fragmentary remains, there have been many contradictory size estimates for megalodon, as they can only be drawn from fossil teeth and vertebrae. With the 2025 study suggesting that the animal had a more elongated slender appearance. Mature male megalodon may have had a body mass of , and mature females may have been , assuming that males could range in length from and females . Related to megalodon, ''Otodus angustidens'' and ''Otodus chubutensis, O. chubutensis'' reached the large sizes too. Each was estimated at and , respectively.
* Other giant mackerel sharks were Pseudoscapanorhynchidae from the Cretaceous period. ''Cretodus'' had a size range of (for ''C. crassidens''), ''Leptostyrax'' reached lengths of .
* The Cenozoic ''Parotodus'' reached up to in length.
* The heaviest thresher shark was likely ''Alopias grandis''. It was similar in size or even larger than the extant great white shark and probably did not have an elongated dorsal tail, characteristic of modern relatives.

Ground sharks (Carcharhiniformes)

The Cenozoic ''Hemipristis serra'' was considerably larger than its modern-day relatives and had much larger teeth. Its total length is estimated to be at long.

Hybodonts (Hybodontiformes)

One of the largest Hybodontiformes, hybodontiforms was the Jurassic ''Asteracanthus'' with body length of up to . ''Crassodus, Crassodus reifi'' is known from less materials, however it is estimated that reached over .

Ctenacanthiformes

The largest member of ctenacanthiformes is ''Saivodus striatus'' with estimated length around .

Skates and allies (Rajiformes)

The giant Sclerorhynchidae, sclerorhynchid ''Onchopristis'' reached about in length.

Eugeneodonts (Eugeneodontida)

The largest known Eugeneodontida, eugeneodont is an as-yet unnamed species of ''Helicoprion'' discovered in Idaho. The specimens suggest an animal that possibly exceeded in length. Another fairly large eugeneodont is ''Parahelicoprion''. Being more slimmer than ''Helicoprion'', it reached nearly the same size, possibly up to in length. Both had the largest sizes among the animals of Paleozoic era.

Lobe-finned fish (Sarcopterygii)

Coelacanths (Actinistia)

The largest coelacanth is Cretaceous ''Mawsonia (fish), Mawsonia gigas'' with estimated total length up to . Jurassic ''Trachymetopon'' may have reached size close to that, about . An undetermined Mawsoniidae, mawsoniid from the Maastrichtian deposits of Morocco probably reached in length.

Lungfish (Dipnoi)

Cretaceous ''Ceratodus'' sp. from Western Interior Seaway, Western Interior is estimated to had a length around .

Stem-tetrapods (Tetrapodomorpha)

* Not only the largest known Rhizodontida, rhizodont, but also the largest lobe-finned fish was the long ''Rhizodus''. Another large rhizodonts were ''Strepsodus'' with estimated length around and ''Barameda'' estimated at in length.
* Tristichopteridae, Tristichopterid ''Hyneria'' reached length up to .

Ray-finned fish (Actinopterygii)

Acipenseriformes

* ''Gyrosteus'', which belongs to extinct acipenseriform family Chondrosteidae, is estimated to have standard length about .
* The largest known fossil sturgeon is "''Acipenser''" ''gigantissimus'' known from fragmentary remains, which is estimated to reach up to .Nessov, L.A. (1997). ''Cretaceous nonmarine vertebrates of northern Eurasia.'' Saint Petersburg: University of Saint Petersburg Institute of Earth Crust, 218 pp. [in Russian].
* The largest known fossil paddlefish is unnamed remain from Judith River Formation, it may exceeded , known remains exceeded size of recently extinct Chinese paddlefish, which scientifically reported to exceed .

Pachycormiformes

The largest known Actinopterygii, ray-finned fish and largest bony fish of all time was the pachycormid, ''Leedsichthys problematicus'', at around long.Liston, J., Newbrey, M., Challands, T., and Adams, C., 2013, "Growth, age and size of the Jurassic pachycormid ''Leedsichthys problematicus'' (Osteichthyes: Actinopterygii) in: Arratia, G., Schultze, H. and Wilson, M. (eds.) ''Mesozoic Fishes 5 – Global Diversity and Evolution''. Verlag Dr. Friedrich Pfeil, München, Germany, pp. 145–175 Earlier estimates have had claims of larger individuals with lengths over .

Ichthyodectiformes

The largest known of ichthyodectiform fish was ''Xiphactinus'', which measured up to long. ''Ichthyodectes'' reached long, twice lesser than ''Xiphactinus''.

Pycnodontiformes

The largest known pycnodontiform was ''Gyrodus, Gyrodus circularis'', with length up to .

Bichirs (Polypteriformes)

The Late Cretaceous ''Bawitius'' was likely the largest bichir of all time. It reached up to in length.

Opahes, ribbonfishes, oarfishes and allies (Lampriformes)

''Megalampris'' was likely the largest fossil opah. This fish was around in length when alive, which is twice the length of the largest living opah species, ''Lampris guttatus''.

Salmon and trout (Salmoniformes)

The largest salmon was ''Oncorhynchus rastrosus'', varying in size from and to and .

Pufferfishes, boxfishes, triggerfishes, ocean sunfishes and allies (Tetraodontiformes)

* ''Austromola angerhoferi'' had total body length about , and total height , comparable with largest ocean sunfish.
* Some extinct species of ''Balistes'' like ''B. vegai'' and ''B. crassidens'' are estimated to have total length up to .

Lizardfishes (Aulopiformes)

The largest Aulopiformes, lizardfish was ''Stratodus'' which could reach length of .

Echinoderms (Echinodermata)

Crinozoa

Sea lilies (Crinoidea)

The longest stem of ''Seirocrinus, Seirocrinus subangularis'' reached over .

Asterozoa

Starfish (Asteroidea)

''Helianthaster'' from Hunsrück Slate had a radius of about .

Graptolites (Graptolithina)

The longest known graptoloid graptolite is ''Stimulograptus, Stimulograptus halli'' at . It was found in Silurian deposits of the United Kingdom.

Kinorhynchs (Kinorhyncha)

Cambrian Kinorhyncha, kinorhynchs from Qingjiang biota, also known as "mud dragons", reached in length, much larger than extant relatives that grow only a few millimeters in length.

Arthropods (Arthropoda)

Dinocaridida

Gilled lobopodians

Based on the findings of mouthparts, the Cambrian gilled lobopodian ''Omnidens, Omnidens amplus'' is estimated to have been . It is also known as the largest Cambrian animal known to exist.

Radiodont (Radiodonta)

The largest known Radiodonta, radiodont is ''Aegirocassis benmoulai'', estimated to have been at least long.

Chelicerata

Sea spiders (Pycnogonida)

The largest fossil sea spider is ''Palaeoisopus, Palaeoisopus problematicus'' with legspan about .

Horseshoe crabs and allies (Xiphosura)

* ''Willwerathia'' reached in carapace width and was the largest species of basal ("Synziphosurina, synziphosurine") xiphosurans. However, the Devonian ''Maldybulakia'' reached nearly and was assigned to xiphosurans in 2013.
* Horseshoe crab trackway Trace fossil, icnofossil ''Kouphichnium, Kouphichnium lithographicum'' from Cerin in Ain indicates length of animal .

Chasmataspidids (Chasmataspidida)

The largest Chasmataspidida, chasmataspidids were the Ordovician ''Hoplitaspis'' at in length and similar in size range ''Chasmataspis''.

Eurypterids (Eurypterida)

* The largest known Eurypterida, eurypterid was ''Jaekelopterus rhenaniae'' at in length, which is also the largest arthropod known to exist. ''Erettopterus, Erettopterus grandis'' possibly reached this same length but this is based on an incomplete telson only. A close contender was ''Acutiramus, Acutiramus bohemicus'' at in length. The largest Megalograptidae, megalograptid as well as the largest Ordovician eurypterid was ''Pentecopterus''. It reached up to in length. All these were Eurypterina, eurypterine eurypterids.
* The largest Stylonurina, stylonurine eurypterid was ''Hibbertopterus'', with in length.

Arachnids (Arachnida)

* There are three contenders for largest-known arachnid as well as the largest scorpions of all time: ''Pulmonoscorpius kirktonensis'', ''Brontoscorpio, Brontoscorpio anglicus'' and ''Praearcturus, Praearcturus gigas''. Each was estimated to have been , and up to , respectively.
* ''Mongolarachne jurassica'' is the largest described fossil spider, with the total body length of female is approximately while the front legs reach about in length. ''Dinodiplura, Dinodiplura ambulacra'' had larger body length, combined length of carapace and opisthosoma reaches .
* The largest of prehistoric whipscorpions and possibly the largest-known whipscorpion ever discovered was ''Mesoproctus, Mesoproctus rayoli''. The type specimen has body length reaching with a carapace of in length, while another specimen has a carapace of in length and in width, comparable or even larger than the extant ''Mastigoproctus''.
* The largest Ricinulei to ever exist was ''Curculioides, Curculioides bohemondi'' with a body length of .
* The largest fossil Acariformes, acariform mite and also the largest Erythraeoidea, erythraeoid mite ever recorded was ''Immensmaris, Immensmaris chewbaccei'' with idiosoma of more than in length.
* The largest known Trigonotarbida, trigonotarbid was ''Kreischeria'' with a minimal length of . The second largest was ''Pleophrynus'' at in length.

Artiopods (Artiopoda)

''Retifacies'' probably reached up to . ''Tegopelte'' is another one example of large non-trilobite artiopod, reached long and was the largest of the Burgess Shale bilaterians, surpassing all other benthic organisms by at least twice.

Trilobites (Trilobita)

Some of trilobites exceeded in length. A nearly complete specimen of ''Isotelus, Isotelus rex'' from Manitoba attained a length over , and an ''Ogyginus, Ogyginus forteyi'' from Portugal was almost as long. Fragments of trilobites suggest even larger record sizes. An isolated pygidium of ''Hungioides, Hungioides bohemicus'' implies that the full animal was long.

Myriapods (Myriapoda)

The largest known Myriapoda, myriapod by far was ''Arthropleura''. Measuring long and wide. Some specimens could have been even larger, up to in length and in weight.

Non-hexapod crustaceans (Crustacea)

Cycloids (Cyclida)

The largest Cyclida, cyclid was ''Opolanka decorosa'', the Late Triassic ''Halicyne''-like cycloid which reached over across the carapace.

Remipedes (Remipedia)

''Tesnusocaris'' had body length at least , larger than all living Remipedia, remipedes which can reach up to .

Insects (Insecta)

Sawflies, wasps, bees, ants and allies (Hymenoptera)

* The largest known of this group was the giant ant ''Titanomyrma, Titanomyrma giganteum'' with Eusociality, queens growing to . It had a wingspan of .
* ''Apis lithohermaea'' is one of the largest honey bees ever found, comparable in size to the modern ''Apis dorsata''.
* The giant horntail ''Ypresiosirex, Ypresiosirex orthosemos'' reached in length including the incomplete ovipositor. Another example of a giant sawfly is ''Hoplitolyda duolunica'', with wingspan over .

Fleas (Siphonaptera)

The largest known in Siphonaptera was probably ''Pseudopulex, Pseudopulex magnus'', growing to in length.

Earwigs (Dermaptera)

Extinct as recently as after 1967 and also submitted as the Holocene subfossils, the Saint Helena earwig, Saint Helena giant earwig (''Labidura herculeana'', with synonym ''Labidura loveridgei'') reached in length including forceps long.

Chresmodidae

Chresmodidae had long specialized legs like of the modern Gerridae family. One of the Chresmodidae, ''Chresmoda, Chresmoda obscura'', could have reached a size of about .

Beetles (Coleoptera)

One of the largest known fossil beetles in the taxonomic rank, superfamily Scarabaeoidea is ''Protognathinus, Protognathinus spielbergi''. It had total length including mandibles about . The largest fossil Scarabaeidae, scarabaeid was ''Oryctoantiquus, Oryctoantiquus borealis'' with an estimated body length of .

Titanopterans (Titanoptera)

Related to modern orthopterans, titanopterans from the Triassic period were much larger. The wingspan of ''Gigatitan, Gigatitan vulgaris'' was up to . ''Clatrotitan, Clatrotitan andersoni'' also reached a huge size, having a forewing long.

Antlions and related net-winged insects (Neuroptera)

''Makarkinia adamsi'' from the Crato Formation is estimated to have the longest forewings of any neuropteran species, estimated at .

Cockroaches, termites, mantises and allies (Dictyoptera)

* Some Carboniferous cockroach-like insects grouping in Blattoptera like ''Archoblattina beecheri'' and ''Necymylacris (Xenoblatta) scudderi'' could reach around 9 centimetres in total length, which is comparable to a modern ''Megaloblatta longipennis''.
* Cretaceous cockroach ''Ptiloteuthis, Ptiloteuthis foliatus'' had a long wing.
* Found in the Miocene of Austria, the giant termite ''Gyatermes, Gyatermes styriensis'' reached in body length and had a wingspan of .

Dragonflies, damselflies and griffinflies (Odonatoptera)

* The largest known odonatopteran insect was ''Meganeuropsis permiana'' with a single wing of . ''Meganeura'' had a long wing.
* Triadotypidae, Triadotypid odonatan ''Reisia, Reisia gelasii'' (=''Triadotypus guillaumei'') from Triassic had long wing, and wingspan can be .

Mayflies (Ephemeroptera)

* The largest known mayfly is Permian ''Ponalex, Ponalex maximus'', with long hindwing. Cretaceous ''Epicharmeropsis, Epicharmeropsis quadrivenulosus'' had long forewing.
* Although ''Bojophlebia, Bojophlebia prokopi'' from the Upper Carboniferous of Moravia (Czech Republic) with a wingspan of is described as the largest mayfly, later study shows that this insect is not related to mayflies.

Palaeodictyoptera

The largest known palaeodictyopteran was ''Mazothairos'', with an estimated wingspan of up to . If a subcircular wing known from Piesberg Quarry belongs to a palaeodictyopteran, it possibly had single wing length at least .

Archaeognatha (jumping bristletails) and other wingless primitive insects

* The largest known Machilidae, machilid is Triassic ''Gigamachilis'', with body length not counting the length of the Cercus, filament, and estimated total length about .
* The largest specimens of the extinct suborder Monura reached or more, not counting the length of the filament.
* Although ''Ramsdelepidion'' was once considered as a -long silverfish, it was later considered that classification is uncertain and just treated as Crown group, stem group insect.
* The wingless early insect ''Carbotriplura'' had body length about without tail filaments.

Arrow worms (Chaetognatha)

The Cambrian stem-Chaetognatha, chaetognathan ''Timorebestia koprii'' had reached up to in body length and including the antennae. ''Capinatator'' had a third of length, about , but it is not considered as stem member and still had length similar to the largest modern arrow worms.

Ringed worms (Annelida)

''Websteroprion'' is the largest known fossil eunicidan Annelida, annelid, with estimated length ranges , however comparison with closely related extant taxa indicates length around . It also had the biggest scolecodonts of any prehistoric polychaete, up to in length and possibly larger.

Molluscs (Mollusca)

Snails and slugs (Gastropoda)

* The largest known Gastropoda, gastropods were in the genus ''Campanile (gastropod), Campanile'', with the extinct ''Campanile giganteum'' having shell lengths up to or even more than .
* The largest known cowrie is ''Vicetia (gastropod), Vicetia bizzottoi'', with shell length of .
* ''Pebasiconcha immanis'' is the largest land snail ever known, shell height is with a partial specimen that may exceed in height.

Bivalves (Bivalvia)

* The largest known bivalve ever as well as the largest Inoceramidae, inoceramid was ''Platyceramus platinus'', a giant that usually had an axial length of , but some individuals could reach an axial length of up to . Another large prehistoric bivalve was ''Inoceramus''. In 1952, -long specimen of ''Inoceramus steenstrupi'' was found in the Late Cretaceous deposits of Greenland.
* Some Permian Alatoconchidae, alatoconchid genus like ''Shikamaia'' had shell length about . Previous estimation reconstructed length of ''Shikamaia'' around .
* The longest Ostreida, ostreid is ''Konbostrea'', with shell height reaching up to .
* Rudists, Rudist ''Titanosarcolites'' had overall size around .

Tusk shells (Scaphopoda)

* Complete shell length of tusk shell ''Prodentalium, Prodentalium onoi'' is estimated to be over .

Cephalopods (Cephalopoda)

Nautiloids (Nautiloidea)

The largest and longest known of Nautiloidea, nautiloids was ''Endoceras, Endoceras giganteum'' with a shell length of . There is a record of individual whose shell length had reached , but it is doubtful.

Ammonites (Ammonoidea)

The largest known ammonite was ''Parapuzosia seppenradensis''. A partial fossil specimen found in Germany had a shell diameter of , but the living chamber was incomplete, so the estimated shell diameter was probably about and weighed about when it was alive. However, a later study estimates shell diameter up to around .

Belemnites (Belemnoidea)

The largest known belemnite was ''Megateuthis gigantea'', reaching about in maximum diameter and length of rostrum, respectively.

Squids, octopuses, cuttlefishes and allies (Neocoleoidea)

* A specimen of Octopus, Octopod, a member of family Muensterellidae and Enchoteuthinae, ''Enchoteuthis, Enchoteuthis melanae'' (NDGS 241) which was previously attributed to ''Tusoteuthis, Tusoteuthis longa'' (another more dubious member), had a mantle length of up to , comparable to the modern-day giant squid. Previously, this taxon was considered similar to the giant squid, with total length including arms over . However, considering other fossil relatives, the total length including arms is estimated to be less than , to be realistic and reasonable.
* Both non-octopod ''Yezoteuthis'' and Squid, teuthid ''Haboroteuthis'' are estimated to be similar in size to the modern-day giant squid. Incomplete jaw specimen from Yezo Group (KMNH IvP 902007) is twice as large as those of ''Yezotuethis''.

Brachiopods (Brachiopoda)

The largest brachiopod ever evolved was ''Striatifera, Striatifera striata'' from Akkermanovka Quarry, Russia, with height up to . Another huge brachiopod was the Carboniferous ''Gigantoproductus giganteus'', with shell width from to over . ''Titanaria, Titanaria costellata'' had large and long shell in width, nearly as large as ''Gigantoproductus''.

Hyoliths (Hyolitha)

The largest hyolith is ''Macrotheca almgreeni'', with length about .

Cnidarians (Cnidaria)

Jellyfishes and allies (Medusozoa)

The largest fossil jellyfish is Cambrian ''Cordubia, Cordubia gigantea'', with diameter of . Specimens from the Cambrian of Wisconsin reached in length.

Vendobionts (Vendobionta)

Petalonamids (Petalonamae)

Longest specimens of ''Trepassia, Trepassia wardae'' (also known as ''Charnia wardi'') reached in length. ''Charnia, Charnia masoni'' is known from specimens as small as only , up to the largest specimens of in length.

Proarticulata

''Dickinsonia, Dickinsonia tenuis'' reached in length, that makes it one of the largest precambrian organisms.

Sponges (Porifera)

The largest known Permian sponge ''Gigantospongia'' had diameter up to .

See also

* Dinosaur size
* Largest organisms
* Megafauna

References

Sources

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{{DEFAULTSORT:Largest Prehistoric Organisms
Lists of prehistoric animals
Lists of largest animals, Prehistoric