''Thylacoleo'' ("pouch lion") is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of carnivorous

marsupial Marsupials are a diverse group of mammals belonging to the infraclass Marsupialia. They are natively found in Australasia, Wallacea, and the Americas. One of marsupials' unique features is their reproductive strategy: the young are born in a r ...

s that lived in

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

from the late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...

(until around 40,000 years ago), often known as marsupial lions. They were the largest and last members of the family Thylacoleonidae, occupying the position of

apex predator An apex predator, also known as a top predator or superpredator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the hig ...

within Australian ecosystems. The largest and last species, ''Thylacoleo carnifex'', approached the weight of a

lion The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'', native to Sub-Saharan Africa and India. It has a muscular, broad-chested body (biology), body; a short, rounded head; round ears; and a dark, hairy tuft at the ...

ess. The estimated average weight for the species ranges from .

Taxonomy

The first ''Thylacoleo'' fossil findings, discovered by Thomas Mitchell were found in the 1830s in the Wellington Valley of New South Wales, though not recognised as such at the time. The generic holotype, consisting of broken teeth, jaws, and a skull was discovered by a pastoralist, William Avery, near Lake Colungolac from which the species ''Thylacoleo carnifex'' was described by

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...

. It was not until 1966 that the first nearly-complete skeleton was found. The only pieces missing were a foot and the tail. Currently, the

Nullarbor Plain The Nullarbor Plain ( ; Latin: feminine of 'no' and 'tree') is part of the area of flat, almost treeless, arid or semi-arid country of southern Australia, located on the Great Australian Bight coast with the Great Victoria Desert to its no ...

of West Australia remains to be the greatest finding site. These fossils now reside at the Australian Museum. The genus was first published in 1859, erected to describe the type species ''Thylacoleo carnifex''. The new taxon was established in examination of fossil specimens provided to

. The familial alliance takes its name from this description, the so-called marsupial lions of Thylacoleonidae. The colloquial name "marsupial lion" alludes to the genus name, which was named after its superficial resemblance to the placental lion and its ecological niche as a large predator. Genus: ''Thylacoleo'' (''Thylacopardus'') – Australia's marsupial lions, that lived from about 2 million years ago, during the Late Pliocene Epoch and became extinct about 40,000 years ago, during the

Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...

Epoch. Three species are known: *''Thylacoleo carnifex'' The holotype cranium was collected from Lake Colongulac in 1843 by pastoralist William Adeney. A partial rostrum collected by Adeney in 1876 from the same locality would later be found to belong to the same individual. It was not until 1966 that the first nearly-complete skeleton was found. *''Thylacoleo crassidentatus'' lived during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

. *''Thylacoleo hilli'' lived during the Pliocene and was half the size of ''T. crassidentatus''. It is the oldest member of the genus. Fossils of other representatives of Thylacoleonidae, such as '' Microleo'' and '' Wakaleo'', date back to the Late Oligocene Epoch, some 24 million years ago. ''T. hilli'' was described by Neville Pledge in a study published in the records of the South Australia Museum in 1977. The holotype is a third premolar, discovered at a cave in Curramulka in South Australia, exhibiting the carnivorous characteristics of the genus and around half the size of ''T. carnifex''. This tooth was collected by Alan Hill, a speleologist and founding member of the Cave Exploration Group of South Australia, while examining a site known as the "Town Cave" in 1956; the specific epithet ''hilli'' honours the collector of the first specimen. Material found amidst the fauna at

Bow River The headwaters of the Bow River in Alberta, Canada, start at the Bow Glacier and Bow Lake (Alberta), Bow Lake in Banff National Park in the Canadian Rockies, Canadian Rocky Mountains. The glacial stream that feeds Bow Lake (Alberta), Bow Lake ...

in New South Wales, dated to the early

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 A fragment of an incisor, unworn and only diagnosable to the genus, was located at a site in Curramulka, close to the Town Cave site, and referred to the species for the apparent correlation in size when compared to the better known ''T. carnifex''. The marsupial lion is classified in the order Diprotodontia along with many other well-known marsupials such as kangaroos,

possums Possum may refer to: Animals * Didelphimorphia, or (o)possums, an order of marsupials native to the Americas ** Didelphis, a genus of marsupials within Didelphimorphia *** Common opossum, native to Central and South America *** Virginia opossum, ...

, and the

koala The koala (''Phascolarctos cinereus''), sometimes inaccurately called the koala bear, is an arboreal herbivorous marsupial native to Australia. It is the only Extant taxon, extant representative of the Family (biology), family ''Phascolar ...

. It is further classified in its own

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

, the Thylacoleonidae, of which three

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

and 11

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

are recognised, all extinct. The term marsupial lion (lower case) is often applied to other members of this family. Distinct possum-like characteristics led ''Thylacoleo'' to be regarded as members of Phalangeroidea for a few decades. Though a few authors continued to hint at phalangeroid affinities for thylacoleonids as recently as the 1990s, cranial and other characters have generally led to their inclusion within vombatiformes, and as stem-members of the wombat lineage. Marsupial lions and other ecologically and morphologically diverse vombatiforms were once represented by over 60 species of

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...

herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...

, terrestrial and

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

forms ranging in size from 3 kg to 2.5 tonnes. Only two families represented by four

species (koalas and three species of wombat) have survived into modern times and are considered the marsupial lion's closest living relatives.

Evolution

The ancestors of thylacoleonids are believed to have been

herbivore A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...

s, something unusual for carnivores. They are members of the Vombatiformes, an almost entirely herbivorous order of marsupials, the only extant representatives of which are

s and

wombat Wombats are short-legged, muscular quadrupedal marsupials of the family Vombatidae that are native to Australia. Living species are about in length with small, stubby tails and weigh between . They are adaptable and habitat tolerant, and are ...

s, as well as extinct members such as the

diprotodontids Diprotodontidae is an extinct Family (biology), family of large herbivorous marsupials, endemic to Australia and New Guinea during the Oligocene through Pleistocene periods from 28.4 million to 40,000 years ago. Description The family primaril ...

and palorchestids. The group first appeared in the Late

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

. The earliest thylacoleonids like '' Microleo'' were small possum-like animals, with the group increasing in size during the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

, with representatives like the leopard-sized '' Wakaleo.'' The genus ''Thylacoleo'' first appeared during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

. The youngest representative of ''Thylacoleo'' and the thylacoleonids, ''T. carnifex'', is the largest known member of the family. The earliest thylacoleonids are thought to have been arboreal (tree dwelling) animals, while ''Thylacoleo'' is thought to be terrestrial with some climbing capabilities.

Description

''T. carnifex'' is the

largest Large means of great size. Large may also refer to: Mathematics * Arbitrarily large, a phrase in mathematics * Large cardinal, a property of certain transfinite numbers * Large category, a category with a proper class of objects and morphisms (or ...

carnivorous

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

known to have ever existed in Australia, and one of the largest

metatheria Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as wel ...

n carnivores known (comparable to '' Thylacosmilus'' and '' Borhyaena'' species, but smaller than ''Proborhyaena gigantea''). Individuals ranged up to around high at the shoulder and about from head to tail. Measurements taken from a number of specimens show they averaged in weight, although individuals as large as might not have been uncommon, and the largest weight was of . This would make it comparable to female lions and female

tiger The tiger (''Panthera tigris'') is a large Felidae, cat and a member of the genus ''Panthera'' native to Asia. It has a powerful, muscular body with a large head and paws, a long tail and orange fur with black, mostly vertical stripes. It is ...

s in general size. Estimates of the size of ''T. carnifex'' based on dental remains are typically dubious, in contrast to estimates based on proximal limb bone circumference.

Skull

Like other thylacoleonids, ''Thylacoleo'' had blade-like third

premolar The premolars, also called premolar Tooth (human), teeth, or bicuspids, are transitional teeth located between the Canine tooth, canine and Molar (tooth), molar teeth. In humans, there are two premolars per dental terminology#Quadrant, quadrant in ...

teeth in the upper and lower jaws, that functioned as the

carnassial Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified f ...

teeth, with these teeth being present much further forwards in the jaw than in other mammals. Compared to earlier thyacoleonids, the third premolars were considerably enlarged. ''Thylacoleo'' also had a proportionally large pair of first

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

s in the upper and lower jaws, which functioned analogously to other carnivores'

canine teeth In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, eye teeth, vampire teeth, or fangs, are the relatively long, pointed teeth. In the context of the upper jaw, they are also known as '' fangs''. They can appear more fl ...

. They also had true canines but they served little purpose as they were stubby and not very sharp. Compared to earlier thylacoleonids, the number of molar teeth was reduced. Pound for pound, ''T. carnifex'' had the strongest bite of any

species, living or extinct; a ''T. carnifex'' weighing had a bite comparable to that of a 250 kg African

, and research suggests that ''Thylacoleo'' could hunt and take prey much larger than itself. Larger animals that were likely prey include '' Diprotodon'' spp. and giant kangaroos. It seems improbable that ''Thylacoleo'' could achieve as high a bite force as a modern-day lion; however, this might have been possible when taking into consideration the size of its brain and skull. Carnivores usually have rather large brains when compared to

marsupials, which lessens the amount of bone that can be devoted to enhancing bite force. ''Thylacoleo'' however, is thought to have had substantially stronger muscle attachments and therefore a smaller brain. Some later studies questioned the ability of the canine teeth to deliver a killing bite. Using

3D modeling In 3D computer graphics, 3D modeling is the process of developing a mathematical coordinate-based Computer representation of surfaces, representation of a surface of an object (inanimate or living) in Three-dimensional space, three dimensions vi ...

based on

X-ray computed tomography An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

scans, marsupial lions were found to be unable to use the prolonged, suffocating bite typical of living big cats. They instead had an extremely efficient and unique bite; the incisors would have been used to stab at and pierce the flesh of their prey while the more specialised carnassials crushed the windpipe, severed the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

, and lacerated the major

blood vessel Blood vessels are the tubular structures of a circulatory system that transport blood throughout many Animal, animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the Tissue (biology), tissues of a Body (bi ...

s such as the

carotid artery Carotid artery may refer to: * Common carotid artery, often "carotids" or "carotid", an artery on each side of the neck which divides into the external carotid artery and internal carotid artery * External carotid artery, an artery on each side of ...

and

jugular vein The jugular veins () are veins that take blood from the head back to the heart via the superior vena cava. The internal jugular vein descends next to the internal carotid artery and continues posteriorly to the sternocleidomastoid muscle. Struc ...

. Compared to an African lion which may take 15 minutes to kill a large catch, the marsupial lion could kill a large animal in less than a minute. The skull was so specialized for big game that it was very inefficient at catching smaller animals, which possibly contributed to its extinction.

Postcranium

''Thylacoleo'' had highly mobile and powerful forelimbs used to grapple prey, with each manus having a single very large retractable hooked claw set on large semi-opposable thumbs, which are suggested to have been used deal a killing blow. The hind feet had four functional toes, the first digit being much reduced in size, but possessing a roughened pad similar to that of

, which may have assisted with climbing. The discovery in 2005 of a specimen which included complete hind feet provided evidence that the marsupial lion exhibited

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, but is an unusual condition in humans. The term is . Classification Syndactyly can be simple or complex. * In simple syndactyly, adja ...

(fused second and third toes) like other diprotodonts. Its strong forelimbs and retracting claws mean that ''Thylacoleo'' possibly climbed trees and perhaps carried carcasses to keep the kill for itself (similar to the

leopard The leopard (''Panthera pardus'') is one of the five extant cat species in the genus ''Panthera''. It has a pale yellowish to dark golden fur with dark spots grouped in rosettes. Its body is slender and muscular reaching a length of with a ...

today). The climbing ability would have also helped them climb out of caves, which could therefore have been used as dens to rear their young. Specialised tail bones called chevrons strengthened the tail, likely allowing the animal to use it to prop itself up while rearing on its hind legs, which may have been done when climbing or attacking prey. The

lumbar In tetrapod anatomy, lumbar is an adjective that means of or pertaining to the abdominal segment of the torso, between the diaphragm (anatomy), diaphragm and the sacrum. Naming and location The lumbar region is sometimes referred to as the lowe ...

region is relatively rigid and straight, and suggests that the lower back was relatively inflexible.

Ecology

When ''Thylacoleo'' was first described by Richard Owen, he considered it to be a carnivore, based on the morphology of its skull and teeth. However other anatomists, such as

William Henry Flower Sir William Henry Flower (30 November 18311 July 1899) was an English surgeon, museum curator and comparative anatomist, who became a leading authority on mammals and especially on the primate brain. He supported Thomas Henry Huxley in an ...

disagreed. Flower was the first to place ''Thylacoleo'' with the Diprotodonts, noting its skull and teeth to be laid out more like those of the

and the

, and suggested that it was more likely a herbivore. Owen did not disagree with Flower's placement of ''Thylacoleo'' with the Diprotodonts, but still maintained that it was a carnivore, despite its herbivorous ancestry. Owen found little support in his lifetime, despite the pointing out of ''Thylacoleos retractable claws, something only found in mammalian carnivores, and its lack of any ability to chew plant material. In 1911, a study by Spencer and Walcott claimed that certain marks on the bones of megafauna had been made by ''Thylacoleo'', but according to Horton (1979) they were not sufficiently rigorous, resulting in their arguments being strongly challenged by later scholars, such as Anderson (1929), and later Gill (1951, 1952, 1954), thereby leaving the issue unresolved. Besides the most common hypothesis that it was an active predator, a variety of other theories existed in the late 19th to early 20th centuries as to the diet and feeding of ''Thylacoleo'', with hypotheses of it being a scavenger filling the ecological niche of

hyenas Hyenas or hyaenas ( ; from Ancient Greek , ) are feliformia, feliform carnivoran mammals belonging to the Family (biology), family Hyaenidae (). With just four extant species (each in its own genus), it is the fifth-smallest family in the orde ...

, being a specialist of crocodile eggs, or even a melon-eater. As late as 1954, doubts were still being raised as to whether it was actually a hypercarnivore. In 1981, another paper was published arguing that certain cuts to bones of large marsupials had been caused by ''Thylacoleo''. This paper by Horton and Wright was able to counter earlier arguments that such marks were the result of humans, largely by pointing out the presence of similar marks on the opposite side of many bones. They concluded that humans were extremely unlikely to have made the marks in question, but that if so "they had set out to produce only marks consistent with what ''Thylacoleo'' would produce". Since then, the academic consensus has emerged that ''Thylacoleo'' was a predator and a hypercarnivore. The marsupial lion's limb proportions and muscle mass distribution indicate that, although it was a powerful animal, it was not a particularly fast runner. Paleontologists conjecture that it was an

ambush predator Ambush predators or sit-and-wait predators are carnivorous animals that capture their prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey u ...

, possibly using leaping. Incisions on bones of the extinct large kangaroo '' Macropus titan'', and the general morphology of ''Thylacoleo'' suggests that it fed in a similar manner to modern cheetahs, by using their sharp teeth to slice open the ribcage of their prey, thereby accessing the internal organs. They may have killed by using their front claws as either stabbing weapons or as a way to grab their prey with strangulation or suffocation. Like many predators, it was probably also an opportunistic

scavenger Scavengers are animals that consume Corpse decomposition, dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a he ...

, feeding on

carrion Carrion (), also known as a carcass, is the decaying flesh of dead animals. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...

and driving off less powerful predators from their kills. It also may have shared behaviours exhibited by recent diprotodont marsupials such as kangaroos, like digging shallow holes under trees to reduce body temperature during the day. Trace fossils in the form of claw marks and bones from caves in

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

analyzed by Gavin Prideaux et al. indicate marsupial lions could also climb rock faces, and likely reared their young in such caves as a way of protecting them from potential predators. Analysis of finds on the Nullabor Plain suggests that ''Thylacoleo carnifex'' inhabited open, arid environments similar to those found across much of Australia today. A 1985 study suggested that ''Thylacoleo carnifex'' was an apex predator that primarily fed on large bodied prey, which may have included the large kangaroos '' Sthenurus'', '' Procoptodon, Protemnodon, Macropus'' and ''

Osphranter ''Osphranter'' is a genus of large marsupials in the family Macropodidae, commonly known as kangaroos and wallaroos (among other species). It contains the largest extant marsupial, the red kangaroo (''O. rufus''). In 2019, a reassessment of mac ...

'' as well as possibly the largest Australian marsupial, the rhinoceros-sized vombatoid '' Diprotodon''.

Extinction

''Thylacoleo'' is thought to have become extinct around 40,000 years ago as part of the

Late Pleistocene megafauna extinctions The Late Pleistocene to the beginning of the Holocene saw the extinction of the majority of the world's megafauna, typically defined as animal species having body masses over , which resulted in a collapse in faunal density and diversity acro ...

, essentially simultanteously with the vast majority of

Australian megafauna The term Australian megafauna refers to the megafauna in Australia (continent), Australia during the Pleistocene, Pleistocene Epoch. Most of these species became extinct during the latter half of the Pleistocene, as part of the broader global L ...

. It has been contested as to the relative importance of climatic change vs the impact of recently arrived

Indigenous Australians Indigenous Australians are people with familial heritage from, or recognised membership of, the various ethnic groups living within the territory of contemporary Australia prior to History of Australia (1788–1850), British colonisation. The ...

(who arrived in Australia around 50-60,000 years ago) in the extinctions. There is limited evidence of human interaction with extinct megafauna in Australia.

References

External links

New study finds no evidence for theory humans wiped out megafauna

''Thylacoleo'' in Pleistocene Australia

Western Australian Museum: ''Thylacoleo'' - a voracious hunter
{{Taxonbar, from=Q312099 Prehistoric vombatiforms Prehistoric mammals of Australia Pliocene marsupials Pleistocene marsupials Pleistocene genus extinctions Carnivorous marsupials Prehistoric marsupial genera Taxa named by Richard Owen Fossil taxa described in 1859 Apex predators Extinct animals of Australia