''Dentaneosuchus'' is a genus of large bodied sebecid

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably mor ...

from the

Middle Eocene The Eocene ( ) is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''Ēṓs'', ' Dawn') a ...

of Issel and Réalmont (

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

). Originally described as ''Atacisaurus crassiproratus'', the discovery of additional remains led to it being placed in a separate

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 ...

in 2023. It was tentatively recovered as the basalmost member of the family

Sebecidae Sebecidae is an extinct family of prehistoric terrestrial sebecosuchian crocodylomorphs, known from the Late Cretaceous and Cenozoic of Europe and South America. They were the latest surviving group of non-crocodilian crocodylomorphs. The oldes ...

. Because of this ''Dentaneosuchus'' could play an important part in deciphering the origins and dispersal of European sebecids, as their presence on the continent, far away from their primary range in South America, is still not entirely resolved. It reached a similar size to the enormous '' Barinasuchus'', making it not only one of the biggest sebecids but also the biggest terrestrial carnivore of Cenozoic Europe. ''Dentaneosuchus'' would have been an apex predator of its environment, capable of taking large prey such as ''

Lophiodon ''Lophiodon'' (from , 'crest' and 'tooth') is an extinct genus of mammal related to chalicotheres. It lived in Eocene Europe , and was previously thought to be closely related to ''Hyrachyus''. ''Lophiodon'' was named and described by Georges ...

''. However, for as of yet unknown reasons crocodylomorphs would lose their spot as top predator in this part of the world by the end of the Eocene, with ''Dentaneosuchus'' representing one of the last members of its group in Europe.

History and naming

The first fossil of ''Dentaneosuchus'', a mandibular symphysis catalogued as specimen MHNT.PAL.2006.0.53., was discovered in the Sables du Castrais Formation near Issel in southern

and assigned to the genus '' Atacisaurus'' by Gaston Astre in 1931, creating the name ''Atacisaurus crassiproratus''. When describing ''

Iberosuchus ''Iberosuchus'' (meaning "Iberian crocodile") is a genus of extinct sebecosuchian mesoeucrocodylian found in Western Europe from the Eocene. Remains from Portugal was described in 1975 by Antunes as a sebecosuchian crocodilian. This genus has on ...

'' in 1975,

Miguel Telles Antunes Dr. Miguel Telles Antunes (born 11 January 1937) is a Portuguese academic, specializing in paleontology, zooarchaeology, and geology. Antunes is a ranking member of various institutions, including the Lisbon Academy of Sciences, Nova Universi ...

considered the possibility that the Issel remains may have belonged to the same animal, tentatively referring the symphysis to his new genus, and Ortega ''et al.'' (1996) agreed with this placement. In 2018 Godinot and colleagues went as far as to fully place the specimen in ''Iberosuchus'' while retaining the species name, creating the new combination ''Iberosuchus crassiproratus''. However, the referral of various European sebecid specimens to ''Iberosuchus'' was at times done under less than ideal conditions, as much of the material didn't overlap and the assignment was in large parts based on very few characters not exclusive to the genus. Excavations in France meanwhile continued to yield sebecid material, including specimens discovered in 1997 near Réalmont. It is possible that this specimen was a once nearly complete skull, however, it was damaged during the dig, with much associated material being gathered from the surrounding debris. Despite this a lot of material could be gathered regardless, which remain in the collection of the

Muséum de Toulouse The Muséum de Toulouse (, MHNT) is a museum of natural history in Toulouse, France. It is located in the Busca-Montplaisir neighborhood of the city, houses a collection of more than 2.5 million items, and has some of exhibition space. I ...

until the fossils were studied by Martin and colleagues. Martin ''et al.'' compared the Réalmont material with both ''Iberosuchus'' and the Issel symphysis, determining that there were no differences between the mandibular remains from the two localities yet clear deviations from ''Iberosuchus macrodon''. As the Issel material had been validly described and diagnosed in 1931, the species name could be retained, however the matter of the genus name was more complicated. When naming ''Atacisaurus'', Astre declared ''A. glarea'' the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, but in the following years the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

had been lost and available figures failed to show any diagnostic traits. Material previously assigned to ''Atacisaurus glarea'' meanwhile was initially considered to serve as a

lectotype In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes ...

, but lacked shared features with the lost material and was instead found to have belonged to a

gavialoid Gavialoidea is one of three superfamilies of crocodylians, the other two being Alligatoroidea and Crocodyloidea. Although many extinct species are known, only the gharial ''Gavialis gangeticus'' and the false gharial ''Tomistoma schlegelii'' are ...

then named ''

Kentisuchus astrei ''Kentisuchus'' is an extinct genus of gavialoid crocodylian, traditionally regarded as a member of the subfamily Tomistominae. Fossils have been found from England and France that date back to the early Eocene. The genus has also been recorded f ...

''. This rendered ''Atacisaurus'' a

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

, leading Martin and colleagues to coin a new genus name for ''A. crassiproratus'', ''Dentaneosuchus''. The name ''Dentaneosuchus'' derives from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

"dentaneo", which roughly translates to "showing teeth" or "frightfull" in allusion to its hypothesized role as

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 ...

, and the Greek "souchos" meaning crocodile, derived from the name of the Egyption deity

Sobek Sobek (), also known as Suchus (), was an ancient Egyptian deities, ancient Egyptian deity with a complex and elastic history and nature. He is associated with the Nile crocodile and is often represented as a crocodile-headed humanoid, if not a ...

Description

Skull

The skull of ''Dentaneosuchus'' was altirostral, meaning that unlike in modern crocodilians, it was higher than it was wide. This is clearly shown by the preserved

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

. The nares are preserved in the form of two narial openings separated by processes of the premaxilla and

nasal bone The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...

that meet in the middle. They, like the skull, are higher than wide and face forward. The premaxilla contains five teeth on either side, with the bone bulging around the roots of tooth. The first premaxillary tooth, located close to the midline, is the smallest and the teeth get progressively larger until reaching their maximum size at the fourth tooth, which is twice the size of the second. The fifth is smaller again, about as large as the third tooth. The premaxillary teeth are followed by a pronounced notch, which likely received an enlarged dentary tooth. Very little of the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

is preserved, but it still reveals important information on the skull of ''Dentaneosuchus''. The maxilla appears to be fused to the

, obscuring the suture between the two. Furthermore, the way the two elements connect shows that the rostrum of ''Dentaneosuchus'' would have been

trapezoid In geometry, a trapezoid () in North American English, or trapezium () in British English, is a quadrilateral that has at least one pair of parallel sides. The parallel sides are called the ''bases'' of the trapezoid. The other two sides are ...

in cross section, meaning it was broader around the toothrow and narrowed towards the top. More is known of the nasal, which is preserved in two large chunks. The first is connected to the maxillary fragment, while the more posterior piece is still connected to the skull table. The nasal duct was separated by a

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

and the surface of the nasal bone shows no suture, indicating that rather than being paired, the nasal bones were fused into a single elongated element. The nasal was long, stretching from the front of the rostrum where it contacts the premaxilla and likely contributed to the bony wall separating the nares to the

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

. As the bone tapers towards the front of the skull, it takes on a wand-like appearance. The prefrontals are plate-like bones situated atop the head and overhanging the eye sockets. The

lacrimal bone The lacrimal bones are two small and fragile bones of the facial skeleton; they are roughly the size of the little fingernail and situated at the front part of the medial wall of the orbit. They each have two surfaces and four borders. Several bon ...

s are only poorly preserved, but face more to the sides than the prefrontals. The various bones of the

skull table The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparati ...

( frontal, parietal,

supraoccipital The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone lies over the occipital lobes of the cere ...

and exoccipital) are all fused into a single mass. In ''Dentaneosuchus'' the space between the orbits and the

supratemporal fenestrae Temporal fenestrae are openings in the Temple (anatomy), temporal region of the skull of some Amniote, amniotes, behind the Orbit (anatomy), orbit (eye socket). These openings have historically been used to track the evolution and affinities of re ...

is preserved. Only a small piece of the

quadratojugal The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...

is preserved. The

mandibular symphysis In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral ha ...

is formed by the fusion of both dentaries and a part of the

splenial The splenial is a small bone in the lower jaw of reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology ...

, encompassing the first seven teeth of the lower jaw and being overall spoon-shaped. A total of at least 19 teeth is thought to have been present in the mandible of ''Dentaneosuchus''. The teeth of the lower jaw initially form a semicircle at the tip of the lower jaw extending from the first dentary tooth to the fourth, after which there is a slightly larger space before the fifth tooth. However this small break is not to be confused with a true gap in the dentition (

diastema A diastema (: diastemata, from Greek , 'space') is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to ...

) as seen in some other crocodylomorphs. From the fifth onward, the teeth are organized in a single, straight row of closely spaced

alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * M ...

. The overall shape of the toothrow creates two distinct waves, with the top of the first wave being crowned by the fifth dentary tooth. The largest tooth of the lower jaw is however the fourth, as typically the case, and the teeth behind it gradually decrease in size. It is uncertain how that continues onto the second wave, as it is too poorly preserved to determine. Both the angular and surangular bone contribute to the mandibular fenestra and form the back of the lower jaw. The fenestra itself is noted for its strange,

boomerang A boomerang () is a thrown tool typically constructed with airfoil sections and designed to spin about an axis perpendicular to the direction of its flight, designed to return to the thrower. The origin of the word is from Australian Aborigin ...

-like shape. Although the teeth of ''Dentaneosuchus'' are generally robust thanks to the nearly circular tooth roots, they are still truly ziphodont, with slight compression and

carinae ''Carinae'' was an area of ancient Rome. It was one of its most exclusive neighborhoods, where many of the senatorial class lived. Florus described the ''Carinae'' as the "''most celebrated part of the city''" (''celeberrima pars urbis''). Desc ...

covered in fine serrations.

Postcrania

Although the skull material makes up the majority of known ''Dentaneosuchus'' remains, a variety of postcranial fossils have also been collected. This includes a nearly complete

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

, which is a robust bone with a well-defined deltopectoral crest. The

ischium The ischium (; : is ...

is incomplete, with one articular process missing and the other being highly eroded. However, the preserved elements show that the anatomy is unique and the anterior articular process in particular is covered in a complex system of muscle insertions and tendon passages. This region is notably better developed in ''Dentaneosuchus'' compared to what is seen in modern crocodiles, but Martin and colleagues hesitate to draw any specific conclusions in regards to the musculature from this. Only a single

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

is known and primarily composed of the centrum, with much of the

neural spine Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

missing. The vertebra is amphicoelous and equally wide, long and high. Four

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of Extant taxon, extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, Temnospondyli, ...

have been discovered, but as no sebecid preserves articulated armor it is not certain where on the body they would have been located. Martin and colleagues describe two types of osteoderms, both of which are tipped with a pronounced central crest and show highly indented outlines. The larger type is sub-trapezoid, while the smaller osteoderm variety is ovoid and longer than wide. Both bear some resemblance to those of '' Baurusuchus'', but are sufficiently distinct. Prior studies on the osteoderms of various Notosuchians have indicated that these bones were much more deeply nested in the skin than they are in modern crocodiles and possibly covered in a thick, leathery layer similar to what is observed in

softshell turtle Trionychidae is a family of turtles, commonly known as softshell turtles or simply softshells. The family was described by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can adapt to li ...

Size

As the skulls of most sebecid genera do not exceed in total length (''

Langstonia ''Langstonia'' (meaning " rocodileof Langston", in honor of paleontologist Wann Langston, Jr.) is an extinct genus of notosuchian crocodylomorph of the family Sebecidae. It lived in the middle Miocene (specifically in the Laventan land-mammal ...

'' barely surpasses this size at ), it can be said that ''Dentaneosuchus'' is among the largest known sebecids. The lower jaw of this genus measures up to (not accounting for the retroarticular process), which puts it in a similar size range as the giant '' Barinasuchus'' from 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 ...

of South America. In fact, with a preserved mandibular length of and an estimated total mandibular length of close to , ''Barinasuchus'' may be only slightly larger than ''Dentaneosuchus''. ''Dentaneosuchus'' could have even exceeded ''Barinasuchus'' in skull length considering that the type specimen from Issel is slightly larger than the more complete material from Réalmont. This does however leave the issue of determining body size from skull length. This is rendered especially difficult by the lack of fully preserved postcranial skeletons for members of this group, which means that body size is generally estimated based on the proportions of other terrestrial Notosuchians, leading to vastly different results. Using the proportions of the incomplete peirosaurid ''

Uberabasuchus ''Uberabasuchus'' ("Uberaba crocodile")''Uberabasuchus''
at

Stratiotosuchus'', Molnar and de Vasconcellos calculated that the body length of ''Barinasuchus'' could range anywhere from to a gigantic . Martin and colleagues suggest a much more conservative body length with a proportionally bigger head, estimating the total body length of the two at between . Regardless of the specifics, this renders ''Dentaneosuchus'' the largest terrestrial predator of Cenozoic Europe.

Phylogeny

Phylogenetic analysis conducted on the material of ''Dentaneosuchus'' places it in the family

, which was recovered as closely related to the South American

Baurusuchidae Baurusuchidae is a Gondwanan family of mesoeucrocodylians that lived during the Late Cretaceous. It is a group of terrestrial hypercarnivorous crocodilians from South America (Argentina and Brazil) and possibly Pakistan. Baurusuchidae has been, ...

with which it forms

Sebecosuchia Sebecosuchia (meaning "Sobek crocodiles") is an extinct group of mesoeucrocodylian crocodyliforms that includes the families Sebecidae and Baurusuchidae. The group was long thought to have first appeared in the Late Cretaceous with the baurusu ...

. Several features of ''Dentaneosuchus'' allow it to be easily distinguished from other groups of ziphodont Notosuchians. The fused nasals and splenials, shape of the supratemporal fenestrae and presence of a large notch between the premaxilla and maxilla are among several cranial features that clearly set it apart from members of the

Peirosauridae Peirosauridae is a Gondwanan family of mesoeucrocodylians that lived during the Cretaceous period. It was a clade of terrestrial crocodyliforms that evolved a rather dog-like skull, and were terrestrial carnivores. It was phylogenetically defined ...

. From baurusuchids it differs mostly in the anatomy of the lower jaw, including the longer toothrow and position of the dentary-surangular suture relative to the mandibular fenestra. Many of the traits do however line up with sebecids, explaining its placement. Within Sebecidae, ''Dentaneosuchus'' was recovered as having affinities with the German ''Bergisuchus''. While Martin and colleagues raise the possibility that some of the difference between the two could change with age, they conclude that it would be premature to make any conclusive statements on what this may imply. Furthermore, the authors also point out that there are still many unknowns regarding the anatomy of ''Dentaneosuchus'' that would greatly impact its phylogenetic placement and how future discoveries could change its position drastically. A later study from 2025 recovered broadly similar results, featuring the same close relationship between the European taxa ''Bergisuchus'' and ''Iberosuchus''. The key difference lies in the fact that the phylogeny published by Bravo and colleagues regards the European forms as forming a separate sister group to true sebecids alongside the early Paleocene Patagonian ''

Tewkensuchus ''Tewkensuchus'' ("forehead crocodile") is an extinct genus of large-bodied sebecoid notosuchian from the Paleocene of Argentina. The genus was described on the basis of fragmentary skull remains alongside a few vertebrae and finger bones collect ...

'', which in the study remains unnamed.

Age

The precise age of ''Dentaneosuchus'' and European sebecids in general is subject to change as the various Paleogene localities of Europe are studied more closely and more information important for the stratigraphy is found. ''Iberosuchus'' stems from strata previously thought to have been deposited prior to the Bartonian, with a mammalian tooth from the locality suggesting an age between the middle

Lutetian The Lutetian is, in the geologic timescale, a stage (stratigraphy), stage or age (geology), age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it ...

and Bartonian, while the layers directly overlying the ''Iberosuchus'' horizon have been dated to the Bartonian itself based on the presence of '' Anchilophus''. The pre-Bartonian age was later corroborated by Badiola & Cuesta (2008), who place it firmly within the MP13-14

biozone In biostratigraphy, biostratigraphic units or biozones are intervals of geological strata that are defined on the basis of their characteristic fossil taxon, taxa, as opposed to a Lithostratigraphy, lithostratigraphic unit which is defined by the ...

s (Lutetian), a similar age as the Spanish Duero Basin and much older than the locality of Réalmont in France. Both the type locality of ''Dentaneosuchus'' near Issel and the locality of the referred material in Réalmont are part of the Sables du Castrais Formation, but may date to different ages. The referred material from Réalmont for instance has been dated to the Bartonian, corresponding to biozone MP16, while the age of the type locality in Issel is less clear. Godinot for instance argues that the locality may be older than the Bartonian, suggesting an

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

to Lutentian age. Martin and colleagues however counter that the exact provenance of the material is not known and that the similarities between the type material and the referred fossils could indicate that they are of the same age. For this reason, the range of ''Dentaneosuchus'' is currently confined to the Bartonian stage of the Eocene.

Paleobiogeography

The origins of European sebecids remains a debated subject and is shrouded in a variety of questions due to the poor record of the group, especially outside of South America. The fact that sebecosuchians are a primarily

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

n clade means that the origin of the European species may trace back to as early as the Cretaceous. While tentative at most, the phylogenetic position of ''Dentaneosuchus'' as well as ''Iberosuchus'' and ''Bergisuchus'' could suggest a link to older, Cretaceous sebecids native to Europe such as ''

Ogresuchus ''Ogresuchus'' is an extinct sebecid known from the Upper Cretaceous (Maastrichtian stage) Tremp Formation in Spain. It is the oldest known member of the Sebecidae and it is also the only known Mesozoic sebecid. The type species, ''O. furatus'', ...

'' and ''

Doratodon ''Doratodon'' is an extinct genus of Late Cretaceous crocodylomorph that may have been a member of the Sebecosuchia. ''Doratodon'' was a relatively small animal with ziphodont teeth, meaning the teeth had flattened sides and serrated edges. Two ...

'', however both of which are equally poorly understood. Another hypothesis proposed by

Eric Buffetaut The given name Eric, Erich, Erikk, Erik, Erick, Eirik, or Eiríkur is derived from the Old Norse name ''Eiríkr'' (or ''Eríkr'' in Old East Norse due to monophthongization). The first element, ''ei-'' may be derived from the older Proto-Nor ...

suggests that the European sebecids could have arrived in Europe by traveling through North America. This is in part based on the fact that European fauna following the early Eocene is heavily shaped by faunal interchange with

Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...

n groups, arriving from Asia and North America. This includes Eocene alligatoroids, crocodyloids and planocraniids, with the later group being endemic to Laurasia and absent from the sebecosuchian-dominated Gondwana. However a major issue with this hypothesis is the complete absence of any sebecid material in continental North America, with the only potential material being a ziphodont tooth from

Cuba Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...

. If not coming from European ancestors or via an unrecorded dispersal via North America, then the possibility arises that the Paleogene sebecids of Europe may have immigrated through Africa. This hypothesis was also written about by Buffetaut, but while the evidence is more substantial than for a North American origin, it is still sparse. The most significant find for African sebecids is the discovery of ''

Eremosuchus ''Eremosuchus'' is an extinct genus of sebecosuchian mesoeucrocodylian. Fossils have been found from El Kohol, Algeria of Eocene age. It had serrated, ziphodont teeth. The genus was originally referred to the family Trematochampsidae in 1989. ...

'' in Ypresian strata of

Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...

. This would date ''Eremosuchus'' to about the same time as the earliest Paleogene sebecids of Europe, and the two are also united in similar skull and osteoderm anatomy. Other isolated remains from the Upper Eocene have been found in

Libya Libya, officially the State of Libya, is a country in the Maghreb region of North Africa. It borders the Mediterranean Sea to the north, Egypt to Egypt–Libya border, the east, Sudan to Libya–Sudan border, the southeast, Chad to Chad–L ...

and

Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...

, lending further credence to African holdouts of the group and a possible link between them and the European forms. However, as most of the material is fragmentary, further research and fossil discoveries would be needed to substantiate the hypothesis. Martin and colleagues further consider the origin of sebecids as a whole following the discovery of ''Dentaneosuchus'', proposing two additional models for their evolution. The first suggests not a Gondwanan origin for the family, but one centered in Europe, dispersing into Africa and

rafting Rafting and whitewater rafting are recreational outdoor activities which use an inflatable raft to navigate a river or other body of water. This is often done on whitewater or different degrees of rough water. Dealing with risk is often a ...

across the

Atlantic The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for se ...

to South America in a fashion similar to

caviomorph Caviomorpha is the rodent parvorder that unites all New World hystricognaths. It is supported by both fossil and molecular evidence. The Caviomorpha was for a time considered to be a separate order outside the Rodentia, but is now accepted as ...

rodents. Another possibility raised by them is that sebecids originated in Africa and from there dispersed independently into Europe and South America. Both ideas run contrary to the traditional interpretation that sebecids are of South American origin and would require further testing and most importantly better fossil material.

Paleobiology

The massive size of ''Dentaneosuchus'' matches the increase in size undergone by contemporary mammal species of Europe. Studies on parts of the mammal fauna of the Geiseltal in

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

for instance reveal that gigantism during the Eocene may be tied to biotic factors such as climate and available resources. The cooling climate of the Eocene could have been one contributing factor to the increased size of ''Dentaneosuchus'', as modern crocodilians display greater size at greater

latitudes In geography, latitude is a geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at the south pole to 90° at the ...

in accordance with

Bergmann's rule Bergmann's rule is an ecogeographical rule that states that, within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, while populations and species of smaller size are found in warmer ...

. However, it is not clear if this rule is as easily applied to terrestrial Notosuchians both due to their distant phylogenetic relationship with modern crocs and their different lifestyle. While the precise details of which prey ''Dentaneosuchus'' preferred are not known and require isotopic analysis to determine, the great size alone is a good indicator for the fact that this sebecid was an apex predator in its environment. ''Dentaneosuchus'' would have likely been capable of preying on animals its own size and possibly larger. This includes the early

perissodactyl Perissodactyla (, ), or odd-toed ungulates, is an order of Ungulate, ungulates. The order includes about 17 living species divided into three Family (biology), families: Equidae (wild horse, horses, Asinus, asses, and zebras), Rhinocerotidae ( ...

'' Lophiodon lautricense'', which could reach a weight of up to and was found in the same deposits as the sebecid. Other predators native to continental Europe that may have been in competition with ''Dentaneosuchus'' includes planocraniid crocodiles like ''

Boverisuchus ''Boverisuchus'' is an extinct genus of planocraniid crocodyliforms known from the early to middle Eocene (Ypresian to Lutetian stages) of Germany and western North America. It was a relatively small crocodyliform with an estimated total length ...

'', large terrestrial birds and hyaenodontid mammals. The dominance of crocodylomorphs as apex predators in the early stages of the Cenozoic is likely to be explained through the absence of significant mammalian carnivores. This is most noticeable in Paleogene Europe and in South America until the Late Miocene. However, this dominance would not last and ''Dentaneosuchus'' was likely among the last large non-mammalian predators left, as they appear to have disappeared throughout the course of the Bartonian. The reasons for their extinction both in Europe and South America remain unknown, but may include a lack of suitable prey, competition from mammalian predators, changes in climate and environment or other biotic or even abiotic factors as of yet undiscovered.

References

{{Notosuchia, Z. Sebecidae Eocene crocodylomorphs Eocene reptiles of Europe Fossils of France Fossil taxa described in 2023 Prehistoric pseudosuchian genera