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Mekosuchus is a genus of extinct Australasian mekosuchine crocodilian. Species of Mekosuchus were generally small-sized, terrestrial animals with short, blunt-snouted heads and strong limbs. Four species are currently recognized, M. inexpectatus, M. whitehunterensis, M. sanderi and M. kalpokasi, all known primarily from fragmentary remains.
Australosuchus is an extinct monospecific genus of crocodylian belonging to the subfamily Mekosuchinae. The type and only known species Australosuchus clarkae lived during the Late Oligocene and the Early Miocene in the Lake Eyre Basin of South Australia. It was described in 1991 by Paul Willis and Ralph Molnar from fossil material discovered at Lake Palankarinna.
Paludirex is an extinct genus of mekosuchine crocodylian from the Pliocene and Pleistocene of Australia. A large and robust semi-aquatic ambush hunter capable of attaining lengths of up to 5 m (16 ft), it was likely the top predator of Australia's waterways prior to the appearance of modern saltwater crocodiles. Two species are known, the smaller Paludirex gracilis and the larger Paludirex vincenti. A third as of yet unnamed species may have also existed.
Harpacochampsa is a poorly known Early Miocene crocodilian from the Bullock Creek lagerstätte of the Northern Territory, Australia. The current specimen consists of a partial skull and fragments of a long, slender snout reminiscent of that of a false gharial, demonstrating that it was a piscivore in life.
Aldabrachampsus is an extinct genus of small horned crocodile known from fragmentary remains. It lived during the Pleistocene on Aldabra Atoll, Seychelles in the western Indian Ocean. The name Aldabrachampsus dilophus means "Two-crested crocodile from Aldabra". It was a small animal, reaching a length of 2–2.5 m, comparable in size to the smallest extant crocodilians.
Euthecodon is an extinct genus of long-snouted crocodile. It was common throughout much of Africa during the Neogene, with fossils being especially common in Kenya, Ethiopia, and Libya. Although superficially resembling that of gharials, the long snout was a trait developed independently from that of other crocodilians and suggests a diet of primarily fish. Euthecodon coexisted with a wide range of other crocodiles in the areas it inhabited before eventually going extinct during the Pleistocene.
Prodiplocynodon is an extinct genus of basal crocodyloid crocodylian. It is one of the only crocodyloids known from the Cretaceous and existed during the Maastrichtian stage. The only species of Prodiplocynodon is the type species P. langi from the Lance Formation of Wyoming, known only from a single holotype skull lacking the lower jaw.
Crocodyloidea is one of three superfamilies of crocodilians, the other two being Alligatoroidea and Gavialoidea, and it includes the crocodiles. Crocodyloidea may also include the extinct Mekosuchinae, native to Australasia from the Eocene to the Holocene, although this is disputed.
Rimasuchus is an extinct genus of crocodile from the Miocene of Egypt and possibly Libya. Only one species - Rimasuchus lloydi - is currently known. It was previously thought to be a species of Crocodylus, but is now thought to be more closely related to the modern African dwarf crocodiles (Osteolaemus).
Tomistominae is a subfamily of crocodylians that includes one living species, the false gharial. Many more extinct species are known, extending the range of the subfamily back to the Eocene epoch. In contrast to the false gharial, which is a freshwater species that lives only in southeast Asia, extinct tomistomines had a global distribution and lived in estuaries and along coastlines.
Osteolaeminae is a subfamily of true crocodiles within the family Crocodylidae containing the dwarf crocodiles and slender-snouted crocodiles, and is the sister taxon to Crocodylinae.
"Crocodylus" megarhinus is an extinct species of crocodile from the Eocene of Egypt. A partial skull was found by British paleontologist Charles William Andrews in the Fayum Depression. Andrews named Crocodylus megarhinus in 1905 on the basis of the holotype skull. A complete skull was also uncovered from Egypt in 1907 but was not recognized as "C." megarhinus until 1927.
Crocodylus thorbjarnarsoni is an extinct species of crocodile from the Pliocene and Pleistocene of the Turkana Basin in Kenya. It is closely related to the species Crocodylus anthropophagus, which lived during the same time in Tanzania. C. thorbjarnarsoni could be the largest known true crocodile, with the largest skull found indicating a possible total length up to 7.6 m (25 ft). It may have been a predator of early hominins. Crocodylus thorbjarnarsoni was named by Christopher Brochu and Glenn Storrs in 2012 in honor of John Thorbjarnarson, a conservationist who worked to protect endangered crocodilians.
Crocodylus checchiai is an extinct species of crocodile from the Miocene to Pliocene of Libya and Kenya. C. checchiai was named in 1947 based on a skull from the Sahabi Formation. Remains from the lower Nawata Formation in the Turkana Basin of Kenya that were first attributed to the Nile crocodile have now been reassigned to C. checchiai, extending its geographic range. The morphology of the species, in particular the pronounced rostral boss, indicates that it may be the connecting link between African and American species of the genus Crocodylus.
Brochuchus is an extinct genus of crocodile known from the Early Miocene Hiwegi Formation of Rusinga Island in Lake Victoria, Kenya; it was originally named as a species of Crocodylus. It contains two species, B. parvidens and B. pigotti. Brochuchus belongs to the family Crocodylidae, which includes all living crocodiles. The closest living relative of Brochuchus is Osteolaemus, the dwarf crocodile. Compared to Osteolaemus, which has a small body and blunt snout, Brochuchus has a more generalized crocodylid anatomy. Brochuchus is characterized by a flat and relatively narrow skull, and although it is larger than Osteolaemus it is smaller than most other crocodylids. It has two prominent bumps on the surface of its snout.
Ultrastenos is an extinct genus of Australian mekosuchine crocodilian first described in 2016. The type species Ultrastenos willisi was discovered at Riversleigh in northwestern Queensland, Australia, and lived during the Late Oligocene era. Following its discovery, it was speculated that Ultrastenos was a slender-snouted animal similar to modern gharials or freshwater crocodiles and that it may have inhabited forest pools and fed on small vertebrates like frogs and lizards. This is based on the peculiar shape of its mandible, which is wide towards the base of the head but constricts rapidly, leading into a narrow and gracile rostrum. Assuming that the holotype skull belonged to an adult individual, Ultrastenos may have been a rather small animal, approximately the size of a modern freshwater crocodile. However, Ultrastenos is only known from very fragmentary remains and thus among the most enigmatic mekosuchines. In a 2023 study multiple authors argue that the fragmentary nature of the animal means that further studies are required to truly test the hypothesis proposed in its original description, especially following the discovery of what is thought to have been a close relative.
Kalthifrons is an extinct monospecific genus of mekosuchine crocodylian known from the Pliocene Tirari Formation of Australia. More specifically, Kalthifrons was recovered from the Mampuwordu Sand Member, which underlies the younger sediments of the Pompapillina Member. This is significant, as the latter preserves some of the earliest records of the genus Crocodylus in Australia, which would eventually go on to replace mekosuchines. It is currently unclear whether or not the Tirari Crocodylus directly outcompeted Kalthifrons or simply moved into the region after the niche was left empty by the extinction of the local mekosuchines. Should the later be the case, then Kalthifrons may have simply been the victim of global cooling and aridification. A point in favour of the competition hypothesis is that both Kalthifrons and the Tirari Crocodylus have broadly similar skull forms, with both being interpreted as generalist semi-aquatic predators much like many of today's crocodiles. Though far from large, Kalthifrons was nonetheless bigger than many other mekosuchines such as Trilophosuchus and Mekosuchus. The genus is monotypic, meaning it contains only a single species, Kalthifrons aurivellensis.
Sacacosuchus is an extinct monospecific genus of marine gavialid that lived along the coast of the south-east Pacific from approximately 19 to 6.3 million years ago. Its fossils have been found in the Chilcatay and Pisco Formations of Peru, where it coexisted with the much larger Piscogavialis. Based on its skull, Sacacosuchus was most likely a generalist feeder with an estimated total body length of 4.32 m (14.2 ft). Its extinction is thought to have been caused by a combination of factors including falling sea levels and global cooling.
Kinyang is an extinct genus of osteolaemine crocodile from the Early to Middle Miocene of Kenya. Two species are currently known, K. mabokoensis from the Lake Victoria basin and K. tchernovi from the Lake Victoria and Lake Turkana basin. Kinyang had an exceptionally broad and robust skull, much wider than that of any living crocodile species. This might have allowed it to attack and kill prey its own size or even bigger. Kinyang is notably larger than its contemporary relative Brochuchus. While the precise reasons for the extinction of Kinyang are not known, it coincides with a larger faunal turnover that saw osteolaemines replaced by the still dominant crocodylines. One reason for this shift may have been the drying climate of Africa at the time, which caused rainforests to be replaced by more open environments and disrupted the nesting behavior of osteolaemines due to their dependence on foliage.
Varanosuchus is an extinct genus of atoposaurid neosuchian from the Early Cretaceous Sao Khua Formation of Thailand. Varanosuchus is known from three individuals which preserve assorted postcranial material and a complete skull. The skull of Varanosuchus was altirostral, meaning it wasn't flattened like in modern crocodilians and instead much deeper, while the limbs were slender and straight, leading to it somewhat resembling a monitor lizard. Little is known about the ecology of atoposaurids, however, based on the slender, erect limbs, the altirostral skull and the well ornamented osteoderms it has been suggested that Varanosuchus was a terrestrial animal with some semi-aquatic affinities. Only a single species is recognized, Varanosuchus sakonnakhonensis.
References
- 1 2 3 4 5 6 7 8 Martin, J. E.; Naksri, W.; Lauprasert, K.; Wongko, K.; Chompusri, S.; Sila, S.; Claude, J. (2023). "An early diverging crocodylid from the Middle Miocene of Thailand highlights the role of SE Asia for the radiation of the Crocodyloidea". Historical Biology. doi:10.1080/08912963.2023.2278152.
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