Rimasuchus Temporal range: Miocene Early | |
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Scientific classification | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Crocodilia |
Family: | Crocodylidae |
Subfamily: | Osteolaeminae |
Genus: | † Rimasuchus Storrs, 2003 |
Type species | |
†Rimasuchus lloydi (Fourtau, 1918) | |
Synonyms | |
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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 ).
The first fossil of Rimasuchus an incomplete skull with associated mandible, was collected by lieutenant colonel Arthur H. Lloyd in the early 20th century in Wadi Moghara, Egypt. The holotype specimen, CGM 15597, was given to the Egyptian Geological Museum and described by Fourtau in 1920 under the name Crocodylus lloydi. Other material includes an uncatalogued skull housed at the Natural History Museum, London (likewise from Wadi Moghara) and fossils found at Gebel Zelten in Libya. [2] Eventually other skulls further south in Africa ended up being assigned to "Crocodylus" lloydi , with the oldest and southern-most material stemming from Namibia and the youngest fossils from Tanzania and Kenya in East Africa. [3] [4] This would have given the taxon a massive range both geographically and stratigraphically, spanning large parts of the continent from the Miocene up to the Pleistocene. However revisions of these fossils soon reduced the range of "Crocodylus" lloydi back to its original state. In 2003 the Namibian material was named Crocodylus gariepensis by Martin Pickford, who suggested that it was the true ancestor of the Nile crocodile. [5] Pickford found his argument strengthened when shortly prior to the release of the publication "C." lloydi was found to be a distinct genus, named Rimasuchus. [3] In 2010 Christopher Brochu and colleagues named Crocodylus anthropophagus based on remains from Tanzania [6] and two years later Crocodylus thorbjarnarsoni was named from Kenya. [7] With the Kenyan specimens assigned to their own species, previous size estimates indicating that Rimasuchus grew to massive sizes and even preyed on humans were rendered out of date. Furthermore, with their description Rimasuchus was effectively removed from the fossil record of East Africa and the Pleistocene.
The generic name "Rimasuchus" comes from the Latin words rima, meaning "crack", which is referencing the East African rift valley. [3] However the fact that later studies have shown the absence of Rimasuchus in the region renders the name somewhat ironic. [8] The species name honors Arthur H. Lloyd, who initially discovered the fossils in Egypt.
Early studies on Rimasuchus generally thought it to be a member of the genus Crocodylus within the Crocodylinae. Given its age it was believed for some time to have been the direct ancestor to the modern Nile crocodile. [4] However most later studies came to agree that it was much more closely related to the Osteolaeminae, which includes both species of extant dwarf crocodiles. Given this placement, which was later supported by the animal being considered a distinct genus, the hypothesis that it was ancestral to Nile crocodiles has generally fallen out of favour. Pickford came to consider "Crocodylus" gariepensis the true ancestor of Nile crocodiles in 2003, however much like Rimasuchus it too was later recovered to likely fall within Osteolaeminae. [5]
A 2018 tip dating study by Lee & Yates simultaneously using morphological, molecular (DNA sequencing), and stratigraphic (fossil age) data established the inter-relationships within Crocodylidae [9] and in 2021, Hekkala et al. were able to use paleogenomics, extracting DNA from the extinct Voay , to better establish the relationships within Crocodylidae, including the subfamilies Crocodylinae and Osteolaeminae. [10] Their results confirmed Rimasuchus' status as an osteolaemine. In their phylogenetic tree Rimasuchus was recovered as the closest relative to the two modern dwarf crocodile species and more derived than Brochuchus .
Crocodylidae |
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(crown group) |
Restricting the analysis to work based on morphological data alone also finds it to be an osteolaemine, although the internal relationships of the clade differ slightly. [11] Here, it takes a more basal position, neither especially close to the extant forms nor to the long-snouted Euthecodon.
Crocodylidae |
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(crown group) |
Crocodylinae is a subfamily of true crocodiles within the family Crocodylidae, and is the sister taxon to Osteolaeminae.
Mekosuchinae is an extinct clade of crocodilians from the Cenozoic of Australasia. They represented the dominant group of crocodilians in the region during most of the Cenozoic. They first appear in the fossil record in the Eocene in Australia, and survived until the arrival of humans: in the Pleistocene in Australia and within the Holocene in the Pacific islands of Fiji, New Caledonia and Vanuatu.
Crocodylus is a genus of true crocodiles in the family Crocodylidae.
The Philippine crocodile, also known as the Mindoro crocodile, the Philippine freshwater crocodile, the bukarot in Ilocano, and more generally as a buwaya in most Filipino lowland cultures, is one of two species of crocodiles found in the Philippines; the other is the larger saltwater crocodile (Crocodylus porosus). The Philippine crocodile, the species endemic only to the country, went from data deficient to critically endangered in 2008 from exploitation and unsustainable fishing methods, such as dynamite fishing. Conservation methods are being taken by the Dutch/Filipino Mabuwaya foundation, the Crocodile Conservation Society and the Zoological Institute of HerpaWorld in Mindoro island. It is strictly prohibited to kill a crocodile in the country, and it is punishable by law.
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 of southern Australia. The generic name Australosuchus means "Southern crocodile". It was described in 1991 from fossil material discovered at Lake Palankarinna in South Australia.
Mecistops is a genus of crocodiles, the slender-snouted crocodiles, native to sub-Saharan Africa.
Gavialosuchus is an extinct genus of gavialoid crocodylian from the early Miocene of Europe. Currently only one species is recognized, as a few other species of Gavialosuchus have since been reclassified to other genera.
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.
Voay is an extinct genus of crocodile from Madagascar that lived during the Late Pleistocene to Holocene, containing only one species, V. robustus. Numerous subfossils have been found, including complete skulls, noted for their distinctive pair of horns on the posterior, as well as vertebrae and osteoderms from such places as Ambolisatra and Antsirabe. The genus is thought to have become extinct relatively recently. It has been suggested to have disappeared in the extinction event that wiped out much of the endemic megafauna on Madagascar, such as the elephant bird and Malagasy hippo, following the arrival of humans to Madagascar around 2000 years ago. Its name comes from the Malagasy word for crocodile.
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.
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" affinis is an extinct species of crocodyloid from the Eocene of Wyoming. Fossils were first described from the Bridger Formation by American paleontologist Othniel Charles Marsh in 1871. Marsh described the species, along with every other species of crocodyloid in the Bridger Formation, under the genus Crocodylus. The known specimen of "Crocodylus" affinis is a skull found at Grizzly Buttes, Wyoming, measuring 13 inches in length on the upper surface. Recent phylogenetic studies of crocodyloids show that "C." affinis is not a species of Crocodylus, but a genus has not yet been erected to include the species. Other Bridger species such as Crocodylus clavis and Brachyuranochampsa zangerli have been synonymized with "C." affinis.
"Crocodylus" acer is an extinct species of crocodyloid from the Eocene of Utah. A single well preserved skull was described by paleontologist Edward Drinker Cope in 1882 and remains the only known fossil of the species. It was found from the Wasatchian-age Green River Formation. "C." acer had a long, narrow snout and a low, flattened skull.
"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 palaeindicus is an extinct species of crocodile from southern Asia. C. palaeindicus lived from the Miocene to the Pliocene. It may be an ancestor of the living Mugger crocodile.
The West African crocodile, desert crocodile, or sacred crocodile is a species of crocodile related to — and often confused with — the larger and more aggressive Nile crocodile.
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.
Crocodylus falconensis is an extinct species of crocodile known from the early Pliocene of the lower part of the Vergel Member of the San Gregorio Formation of Venezuela. C. falconensis was named in 2013 after Falcón State and is thought to be the basalmost species of Crocodylus found in the Neotropics.
"Crocodylus" gariepensis is an extinct species of crocodile that lived in southern Africa during the Early Miocene about 17.5 million years ago (Ma). Fossils have been found along a bank of the Orange River in Namibia, near its border with South Africa.