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Cerrejonisuchus
''Cerrejonisuchus'' is an extinct genus of dyrosaurid crocodylomorph. It is known from a complete skull and mandible from the Cerrejón Formation in northeastern Colombia, which is Paleocene in age. Specimens belonging to ''Cerrejonisuchus'' and to several other dyrosaurids have been found from the Cerrejón open-pit coal mine in La Guajira. The length of the rostrum is only 54-59% of the total length of the skull, making the snout of ''Cerrejonisuchus'' the shortest of all dyrosaurids.
==Description==
At an estimated length of to , ''Cerrejonisuchus'' was small for a dyrosaur. This size estimate is based on the dorsal skull lengths of specimens UF/IGM 29 and UF/IGM 31. ''Cerrejonisuchus'' has the shortest body length of any known dyrosaur, much smaller than that of the longest dyrosaur, ''Phosphatosaurus gavialoides'', which was to in length.〔
Currently the only known specimens of ''Cerrejonisuchus'' are UF/IGM 29 (the type specimen), UF/IGM 30, UF/IGM 31, and UF/IGM 32. Of these, UF/IGM 29 and UF/IGM 31 are thought to represent fully mature individuals while UF/IGM 32 is thought to represent a less mature individual. In UF/IGM 31, the neurocentral sutures of the anterior dorsal vertebrae are closed, an indication of morphological maturity. Additionally, the presence of well-developed osteoderms is likely to be an indication that the animal was mature because in living crocodylians, the osteoderms begin calcification after 1 year and grow to articulate with other osteoderms to form a dermal shield at maturity. Also, the sutures that separate the bones of the skull in both specimens are fully fused, suggesting that the individuals have reached a late ontogenic stage. In contrast, UF/IGM 32 has an unfused nasal suture, suggesting that it was less mature than the other individuals. UF/IGM 32 is also noticeably smaller than the other specimens.〔
Relative to the entire skull length, the rostrum of ''Cerrejonisuchus'' is the shortest of any dyrosaurid. It, along with ''Chenanisuchus'', are the only short-snouted dyrosaurids. The snout of ''Cerrejonisuchus'' is narrow and consistent in width from the external nares, or nostril openings, to the orbits, or eye sockets. The margin of the snout, unlike that of many long-snouted dyrosaurids, is smooth rather than festooned. "Festooned" refers to the lateral undulations in the maxillae and premaxillae that form around the tooth sockets, or alveoli. The external nares are positioned extremely anteriorly at the very tip of the snout. The orbits are oriented anterodorsally, facing upward and slightly forward. The dentition of ''Cerrejonisuchus'' is generally homodont, although the third maxillary tooth is enlarged and the fourth is somewhat smaller than the rest. They are conical, labiolingually compressed, each having a relatively rounded apex. The carinae, or tooth edges, are strongly developed both anteriorly and posteriorly. The premaxillary teeth are generally thinner and longer than the maxillary teeth. Like ''Chenanisuchus'', ''Cerrejonisuchus'' visibly lacks striations on the tooth surfaces. Unlike many other dyrosaurids, including ''Dyrosaurus maghribensis'', ''Atlantosuchus coupatezi'', ''Guarinisuchus munizi'', ''Phosphatosaurus gavialoides'', and ''Sokotosuchus ianwilsoni'', the teeth of ''Cerrejonisuchus'' are not curved.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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