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''Aktiogavialis'' is an extinct genus of crocodylian from the Oligocene epoch some 30 million years ago. Only one species in the genus, ''Aktiogavialis puertoricensis'', has been described so far. As a typical gavialoid, ''Aktiogavialis'' followed the standard crocodilian body plan. An elongated, squat quadrupedal body terminated in a long, laterally flattened tail at one end, and a specialized, narrow snout at the other. As with the other members of its family, the snout of ''Aktiogavialis'' was extremely long and narrow, tapering into a thin structure past the eye sockets. Based on the fragmentary remains recovered, the species was differentiated from other members of its family by unique positioning and geometry of its skull elements.〔 Phylogenetic analysis indicates its closest relatives were the extinct gavials ''Gryposuchus'' and ''Siquisiquesuchus''.〔 The type species of the genus, ''A. puertoricensis'', was described in 2007. The holotype, designated UPRMP 3094, was discovered in Puerto Rican deposits dating from the Oligocene epoch some 30 million years old. The deposits, part of the San Sebastián Formation along the Río Guatemala in Puerto Rico, have been an adequate supply of other crocodylian fossils. ''Aktiogavialis'' remains recovered were extremely fragmentary, consisting of an incomplete skull featuring elements of the braincase and other scattered cranial elements.〔 Marine sediments and nanofossils form part of the deposits where the specimen was found, indicating a marine distribution for ''. puertoricensis''. This is in contrast with the living gavialoids, which reside entirely in the freshwater rivers of South Asia.〔 〕 While fossils found in prehistoric deltaic sediments possibly have been washed onto the delta from inland sources, the ''Aktiogavialis'' specimen found so far was from a location that had essentially been islandic. This has led to conclusions that gavialoids were partially or primarily saltwater reptiles prior to the evolution of the group's one or two extant species.〔 The genus' name, ''Aktiogavialis'', is derived from the Greek words ''aktios'' (river) and ''gavialis'' (gavial). This roughly translates to "shore gavial", referring to its rather estuarine distribution. The specific name ''puertoricensis'' means "from Puerto Rico", in reference to the specimen's country of origin.〔 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Aktiogavialis」の詳細全文を読む スポンサード リンク
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