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''Secodontosaurus'' (meaning "cutting-tooth lizard"), an extinct genus of "pelycosaur" synapsid that lived from between about 285 to 270 million years ago during the Early Permian. Like the well known ''Dimetrodon'', ''Secodontosaurus'' is a carnivorous member of the Eupelycosauria family Sphenacodontidae and has a similar tall dorsal sail. However, its skull is long, low, and narrow, with slender jaws that have teeth that are very similar in size and shape—unlike the shorter, deep skull of ''Dimetrodon'' ("two-measure tooth"), which has large, prominent canine-like teeth in front and smaller slicing teeth further back in its jaws. Its unusual long, narrow jaws suggest that ''Secodontosaurus'' may have been specialized for catching fish or for hunting prey that lived or hid in burrows or crevices. Although no complete skeletons are currently known, ''Secodontosaurus'' likely ranged from about in length, weighing up to . Fossils of ''Secodontosaurus'' have been found in Texas in North America in the Wichita and the Clear Fork groups of Early Permian formations. In recent years, teams from the Houston Museum of Natural Science have recovered remains in the Clear Fork Red Beds of North Texas that appear to be new specimens of ''Secodontosaurus''. These discoveries are mentioned in online blogs 〔Dig Into the Past, Dispatches From South Dakota: Willie The Dimetrodon (2 ), 12 October 2011 http://blog.hmns.org/2011/10/dispatches-from-south-dakota-willie-the-dimetrodon-day-2/〕〔Robert Bakker, Secodontosaurus: The "Fox-Faced Finback" Prehistoric CSI, 26 October 2007 http://hmnspaleo.blogspot.com/2007/10/secodontosaurus-fox-faced-finback.html〕 but so far have not been formally described. The name ''Secodontosaurus'' comes from Latin ''seco'' "to cut" + Greek ''odous'' (''odont''-) "tooth" + Greek ''sauros'' "lizard" and is based on the anatomical term "secodont" for teeth with cutting edges designed to tear or slice flesh. Paleontologist Robert Bakker 〔 has dubbed ''Secodontosaurus'' the "fox-faced finback" after its long jaws. ==Description== A number of partial fossil remains of ''Secodontosaurus'' have been identified from its characteristic long skull and jaws.〔 The postcranial skeletal material from different individuals includes parts of the backbone with clear evidence of a tall sail very similar to that of ''Dimetrodon''. The limbs and tail are incompletely known but probably resembled those of ''Dimetrodon'' as well. Like ''Dimetrodon'', ''Secodontosaurus'' would have had a short neck, robust body, short limbs, and a long tail. In light of such similarities, some skeletal remains with missing or fragmentary skulls that were previously identified as ''Dimetrodon'' may in fact belong to ''Secodontosaurus''. A key noncranial difference can be found in the axis neck vertebra, which has a tall and broad neural spine in ''Dimetrodon'' but has a lower neural spine in ''Secodontosaurus''. Robert R. Reisz and others〔 described the skull in detail in 1992, based mostly on a nearly complete skull specimen (MCZ 1124) about 27 cm (11 in) long, preserved with a left mandible. In addition to the long, low skull and nearly uniform size of the teeth that contrast with ''Dimetrodon'', the anterior teeth of the upper jaw are slanted back and those of the lower jaw are directed forward for grasping prey. Its rather crocodile-like skull suggests that ''Secodontosaurus'' could have been semi-aquatic and may have fed on fish and small swimming amphibians. However, Reisz and his coauthors noted that a tall sail would seem to be a hindrance in pursuit of quick-moving creatures underwater. Instead, the long, narrow snout with forward slanting teeth at the mandible tip might have allowed ''Secodontosaurus'' to probe after small animals hiding in burrows and other tight spaces. 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「Secodontosaurus」の詳細全文を読む スポンサード リンク
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