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Stegomosuchus
''Stegomosuchus'' is an extinct genus of small protosuchian crocodylomorph. It is known from a single incomplete specimen discovered in the late 19th century in Lower Jurassic rocks of south-central Massachusetts, United States. It was originally thought to be a species of ''Stegomus'', an aetosaur (a type of armored herbivorous reptile), but was eventually shown to be related to ''Protosuchus'' and thus closer to the ancestry of crocodilians. ''Stegomosuchus'' is also regarded as a candidate for the maker of at least some of the tracks named ''Batrachopus'' in the Connecticut River Valley.
==Discovery==
The holotype and only known specimen of ''Stegomosuchus'' (AM 900) was discovered at what was then known as the Hines Quarry, east of East Longmeadow, Massachusetts, just before the turn of the 20th century. It was found below the surface, in red sandstone used for building material. This site is now called the Hoover Quarry; it has also yielded invertebrate trace fossils and dinosaur tracks (''Eubrontes''). The rocks are now known to belong to the Portland Formation. While thought to be Triassic when ''Stegomosuchus'' was originally described,〔 the Portland Formation is now known to date to the Early Jurassic, including the Hettangian and Sinemurian stages (approximately 200 to 190 million years ago).
Its discoverer, G. B. Robinson, took home the blocks containing the specimen and placed them in his door yard, where they were exposed to the elements for "about seven years." The fossil was then found and obtained by Mr. and Mrs. E. D. White, and the specimen was then described by B. K. Emerson and F. B. Loomis in 1904. At that point, the specimen was in three blocks. The bones had been largely preserved as impressions, and the two main blocks had upper and lower impressions of the skull, twenty-eight pairs of armor plates situated along the spine up to the pelvis, right arm (minus the hand) and shoulder blade, and left foot.〔 Emerson and Loomis interpreted the impressions as showing another row of armor along the sides, but this was later shown to be a mistake. AM 900 was a small animal, with a skull estimated at long and across, and a body length from snout to pelvis of . Emerson and Loomis described the specimen as a new species of ''Stegomus'' (''S. longipes''), an aetosaur known from slightly older rocks.〔
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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