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''Batrachotomus'' is a genus of prehistoric archosaur. Fossils of this animal have been found in southern Germany and dated from the Ladinian stage of the Middle Triassic period, around 228 to 231 million years ago. ''Batrachotomus'' was described by palaeontologist David J. Gower 22 years after its discovery. The locality where ''Batrachotomus'' lived was a swampy region and the name comes from the Greek ''batrachos/βάτραχος'' (frog) and ''tome/τομή'' (cutting, slicing), which refers to its preying on the large amphibian ''Mastodonsaurus''.〔Gower (1999), p. 6.〕 In contrast with sprawling reptiles, like crocodiles, this large carnivore was very agile with locomotor superiority due to its erect stance. A remarkable feature seen on its back was a row of paired, flattened bony plates. ''Batrachotomus'' was possibly an early relative of ''Postosuchus'',〔Gower (1999), p. 1.〕 which lived during the dawn of the dinosaurs. == Description == ''Batrachotomus'' was a heavily built, large quadrupedal reptile reaching in length. A trait that characterized ''Batrachotomus'', compared to other crurotarsans, was a series of paired small plates on its back which were attached to each vertebra.〔Gower and Schoch (2009), p. 117.〕 These bony deposits forming scales are called osteoderms.〔 Flattened and leaf-shaped, these extended from behind the head along the column and reducing in size, ended at the tail.〔 There is also evidence that osteoderms were present on the ventral region of the tail, as seen in ''Ticinosuchus ferox'', and even on the flank, belly and limbs.〔〔Gower and Schoch (2009), p. 104.〕 Like other rauisuchians, ''Batrachotomus'' walked with an erect posture, although the limbs were not located directly under the trunk. The limbs were not equal in length as the forelimbs were about 70% of the hindlimbs.〔〔Gower and Schoch (2009), p. 109.〕 The toe bones (phalanges) are poorly preserved and the only well known bone is a fifth metatarsal (bone in hindlimbs attached to the toe bones) which was hooked in shape.〔 However, hypotheses suggest that probably each forelimb had four toes and each hindlimb five.〔Gower and Schoch (2009), p. 119 (Figure 8).〕 ''Batrachotomus'' had a tall and narrow skull estimated at in length.〔Gower (1999), p. 7.〕 It had five pairs of fenestrae (skull openings), two pairs of which were for the eyes (called orbits) and the nostrils. Behind the orbits were two temporal fenestrae. These holes probably helped to reduce the weight of the skull and enabled the jaw to open more widely.〔Benton (2005), p. 112.〕 As a typical archosaur, ''Batrachotomus'' had two antorbital fenestrae between the orbits and nostrils, and a fifth pair of small openings at the rear part of the lower jaw. The jaws contained sharp teeth which were compressed laterally and unequal in size and shape,〔〔Gower (1999), p. 37.〕 and this variation of tooth shape is known as heterodonty.〔〔Gower (1999), p. 38.〕 The teeth on the premaxillae (bones at the very tip of the upper jaw) were slender, unlike those of the maxillae (the main tooth-bearing bones in the upper jaw) which had a straight posterior edge.〔Gower (1999), pp. 37–38.〕 The upper jaw bore 30 teeth, with each premaxilla carrying about 4 teeth and each maxilla 11, while the lower jaw held 22 teeth.〔 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「Batrachotomus」の詳細全文を読む スポンサード リンク
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