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or Anomodontia Thermorpha

reptiles, mammals and theriodontia

THERMORPHA, or ANOMODONTIA, an order of extinct (Triassic and Perman) reptiles. ((The dominant group among, the ear liest reptiles in each quarter of the globe where they have as yet been discovered;' say Wood ward, °is directly intermediate in skeletal char acters between the highest labyrinthodonts (Mastododonsaurus and its allies) and the lower mammals (Monotremata). Its members first received the name Anomodontia in allusion to the varied modifications of the dentition, so unusual among reptiles. They were afterward •named Theromorphia or Theromora . . . in allusion to the many obvious resemblances in their skeleton to that of monotreme mammals!) These similarities are chiefly of the dentition, zygomatic arch, pelvis, cruso-tarsal joint, scapula and occasional doubling of the occipital condyle. The general shape of the skull is often closely mammalian, but its details show its unquestion able reptilian features. Three suborders are recognized — Pareiosaursa, Theriodontia and Anomodontia.

The theromorphs were all land-reptiles with short, stout limbs and powerful jaws. Some were massive and of great size, like great alli gators with turtle-like or even doglike heads; others small and probably as agile as a weasel. They were the predatory beasts of their age, and were adapted in powers and characteristics to the pursuit of a large variety of animal prey. The most unreptile-like were those of the sub order Theriodontia.

It is a natural suggestion that the race of mammals, undoubtedly of reptilian origin, must have descended from this group, whose bones (numerous in the Triassic rocks of the western United States) show so many mammalian fea tures; but thus far no direct connection can be shown. The dinosaurs, however, seem cer tainly to have descended from this stock.

Consult Woodward, 'Vertebrate (London 1898) ; Gadow, 'Amphibia and Rep tiles' (New York 1901), wherein many further references to details will be found.