THEROMORPHA 179 



Order 5. THEROMORPHA. Cope. (Anomodontia, Seeley, non Owen.) ^ 



Primitive land reptiles tvith more or less biconcave vertebrae and limbs adapted for 

 habitual support of the body. Investing bones of temporal region either forming a 

 continuous shield or contracting into a single broad arcade, sometimes irregularly 

 perforated. Quadrate fixed, often reduced in size. Pineal foramen present. Teeth 

 thecodont, occasionally wanting. Pectoral arch with well -developed epiicoixicoicls 

 (precoracoids), clavicles, and T-shaped interclavicle, besides scapulae and coracoids. 

 All the elements in both limb girdles either fused or immovably united by suture. 

 Humerus with enfepicondylar foramen and prominent delto-pectorcd crest. Extremities, 

 pentadactylate. Sacrum consisting of two to six vertebrae ; anterior ribs completely or 

 imperfectly double-headed, abdominal ribs wanting. 



Many widely dissimilar characters are exhibited by the various groups of 

 ancient reptiles, which have received the general designation of Theromorpha, 

 in allusion to their resemblance in certain skeletal peculiarities to the lowest 

 mammals {2Ionotrem.ata). They are also often called Anomodonts, on account 

 of their remarkable dentition. There can be no doubt that these creatures 

 occupy an intermediate position between the highest Labyrinthodonts, such as 

 Mastodonsaurus, and monotreme mammals ; and it is altogether probable that 

 from amongst some of their number with one robust zygomatic arch and 

 triconodont teeth, the Mammalia arose. 



Theromorphous reptiles represent not only a transitional stage between 

 mammals and amphibians, but they form a collective group, uniting in them- 

 selves characters that are elsewhere found distributed amongst various 

 subdivisions of both reptiles and mammals. No other reptilian order has 

 the three elements of the pelvic arch on each side fused into an innominate 

 bone, as in mammals. The intimate union of the bones of the pectoral arch is 

 paralleled among the Salamandridae and Sauropterygia ; and the sacrum, formed 

 sometimes of a number of vertebrae, resembles that of Dinosaurs and mammals. 

 The differentiation of the marginal teeth into incisors, canines, and molars, and 

 the occasional development of a strikingly mammalian form of limb {Therio- 

 desmus) and a tripartite or even dicondylic basiocciput (Cynognathus), are 

 significant characters. A distinguishing feature between this order and 

 Squamata is the fixation of the quadrate ; and the absence of a lateral 

 temporal vacuity, with an arcade above and below, distinguishes it from all 

 other Archosauria (Rhynchocephalians, Dinosaurs, Crocodiles, and Pterosaurs). 



The term Anomodontia, although restricted by Owen to the group of 

 Dicynodonts, is made synonymous by some authors with Theromorpha, or 

 Theromora, as they are sometimes called. 



^ Literature : 



Cope, E. D., The Reptilian order CotyloSauria (Proc. Amer. Phil. Soc. vol. XXXIV. p. 4-36), 1896. 

 —Ibicl. vol. XXXV. (1896), p. 122.— Neivton, E. T., Some new Reptiles from the Elgin Sandstone 

 (Phil. Trans, vol. CLXXXIV. p. 436), 1893.— Owe?i, R., On Dicynodon (Trans. Geol. Soc. vol. VII. 

 p. 59), 184.5. — On some Reptilian fossils from South Africa (Quar. Journ. Geol. Soc. vol. XVI. p. 49), 

 I860.— J5iV?. vols. XXXII. (1876), p. 95 ; XXXVI. (1880), p. 414 ; XXXVII. (1881), p. 261 ; and 

 XL. (1884), p. 146.— On Dicynodont Reptiles (Phil. Trans, vol. CLII. p. 442), 1862.— Catalogue of the 

 fossil Reptilia of South Africa in the British Museum. London, 1876. — Seeleij, H. G., Researches 

 on the Anomodont Reptiles and their allies (Phil. Trans, vol. CLXXIX. p. 59), 1888. — Ibid. vols. 

 CLXXX. (1889), p. 215 ; CLXXXIII. (1892), p. 311 ; CLXXXIV. (1893), p. 488 ; CLXXXV. (1894), 

 p. 987 ; and CLXXXVL (1895), p. 59. Also Ann. Mag. Nat. Hist. [7], vol. i. (1898), p. 164, and 

 Quar. Journ. Geol. Soc. vol. LVI. (1900). 



