DIXOSAURIA. 385 



Anchisaurus Marsh (Fig. 210), small forms with bird-like skull, Trias, 

 Connecticut; and other allied genera from the U.S. Zanclodon Plien., 

 Keuper, Wiirtemburg, and several allied genera from France, England, 

 India and S. Africa. Ceratosaurus Marsh, 17 feet, skull larger than usual, 

 nasal bones with a median projection, which may have supported a horn, 

 U. Jura, Colorado, and other genera. Megalosaurus Buckland, the largest 

 Theropod, Lias to Wealden, Europe and N. America. Allosaurus Marsh. 

 Compsognathus Wagner, vertebrae and limb bones hollow ; the cervical 

 vertebrae are elongated ; the skull is bird-like ; tail long ; small anterior, 

 long posterior limbs ; manus and pes with 3 functional digits, digits 1 and 5 

 reduced ; femur shorter than tibia ; pelvis not avine, with pubic and 

 ischiadic symphysis ; pubis directed forwards ; hind-limb very avine ; 

 astragalus with ascending process ; one specimen only known, from the 

 Solenhofen slates. Hallopus Marsh, very similar to preceding, manus with 

 4 digits, pes with 3, calcaneum with a heel process, astragalus without 

 ascending process, U. Jura, Colorado. Coelurus Marsh, skull unknown, 

 all bones hollow, U. Jura, England and N. America. 



Order 2. SAUROPODA. 

 Herbivorous, quadrupedal, plantigrade Dinosaurs with five hoofed 



FIG. 211. Brontosaurus excelsus x T i s (from Woodward, after Marsh). 



digits on each limb. The teeth are spatulate with anterior and posterior 

 cutting edges. The cranium is completely ossified and there is a large 

 preorbital vacuity. The anterior vertebrae are much hollowed out 

 laterally. Limbs nearly equal in size. The neural canal in the sacrum is 

 expanded to two or three times the size of the brain cavity. The bones 

 of the pelvis are distinct and the acetabulum is perforated. The pubes 

 project ventral wards and meet in a cartilaginous symphysis ; there is no 

 postpubis ; the femur is without a prominent inner (fourth) trochanter ; 

 distal row of carpals and tarsals unossified ; astragalus without ascending 

 process. Some of them are of enormous size, and they are remarkable 

 for the relatively minute size of the skull ; Ailantosaurus estimated to 

 have attained a length of 115 feet. The skull is in most of them imper- 

 fectly known. Their remains are known from the Jurassic and Cretaceous. 

 Cetiosaurus Owen, skull unknown, M. Jura, England. Atlantosaurus 

 Marsh, probably the largest land animal known, to 115 feet, U. Jura, 

 Wyoming, Colorado. Morosaurus Marsh, U. Jura, Wyoming. Bronto- 

 saurus Marsh (Fig. 211), to 60 feet, very small skull and minute cranial 

 cavity, U. Jura, Wyoming, Colorado. Diplodocus Marsh, teeth slender 

 and cylindrical, continued to the anterior end of the jaws ; the external 

 narial opening is single and is placed at the apex of the skull, the nasals 

 z. II. c c 



