CET: ATOPSIA. This group includes the horned dinosaurs. land reptiles of gigantic size and formidable appearanee. which were evolved in late Mesozoic time after the dinosaur race had guru to decline. They are probably highly spe cialized I le:eendant: from the Stegosanrian race. Their remains been found in the Upper Cretaceous rocks of Europe, but the best material has come from the Laramie group of W yoming abd olorado, The prominent feature of these annuals is the large size of the head. hi Tri ceratops (q.v.), which attained a length of 25 feet. the head has a length of 0 feet, and it is pro bled with throe formidable horns, and with a broad posterior expansion or crest, formed from the parietal bones, that projects some dis tance over the neck. The jaws have strong beaks front and Iwo-root ed teeth in their posterior portions. The skeletons of these dinosaurs are heavily built, the bones are solid, the live-toed fore limbs and the three or four-toed hind limbs are about equal in size, the feet were digitigrade, and the toes were hoofed like those of a rill Tile body was proteeted by rt thick hide, sometimes armored with bony plates, and the tail was smaller than in any other dinosaurs. The best-known genera are Agathaumus, Tri ceratops (q.v.), and Sterrholophus.
Onxonoeotm. These are the most bird-like of the dinosattrs, with small five-toed fore limbs, and well-developed three-toed hind limbs. All the limb-bones a•e hollow'. They were unarmored, herbivorous animals with bipedal walking, run ning, or leaping motion. Iguanodon (q.v.), of the Belgian Jurassic, with a length of 20 feet, is perhaps the beSt-known genus. Claosaurns or Thespesius (q.v.), from the North American Cre taetous rocks, attained a length of 35 feet.
liadrosaurus (q.v.), from the Laramie group, hod a spoon-bill beak, like that of Ornithorhyn ehus. Ilere. also, belongs Nanosaurus. the small est k n dinosaur, which was scarcely as large as a domestic fowl, found in the Upper Jurassic rocks of Colorado.
Fossil remains of dinosaurs arc to be seen only in the larger museums of the country. The American Museum of Natural history in Cen tral Park. New York City, has the finest series of skeletons. twiny of which are accompanied by water-eolo• restorations of these animals. Other museums where dinosaurs may be seen are the United States National at Washington. Peabody Museum of Yale University, Carnegie Museum at Pittsburg. where a complete skele ton of Dipiodoeus is mounted. the Field Colum bian NInseum at Chicago, and the museum of the University of Wyoming at Laramie.
IttimmbaArnY. :Marsh, "The Dinosaurs of North .kmeriea." Annual le•port of the Unit, d s Surrey. vol. xvi.. part i. (Washington, IS90) t Lucas, .t ainia/s of the Past I New York. 19o1) ; Woodward. Outlines of Ver bratr Pahroniology for St inlcnts of Zoidogy ( ('ambridge. 1St*: ) ; II atelier, "M)10(104'119, Its Osteology. etc." Memoirs of the Por n( this' nut. vets i. 1 (Pittsburg. 1901): •e•imer. "The Reconstruction of a Cretaeeons Dinosaur, Claosan•us anneetens, Marsh." Trn HR.
no tb, nerl e,cl ,temleyny of Seirnees.
t.ol. xi. (New tlsvrrn, 1902). See, also, s at's: Bitox.ros%tlors: Cva.yrosAt'ars; Dieu).
WWI St ITADIVISAURI:S; Mt:“A.1,11S.Witt'S; S: THISPESII S; TIIRTICAToPS,