202 DINOSAURS OF NORTH AMERICA. 



NANOSAURUS. 



Teeth compressed aud pointed, and in a single uniform row. Cervi- 

 cal and dorsal vertebra? short and biconcave. Sacral vertebra? three( ?). 

 Anterior caudals short. Ilium with very short, pointed front and nar- 

 row posterior end. Fore limbs of moderate size. Limb bones and 

 others very hollow. Femur curved and shorter tban tibia. Fibula 

 pointed below. Metatarsals very long and slender. 



The genera thus defined contain all the known forms of the typical 

 Ornithopoda from the American Jurassic. They are, moreover, the 

 earliest representatives of this group known in tins country from osse- 

 ous remains, as such fossils have not yet been found in the Triassic, 

 where the oldest dinosaurs occur. Some of the bird-like footprints in 

 the Connecticut Eiver sandstone may indeed have been made by dino- 

 saurs of this group, but there is no positive evidence on this poiut. 

 The American Cretaceous forms of the typical Ornithopoda, so far as 

 at present known, are all of large size aud highly specialized, and this 

 appears to be true also of the Old World species. 



RESTORATION OF LAOSAURTS. 

 Plate LVII. 



The present restoration in outline of Laosaurus eonsors, one-tenth 

 natural size, will serve to show the form and proportions of one of tbe 

 most bird-like of the smaller Jurassic Ornithopoda and its contrast 

 with the more massive Camptosaurus from the same horizon. A com- 

 parison of this restoration with that of Hypsilophodon from the English 

 NYealden (PI. LXXXIV) is especially instructive, as the two animals 

 were near allies, although from different geological horizons. 



The position here chosen for the restoration of Laosaurus is one 

 which would seem to have been natural to the animal when standing 

 at rest. This would mean a height of about 4 feet, with 8 feet in 

 length. That the animal was bipedal in its usual locomotion on land is 

 assumed in this case from the general structure, especially the very 

 small and weak fore limbs, and the large size and strong articula- 

 tions of the posterior limbs. When walking upright, as here repre- 

 sented, it seems probable that the animal would touch the ground with 

 its tail; but this is by no means certain. That reptiles of similar 

 structure and proportions could walk on their hind feet without leav- 

 ing a mark of the tail is clearly indicated by many long series of bipedal 

 footprints left in the sandstone of the Connecticut Valley, some of 

 which have already been described and figured in this paper. In the 

 present species the tail was powerful aud more or less compressed, 

 thus suggesting its use in swimming. 



