4g6 THE TRIASSIC PERIOD 



weakness of the fore limbs, and the kangaroo-like attitude, are the 

 most obvious features. The bones of the upright- walking forms 

 were hollow, and some other structural features resemble those of 

 birds. The reduction of the toes of the hind feet to four, with one 

 of them much shorter than the others, caused their three-toed tracks 

 to be mistaken for those of birds, until recently. The dinosaurs 

 had wide range, living in the Rocky Mountains, along the Atlantic 

 coast from Carolina to Prince Edward Island, in western Europe, 

 India, and South Africa. 



Before the close of the period the reptilian tribe sent delegations 



Fig. 420. A Triassic sauropterygian, Lariosaurus balsami, restored; about i/n 

 natural size; from the Muschelkalk, Lombardy, Italy. (After Woodward.) 



to sea (Fig. 420), but marine forms were more plentiful in the next 

 period. 



Advent of mammals. Of especial interest is the appearance of 

 early form of mammals. They were small, and so primitive in 

 type that it is not altogether certain that they were mammals; but 

 they are commonly regarded as such, with kinship to the marsupials. 

 Their appearance while reptiles were yet dominant suggests that 

 mammals diverged from the primitive stock much earlier. In view 

 of the mammalian dominance of later times, it is noteworthy that 

 they developed but slowly and feebly during the Mesozoic era. 



Marine life. Except along the Pacific coast, there is, in North 

 America, little record of the marine life of the Triassic period; but 

 in Europe the record is better. While the sea withdrew from the 

 northwestern part of Europe during the Permian period, it lingered 

 about the Mediterranean, in Russia, Turkestan, and northwestern 

 India, and probably on the continental platform in or near Siberia. 

 The Mediterranean, the Himalayan, and the Siberian regions are 

 the best known tracts into which the shallow-water marine life of 





