LIFE IN THE MESOZOIC EPOCH 



•467 



their flattened relatives, the Skates and Rays. Ganoids [Ganoidei) 

 abounded, and some of them appear to have been ancestral to 

 Sturgeons. 



07-dinary Bony Fishes ( Teleostei) are the dominant members 

 of their class at the present day, and date back to the later stages 

 of the Mesozoic epoch. Some of the older types, less well adapted 

 than they to an aquatic life, have gradually declined since the 

 time of their first appearance. 



Mesosoic Amphibians (Amphibia). — The armoured Amphibians 

 i^Stegocepkala) of the palseozoic 

 lived on into the earlier part of 

 this epoch, to which belonged the 

 laro-est known member of the order 

 [Mastodonsaui'us), the head of which 

 was about four feet long. The 

 teeth and footprints (fig. 1324) of 

 this and related forms were charac- 

 teristic, and have been known to 

 geologists for a comparatively long 

 time. The former were conical, and 

 exhibit in cross-section very elabo- 

 rate folds of enamel, which suggested 

 the name of " Labyrinthodon" {i.e. 

 labyrinth tooth). The footprints 

 look something like the impressions 

 of clumsy hands, hence the old name 

 " Cheirotherium" {i.e. hand-animal). 



Mesozoic Reptiles (Reptilia) 

 ckocephala), of which the Tuatara {Hatteria) is the only living 

 representative, includes a number of species which were widely 

 distributed in the early part of this epoch. Some of them were 

 as much as 6 feet in length. 



One of the most interesting extinct orders of the class, the 

 Varied- Toothed Reptiles {Anoiuodontia) includes characteristic 

 land -forms which lived during the later part of the Palaeozoic 

 epoch and the earlier part of the Mesozoic. The interest attaching 

 to them lies in the fact that in certain respects they were inter- 

 mediate in structure between the Armoured Amphibians and the 

 lower Mammals, so that they probably represent the stock from 

 which the last class has taken origin. Among mesozoic types may 



Fig. 1324. — Labyrinthodon. A, Tooth and foot- 

 prints (reduced); B, part of cross-section of tooth 

 (enlarged). 



-The ancient order {Rhyn- 



