THE TRIASSIC PERIOD 



215 



Another important advance among the Cephalopods was the 

 first appearance of the Dibranchs, which include the highest of all 

 Mollusks. Of these Dibranchs perhaps the most characteristic 

 belonged to a group known as Belemnites (see Fig. 143), though 

 these were not abundant. A fuller discussion of the Dibranchs 

 will be given in the next chapter. 



Arthropods. — Among Crustaceans neither Trilobites nor Eu- 

 rypterids, so impo tant in the Paleozoic, continued into the Meso- 

 zoic, but the Eucrustaceans showed a notable 

 advance by the first appearance of the so-called 

 long-tailed Decapods (Macrura) or Lobster 

 family, which rank among the highest of all 

 Crustaceans (Fig. 128). 



Insects also showed distinct progress by the 

 addition of the Beetle tribe, which ranks next 

 to the highest of all insects. 



Fishes. — Selachians, Dipnoans, and Ganoids 

 (Fig. 129) all continued with the Ganoids pre- 

 dominant. Teleosts had not yet appeared. 



Amphibians. — Though somewhat dimin- 

 ished as compared with the later Paleozoic, the 

 Amphibians were still numerous and often not- 

 able for their great size. In general they were 

 much like the late Paleozoic forms. Mastodon- 

 saurus attained a length of 15 or 20 feet and 

 had a skull 4 feet long. The Bunter series of 

 Germany is particularly rich in fine fossil Am- 

 phibians. By the close of the Triassic the 

 Amphibians had declined remarkably, so that 

 among the land Vertebrates, of which they were the ancestors, 

 they never again assumed a position of importance. 



Reptiles. — Because of the great abundance, size, and variety 

 of Reptiles, the Mesozoic era is often called the " Age of Reptiles." 

 Even in the Triassic most of the more important and interesting 

 now extinct groups had appeared, such as the swimming Reptiles 

 (e.g. Enaliosaurs) ; walking Reptiles (e.g. Dinosaurs); and flying 

 Reptiles (e.g. Pterosaurs). Since these remarkable reptilian forms 

 reached their climax of development later in the Mesozoic, a fuller 

 discussion will be reserved for a subsequent chapter. In passing, 

 however, it may be mentioned that Dinosaurs, often of great size, 



cr 



Fig. 128 

 A Triassic long- 

 tailed Macruran 

 Decapod, P em- 

 phi x Sueurii. 

 (From Naumann.) 



