THE PENNSYLVANIAN PERIOD. 



609 



labyrinthine arrangement, as shown in Fig. 283. It will be recalled 

 that the holoptychian fishes had a very similar dental structure. The 

 labyrinthodonts differ from the forms referred to the next suborder 

 in having well ossified, biconcave vertebrae, a specialization known to 

 have been reached early in this period. 

 Moreover, the teeth are much more highly 

 labyrinthine than in the known Temno- 

 spondyli. These features remove the 

 labyrinthodonts from the direct line of 

 ancestry of some, if not of all, the reptiles. 

 Their skulls reached a maximum length 

 of half a meter or more in the Carbon- 

 iferous period, and by Triassic times, they 

 had attained a length of at least a meter 

 and a quarter, from which the full length 

 of the animal is inferred to have been 

 four or five meters; but in general, if 

 compared with modern crocodilians, they 

 must be regarded as of only moderate 

 size. 



The Temnospondyli differed from the 

 true labyrinthodonts in the divided (rha- 

 chitomous) structure of their vertebra?, 

 whence the name. Such vertebrae are 

 thought to have been possessed by the 

 earliest known amphibians from the Lower 

 Carboniferous of Scotland, and forms with 

 similar vertebrae have been found in the FlG 282.— Carboniferous amphib- 



~ .. .. „,.. _ _ ,. ian Lepterpeton dobbsi Huxley: 



upper Carboniferous. The Temnospondyli a microsaurian from Kilkenny, 

 are, however, imperfectly known in the jfg^ about * natural size - 

 Carboniferous, though they doubtless lived 



then in abundance and may have made many of the known foot- 

 prints. They reached their highest development in the Permian, and 

 are supposed by many paleontologists to be the ancestors of all 

 modern reptiles. 



Not much is known of the food and life-habits of any of these 

 amphibians. From their teeth, it is inferred that they were predaceous 

 and lived on fish, crustaceans, insects, and other amphibians. At 



