474 AN INTRODUCTION TO ZOOLOGY 



years ago, and some think very much longer than this. These first 

 quadrupeds were the AMPHIBIA, swamp-dwelling creatures some- 

 what resembling the newts and salamanders of to-day, and from 

 which the tailless forms like frogs and toads arose later. Towards 

 the end of the Devonian period appeared a specialised group, the 

 Stegocephalia, found all over Europe and North America. To this 

 belonged a form termed Eryops, which, while appearing at a some- 

 what later time, is interesting, since it is but little specialised, and 

 *from similar forms the early reptiles could have arisen. In appear- 

 ance it is not unlike a large newt, although its skeleton and, in 

 particular, its skull is of a more advanced type. The first true 

 Reptiles made their appearance in the Carboniferous period, and 

 by the end of it and the beginning of the Permian, we find them 

 committed to at any rate two different lines of development, which 

 we shall follow separately. The differences between these early 

 Reptiles and the Amphibia are very slight, so that the line of 

 demarcation between them is difficult to draw. 



The first reptiles to notice are a group, the Pelycosauria, of world- 



FIG. 167. Restoration of the Permian reptile, Limnoscelis paludis, from 

 New Mexico. -After a model by Lull. 



wide distribution, and of which Limnocelis will serve as a little- 

 specialised type. It is slightly more lizard-like than Eryops, and 

 more adapted for life on dry land. As a rule, the members of this 

 group remained little modified, but certain forms like Edaphosaums 

 and its allies had the neural spines of the vertebrae enormously 

 elongated and a large web-like extension of the skin between them. 

 These strange forms rarely exceeded a length of 5 feet, and soon 

 died out. From the Pelycosauria were derived a second group, 

 the Theriodontia, or reptiles with mammal-like teeth, first appearing 

 in Upper Permian beds in South Africa. They are far more adapted 

 to life on land, and progressed fairly rapidly, holding their bodies 

 well up off the ground and running like a mammal instead of crawling 

 like a lizard. From this group in the Triassic period arose, the 

 primitive Mammalia, whose remains have been found in the upper 

 strata of this series in South Africa. Thus we have derived from the 

 one specialisation of the early Reptiles, the Mammals, a group 

 destined to spread over the whole world, to become adapted to 



