FAUNAL RELATIONS OF EARLY VERTEBRATES 167 



before the close of the Pennsylvanian, one the derivative of Upper 

 Carboniferous, possibly sub-Carboniferous stock, the other a later 

 development, and both continuing for a brief period in Europe during 

 Permian times. Of all the remainder of the air-breathers not one 

 can be compared with forms known elsewhere in the world, save in 

 the general characters, ordinal characters at best. 



These facts can mean but one thing, the faunal isolation of land 

 and freshwater vertebrates during all of the so-called Permian times 

 in America. The faunistic evolution here was great, however. At 

 least three very distinct phyla of reptiles and as many of amphibia are 

 known with certainty: the Pelycosaurs (Naosaurus, Dimetrodon, 

 etc.), derivatives of a prior type which had branched off before the 

 close of the Pennsylvanian; the true Cotylosaurs (Diadectes, etc.) 

 with, in some cases, singular developments of dermal carapace, 

 strongly suggestive of the turtles, unknown elsewhere; and a third 

 type (Labidosaurus, Pariotichus, etc.), for the present nameless, 

 small crawling reptiles with large head, short tail, short limbs, whose 

 nearest, but remote relatives are found among the pareiasaurs of 

 South Africa, doubtless derived from the same common stock as the 

 pareiasaurs, but modified by long isolation. Of the amphibia the 

 most numerous and best developed are those with temnospondylous 

 vertebrae, that is those which have the vertebrae divided into separate 

 elements, the type from which the mammals doubtless eventually 

 arose, as well as the cotylosaurs, and pareiasaurs. This group is also 

 abundantly represented in the Lower Permian of Europe, but reached 

 the highest expression in the Texas Permian (Eryops) A second 

 type, represented by a few forms, in America, known from the latter 

 part of the Pennsylvanian throughout the Permian (Diplocaulus, 

 Crossotelos, etc.) represents sparsely the continuation of the microsaurs 

 perhaps, but with marked modifications in structure peculiar to the 

 American forms which separate them widely from their Permian 

 relatives of Europe. The third, representing the earliest known type 

 of the modern amphibians (Lysorophus) , is, so far, entirely peculiar 

 to our Permian, another evidence of isolated evolution. There are 

 no known representatives of the stereospondylous types of Stegocepha- 

 lia, that is the true labyrinthodonts, which, however, as we shall see, 

 suddenly reappear in the Upper Trias, and doubtless were represented 



