CHAPTER IV. 



THE MORPHOLOGY OF THE COAL MEASURES AMPHIBIA. 



The anatomy of the Coal Measures Amphibia presents many primitive types of 

 structure. Their organization represents a stage passed through in the ontogeiiyu-6^*'''''^*^' 

 of higher vertebrates. The animals are similar in a general way, yet so diverse are 

 the modifications which they have suffered imder different environmental conditions, 

 that close scrutiny is needed to discern the exact relationship of the forms. Our 

 knowledge of this relationship is based on the structures preserved, which are 

 largely skeletal, since little is known of the soft anatomy (471) of the air-breathing 

 vertebrates of the Coal Measures. The pubis is ossified in the Paleozoic Amphibia 



cucom. 



I 



\ 



Fig. 6. — Generalized figure of dorsum of an eariy amphibian 

 skull to show position of elements and terminology 

 adopted in this work. The outline is based on that 

 of Eryops, but is in no way intended to indicate that 

 form. 



a. com, anterior commissure of lateral-line canals; com, 

 commissural communication between infra- and supra- 

 orbital lateral-line canals; fr, frontal; inf, interfrontal; 

 inn, intemasal; info, infraorbital lateral-line canal; it, 

 intertemporal; jl, jugal lateral-line canal; j, jugal; 

 lar, lacrimal; mx, maxilla; n, nasal; oc, occiput; occ, 

 occipital cross-commissure of the lateral-line system; 

 or, orbit; par, parietal; pof, postfrontal; pmx, premax- 

 illa; p}, prefrontal; po, postorbital; pp, postparietal; 

 q, quadrate; qj, quadratojugal ; spo, supraorbital 

 lateral-line canal; sq, squamosal; spt, supratemporal; 

 /, temporal lateral-line canal ; lab, tabulare. 



later than the ischium and ilium ; the carpus and tarsus are cartilaginous ; the verte- 

 brae consist of a pleurocentrum and two neurocentra, thus paralleling conditions in 

 modem mammalian embryos. 



(a) The skull of the Coal Measures Amphibia has (fig. 6) essentially the same 

 structvire in the different groups. It is largely formed of bones of intramembranous 

 origin, representing the face bones of the mammalian skull. The skull in life was 

 doubtless a chondrocranium with the membrane bones laid down upon the carti- 

 laginous box containing the sense-organs, as in the sturgeon (Acipenser), where the 

 surface bones of the face were probably originally scales, which later became consol- 

 idated into large bony scutes. The membrane bones of the early Amphibia may 

 have been originally derived from scales, but at present nothing is known of this 

 origin ; doubtless the elements had an intramembranous origin in the ancestors of 



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