seen among osteolepids in the series Osteolep i s . Meqal ichthys . Ectosteorhach i s , in which the 

 toothed medial plate is progressively shortened. As far as 



-fig. 5" 

 the degree of dissociation of the vomers is concerned, there is apparently a correlation with the 

 length of the paraspheno i d. The degree of development of the posterior branch, like the presence 

 of a vertical toothed plate, is apparently a characteristic of genera or families. The majority 

 of osteolepids ( Ectosteorhach is . Osteolep i s . Clyptomus . Meqal ichthys . Thurs jus ) have a short 

 posterior branch which, on the other hand, is well developed in Platvcephal ichthys , Panderi chthys , 

 Eusthenopteron . Eusthenodon . The vertical plate is lacking in Meqal ichthys . According to the 

 theory of Kulczycki, the latter characteristic in conjunction with the short posterior branch of 

 the vomers testifies to the prim i t i veness of the form. 



Since in Ectosteorhach i s as well as in Porolep i s the vomers are not encountered along the 

 medial suture, it is difficult to judge if they had an i ntervomerine canal which was able to pass 

 even in soft tissues. (Thomson, 1964) 



As is evident from the analysis presented of data on the formation of the snout of Rhipidistia, 

 there still remain many unclear and debatable points about this problem. Apparently, however, the 

 series of peculiarities in the formation of the ethmoid taken by Jarvik as a basis for the division 

 of two phylogenetic trunks of Rhipidistia is not justified. They have obviously much less 

 significance in taxonomy being characteristic of genera or at best, families. 



— p. 1364 — 



Comparative anatomy of the snout of Rhipidistia thus still does not present proof for the resolution 

 of the question about the origin of amphibians from one or from several groups of lungfishes. 

 Also, available data indicate that the Rhipidistia are much more diverse than was assumed earlier, 

 and it is completely possible that further study of this group will lead to significant altera- 

 tions in its taxonomy. However, all known Rhipidistia reveal an obvious similarity in the chief 

 features of the formation of the ethmoid (in nervous and circulatory systems, in the internasal wall, 

 in the nasal cavities) which testifies to the utility of considering them one. 



There rema in ( 

 snout of Rhipidistia 

 position of the cana 

 (the different posit 

 these small differen 

 branchial apparatus 

 (Jarvik, 1964). Unf 

 and therefore making 

 affirms that the con 

 the scales of Osteol 

 assertion is without 

 and Osteolep i s ) the 

 The difference betwe 

 synchronomor ial) of 

 evolutionary stages 

 and Osteolep i formes 

 pg. 420), i.e., they 

 a very s imi lar const 

 presence of a broad 



bes i des q 

 which su 

 Is of som 

 ion of ram 

 ces one sh 

 of Eus then 



est ionable 

 port the h 

 blood ves 

 us opthalm 

 ould add a 

 op teron an 



ortuna tely 



any such 



f i rma t i on 



ep i T.ormes 



f ounda t i 



scales hav 



en them ba 



the later 



of develop 



the scales 



had a sin 



rue t i on of 



pulp cavit 



, however, 

 broad gene 

 of his hyp 

 and Porole 

 ce in 

 e an almos 

 sically co 

 layers of 

 ent. As 

 were appa 

 gle means 

 the teeth 

 . This a 



cts) only a few pecu 

 theses of Jarv ik, in 

 s and the quantity 

 s superf ic ial i s VII, 



the later data of J 

 lyptolep i s and the f 

 e branchial apparatu 



zat ions i s clearly 



sis lies in the dif 

 ormes presented by 

 s t primitive represe 

 dentical formation ( 



down to the methods 

 tin. These methods 

 ig himself affirms, 

 tly covered by cyclo 

 format ion. In add i t 

 f f er ing in the s impl 

 rings these forms 



1 iar i t ies of 



part icular, 

 f neural bran 



vena cerebra 

 arvik about t 

 ormat ion of t 

 s is unknown 

 premature. B 

 ferences in t 

 rv ig ( T . Orv i 

 ntatives of t 

 Orvig, 1957, 



of formation 

 obviously bea 

 in the ancest 



orial layers 

 i on, Porolep i 

 e plication o 

 together. 



the formation of the 

 the differences in the 



• 



table to page 406). 



(cyclomorial or 

 r witness to different 

 ral forms of Poroleo i formes 

 of dentin (Orvig, 1957, 

 and Osteolep i s had 

 the walls and in the 



In our view, the m i crostructure of the integumentary bones, scales and teeth of Rhipidistia 

 provides the possibility not only more clearly to present the stages of their evolutionary develop- 

 ment and the phylogenetic links between separate groups but also in some degree to clarify the 

 closeness of one or another representatives to the ancestral forms of tetrapods. Data on the 

 m icrostructure of integumentary bones and teeth of ancient tetrapods, e.g., Stegecephal ia, testify 

 in particular to the greatest closeness to them of one of the representatives of Osteolep i formes, 

 i.e., Panderichthys (Vorob'eva, I96O, I962). 



The methods of Jarvik which served as the foundation for the hypothesis of the polyphyletic 

 origin of terrestrial vertebrates have been justly criticized by several paleontologists (Thomson, 

 1962; Gross, 1964). The basic defects are the limitation of the scope of investigation (e.g., the 

 snout of Rhipidistia) and the small number of forms analyzed. At the outset, the fact that 

 primarily two representatives of lungfishes ( Porolep i s and Eusthenopteron ) are considered as initial 

 forms for amphibians which are also distant in taxonomic position and geological age, predetermines 



• 



