TRIASSIC FISHES FROM SPITSBERGEN 
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attempt to show a common plan of organisation in the skeleton of the extremities in 
all vertebrates resulted, as we know, in his very much debated Archipterygium theory. 
As early as 1865 then and later in several works he expresses, with regard to the 
skeleton of the paired fins in the ganoids and Teleosts, the view that it had probably 
originated by reduction of an Elasmobranchian-like one. Gegenbaur’s work in this depart¬ 
ment aroused general interest for the study of fish fins in general and the result of this 
soon became apparent in the literature. 
In 1876 the fin-fold theory was clearly put forward for the first time by Balfour 
(1876, pp. 132—135) and was supported not long afterwards by Thacher (1877 a, b) and 
Mivart (1879, pp. 458—482) as well. As the endoskeleton in the ventral fins of the 
sturgeons resembled in a number of respects that of the unpaired fins, this was inter¬ 
preted by Thacher as an argument for the correctness of the fin-fold theory. The skeleton 
of the ventral fins of the sturgeons was considered to be very primitive, even more 
primitive than that of the Elasmobranchs. 
Starting out from the views put forward by Gegenb'aur and putting before himself 
the question of what had become of the different elements in the abdominal fins of the 
Selachians, v. Davidoff (1879, 1880, 1884) undertook an investigation of the ventral fins 
in the Teleostomes, in which he paid attention not only to the osteology, but also the 
myology and neurology. He then thought that he was able to show that the plate in 
Amia, Lepidosteus, Polypterus and Teleosts that preceding authors had interpreted as the 
pelvis, really corresponded most closely to the basale metapterygii of the Elasmobranchs, 
while the pelvis was reduced or rudimentary (Polypterus). 1 ) According to v. Davidoff 
the sturgeons, to judge from the development of their ventral fins, had entered on quite 
a different direction of development from that of the above-mentioned Teleostomes. For 
he considered that in the sturgeons the basale metapterygii was absent, but that the 
pelvis was present, although its caudaDpart in different genera and species showed a 
more or less strong subdivision into segments, a phenomenon that he considered to be 
secondary. In the last-mentioned point, however, he fairly soon modified his view, owing 
to a work published by v. Rautenfeld in 1882. 
In this work v. Rautenfeld (1882, pp. 3 o— 32 , 44—45) came to the conclusion that 
the process of subdivision that v. Davidoff considered he was able to verify in the pelvis 
of the sturgeons, was really the operation of a process of fusion of basal segments of 
the endoskeletal radials. Farthest anteriorly a number of basal segments had, according- 
to his opinion, already fused to a single plate, which he calls the basal plate and 
homologizes with the basale propterygii of the Elasmobranchs. In general he considered 
the skeleton of the paired fins of the Ganoids Teleosts as reduced. The so-called pelvis 
of the Teleosts, which v. Davidoff took to be the basale metapterygii, he considers as 
a basale propterygii arisen in the same way as in the sturgeons. 
Olga Metschnikoff (1880, pp. 426—427) was of the opinion that the pelvis and 
metapterygeal stem together formed the elements of a single branchial arch. 
Wiedersheim (1892, pp. 60—84) in his work «Das Gliedmafienskelett der Wirbel- 
tiere® appears as an eager partisan of the fin-fold theory. He maintained that the 
J ) v. Davidoff took the little paired or unpaired piece of cartilage between the anterior ends of the basale 
metapterygii of either side in Polypterus as a rudiment of the pelvic girdle. 
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