ON THE NAMES PLESIOSAURIA AND SAUROPTERYGIA. 



221 



13. On the Use of tbe Names Plesiosauria and Sauropterygia. 

 By a. A. Boulenger, F.R.S., F.Z.S. 



[Received October 6, 1017 : Read November 6, 1917.1 



Index. 



Systematic : Pa«;e 

 On the names Plesiosauria and Sauropterygia , 221 



I wish to point out the misapplication, or rather inverted 

 application, of the names Plesiosauria and Sauropterygia by some 

 of the most recent writers on the classification of fossil Reptiles. 



The order Plesiosauria was so named, and properly defined, by 

 de Blainville in 1835 * ; the genus Plesiosaurus was then its only 

 representative. 



When, in 1839, Owen f accepted the name Enaliosauria 

 (Conybeare, 1821) for the marine Reptiles known as Plesiosaurs 

 and Ichthyosaurs, which were associated in one order, he desig- 

 nated the former as Plesiosauri and the latter as Ichthyosauri. 

 After the relationship of the Nothosaurs to the Plesiosaurs had 

 been recognised by Hermann von Meyer, they were placed 

 together as Plesiosauri by Quenstedt in 1852 J. 



Plesiosauria (1835-1852) is the earliest name for the order in 

 question, it is open to no objection, and it should therefore be 

 used, as it has been by Huxley, Gegenbaur, Cope, Baur. Hay, 

 and myself. 



In 1859, Owen §, dropping the artificial group Enaliosauria, 

 proposed to call Sauropterygia and Ichthyopterygia the two orders 

 on which he had already bestowed names which there was no 

 need to change. The Sauropterygia were defined as long-necked 

 marine Reptiles with fin-like limbs with not more than five 

 digits. Owen insisted on the character of the limbs as distinctive 

 of the order and, although accepting the proposition that the 

 Nothosaurs should be included, remarked, rather inconsistently: — - 

 " I continue, as in my former Report of 1841, to regard the fin- 

 like modification of the limbs as a better ordinal character than 

 the number of vertebras in any particular region of the spine 



The Plesiosaurus, with its very numerous cervical 



vertebra?, sometimes thirty in number, may be regarded as the 

 type of the Sauropterygia or pentadactyle sea-lizards." 



It is therefore perfectly clear, and beyond discussion, that the 



* Ann Mas. Paris (3) iv. p. 241. — Reference to this important contribution to 

 the classification of Reptiles has unfortunately been omitted from 0. P. Hay's most 

 useful bibliography, Bull. U.S. Geol. Surv. no. 179, 1902. 



f Hep. Brit, Assoc. 1839, p. 45 ; also 1841, p. 60. 



X Haudhuch der Petrefaktenknnde, p. 130, 



§ Rep. Brit Assoc. 1859, p. 159. 



