THE VERTEBRAE 95 



caudals, two sacrals, and a long tail. In no embolomerous amphib- 

 ian is the number of vertebrae known. 



The numbers of presacral and sacral vertebrae in reptiles may be 

 tabulated as follows: 



Presacral Sacral 



Cotylosauria 23-26 1-3 



Chelonia 18 2-3 



Theromorpha 23-27 2-3 



Therapsida 25-28 2-7 



Nothosauria 40~42 2 



Plesiosauria 40-105 3-4 



Proganosauria 29-34 2 



Ichthyosauria 40-65 o 



Sauranodon (Saphaeosaurus) 22-23 2 



Kionocrania (Lacertilia) 22-74 0-2 



Rhiptoglossa 16 2 



Dolichosauria 29 2 



Mosasauria 29-42 o 



Rhynchocephalia 25 2 



Rhynchosauria 23-24 2 



Choristodera 23-26 2 



Pseudosuchia 23-26 2 



Phytosauria 26 2 



Eusuchia 23-24 2 



Thalattosuchia 25 2 



Theropoda 23 2-5 



Sauropoda 26 4-5 



Stegosauria 27 3-4 



Trachodontia 30-34 8-9 



Iguanodontia 24-28 4-5 



Ceratopsia 24 7 



The earliest reptiles had functional ribs and a sacrum, and we may 

 omit the very variable tail in our comparisons. The majority of 

 terrestrial reptiles, it is seen, have between twenty-three and twenty- 

 six presacral vertebrae. In all probability the earliest reptiles were 

 lowland and crawling in habit, and it is legitimately presumable that 

 they had not less than twenty-three nor more than twenty-six verte- 

 brae in front of the sacrum, a single sacral, and not more than sixty 

 caudals, the largest number found in any early reptile, or altogether 

 between eighty and ninety vertebrae in the whole column, as against 

 thirty-five in modern turtles and four hundred and fifty in some 

 modern snakes. The smallest number of presacral vertebrae known 

 in any reptile — sixteen — is recorded for Brooksia, a recent cha- 

 meleon lizard. 



