Page:The Osteology of the Reptiles.pdf/113

Rh, two sacrals, and a long tail. In no embolomerous amphibian is the number of vertebrae known.

The numbers of presacral and sacral vertebrae in reptiles may be tabulated as follows:

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 vertebrae 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 chameleon lizard.