caudals, 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:
| 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 | 0 | ||
| Sauranodon (Saphaeosaurus) | 22–23 | 2 | ||
| Kionocrania (Lacertilia) | 22–74 | 0–2 | ||
| Rhiptoglossa | 16 | 2 | ||
| Dolichosauria | 29 | 2 | ||
| Mosasauria | 29–42 | 0 | ||
| 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 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.
