Editing Snake skeleton (section)

===Taxonomic key of skull modifications===
Modifications of the skull in the European genera:

*I. Quadrate articulating with the cranium, supratemporal absent; mandible much shorter than the skull, with coronoid bone; maxillary small, on lower aspect of cranium; pterygoids not extending to quadrate; nasals forming long sutures with the premaxillary, prefrontals, and frontal: ''[[Typhlops]]''.
*II. Quadrate suspended from the supratemporal; mandible at least as long as the skull; pterygoids extending to quadrate or mandible.
:*A. Mandible with coronoid bone; nasals in sutural contact with frontals and prefrontals; transverse bone short, not projecting much beyond cranium; maxillary not half as long as mandible, which is not longer than skull (to occiput): ''[[Eryx (snake)|Eryx]]''.
:*B. No coronoid bone; nasals isolated.
::*1. Maxillary elongate, not movable vertically.
:::*a. Maxillary half as long as mandible.
::::*Supratemporal half as long as skull, projecting far beyond cranium; mandible much longer than skull: ''[[Tropidonotus]]''.
::::*Supratemporal not half as long as skull, projecting far beyond cranium; mandible much longer than skull: ''[[Zamenis]]''.
::::*Supratemporal not half as long as skull, projecting but slightly beyond cranium; mandible much longer than skull: ''[[Coluber]]''.
::::*Supratemporal not half as long as skull, not projecting beyond cranium; mandible not longer than skull: ''[[Coronella]], [[Contia]]''.
:::*b. Maxillary not half as long as mandible, which is longer than skull; supratemporal not half as long as skull, projecting beyond cranium.
::::*Quadrate longer than supratemporal; maxillary much longer than quadrate, nearly straight in front of prefrontal; a large vacuity between the frontal bones and the basisphenoid: ''[[Coelopeltis]]''.
::::*Quadrate not longer than supratemporal; maxillary little longer than quadrate, strongly curved in front of prefrontal:''[[Macroprotodon]]''
::::*Quadrate longer than supratemporal; maxillary little longer than quadrate, nearly straight in front of prefrontal: ''[[Tarbophis]]''
::*2. Maxillary much abbreviated and erectile; supratemporal not half as long as skull; mandible much longer than skull; basioccipital with a strong process.
:::*Maxillary bone solid: ''[[Vipera]]''.
:::*Maxillary bone hollow: ''[[Agkistrodon|Ancistrodon]]''.
:::*The vertebrae number 130 to 500 - in the European forms 147 (''[[Vipera ursinii]]'') to 330 (''[[Coluber leopardinus]]'').