HISSS 2 (Herpetological Investigations: Systematic Serpentes Sourcebook).

During the past year I compiled data on variation in the head shields of snakes to supplement the main scutellation counts presented in HISSS 1. This version (HISSS 2, containing 4355 species) now includes 11 characters of the snake head plus the infraorder and family for a total of 27 characters. These include the following: 1) IO (Infraorder, including SCO [Scolecophidia], HEN [Henophidia], and ALE [Alethinophidia], 2) Family, 3) Genus, 4) Species, 5) LOA (Overall or total length in m), 6) RTL (Relative tail length as % LOA), 7) ELEV (Elevation above sea level in m), 8) MSR (Midbody scale rows), 9) C (Carination of dorsal scales), 10) VEN (Ventrals), 11) CS (Cloacal shield), 12) SC (Subcaudals), 13) ST (Subcaudal type), 14) IN (Internasals), 15) PF (Prefrontals), 16) L (Loreals), 17) PR (Preoculars, including presuboculars), 18) PO (Postoculars, including postsuboculars), 19) SL (Supralabials), 20) slo (Number of supralabials entering the orbit or contacting the eye), 21) AT (Anterior or primary temporals), 22) PT (Posterior or secondary temporals), 23) IL (Infralabials), 24) CO (Circumorbitals or circumoculars), 25) RM (Reproductive type, 0 = oviparous or egg laying, V = viviparous/ovoviviparous or live bearing), 26) OS (Offspring or number of hatchlings and neonates), and 27) Age (Maximum longevity in years).

The number of suboculars, when present, has been omitted in lieu of the circumorbital number, which is a more important and useful character that not only includes the suboculars but also the other scales surrounding the eye. When the reproductive mode is unknown for a species it is coded with the same condition as present in its congeneric taxa.

I continue to update and improve this database so anyone wishing to contribute by sending me data that will correct errors, fill in missing data fields, or expand the ranges of the variable characters is certainly most welcome.