Regional Morphology

This is relevant for Pit Vipers in Mexico and Central America.

Morphological identification key

Crotalinae

Is there a "rattle" or a knob-like projection on the end of the tail?	yes		Are there several enlarged shields on the top of the head (generally 9, sometimes 11)?	yes	Sistrurus catenatus, Crotalus ravus
no			no

			Crotalus sp.(excluding Crotalus ravus)


	Are there several enlarged shields on the top of the head (generally 9)?	yes				Agkistrodon sp.

no

Are there protruding, spiky scales underneath the tip of the tail?	yes				Lachesis sp.

no

Are there characteristic markings in the form of open triangles or arrowheads?	yes				Bothrops asper

no

Atropoides sp. Bothriechis sp. Cerrophidion sp. Mixcoaltlus sp. Metlapilcoatlus sp. Ophryacus sp. Porthidium sp.