Order Summary for Heterodontiformes

Order Summary for Heterodontiformes
Main Ref	:	Nelson, J.S., 1994
Order	:	Heterodontiformes bullhead and horn sharks
Class	:	Elasmobranchii
Sister Order	:	Orectolobiformes 170 M years
Ref.	:	Shirai, S., 1996 \|
First Fossil Record	:	middle Jurassic
Occurs in	:		Marine	Fresh	Brackish
Remark	:	Two dorsal fins, each with a spine; anal fin present; five gill slits; eyes without nictitating fold; spiracle present but small; nostrils connected with mouth by deep grove.
Class etymology	:	Greek eulanein, elasmos = metal beaten out + Greek brangchia = gills. Ref. 45335.
Order etymology	:	Greek, heteros = other + Greek, odous = teeth + Latin, forma = shape (Ref. 45335).
Families	:	( n = 1 ) Heterodontidae