Evolution & Systematics

Asteroid sare a phylogenetically diverse group, possessing approximately 1,600 species worldwide (Lafay et al. 1995).  The phylogenetic relationship between the asteroid families is slowly being untangled, although debate surrounding these relationships continues (Knott & Wray 2000). Previously it was primarily morphological data that determined phylogenies, however more recent phylogenies have combined morphological and molecular data to produce a more accurate estimation (Lafay et al.1995). From examination of the fossil record, it is apparent that the divergence of the extant orders appears to occur rapidly, most of which appeared in the Jurassic period (Figure1) (Lafay et al. 1995). Valvatida is included in this divergence and appears to have evolved in the Jurassic period. Within the Valvatida, the evolution of the Goniasteridae family appeared to occur in the Bajocian, or middle Jurassic (figure 1) (Lafay et al. 1995). 

figure 1. modified from (Lafay et al. 1995) a) Phylogenetic relationship between current families of Asteroids. b) The evolutionary history of the orders of Asteroids