Evolution & Systematics

Figure 1. Phylogenetic tree of Echinodermata taxa, (Ruppert et al, 2004).

This tree represents the phylogeny of the living taxa within the phylum of Echinodermata. At each split in the tree, different morphological characteristics separate one taxa from another. The following is a description of the morpholical characteristics of each taxonomic group of which Echinometra mathaei is a member.

1: Echinodermata - Characterised by a water-vascular system, pentamorous symmetry and mutable connective tissue

3:Eleutherozoa - Characteristed by ventral oral surface, tube feet for locomotion, presence of a madreporite, movable spines and a mobile lifestyle.

5:Cryptosyringida - Characterised by radial nerves in the epineural canal.

7: Echinozoa - Ambulacra and oral surface cover most of the body, they have a ring of ossicles around the pharynx and the hemal system contains a rete mirible.

8:Echinoidea - Periproct has 5 ocular and 5 genital plates and Aristotle's lantern is present. Ossicles are fused to form a test and have echinopluteus larvae (Ruppert et al, 2004).

Speciation within the Echinometra genus is fairly diverse. The Echinometra genus has a fossil record dating back to the Palaeocene, however only one species appears to have been present at the time (McCartney etal., 2000). Currently there are 4 recognized species in the Indo West Pacific, and speciation is believed to have occurred approximately 3 million years ago (Palumbi, 1996).