Phylogeny of T. gratilla adapted from marinespecies.org

This tree represent an adaptation from marinespecies.org of the Echinodermata phylum broken down through the class, order, family, genus, species of T. gratilla.  Showing preference for Echinoids most of the phylum has been left out to focus on the key species being described.  

1. The first split represents the subphylum within the echinodermata, Echinozoa is defined by a globoid body with meriodional symmetry (Howard & John 2014).   
2. Echinoidea (class) is defined by 5 ocular and 5 gentile plates present as well as the unique aristotle's lantern (Ruppert et al. 2004)
3. Carinacea and infraclass of echinoidea includes 3 orders extant and fossil one of then including the camarodonta (Encyclopedia of Life 2010)
4. Camarodont (order) defined by their lantern struture, all extant camarodont have imperforate tubercles and echinid-style ambulacral plate compounding (Encyclopedia of Life 2010)
5. Echinidea a clade uniting the family's including the superfamily odontophora (WoRMS 2014)
6. Odontophora (Kroh and Smith 2010) a superfamily that encompasses 4 familys including Toxopneustidae
7. Toxopneustidae (family) defining characteristic the peristome and opening through the test, a sharp margin with prominent buccal notches (WoRMS 2014). 
8. Tripneustes gratilla species three extant species within Tripneustes that all share similar morphological characteristics they were considered to be the same species for a period of time (Lawrence Agatsuma 2004). The key species in the study commonly known as the collector urchin and can be defined from the other species via mitochondrial DNA analysis (Lawrence & Agatsuma 2007).