Barras, C. G. (2007). Phylogeny of the Jurassic to Early Cretaceous ‘Disasteroid' Echinoids (Echinoidea; Echinodermata) and the origins of Spatangoids and Holasteroids. Journal of Systematic Palaeontology. 5(2): 133-161.

155264

10.1017/s147720190600201x [view]

Barras, C. G.

2007

5(2): 133-161

Publication

The ‘disasteroids’ are a morphologically unusual group of echinoids characterised by having a disjunct, or divided, apical disc. The group is now recognised as being basal to the two extant orders of irregular echinoid, the Holasteroida and Spatangoida. There are a number of theories that detail the pathway leading from the ‘disasteroids’ to the holasteroids and spatangoids, but all lack a rigorous phylogenetic hypothesis. Following a re-examination of ‘disasteroid’ material, the number of valid ‘disasteroid’ genera is here reduced to 16, including the new genus Smithiaster. New plating diagrams of the majority of these taxa are presented and form the basis of an analysis of ‘disasteroid’ phylogenetic relationships. The new analysis provides a phylogenetic hypothesis linking the ‘disasteroids’ to the basal Atelostomata (Hyboclypus and Aulacopygus) and also to the Holasteroida and Spatangoida. The phylogeny also confirms that the problematic genera Desorella, Infraclypeus and Menopygus, together with the ‘disasteroid’ Grasia, form a monophyletic group the Desorellidae, in the stem group Atelostomata.

Echinoidea

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