The Echinoid Directory

• Test ovate with distinct anterior sulcus; posterior face obliquely truncate. Test depressed in profile.
• Apical disc ethmophract with four gonopores; posterior of centre.
• Anterior ambulacrum strongly sunken from apex. Pore-pairs large and closely packed in vertical series along outer margins. Most pore-pairs compact, but wider (dash-dash) pore-pairs occur occasionally.
• Anterior petals long and flexed anteriorly; anterior column with pore-pairs only in distal part; adapically one anterior plate to every two posterior plates.
• Posterior petals shorter and bowed, with anterior column distinctly less developed than posterior column.
• Peristome close to anterior border and facing forward into frontal groove. Labrum projecting slightly.
• Labral plate elongate, widening distally; extending to second amb. plate. Sternal plates asymmetric with oblique median suture. Episternal plates offset.
• Periproct on posterior truncate face; small and round.
• Multiple thin fasciole bands  run laterally beneath petals.
• Aboral tubercles distinctly larger towards apex in anterior interambulacral zones.

Albian, USA. Mexico.

Hemiaster riovistae Adkins, 1920, p. 115, by original designation

• W. riovistae (Adkins, 1920); Upper Albian, Southern USA.
• W. longisulcus (Adkins & Winton 1920); Upper Albian, Southern USA.
• W. wenosensis (Adkins, 1920); Upper Albian, Southern USA.
• W. bravoensis (Bose, 1910); Upper Albian, USA and Mexico

Spatangoida, stem group (toxasterids).

Monophyletic?

The pore-pair structure in the frontal groove and plating pattern in the frontal petals shows that this taxon is closely related to Heteraster. Cooke (1955) noted that the degree to which elongated pore-pairs occurred in the frontal groove was very variable. He placed all taxa with multiple rows of 'fasciole' banding into this genus. However, this taxon differs from Heteraster in possessing multiple fasciole bands, which are best developed laterally (see Markov & Solovjev 2002). This is a derived feature that distinguishes Washitaster as a clade.  

Cooke, C. W. 1955. Some Cretaceous echinoids from the Americas. Geological Survey Professional Paper 264-E, 87-112, pls 18-29.

Lambert, J. 1927. Considerations sur les Echinides de la Comanche Serie du Texas. Bulletin de la Societe geologique du France, serie 4, 26, 263-278.

Markov, A. V. & Solovjev, A. N. 2002. Echinoids of the genus Washitaster (Spatangoida): morphology and taxonomic position. Paleontological Journal 16(4), 368-379.