The Echinoid Directory

• Test narrow and laterally compressed; wedge-shaped in profile. No anterior notch.
• Apical disc plating not clear, possibly fused; 2 gonopores (anterior gonopores missing); central.
• Frontal ambulacrum slightly bowed adapically and weakly sunken. Large uniserial pore-pairs in adapical portion.
• Paired ambulacra flush and apetaloid adapically, with microscopic pores only.
• Peristome anterior but test eroded. Possibly oriented obliquely towards the front.
• Plastron plating with elongate labral plate extending to ambulacral plate 2. Sternal plates symmetric; episternal plates possibly paired and at posterior edge of oral surface.
• Periproct on steeply sloping posterior face; just visible in apical view.
• Peripetalous fasciole present; passing close behind apical disc at rear and dipping to become subambital around anterior.
• Enlarged tubercles bordering the anterior ambulacrum.

Early Thanetian, Tertiary; Spain.

Sphenaster larumbensis Jeffery, in Smith et al. 1999, p. 131.

• Only the type species.

Spatangoida, Hemiasterina, Aeropsidae.

Monotypic; presumably paraphyletic by exclusion of Aeropsis. 

Differs from Aceste in having only a weakly sunken frontal ambulacrum and a more wedge-shaped test that lacks a frontal notch. It differs from Cottreaucorys in being taller and more laterally compressed and with differentiated adapical pores in the frontal ambulacrum.

Smith, A. B., Gallemi, J., Jeffery, C. H., Ernst, G. & Ward, P. D. 1999. Late Cretaceous- Early tertiary echinoids from northern Spain: Implications for the Cretaceous-Tertiary extinction event. Bulletin of the Natural History Museum, London (Geology) 55, 81-137.