The Echinoid Directory

• Test at least 1.5 times wider than long with sharp margin.
• Internal supports forming a dense meshwork around periphery. Microcannal system well developed.
• Apical disc with 4 gonopores.
• Petals well developed and closing distally.
• Interambulacral zones very much narrower than ambulacral zones at ambitus and adorally. Columns continuous.
• Basicoronal circlet pentastellate; interambulacral plates much larger than ambulacral plates and projecting strongly.
• Periproct close to peristome, opening in first pair of post-basicoronal plates and at the inner rim of the anal lunule.
• Food grooves bifurcate at edge of basicoronal plate; branching distally to give rise to a mass of fine distal branches.
• Anal lunule present; circular, opening bounded by first and second paired post-basicoronal interambulacral plates.

Upper Oligocene to Miocene of South America (Argentina & Uruguay).

Amplaster coloniensis Martinez, 1984, by original designation.

• A. coloniensis Martinez, 1984; Camacho Formation, Middle to Upper Miocene, Uruguay.
• A. alatus Rossi de Garcia & Levy, 1989; Patagonia Formation, Oligocene or Miocene, Argentina and Uruguay.
• A. ellipticusMooi, Martinez & Parma, 2000; Camacho Formation, Middle to Upper Miocene, Uruguay.

Clypeasteroida; Scutellina; Scutelliformes; Monophorasteridae.

Described in admirable detail by Mooi et al (2000). Differs from Monophoraster in having a much transversely elongate test and a rounder anal lunule that opens within the posterior petals.

R. Mooi, S. Martinez & S. G. Parma 2000. Phylogenetic systematics of Tertiary monophorasterid sand dollars (Clypeasteroida: Echinoidea) from South America. Journal of Paleontology 74, 263-281.