The Echinoid Directory

Mecaster Pomel, 1883, p. 42

Diagnostic Features
  • Test ovate with distinct anterior sulcus; posterior face truncate.
  • Apical disc hemiethmolytic or ethmolytic with four gonopores; wider than long with anterior and posterior gonopores on either side close together; central.
  • Ambulacrum III sunken from apex to peristome (deepest aborally). Pore-pairs differentiated with prominent interporal ridge, presumably associated with funnel-building tube-feet.
  • Paired ambulacra petaloid; petals sunken and bowed; closed distally. Posterior petals generally about half to two-thirds length of anterior petals.
  • Peristome pentagonal and tilted slightly towards anterior.
  • Labral plate longer than wide, extending to third ambulacral plate. Sternal plates large, symmetrical and forming most of oral surface. Episternal plates offset.
  • Periproct small, situated towards top of posterior truncate face.
  • Enlarged subanal pore-pairs present.
  • Peripetalous fasciole present; indented by one plate behind anterior petals. No other fascioles.
Upper Cretaceous (Upper Cenomanian to Maastrichtian), Europe, former SSU, Africa, North and South America.
Name gender masculine
Hemiaster fourneli Agassiz & Desor 1847, p. 16, by original designation.
Species Included
  • M. fourneli Deshayes, in Agassiz & Desor, 1847; Turonian to Maastrichtian, Brazil, North and West Africa.
  • M. africanus (Coquand, 1862); Turonian, Algeria and Brazil.
  • M. longus Cotteau & Gauthier, 1895; Senonian, Iran.
  • M. mutabilis (Lambert, 1933); Turonian, Madacascar and India
  • M. obliquetruncatus Peron & Gauthier, 1880; Turonian, Algeria.
  • M. texanus (Roemer, 1849); Santonian-Campanian, North and central America.
  • M. batnensis (Coquand, 1862); Cenomanian-Turonian, Brazil, North Africa, Texas.
  • M. scutigera (Forbes, 1850); Cenomanian, Portugal.
  • M. victoris (Lambert, 1932); Campanian-Maastrichtian, Algeria, Oman, Turkey.
  • M. cubicus Desor, in Agassiz & Desor; Cenomanian, Middle East.
  • M. arnonensis Neumann, 1999; Santonian, Jordan.
  • many other nominal species of questionable validity have been established (see Neraudeau 1994 for comprehensive list and Smith & Bengtson 1991 for discussion of genus).
Classification and/or Status

Spatangoida, Hemiasterina, Hemiasteridae.



Differs from Hemiaster in having an ethmolytic (or hemiethmolytic) apical disc. It also has much longer and better developed petals than Hemiaster. Closest to Jordaniaster but differs in having a shorter labrum, more symmetrical sternal plates and an ethmolytic rather than ethmophract apical disc.

Smith, A. B. & Bengtson, P. 1991. Cretaceous echinoids from north-eastern Brazil. Fossils and Strata 31, 1-88.

Neraudeau, D. 1994. Hemiasterid echinoids (Echinodermata: Spatangoida) from the Cretaceous Tethys to the present-day Mediterranean. Palaeogeography, Palaeoclimatology, Palaeoecology 110, 319-344.