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The Echinoid Directory

Hemiaster Desor, in Agassiz & Desor, 1847, p. 16

[?=Leucaster Gauthier in Peron 1887, p. 386, (type species L. remenensis Gauthier, 1887, p. 387); =Peroniaster Gauthier 1887, p. 246 (type species P. cotteaui Gauthier, 1887, p. 246); =Integraster Lambert & Thiery, 1924, p. 504; type species Hemiaster ligeriensis d\'Orbigny, 1853; =Malawaster Chiplonker & Badve 1974, p. 52, type species Opissaster subsimilis Fourtau, 1917 ]

Diagnostic Features
  • Test ovate or with weak anterior sulcus; posterior face truncate. Test inflated to somewhat wedge-shaped in profile.
  • Apical disc ethmophract with four gonopores; central.
  • Anterior ambulacrum sunken adapically, with adapical pore-pairs uniserially arranged and enlarged.
  • Paired ambulacra petaloid aborally; petals somewhat bowed and closing distally, with narrow interporal zone. Anterior petals around twice the length of posterior petals.
  • Ambulacral zones not significantly pinched as they cross the peripetalous fasciole immediately beneath the petals.
  • Peristome D-shaped and surrounded by a distinct lip.
  • Labral plate longitudinally elongate and broadening posteriorly; extending to third ambulacral plate. Sternal plates asymmetric with oblique suture; episternal plates offset.
  • Periproct high on posterior truncate face; small.
  • Subanal pore-pairs enlarged.
  • Peripetalous fasciole present; not indented behind anterior petals.
  • Aboral tuberculation fine, dense, not sunken; granulation sparsely developed amongst tuberculation.
Distribution
Lower Cretaceous (Albian) to Upper Cretaceous.
Name gender masculine
Type
Spatangus bufo Brongniart, 1822, p. 84, by subsequent designation of Savin, 1903, p. 22.
Species Included
  • Large numbers of species have been assigned to this genus (see Neraudeau 1994). However, relatively few are known with confidence to share the plate architecture of the type species.
  • H. forbesii Baily, 1855; Upper Cretaceous (Albian - Cenomanian?) South Africa.
  • H. hattaensis Ali, 1989; Maastrichtian, United Arab Emirates
  • H. heberti Peron & Gauthier, 1878; Cenomanian, North Africa
  • H. integer Lambert, 1933; Turonian, Madagascar and India
  • H. noemiae Cotteau & Gauthier, 1895; Senonian, Iran.
  • H. subsimilis Fourtau, 1917; Turonian, India and Madagascar
Classification and/or Status

Spatangoida, Hemiasterina, Hemiasteridae.

Presumably paraphyletic (by exclusion of Bolbaster etc..).
Remarks

Differs from Mecaster in having an ethmophract apical disc rather than a semi-ethmolytic or ethmolytic disc. Differs from Leymeriaster in having the posterior petals less markedly reduced in size. Differs from Holanthus in having no marked narrowing of the ambulacra immediately beneath the petals. The oblique sternal suture and primitive plastron also immediately separate it from Holanthus. Bolbaster is almost globular as opposed to the wedge-shaped Hemiaster.

Although large numbers of species have been assigned to this genus, few will probably turn out to be conspecific. Diagnostic features that distinguish the type species from most others are (1) the asymmetric sternal plates with the oblique median suture: (2) the elongate labral plate that reaches ambulacral plate 3: (3) the ambulacral zones not pinched as they cross the peripetalous fasciole. All so-called Hemiaster need to be checked for these features as none were reported by Neraudeau (1994).

Agassiz, L. & Desor, P. J. E. 1846-1847. Catalogue raisonné des familles, des genres, et des espèces de la classe des échinodermes. Annales des Sciences Naturelles, Troisième Série, Zoologie: 6 (1846), 305-374, pls 15-16; 7 (1847), 129-168; 8 (1847), 5-35, 355-380.


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