The Echinoid Directory

• Test circular in outline and probably depressed in profile.
• Apical disc monocyclic; less than half the test diameter. Genital plates large with multiple gonopores arranged in an arc; genital plate 2 slightly larger and perforated by hydropores. Periproctal plates developed within apical disc circle.
• Ambulacra straight and narrow; biserial. Plating simple with slightly elongate pore-pair on each plate. Single primary tubercle on each plate, usually somewhat heterogeneous in size. In one species (A. immanis Kier) not all ambulacral plates extending to the perradial suture.
• Adradial margins of ambulacral plates bevelled strongly beneath interambulacral plates. The inner surface of ambulacral plates without perradially directed flanges; the radial water vessel thus lay entirely beneath the ambulacral plates.
• Interambulacral zones wide; composed of four columns of large, hexagonal plates. Plates imbricate with small flanges; adradial margin of adradial series denticulate to accommodate ambulacral plates.
• First few adapical plates in adult without primary tubercle and bearing only fine granulation. Otherwise all interambulacral plates bear a single imperforate and non-crenulate primary tubercle surrounded by a large and slightly depressed areole. There is are more or less well defined circle of scrobicular tubercles; circle complete on aboral plates but areoles often confluent adorally so that scrobicular tubercles are confined to lateral margins. Generally there is no granulation or tuberculation outside the scrobicular circle.
• Peristome moderately large; ambulacral plates continue over the peristome together with non-ambulacral plates lacking primary tubercles.
• Lantern large and well developed. Pyramids broad and with shallow foramen magnum; teeth broad and U-shaped, at tip with median point and smaller lateral points.
• Spines long, hollow and lacking a cortex. Variably ornamented, but in type species with large, scattered thorns projecting along the shaft.

Carboniferous - ?Permian, North America, Europe, North Africa, Russia, ?Australia.

Cidaris urii Fleming, 1828, p. 478, by subsequent designation of Bather 1907, p. 453. Generic name Archaeocidaris validated in Opinion 370 under plenary powers, by suppresion under same powers of generic name Echinocrinus Agassiz, 1841. Opinions of the International Commission of Zoological Nomenclature 1955, 11, 301-320.

• A. urii Fleming (1824); Lower Carboniferous, Europe.
• A. immanis Kier, 1958; Pennsylvanian (Dewey Limestone), Upper Carboniferous; Oklahoma, USA.
• A. aliquantula Kier 1958; Kinderhookian, Lower Carboniferous, Iowa, USA.
• A. blairi (Miller, 1891); Meramecian, Lower Carboniferous, Missouri, USA.
• A. legrandensis Miller & Gurley, 1889; Kinderhookian, Lower Carboniferous.
• A. wortheni Hall, 1858; St Louis Group, Lower Carboniferous, USA.
• A. agassizi Hall, 1858; Lower Carboniferous, USA.
• A. newberryi Hambach;
• A. rossica (Buch, 1842); Lower Carboniferous, Russia.
• A. whatlyensis Lewis & Ensom, 1982; Visean, Lower Carboniferous, UK.
• ?A. nerei (Munster, 1839); Lower Carboniferous, Europe.
• A. brownwoodensis Schneider et al.2005; Missourian, Upper Carboniferous, Texas, USA.
• A. apheles Schneider et al. 2005; Missourian, Upper Carboniferous, Texas, USA.
• Plus numerous others.....

Stem group Echinoidea; Archaeocidaridae

Monotypic

Archaeocidaris is distinguished from miocidarids, which have a very similar plate morphology, by having four rather than two columns of interambulacral plates in each zone. Polytaxicidaris is also closely related, but has more than four columns of interambulacral plates in each zone. The type species of Archaeocidaris has long hollow spines with scattered thorns along the shaft, as does the very closely related A. whatleyensis illustrated here. A number of other species assigned to this genus have either smooth or granular spines and should probably be treated as distinct genera or subgenera.

See Lewis & Ensom (1982) and Schneider et al. (2005) for descriptioons of well preserved material and comments on palaeoecology.

Jackson, R. T. 1896 Studies of Palaeechinoidea. Bulletins of the Geological Society of America 7, 171-254, pls 2-9.

Jackson, R. T. 1912. Phylogeny of the Echini, with a revision of Paleozoic species. Memoirs of the Boston Natural History Society 7, 443 pp, 76 pls.

Kier, P. M. 1958. New American Paleozoic echinoids. Smithsonian Miscellaneous Collections 135(9), 26 pp, 8 pls.

Lewis, D. N. & Ensom, P. 1982. Archaeocidaris whatleyensis sp. nov. (Echinoidea) from the Carboniferous Limestone of Somerset, and notes on echinoid phylogeny. Bulletin of the British Museum (Natural History), Geology 36, 77-104.

McCoy. F. 1844. A synopsis of the characters of the Carboniferous limestone fossils of Ireland. University Press, Dublin.

Schneider, C. L., Sprinkle, J. & Ryder, D. 2005. Pennsylvanian (Late Carboniferous) echinoids from the Winchell Formation, North-central Texas, USA. Journal of Paleontology 79, 745-762.