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The Echinoid Directory

Hemipedina Wright, 1855, p. 95

[=Leiodiadema Quenstedt, 1873, p. 350 (objective); = Psilosalenia Quenstedt, 1873, p. 256, type species Psilosalenia germanica Quenstedt, 1873; ?=Archaeodiadema Gregory, 1896, type species A. thompsoni Gregory, 1896; =Phalacropedina Lambert, 1900, type species Hemipedina guerangeri Cotteau, 1858 ]

Diagnostic Features
  • Test usually rather small and depressed with rounded ambitus.
  • Apical disc large; firmly bound to corona; dicyclic with large genital plates and small oval periproct. Plates covered in small scattered granules.
  • Ambulacra straight; with uniserial pore-pairs; plating trigeminate. Plate compounding in acrosaleniid style, with two elements united by a primary tubercle alternating with a single simple plate. All elements reach the perradius.
  • Interambulacral plates only slightly wider than tall, dominated by a single large primary tubercle; tubercle perforate and non-crenulate; areoles small.
  • Tubercles vertically separated by bands of granules even on ambital plates. Remainder of interambulacral plate covered in rather uniform granulation.
  • Peristome relatively large with shallow, open buccal notches.
  • Primary spines long and slender, without cortex and non-verticillate.
  • Perignathic girdle weak - no apophyses, but small ambulacral swellings may be present.
Distribution
Lower Jurassic (Pliensbachian) to ?Late Cretaceous; Europe, North Africa.
Name gender feminine
Type
Pedina etheridgei Wright, 1854, by subsequent designation of Lambert, 1900, p. 6.
Species Included Many fossil species assigned which need revision, including:
Classification and/or Status

Pedinoida, Pedinidae.

Presumably paraphyletic, by exclusion of Caenopedina and probably other genera.
Remarks

Differs from Pseudopedina in having a primary tubercle to each compound triad. Differs from Phymopedina and Diademopsis in having just a single primary tubercle on each interambulacral plate. Differs from Caenopedina in having small and widely separated primary tubercles on interambulacral plates.

Lambert, J. 1900. Étude sur quelques Échinides de l'Infra-Lias et du Lias. Bulletin de la Société des Sciences historiques et naturelles de l'Yonne, 53 (2), 3-57 (for 1899).

Mortensen, T. 1940. A monograph of the Echinoidea. Volume III.1, Aulodonta. C.A. Reitzel, Copenhagen.

Wright, T. 1855. On a new genus of fossil Cidaridae, with a synopsis of the species included therein. Annals and Magazine of Natural History, series 2 16, 94-101.