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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.

Hemipedina bonei Wright, 1856, from the Aalenian (Middle Jurassic) of Cheltenham, England, is a juvenile Plesiechinus ornatus (Buckman, 1845)

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