The Echinoid Directory

Stenechinus Arnold & Clark, 1927, p. 13

Diagnostic Features
  • Test moderately inflated and weakly pentagonal in outline. Plating relatively thin.
  • Apical disc opening small, dicyclic. Periproct large and circular; genital plates all similar in size and rather broad.
  • Ambulacra almost straight, broad, trigeminate throughout; plate compounding with lowest element dominant and upper element reduced to a demi-plate. Each with a large adradially positioned primary tubercle.
  • Pore-pairs wide but non-conjugate and uniserial throughout; closely spaced.
  • Interambulacral zones about 3 times as wide as ambulacral zones.
  • Interambulacral plates with a subcentral primary tubercle and scattered secondary tubercles on either side. The plates are otherwise rather sparsely granular.
  • Interambulacral tubercles perforate and crenulate throughout.
  • Buccal notches well developed.
  • Spines, lantern and perignathic girdle unknown.
Distribution
Eocene (Yellow Limestone Group, mid-early to early mid Eocene), Jamaica.
Name gender masculine
Type
Stenechinus regularis Arnold & Clark, 1927, by original designation.
Species Included
  • S. regularis Arnold & Clark, 1927; Eocene, Jamaica
  • S. perplexus Arnold & Clark, 1927; Eocene, Jamaica
Classification and/or Status

Euechinoidea, Camarodonta, Temnopleuridea, Glyphocyphidae

Subjective junior synonym of Echinopsis Agassiz, 1840

Remarks

Arnold & Clark 1927 originally assigned this taxon to the Pedinoida on account of its having perforate and non-crenulate tubercles. However, as pointed out by Donovan (1993, p. 379) none of the type series is well enough preserved to determine whether tubercles are perforate or not. The specimen illustrated here clearly has crenulate tuberculation where not abraded. Ambulacral plate compounding is also quite distinct from that seen in any Diadematoida in that the lowest of the three elements making up the compound plate is the largest, and thus is identical to that seen in Echinopsis. The only difference between these two type species is that the apical disc in Echinopsis is hemicyclic and in Stenechinus is dicyclic.

Donovan, S. K. 1993. Jamaican Cenozoic Echinoidea. in Wright, R. M. & Robinson, E. (eds). Biostratigraphy of Jamaica Geological Society of America Memoir 182.