The Echinoid Directory

Contributed by Andrew Smith, August 2011

Progonechinus Duncan & Sladen, 1882, p. 43

Diagnostic Features	Test small, subconical in profile. Apical system unknown. Ambulacral plating trigeminate; pore-pairs uniserially arranged. Plate compounding arbaciid, with lower element occluded from the perradial suture and middle element the largest. Compound plates with a primary tubercle and, at the ambitus an inner secondary tubercle. No adoral phyllodes. Interambulacral plates wide with single row of tubercles; the primary tubercle a little larger than the flanking tubercles. ?Basicoronal plate present. Tubercles imperforate and non-crenulate. Peristome rather large and with well developed buccal notches and short tags.
Distribution	Late Paleocene, early Eocene of Pakistan.
Type	Progonechinus eocenicus Duncan & Sladen, 1882, p. 43 by monotypy.
Species Included	Only the type species
Classification and/or Status	Echinacea, Arbacioida, ?Arbaciidae Monotypic.
Remarks	Currently very poorly known. The style of ambulacral plate compounding suggests affinties with Arbaciidae rather than Echinoida or Temnopleuroida. Duncan, P.M. & Sladen, W. P. 1882. The fossil Echinoidea from the Ranikot Series of Nummulitic strata in western Sind. Memoirs of the Geological Survey of India Palaeontologia Indica Series 14, 1(3), fascilculus 2., 21-100, pls 5-20.