The Echinoid Directory

Contributed by Andrew Smith, September 2006

Parorthopsis Smith & Rader, 2009, p. 16

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Diagnostic Features	Tests up to 18 mm diameter circular in outline depressed in profile (height ca. 50% of diameter) with ambitus a little below mid-height; low domal in profile. Apical disc small, dicyclic with plates firmly bound to corona. Genital plates with small tubercles; periproct subovate with smooth outer edge. Forming about half of the apical disc diameter. Ambulacra straight, less than half the interambulacral width. Plating simple, compounding acrosaleniid-style with a primary tubercle overlapping two elements and alternating with a third simple element. All three elements similar in size and with a zig-zag perradial suture. Lowest 6 pores crowded and offset to form a short phyllode; otherwise pore zones uniserial and undifferentiated. Interambulacral plates wide and slightly geniculate at the ambitus. Primary tubercles perforate and non-crenulate. Ambital and subambital plates with large flanking tubercles slightly above the level of the central primary tubercle. Primary tubercles coarser on oral surface than aborally and with slightly incised areoles. Above the ambitus only small secondary tubercles and granulation. Aboral tubercles are imperforate and non-crenulate whereas adoral tubercles are perforate and non-crenulate. The plate surface in between the tuberculation is finely granular with epistroma. Peristome large, somewhat sunken; buccal notches distinct, sharp but shallow, with weak rim.
Distribution	Glen Rose Formation, Lower Albian, Lower Cretaceous, Comal County Texas, USA.
Type	Orthopsis comalensis Whitney & Kellum, 1966, p. 250
Species Included	May also include Orthopsis repellini (Gras, 1848)
Classification and/or Status	Acroechinoidea, Carinacea, Orthopsidae
Remarks	Very like O. granularis (Agassiz) and O. miliaris d'Archaic but with aboral tubercles imperforate in both ambulacral and interambulacral zones. Whitney, M. I. & Kellum, L. B. 1966. Echinoids of the Glen Rose Limestone of Texas. Papers of the Michigan Academy of Science, Arts and Letters 51, 241-263, pls 1-2. Smith, A. B. & Rader, W. L. 2009 Echinoid diversity, preservation potential and sequence stratigraphical cycles in the Glen Rose Formation (early Albian, Early Cretaceous), Texas, USA. Palaeobiodiversity and Palaeoenvironments 89, 7-52.