Orthopsis miliaris (d’Archiac, 1835)

Mohamed Abdelhamid, Marouf Abdel-Aty & Moustafa Azab, Mahmoud, 2012, Turonian-Santonian echinoids from Egypt, Geodiversitas 34 (3), pp. 575-615 : 582

Orthopsis miliaris (d’Archiac, 1835) ( Figs 5E; 6A, B )

Cidarites miliaris d’Archiac, 1835: 179 , pl. 11, fig. 8.

Orthopsis miliaris – Smith & Bengtson 1991: 30, pl.8B-F, text-fig. 23. — Néraudeau et al. 1995: 410, fig. 3f, g. — Smith 1995: 136, pl. 2, figs 4, 5; pl. 3, figs 1-9, 12-14. — Abdelhamid & El Qot 2001: 18, fig. 5K. — El Qot 2010: 266, pl. I, figs 2a-c, 4.

MATERIAL EXAMINED. — Two specimens from the Coniacian-Santonian of Abu Roash (Ostrea and Plicatula unit), ASUARE8-9, Abu Roash echinoid horizon 4 ( REH 4).

DESCRIPTION

Test diameter reaching 14.0-15.0 mm. Adapical surface dome-shaped (H/D = 0.50-0.51). Adoral surface concaved around peristome. Ambulacral area nearly one have the width of interambulacrum (Wa/Wi = 0.49-0.52). Major ambulacral plates are composed of triads of equal-sized simple plates ( Fig. 6B ). Interambulacral area with two columns of primary tubercles, besides two external and two internal columns of secondary tubercles ( Fig. 6A ). Both ambulacral and interambulacral tubercles are perforate and non-crenulated. Peristome deeply sunken (Dp/D = 0.37).

Figures

FIG. 6. — Camera lucida drawings: A, B, plating, tuberculation and poring of ambital interambulacral plates (A) and ambital ambulacral plates (B) in Orthopsis miliaris (d’Archiac, 1835) from the Coniacian-Santonian of Abu Roash; C, D, plating, tuberculation and poring of ambital interambulacral plates (C) and ambital ambulacral plates (D) in Orthopsis ovata (Coquand, 1862) from the Turonian of Wadi Abu Qaada; E, F, plating, tuberculation and poring in Phymosoma abbatei (Gauthier, 1898) from the rudist unit of Abu Roash; E, adapical half ambulacrum; F, adoral half interambulacrum and half ambulacrum; G, plating, tuberculation and poring of adapical half ambulacrum in Phymosoma baylei (Cotteau, 1864) from the Turonian of Wadi Abu Qaada. Scale bars: A, 0.4 mm; B, 0.3 mm; C, D, 1 mm; E, F, 0.8 mm; G, 0.4 mm.