Phymosoma baylei (Cotteau, 1864)

Mohamed Abdelhamid, Marouf Abdel-Aty & Moustafa Azab, Mahmoud, 2012, Turonian-Santonian echinoids from Egypt, Geodiversitas 34 (3), pp. 575-615 : 584-586

Phymosoma baylei (Cotteau, 1864) ( Figs 5I; 6G ; 7A, B )

Cyphosoma baylei Cotteau, 1864: 584 , pl. 1138, figs8-13; pl. 1139, figs 1-6.

Phymosoma baylei – Abdelhamid & El Qot 2001: 13, fig. 4L.

MATERIAL EXAMINED. — Two specimens: one from the Turonian (Wata Formation) of Wadi Dakhl, ASUDLE1, Wadi Dakhl echinoid horizon 1 ( DEH 1) and one from Wadi Abu Qaada, ASUAQE3, Wadi Abu Qaada echinoid horizon 1 ( QEH 1).

DESCRIPTION

Test diameter attaining 24.5-30.0 mm. Adoral surface flattened. Adapical surface convex (H/D= 0.39-0.43). Poriferous zones biserial and wide adapically. Major ambulacral plates trigeminate near peristome, polygeminate with five pore pairs arranged in arc at the ambitus ( Fig. 7A ), whereas near apical disc, each major ambulacral plate carries six pore pairs ( Fig. 6G ). Adradial extrascrobicular surface relatively wide and occupied by secondary tubercles and frequent granules ( Fig. 7B ).

REMARKS

The present species ( Fig.6G ) is distinguished from P. abbatei in having conspicuous and wide biserial poriferous zones in adapical surface, larger ambulacral tubercles in adapical surface, and more ambulacral and interambulacral tubercles per one column (Na = 12 vs 7-10; Ni = 11 vs 7-10). Devriès (1960) indicated that the poriferous zone of P. baylei is uniserial in specimens less than 15 mm diameter and that the biserial arrangement increases with the size of the individuals.

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.

FIG. 7. — Camera lucida drawings: A, B, plating, tuberculation and poring in Phymosoma baylei (Cotteau, 1864) from the Turonian of Wadi Abu Qaada; A, ambital ambulacral plates; B, ambital interambulacral plate; C, D, plating, tuberculation and poring in Phymosoma beadnelli (Gregory, 1906) from the Coniacian-Santonian of Abu Roash; C, adapical ambulacral plates; D, ambital interambulacral plates; E, F, plating, tuberculation and poring in Phymosoma thevestense (Péron & Gauthier, 1879) from the Coniacian-Santonian of Abu Roash; E, ambital interambulacral plates; F, subambital ambulacral plates; G, plating and tuberculation of ambital interambulacral plates in Rachiosoma irregulare Fourtau, 1921 from the Turonian of Wadi Abu Qaada. Scale bars: A, 0.8 mm; B, 0.9 mm; C, D, 1 mm; E, F, 0.5 mm; G, 0.7 mm.