Petalobrissus djelfensis (Thomas & Gauthier, 1889 )

Mohamed Abdelhamid, Marouf Abdel-Aty & Moustafa Azab, Mahmoud, 2012, Turonian-Santonian echinoids from Egypt, Geodiversitas 34 (3), pp. 575-615 : 598

Petalobrissus djelfensis (Thomas & Gauthier, 1889) ( Figs 11I; 13 )

Echinobrissus djelfensis Thomas & Gauthier in Gauthier, 1889: 42, pl. 2, figs 30-32.

Petalobrissus djelfensis – Abdelhamid 1997: 148, fig.6 (2).

MATERIAL EXAMINED. — Six specimens from the Coniacian-Santonian of Abu Roash (Ostrea and Plicatula unit), ASUARE90-95, Abu Roash echinoid horizon 5 ( REH 5)

and seven specimens from the Coniacian-Santonian of Wadi Dakhl (Matulla Formation), ASUDLE15-21, Wadi Dakhl echinoid horizon 3 ( DEH 3).

MEASUREMENTS. — See Table 9.

DESCRIPTION

Test sub-rounded to oval. Maximum height lies at top of periproct. Adoral surface fairly concaved, depressed around peristome. Apical disc tetrabasal, anteriorly eccentric. Ambulacral areas petaloid. Anterior paired petals equal to or slightly shorter than the posterior paired petals, and slightly longer than the frontal petal. The two pores in each pore pair fused. All ambulacral plates beyond the petals are single-pored. Peristome pentagonal, feebly anteriorly eccentric, transverse. Bourrelets and phyllodes moderately developed. Periproct elongate, supramarginal.

REMARKS

The present species is distinguished from P. waltheri by its relatively larger test, more rounded outline (wider test), petal III are relatively shorter ( Fig.13 ), and by having less anteriorly eccentric peristome.

Figures

FIG. 13. — Comparison of Petalobrissus djelfensis (Thomas & Gauthier, 1889) from the Coniacian-Santonian of Abu Roash and Wadi Dakhl (filled quadrangles, dashed line) and Petalobrissus waltheri (Gauthier, 1900) from the Coniacian-Santonian of Abu Roash and Wadi Dakhl (empty quadrangles,solid line). The scatter plots show the relation between test length (L) and each of test width (W), test height (H), length of petal I or V (LI), number of pore pairs in petal I or V (NI), length of petal II or IV (LII), number of pore pairs in petal II or IV (NII), length of petal III (LIII), and number of pore pairs in petal III (NIII).