The Echinoid Directory

Plegiocidaris Pomel, 1883, p. 109

[= Aulacocidaris Lambert, in Savin, 1903, p. 168, type species Cidaris lamberti Savin, 1903; =Abelleicidaris Vadet, 1991, p. 109, type species Cidaris bradfordensis Wright, 1856
]

Diagnostic Features	Test relatively thick; depressed. Apical disc about 50% of test diameter; plating dicyclic; plates uniformly covered in dense granules. Genital plates all similar in size. Periproctal area rather small. Interambulacral zones with 5 or 6 plates in a series. Primary tubercles perforate and crenulate; areoles circular and incised; mamelons becoming proportionally larger adapically. Areoles separated, widely so on ambital and adapical plates. Ambital and adapical interambulacral plates taller than wide; one adapical plate in each zone with a rudimentary tubercle only. Scrobicular tubercles differentiated. Extrascrobicular zones well developed and covered in dense, uniform, secondary tubercles. No sutural pits or furrows. Ambulacra sinuous; pore zones deeply incised. Pore pairs non-conjugate to subconjugate, the two pores separated by a node. Perradial suture depressed but not naked. Marginal series of contiguous primary tubercles and one or two inner series of smaller tubercles. Ambulacral tuberculation uniform throughout. Peristome significantly smaller than apical disc; ambulacral plating biserial in each column. Interradial plate series reaches mouth. Primary spines clavate, with long neck and slightly asymmetrical shaft; distally rounded. Shaft ornamented with dense beaded ribs.
Distribution	Middle Jurassic (Bajocian) to Lower Cretaceous (Aptian); Europe.
Name gender	feminine
Type	Echinus coronatus Schlotheim, 1820, p. 313, by subsequent designation of Savin, 1903, p. 154.
Species Included	P. crucifera (Agassiz, 1840); Oxfordian-Kimmeridgian, Europe. P. marginata (Goldfuss, 1826); Kimmeridgian, Europe. P. coronata (Schlotheim, 1820); Oxfordian-Kimmeridgian, Europe [includes P. monilifera (Goldfuss 1826) as a subspecific variety]. P. punctata (Roemer, 1836); Hauterivian, western Europe. P. salviensis (Cotteau, 1862); Neocomian, France. P. farringdonensis (Wright, 1868); Aptian, UK, France. P. bradfordensis (Wright, 1856); Bajocian-Bathonian, Europe. P. saemanni (Cotteau, 1857), Bathonian, France. P. michaleti (de Loriol, 1905); Hauterivian, France.
Classification and/or Status	Cidaroida; Cidaridae stem group. Probably monophyletic.
Remarks	Vadet (1988) synonymized Goldfuss's P. coronatus and P. monilifera and treated Schlotheim's original designation as a nomen nudum. A modern description of P. crucifera (Agassiz, 1840) is given by Radwanska (1999). The spine morphology and consistently crenulate tuberculation immediately distinguishes this from other cidarids. It is closest to Balanocidaris but differs from that taxon in having a proportionally smaller mamelon and smaller scrobicular tubercles, and subconjugate rather than non-conjugate pore-pairs. Pomel, A. 1883. Classification méthodique et Genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris 503, A. Jourdan, Alger, 131 pp. Vadet, A. 1988. Revision des "Cidaris" d'Oxfordien et du Kimmeridgien Europeens. Memoires de la Societe academique du Boulonnais 4, 1-148, pls 1-25. Radwanska, U. 1999. Lower Kimmeridgian echinoids of Poland, Acta Geologica Polonica 49, 287-364.