The Echinoid Directory

Pseudholaster Pomel, 1883, p. 45

[=Labrotaxis Casey, 1960, p. 260, type species Labrotaxis cantianus Casey, 1960 ]

Diagnostic Features	Test cordate with deep anterior sulcus with sharp carina. Lower surface flat but with keeled plastron. Apical disc subcentral with four gonopores. Paired ambulacra petaloid with elongate and conjugate pore-pairs Columns of pore-pairs of unequal size, the posterior column being 1.5 to 2 times as wide as the anterior column. Frontal groove present from apex to peristome. Peristome oval, typically facing slightly anterior. Plastron plating protosternous: labral plate with horn that extends to meet second sternal plate. Enlarged primary tubercles line the margin of the anterior sulcus and are also developed adapically and along the posterior interambulacral ridge aborally. No fascioles.
Distribution	Cretaceous (Valanginian to Campanian) to Palaeocene, widespread.
Name gender	masculine
Type	Holaster bicarinatus Agassiz, in Agassiz & Desor 1847, p. 29 , by subsequent designation of Lambert, 1917, p. 20.
Species Included	P. bicarinatus (Agassiz, 1847); Albian, Cenomanian of France and UK. P. cantianus (Casey, 1960); Albian, UK. P. depressus Smith & Wright, 2003; Upper Albian, UK. P. blackdownensis Smith & Wright, 2003; Albian, UK. P. latissimus (Agassiz, in Agassiz & Desor, 1847); Albian, western Europe. P. suborbicularis (Brongniart, 1822); Albian-Cenomanian, western Europe. P. cenomanensis (d'Orbigny, 1855); Cenomanian, western Europe. P. prestensis Desor, in Jaccard, 1869; Aptian, Europe. P. benstedi (Forbes, 1852); Aptian, UK. P. caseyi Smith & Wright, 2003; Aptian, UK. P. sequanicus (Bucaille, 1883); Albian-Cenomanian, western Europe. P. declivus (Lambert, 1881); Albian, UK. P. boulei (Lambert, 1896); Campanian, Madagascar. P. tenuiporus (Cotteau); Santonian, France. P. faxensis (Hennig, 1898); Palaeocene, Denmark.
Classification and/or Status	Holasteroida, Cardiasterina stem group. Paraphyletic by exclusion of Cardiaster and the cardiasterids.
Remarks	A currently undivided grade group that contains early members of the holasteroid that retain the primitive protosternous plastron plating. Cardiaster has a rather similar appearance, but has a marginal fasciole and labrum in contact with just one sternal plate. Giraliaster is also very similar in appearance, differing in having a submarginal fasciole. Differs from Protocardiaster only in lacking a marginal fasciole. Pomel, A. 1883. Classification méthodique et Genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles 503, Aldolphe Jourdan, Alger, 131 pp. Smith, A. B. & Wright, C. W. 2003. British Cretaceous echinoids. Part 7, Atelostomata, 1. Holasteroida. Palaeontographical Society Monographs, London. Pp. 440-568, pls 139-182.