The Echinoid Directory

Holectypus Desor, 1842, p. 65

Diagnostic Features	Periproct large and tear-drop-shaped; separated from peristome by no more than two interambulacral plates. Fifth genital plate imperforate. Aboral plating smooth and unornamented by pits.
Distribution	Jurassic (Pliensbachian to Kimmeridgian) ?Early Cretaceous; worldwide.
Name gender	masculine
Type	Discoidea depressa Agassiz, 1839, p. 88 [=Echinites depressus Leske, 1778, p. 164], by original designation.
Species Included	H. depressus (Leske, 1778); Jurassic, Aalenian-Oxfordian, Europe. H. pictaviense Nicolleau & Vadet, 1996; Oxfordian, France. H. corallinus d'Orbigny plus many other nominal Jurassic species.
Classification and/or Status	Holectypoida, Paraphyletic, by the exclusion of Coenholectypus and Coptodiscus.
Remarks	The vast majority of species of Holectypidae belong to this genus, including all those from the Jurassic. There are 62 nominal species, but many should probably be synonimized. This taxon is distinguished from Philolectypus by the position of its periproct. In Holectypus the periproct is separated from the peristome by just one or two interambulacral plates, whereas in Philolectypus it is separated by between four and six plates in each column. Holectypus boschmai Engel 1964 from the Maastrichtian of Limburg, the Netherlands is 20 mm in diameter with 4 gonopores However, it is based on a single specimen found in museum collections and its provenance is almost certainly wrong. Desor, E. 1842. Des Galérites: Monographies d’Echinodermes vivans et fossiles, par Louis Agassiz, Monograph 3, iv + 94 pp., 13 pls. Petitpierre, Neuchâtel. Barras, C. G. 2006. British Jurassic irregular echinoids. Monograph of the Palaeontographical Society no. 625 (part of volume 159 for 2005), 1-168, pls 1-14. Engel. 1964. Zool. Mededel. 39, p. 236, pl. 1, figs 1-2.