The Echinoid Directory

• Test medium to large size, circular in outline and low to subconical in profile.
• Apical disc tetrabasal, forming anterior border to periproct.
• Ambulacra weakly subpetaloid aborally, pore-pairs adapically only weakly differentiated from ambital pore-pairs; narrow, parallel, the posterior ambulacra slightly convex.
• All ambulacral pores double.
• Periproct close to apex and surrounded by disc plates (i.e. the disc is endocyclic). The periproct opens into a deep and sharp anal sulcus that runs from the apex to the posterior margin.
• Peristome slightly anterior, small and circular with slight inward lip.
• Bourrelets hardly developed; a few tubercles on the inner-facing lip to the peristome.
• Phyllodes well developed; pores in arcs of three forming a broad, but not bowed zone.
• No buccal pores.
• Tubercles perforate, crenulate, not arranged in vertical series, slightly larger on adoral surface.

Lower to Middle Jurassic (Toarcian - Bajocian), western Europe.

Hyboclypus agariciformis Wright, 1852, p. 99 [=Pygaster sublaevis M'Coy, 1848, p. 413] by original designation.

• G. sublaevis (M'Coy, 1848); Toarcian - Bajocian, England and France. [Includes Galeropygus dumortieri Talbot Paris, 1908]
  
• G. constantini (Cotteau, 1871); Bajocian-Bathonian (Middle Jurassic) of France.
• G. parviphyllus Barras 2006; Jurassic, England.

Irregularia, stem group Neognathostomata.

Paraphyletic, by the exclusion of Clypeus and theNeognathostomata and the Atelostomata

The "Galeropygidae" traditionally also included Hyboclypus andAulacopygus. These genera, the "hyboclypids", are now recognised as early atelostomates. Galeropygus is distinguished from the "hyboclypids" in having a compact rather than a stretched apical disc. More noticeable differences are seen orally. Galeropygus has extensive phyllodes, whereas the "hyboclypid" phyllodes are short. The "hyboclypids" show a more pronounced bilateral symmetry than does Galeropygus, with a more anterior peristome. Galeropygus is distinguished from the cassiduloids primarily in lacking distinct petals, an apomorphy of the cassiduloids.

Mortensen (1948, p.109) considered Ressopygus a synonym of Galeropygus. Kier (1962, p. 25) points out that the type species of both genera are very similar, differing only in that petals I and V distally curve posteriorly in R. constantini, whereas in G. agariciformis they curve anteriorly. Kier (1962, p. 27) believed that such a minor difference in not sufficient to warrant generic distinction.

P. M. Kier 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections 144 (3), 262 pp.

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.