The Echinoid Directory

Megapneustes Gauthier, in Fourtau 1899, p. 678

[=Fourtaunia Lambert, 1902, p. 53, type species Hypsospatangus santamariae Gauthier in Fourtau, 1900;=Thebaster Checchia-Rispoli, 1941, p. 6, type species Macropneustes fischeri de Loriol, 1880 ]

Diagnostic Features	Test ovate with shallow but distinct anterior sulcus; posterior face truncate. Test depressed in profile with flat base. Apical disc anterior of centre; ethmolytic, tetrabasal with madreporic plate projecting only a short distance beyond the posterior ocular plates. Anterior ambulacrum narrow, composed of tall plates; weakly sunken adapically and continuing to peristome as a sulcus. Adapical pore-pairs small but distinctly larger than supraambital pore-pairs. Paired ambulacra petaloid; weakly depressed. The pore-pairs large and conjugate. Pore columns parallel with relatively narrow perradial zone; extending almost to ambitus and distally open. No occluded plates at petal ends. Peristome anterior; damaged. Plastron plating not known. Sternal plates and episternal plates paired; not indented by adjacent ambulacral zones. Periproct on posterior truncate face; large. Four enlarged subanal pore-pairs on each side. Very thin peripetalous fasciole present; not indented in lateral interambulacra; traces of subanal bilobed fasciole seen (mostly lost through poor preservation in holotype). Aboral tuberculation heterogeneous, with row of larger tubercles on aboral plates inside petals - these plates V-shaped.
Distribution	Eocene, North Africa.
Name gender	feminine
Type	Megapneustes grandis Gauthier, 1899, p. 681, by original designation. Holotype: Museum National d\'Histoire Naturelle, Paris, J01701.
Species Included	M. grandis Gauthier, 1899; Eocene, Egypt. M. baylei (Coquand, 1862); Eocene or Oligocene of Algeria. M. santamariae (Gauthier, 1900); Lower Eocene, Egypt.
Classification and/or Status	Spatangoida, Micrasterina, Macropneustidae. ?
Remarks	Differs from Macropneustes in having aligned primary aboral interambulacral tubercles. Originally distinguished because of its supposed lack of subanal fasciole. Yet the type specimen shows traces of a subanal fasciole on plate 4 beneath the periproct. Fourtau (1904, p. 609) also stated that although the first specimen showed no trace of a subanal fasciole, other specimens do and that it is definitely present. Fourtaunia seems not to differ in any significant way. Gauthier, in Fourtau, R. 1899. Revision des echinides fossiles de l\'Egypte. Memoires de l\'Institut egyptien, fasc. 8, serie 3, p. 678-681, pl. 2, figs 5, 6. Fourtau, R. 1905. Sur quelques "spatangidae" de l\'Eocene d\'Egypte. Comptes Rendu des Association francaise pour l\'avancement des Sciences. 33 session, Grenoble, 1904, 602-613.