The Echinoid Directory

Paleotrema Koehler, 1914, p. 45

[=Palaeotrema Mortensen, 1950, p. 299 (incorrect emendment)]

Diagnostic Features	Test elongate and ovate with convex anterior border; posterior face obliquely truncate. Test wedge-shaped in lateral profile with posterior part of plastron forming keel. Apical disc monobasal with genital plates fused; three gonopores (no gonopore in genital plate 3); closer to anterior than centre. Hydropores extend between posterior gonopores. Ambulacra all similar; flush and apetaloid; composed of narrow plates that are taller than wide. Pores miniscule and rudimentary. Ambulacral plating biserial to apex. Peristome D-shaped and facing downwards. Labral plate longitudinally elongate, extending to rear part of ambulacral plate 1 only. Sternal plates bowed and symmetrical. Episternal plates strongly tapered to posterior and indented by ambulacral plate 6. Periproct on posterior truncate face; supramarginal. Subanal fasciole well developed; rounded. Row of larger spines and tubercles bordering the frontal ambulacrum. Remainder of aboral surface has small scattered tubercles set in a groundmass of granules.
Distribution	Recent, Indo-West Pacific, 175-685 m.
Name gender	neuter
Type	Palaeotropus loveni A. Agassiz, 1881, p. 204, by original designation.
Species Included	P. loveni (Agassiz, 1879); Recent, Malay archipelago. P. ovatum (Koehler, 1914); Recent, Indian Ocean.
Classification and/or Status	Spatangoida, Micrasterina, Palaeotropidae. ?Paraphyletic (by exclusion of Palaeotropus).
Remarks	Differs from Palaeotropus by having ambulacral plating biserial all the way to the apex (not uniserial), and in having three, not two gonopores. Distinguished from Palaeobrissus by having rudimentary pores only in the paired ambulacra aborally, and in having a distinct row of primary tubercles bordering the frontal ambulacrum. Mortensen, T. 1950. A monograph of the Echinoidea. V. Spatangoida 1. C. A. Reitzel, Copenhagen.