The Echinoid Directory

Tripylus Philippi, 1845, p. 344

[=Hamaxitus Troschel, 1851, p. 72 (objective); =Pseudolinthia Markov, 1994, p. 80, type species Pseudolinthia triporata Markov, 1994 ]

Diagnostic Features	Test ovate with shallow but distinct anterior sulcus; posterior face truncate. Apical disc ethmolytic with three gonopores; central. Anterior ambulacrum slightly sunken; pore-pairs uniserial and tube-feet not strongly developed. Petals of subequal length; parallel-sided and sunken; deeply so in the females. Peristome kidney-shaped, facing forward into frontal groove. Labrum projecting to cover peristome in oral view. Labral plate short, not extending beyond first ambulacral plate. Sternal plates symmetrical; episternal plates offset. Periproct on posterior truncate face. Subanal tube-feet scarcely penicillate. Peripetalous fasciole indented behind anterior petals; passing two or three plates below the ends of the petals. Latero-anal part of marginal fasciole present; in interambulacrum 1b and 4a crossing plate 4.
Distribution	Palaeocene, Kazakhstan; Recent, Antarctic and subantarctic.
Name gender	masculine
Type	Tripylus excavatus Philippi, 1845, p. 344; by original designation.
Species Included	T. excavatus Philippi, 1845; Recent, Magellan Strait. T. triporata (Markov, 1994); Palaeocene, Kazakhstan.
Classification and/or Status	Spatangoida, Paleopneustina, Prenasteridae. Monophyletic.
Remarks	Differs from Abatus in having a fully developed latero-anal fasciole, and from Amphipneustes in having both a peripetalous and latero-anal fasciole. Tripylaster has a deeper frontal groove and shorter posterior petals. Although Mortensen (1951) considered Parapneustes to be synonymous, the labrum in the type species, Parapneustes cordatus Koehler, extends to the third or fourth ambulacral plate and is much more massive than the labrum of Tripylus. Mortensen, T. 1951. A monograph of the Echinoidea V. Spatangoida 2. C. A. Reitzel, Copenhagen. Philippi 1845. Arch. Naturges. 11(1), p. 344, 347.