The Echinoid Directory

Contributed by Andreas Kroh, July 2016

Placentinechinus Borghi & Garilli, 2016

Diagnostic Features	Test small, wheel-shaped; profile very low (flattened above and below). Apical disc much larger than the peristome, 75% of test diameter (max. 82% in ); of unknown structure. Ambulacral plating trigeminate, compouning in echinoid style. Pore-pairs arranged in slight arcs of three. One primary tubercle to each compound plate. Interambulacral plates with single central primary tubercle. Flanking secondary tubercles (at ambitus) not enlarged (< half the diameter of primary tubercle). Primary tubercles imperforate and crenulate. Sutural pits at triple junctions; angular and deep, with steep edges; lacking adapically. Low horizontal ridges at the adapical edge of both ambulacral and interambulacral plates. Peristome small (40% of test diameter), with barely visible buccal notches. Girdle composed of low interambulacral ridges and short ambulacral auricles that do not meet perradially. Lantern likely camarodont (incompletely known - only demipyramids and teeth are preserved). Spines short, simple, without cortex, crenulated base. Pedicellariae unknown. No evidence for sexual dimorphism.
Distribution	Early Pleistocene, Gelasian (not older than 2.4 Ma) to Calabrian; Italy.
Type	Placentinechinus davolii Borghi & Garilli, 2016, by original designation.
Species Included	Only the type
Classification and/or Status	Euechinoidea; Camarodonta; Temnopleuroida; Temnopleuridae.
Remarks	Differing from the similarly shaped Monilechinus by its distinctly crenulate tubercles, well developed sutural pits and absence of subequal flanking tubercles ambitally. None of the other temnopleurids or trigonocidarids has a similarly large apical disc in adults. Borghi, E. & Garilli, V. 2016. A new subtropical-temperate brooding echinoid with no marsupium: the first Mediterranean and the last European Temnopleuridae from the Early Pleistocene of Italy. Journal of Systematic Palaeontology. http://dx.doi.org/10.1080/14772019.2016.1184191