The Echinoid Directory

Contributed by Andrew Smith, September 2006

Trochodiadema de Loriol, 1900, p. 70

Diagnostic Features	Test depressed and weakly pentagonal in outline. Apical disc about one-third test diameter; subpentagonal and not obviously projecting posteriorly; plating not firmly bound to corona and lost in all known specimens. Ambulacra straight, trigeminate throughout with all three elements reaching the perradius. Pore-pairs uniserial, undifferentiated. Aboral plates with a small primary tubercle close to the pore-pairs and bounding two elements in each triad. A wide perradial band of fine uniform granulation is present from slightly above the ambitus. Adorally, tubercles much larger and the perradial zone of granules greatly reduced. Interambulacral plates a little wider than long. Each with a single primary tubercle. On adapical plates the primary tubercle is relatively small and adradial in position, but ambital and adoral tubercles are much larger and there may be flanking secondary primary tubercles on adradial and interradial sides of the primary. The remainder of the plate is covered in dense and uniform granulation. Primary tubercles perforate and crenulate. Peristome large; ca. 45% test diameter; weakly sunken; buccal notches deep and sharp and with associated smooth tags along the adradial margins of interambulacral plates. Perignathic girdle of auricles. Spines and lantern unknown.
Distribution	Lower and Upper Cretaceous (Aptian - Maastrichtian); southern Europe, North Africa and the Middle East.
Name gender	neuter
Type	Trochodiadema abramense de Loriol, 1900, p. 70, by original designation
Species Included	T. abramense de Loriol, 1900; Upper Cenomanian, Portugal. T. libanoticum (de Loriol, 1887); Aptian, Egypt. T. isidis Fourtau1921; Aptian, Egypt. T. buhayesi (Smith, 1995); Maastrichtian, Arabian Peninsula.
Classification and/or Status	Euechinoidea, Acroechinoidea, Diadematoida, Heterodiadematidae
Remarks	Very close to Heterodiadema differing from that genus only in lacking the prolonged extension of the periproct into the posterior interambulacrum. de Loriol, P. 1900. Notes pour servir a l'etude des Echinodermes. Revue Suisse de Zoologie 8, 55-96, pls 6-9.