The Echinoid Directory

Echinodiscus Leske, 1778, p. 195

[(=Echinoglycus Leske, 1778, p. 197 (nomen nudum); =Lobophora L. Agassiz, 1841, p. 64, non Curtis, 1825; =Tretodiscus Pomel, 1883, p. 71 (objective); =Tetrodiscus Lambert & Thiey, 1921, p. 323 (nomen vanum)]

Diagnostic Features	Test indented laterally; margin thin and sharp Apical disc central;4 gonopores Internal buttressing developed as dense honeycombed meshwork Petals well developed; posterior pair shorter than the rest Interambulacral and ambulacral zones similar in width at ambitus Posterior ambulacra with long slit-like lunules or notches All interambulacrum disjunct or virtually disjunct on oral surface; separated by enlarged first pair of post-basicoronal ambulacral plates Basicoronal circlet pentastellate with interambulacral plates strongly projecting Periproct oral, close to the posterior margin. Opening at outer edge of first pair of post-basicoronal interambulacral plates Food grooves bifurcating at edge of basicoronals; highly branched distally Tube-feet extending into interambulacral zones
Distribution	Oligo-Miocene to Recent of the Indo-Pacific
Name gender	masculine
Type	Echinodiscus bisperforatus Leske, 1778, by subsequent designation of ICZN 1950
Species Included	E. bisperforatus Leske, 1778; Recent, Indo-Pacific E. auritus Leske, 1778; Recent, Indo-Pacific E. tenuissimus (L. Agassiz, 1847); Recent, Indo-Pacific E. yeliuensis Wang, 1982; Early Miocene, Taiwan E. formosus Yoshiwara, 1901; Middle Eocene, Taiwan E. chikuzenensis Nagao, 1928; Oligo-Miocene, Japan E. transiens Nisiyama, 1968; Oligo-Miocene, Japan
Classification and/or Status	Clypeasteroida; Scutellina; Scutelliformes; Scutellidea; Astriclypeidae Presumed monophyletic
Remarks	One of the most instantly recognizable genera because of its distinctive posterior lunules. The recent species E. auritus has narrow slit-like notches in the two posterior ambulacra but is otherwise similar. Differs from Amphiope in having short posterior petals and slit-like lunules or notches. Mortensen, T. 1948. A Monograph of the Echinoidea IV.2 Clypeasteroida. C. A. Reitzel, Copenhagen. Nisiyama, S. 1968. The echinoid fauna from Japan and adjacent regions, Part II. Palaeontological Society of Japan, Special Paper 13, 1-491, pls 19-30. Wang, C.C. 1982. On the Early Miocene sand dollar Echinodiscus yeliuensis n. sp. from the Taliao Formation of Yeliu, northern Taiwan. Proceedings of the Geological Soceity of China 25, 150-157.