- Like Echinus, but with primary tubercle on every compound ambulacral plate.
- Apical disc dicyclic.
- Ambulacral plating trigeminate, with pore-pairs in oblique arcs of three forming a band often at some distance from the adradial suture.
- Pore-zones forming relatively narrow uniformly wide bands from apex to peristome.
- Interambulacral plates with small central primary tubercle but differentiated from secondaries and tending to form horizontal rows; granulation relatively well developed over remainder of plate.
- Globiferous pedicellariae with tubular blade and paired lateral teeth.
Late Miocene to Recent; Mediterranean, Atlantic and Indo-Pacific.
Echinus gracilis Agassiz, 1869, p. 261, by original designation.
- G. gracilis (Agassiz, 1869); Upper Miocene to Recent, Atlantic.
- G. acutus (Lamarck, 1816); Recent; Atlantic.
- G. alexandri (Danielssen & Koren, 1883); Recent, N. Atlantic.
- G. atlanticus (Mortensen, 1903); Recent, Atlantic.
- G. elegans (Duben & Koren, 1844); Recent, N Atlantic.
- G. lucidus (Doderlein, 1885); Recent, Japan.
- G. stenoporus (Mortensen, 1942); Recent, S. Africa.
- G. affinis (Mortensen, 1903); Recent, N. Atlantic.
|Classification and/or Status
Camarodonta; Echinoida; Echinidae.
Probably paraphyletic by exclusion of Stirechinus and Echinus
Living species are differentiated on details of pedicellarial structure, colouration and spination and thus not applicable to fossil forms. Echinus differs in having primary tubercles on only every second or third compound plate. As this is a derived feature Echinus presumably evolved from a Gracilechinus antecedent, making the genus paraphyletic. Geys (1989) gives a thorough discussion of the fossil record of this genus.
Geys, J. 1989. On the presence of Gracilechinus (Echinoidea, Echinidae) in the late Miocene of the Antwerp area (Belgium). Meded. Werkgr. Tert. Kwart. Geol. 26, 3-10.
Mortensen, T. 1943. A monograph of the Echinoidea Part III, 3. Camarodonta II. C. A. Retzel, Copenhagen.