The Echinoid Directory

Lytechinus A. Agassiz, 1863, p. 24

[=Psilechinus Lutken, 1864, p. 94, objective; =Scoliechinus Arnold & Clark, 1927, p. 23, type species S. axiologus Arnold & Clark, 1927 ]

Diagnostic Features
  • Apical disc generally hemicyclic, with posterior oculars insert.
  • Ambulacral plating trigeminate, with pore-pairs in oblique lines of three; each compound plate with a primary ambulacral tubercle.
  • Interambulacra with small primary tubercle flanked by slightly smaller secondary tubercles on either side. May be multiple equal-sized tubercles on ambital plates.
  • Adapical interradial zone devoid of tubercles.
  • Peristomial membrane with dense plating.
  • Buccal notches sharp and pronounced.
Eocene (Scoliechinus), Oligocene to Recent, widely distributed.
Name gender masculine
Echinus variegatus Lamarck, 1816, by monotypy.
Species Included
  • L. variegatus (Lamarck, 1816); Pliocene - Recent, western Atlantic and Caribbean (includes L. variegatus variegatus & L. variegatus carolinus).
  • L. panamensis Mortensen, 1921; Recent, Gulf of Panama.
  • L. pictus (Verrill, 1867), Recent, west coast of North America (= L. anamesus H. L. Clark, 1912; see Zigler & Lessios, 2004).
  • L. semituberculatus (Agassiz & Desor, 1847); Recent, Galapagos and Clarion Islands.
  • L. callipeplus H. L. Clark, 1912; Recent, Barbados.
  • L. euerces H. L. Clark, 1912, Recent, Gulf of Mexico to Barbados.
  • L. williamsi Chesher, 1968; Recent, Panama.
  • L. crassus Clark, 1945; Pliocene, Fiji.
  • L. okinawa Cooke, 1954; Pliocene, Japan.
  • L. coreyi Grant & Hertlein, 1938; Lower Miocene, California, USA.
  • L. pictus ?; Upper Oligocene, Oregon.
Classification and/or Status

Camarodonta; Echinoida; Toxopneustidae.



Lytechinus differs from Cyrtechinus, Sphaerechinus and Schizechinus in having an aboral naked zone. It differs from Tripneustes in having a primary tubercle to each ambulacral plate and never has pore-pairs in vertical columns as in Tripneustes and Toxopneustes.

Agassiz, A. 1863. List of echinoderms sent to different institutions in exchange for other specimens. Bulletin of the Museum of Comparative Zoology, Harvard College, 1 (2), 17-28.

Mortensen, T. 1943. A monograph of the Echinoidea Part III. 2, Camarodonta 1. C. A. Reitzel, Copenhagen.

Chesher, R. H. 1968. Lytechinus williamsi, a new sea urchin from Panama. Breviora 305, 1-13.

Zigler, K. S. & Lessios, H. A. 2004. Speciation on the coasts of the New World: phylogeography and the evolution of bindin in the sea urchin genus Lytechinus. Evolution 58, 1225-1241