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The Echinoid Directory

Dendraster L. Agassiz, in Agassiz & Desor, 1847, p. 135

[=Orchoporus Lambert & Thiery, 1914, p. 293, type species Orchoporus koehleri (=Scutella perrini Weaver, 1908); =Merriamaster Lambert, 1911, p. 64, type species Scutella perrini Weaver, 1908; =Twitchellia Lambert & Thiery, 1916, p. 171, type species Astrodaspis merriami Clark & Twitchell, 1915 (=Orchoporus lamberti Grant & Hertlein, 1938) ]

Diagnostic Features
  • Test ovate in outline with flat base and low conical profile; margins relatively sharp.
  • Apical disc distinctly posterior of centre; 4 gonopores.
  • Internal radial partitions well developed as dense stellate patchwork with deep interradial channels.
  • Petals well developed; posterior petals distinctly shorter than anterior petals.
  • Interambulacral zones as wide as ambulacral zones at ambitus; tube-feet and food grooves extend over interambulacral zones.
  • All interambulacra disjunct on oral surface; separated by enlarged first pair of post-basicoronal ambulacral plates.
  • Periproct oral, close to posterior margin; opening between second pair of post-basicoronal interambulacral plates.
  • Food grooves present, bifurcating at end of basicoronals and branching extensively; extending onto the aboral surface around the posterior of the test but not reaching ambitus around anterior.
Distribution
Upper Miocene to Recent of western North America.
Name gender masculine
Type
Scutella excentricus Eschscholtz, 1831, p. 19, by monotypy.
Species Included
  • D. excentricus (Eschscholtz, 1831); Pliocene to Recent, Baja California to Alaska [includes D. jacolitoensis Kew, 1920].
  • D. vizcainoensis Grant & Hertlein, 1938; Plio-Pleistocene to Recent, California and Baja California.
  • D. terminalis (Grant & Hertlein, 1938); Recent, California to Mexico (Baja California).
  • D. gibbsii (Remond); Pliocene, California.
  • D. ashleyi (Arnold); Pliocene, California.
  • D. laevis H. L. Clark, 1948; Recent, California to Mexico.
  • D. perrini (Weaver, 1908); Pliocene, California, USA.
  • D. weaveri (Durham & Morgan 1978); Pliocene, California, USA.
  • D. granti Durham, 1950; Pliocene, California
  • D. pacificus Kew, 1920; Pliocene, California
  • Possibly others
Classification and/or Status

Clypeasteroida; Scutellina; Scutelliformes; Scutellidea;   Scutellidae.

Probably monophyetic.
Remarks

The only scutelline to have its apical disc posterior of centre and to have food grooves extending far onto the aboral surface. Dendraster is also the only echinoid known to adopt suspension feeding, by tilting its test out of the sediment obliquely (Timko 1976). It is distinguished from Scaphechinus and Remondella by its more posterior apical disc and short posterior petals and by its submarginal periproct. There seem to be no characters of consequence separating young Dendraster from forms currently placed in the genus Merriamaster and the two are synonymized here, as suggested by Mooi (1997, p. 368).

A detailed and thorough description of the extant species of Dendraster is given by Mooi (1997). A description of their rather unusual feeding mode is given by Timko (1976).

Agassiz, L. & Desor, P. J. E. 1846-1847. Catalogue raisonné des familles, des genres, et des espèces de la classe des échinodermes. Annales des Sciences Naturelles, Troisième Série, Zoologie: 6 (1846), 305-374, pls 15-16; 7 (1847), 129-168; 8 (1847), 5-35, 355-380.

Mooi, R. 1997. Sand dollars of the genus Dendraster (Echinoidea: Clypeasteroida): phylogenetic systematics, heterochrony, and distribution of extant species. Bulletin of Marine Sciences 61, 343-375.

Raup. D. M. 1956. Dendraster: a problem in echinoid taxonomy. Journal of Paleontology 30, 685-694.

Timlo, P. L. 1976. Sand dollars as suspension feeders: a new description of feeding in Dendraster excentricus. Biological Bulletin 151, 247-259.