Clypeasteroida

Keyhole sand dollar Echinodiscus sp., copyright Ria Tan.

Belongs within: Atelostomata.
Contains: Arachnoididae, Clypeaster, Fibulariidae, Laganidae, Neolaganidae, Mellitidae, Scutellidae, Echinarachniidae, Dendrasteridae.

The Clypeasteroida, sand dollars and sea biscuits, are a group of flattened irregular echinoids that are found on or just beneath the sediment surface in sandy or muddy habitats. They can be divided between three suborders; in the Clypeasterina there are two enclosed sphaeridia in each ambulacrum near the peristome, and the Aristotle's lantern has small internal wings and paired supports on the ambulacral basicoronal plates, whereas in Laganina and Scutellina there is only a single enclosed sphaeridium in each ambulacrum, and the Aristotle's lantern has well-developed internal wings and single supports on the interambulacral basicoronal plates (Mooi 1989).

Characters (from Durham 1966): Test ovoid to flattened, with petaloid ambulacra as wide or wider than interambulacra on oral surface; genital plates fused; primary tube feet respiratory, restricted to petals; accessory tube feet numerous, extending outside petals, sometimes reaching into interambulacra; peristome small, no gill slits; lantern without compass, teeth without lateral flanges; test usually with internal supports; spines small, short, numerous, of two types; pedicellariae tridentate, ophicephalous, triphyllous, and globiferous.

<==Clypeasteroida
    |  i. s.: Runa Agassiz 1841 M89
    |           `--*R. comptoni Agassiz 1841 D66
    |         Tournoueraster Lambert 1914 M89
    |           `--*T. decemfissus (Desmoulins 1835) [=Scutella decemfissus] D66
    |--Clypeasterina M89
    |    |  i. s.: Willungaster Philip & Foster 1971 M89
    |    |           `--*W. scutellaris Philip & Foster 1971 M89
    |    |--Arachnoididae D66
    |    `--Clypeaster D66
    |--Laganina [Rotulina] M89
    |    |  i. s.: Pentedium Kier 1967 M89
    |    |           `--*P. curator Kier 1967 M89
    |    |         Durhamella Kier 1968 M89
    |    |           |--*D. ocalana (Cooke 1942) [=Laganum ocalanum] M89
    |    |           `--D. floridana M89
    |    |         Leniechinus Kier 1968 M89
    |    |           `--*L. herricki Kier 1968 M89
    |    |         Tridium Tandon & Srinivasta 1980 M89
    |    |           `--*T. kieri Tandon & Srivastava 1980 M89
    |    |         Marginoproctus Budin 1980 M89
    |    |           `--*M. djakonovi Budin 1980 M89
    |    |         Proescutella Pomel 1883 M89 [=Praescutella (l. c.) D66]
    |    |           `--*P. cailliaudi (Cotteau 1861) [=Scutella cailliaudi] M89
    |    |         Tetradiella Liao & Lin 1981 M89
    |    |           `--*T. sinica Liao & Lin 1981 M89
    |    |--Fibulariidae D66
    |    `--+--Laganidae D66
    |       |--Neolaganidae D66
    |       `--Rotulidae D66
    |            |--Rotula Schumacher 1817 M89 [=Echinotrochus Pomel 1883 D66]
    |            |    `--R. deciesdigitata (Leske 1778) M89 (see below for synonymy)
    |            |--Rotuloidea Etheridge 1872 D66
    |            |    `--*R. fimbriata Etheridge 1872 M89
    |            `--Heliophora Agassiz 1840 [=Radiorotula Lambert & Thiéry 1921; incl. Hemiheliopsis Lambert 1906] D66
    |                 |--*H. orbiculus (Linnaeus 1758) M89 [=Echinus orbiculus M89, *Radiorotula orbiculus D66]
    |                 `--‘*Hemiheliopsis’ fonti Lambert 1906 D66
    `--Scutellina [Scutellaria] M89
         |  i. s.: Porpitella Pomel 1883 M89
         |           `--*P. hayesiana (Desmoulins 1837) M89 (see below for synonymy)
         |         Lenita Desor 1847 M89
         |           `--L. patellaris (Leske 1778) M89 [=Echinites patellaris M89, Echinus patellaris D66]
         |         Eoscutum Lambert 1914 M89
         |           `--E. doncieuxi (Lambert 1905) [=Porpitella doncieuxi] M89
         |         Amplaster Martínez 1985 M89
         |           `--*A. coloniensis Martínez 1985 M89
         |         Sinaechinocyamus Liao 1979 M89
         |           `--*S. planus Liao 1979 M89
         |         Taiwanaster Wang 1984 M89
         |           `--*T. mai Wang 1984 M89
         |         Allaster Nisiyama 1968 M89
         |           `--*A. rotundatus Nisiyama 1968 M89
         |         Faassia Schmidt 1971 M89
         |           `--*F. globosa Schmidt in Schmidt & Sinel’nikova 1971 M89
         |         Kieria Mihály 1985 M89
         |           `--*K. semseyana Mihály 1985 M89
         |         ‘Mennerella’ Schmidt 1971 non Egorov 1950 M89
         |           `--*M. ovata Schmidt in Schmidt & Sinel’nikova 1971 M89
         |         Samlandaster Lambert & Thiéry 1914 M89
         |           `--*S. germanicus (von Beyrich 1847) [=Scutella germanica] M89
         |         Scutulum Tournouer 1869 M89 [=Scutellum (l. c.) non Pusch 1833 D66]
         |           `--*S. parisiense Tournouer 1869 M89
         |         Scutellina Agassiz 1841 M89
         |           |--*S. lenticularis (Lamarck 1816) M89 (see below for synonymy)
         |           `--S. obovata M89
         |--+--Mellitidae D66
         |  `--Protoscutellidae D66
         |       |--Protoscutella Stefanini 1924 M89
         |       |    `--*P. mississippiensis (Twitchell 1915) [=Scutella mississippiensis] M89
         |       |--Mortonella Pomel 1883 [=Mortonia Desor 1858 non Gray 1851] D66
         |       |    `--*M. quinquefaria (Say 1825) M89 (see below for synonymy)
         |       `--Periarchus Conrad 1866 D66
         |            |--*P. altus (Conrad 1865) [=Sismondia alta] M89
         |            `--P. lyelli M89
         |                 |--P. l. lyelli D66
         |                 `--P. l. pileussinensis D66
         `--+--+--+--Scutellidae D66
            |  |  `--Abertella Conrad 1842 M89 [Abertellidae D66]
            |  |       `--*A. aberti (Conrad 1842) [=Scutella aberti] M89
            |  `--Astriclypeidae D66
            |       |--Astriclypeus Verrill 1867 M89 [=Crustulum Troschel 1868 D66]
            |       |    `--*A. manni Verrill 1867 M89 [=*Crustulum manni D66]
            |       |--Amphiope Agassiz 1840 D66
            |       |    `--*A. bioculata (Desmoulins 1835) [=Scutella bioculata] M89
            |       `--Echinodiscus Leske 1778 (see below for synonymy) D66
            |            |--E. bisperforatus Leske 1778 M89 (see below for synonymy)
            |            |--E. auritus D66
            |            `--E. tiliensis Wang 1984 M89
            `--+--Eoscutella Grant & Hertlein 1938 M89 [Eoscutellidae D66]
               |    `--*E. coosensis (Kew 1920) [=Scutella coosensis] M89
               |--+--Echinarachniidae D66
               |  |--Dendrasteridae D66
               |  `--Scutaster Pack 1909 M89 [Scutasteridae D66]
               |       |--*S. andersoni Pack 1909 M89
               |       `--S. vaquerosensis D66
               `--Monophorasteridae D66
                    |--Monophoraster Lambert & Thiéry 1921 M89 (see below for synonymy)
                    |    `--*M. darwini (Desor 1847) M89 [=*Monophora darwini D66]
                    |--Iheringiella Berg 1898 (see below for synonymy) D66
                    |    `--*I. patagoniensis (Desor 1847) M89 (see below for synonymy)
                    `--Karlaster Marchesini Santos 1958 D66
                         `--*K. pirabensis Marchesini Santos 1958 M89

Echinodiscus Leske 1778 [=Echinoglycus Leske 1778, Lobophora Agassiz 1841, Tretodiscus Pomel 1883, Tetrodiscus Lambert & Thiéry 1921] D66

Echinodiscus bisperforatus Leske 1778 M89 [=*Tetrodiscus bisperforatus D66, *Tretodiscus bisperforatus D66; incl. Lobophora bifora Agassiz 1841 D66, Echinoglycus irregularis Leske 1778 M89, *Echinodiscus irregularis M89]

Iheringiella Berg 1898 [=Iheringia Lahille 1898 non Keyserling 1891, Iheringiana Berg 1898, Iheringina Lahille 1899] D66

*Iheringiella patagoniensis (Desor 1847) M89 [=Scutella patagoniensis M89, *Iheringia patagoniensis D66, *Iheringiana patagoniensis D66, *Iheringina patagoniensis D66]

Monophoraster Lambert & Thiéry 1921 M89 [incl. Monophora Deso 1847 non Bory de St Vincent 1804 D66]

*Mortonella quinquefaria (Say 1825) M89 [=Scutella quinquefaria M89; incl. S. rogersi Agassiz 1841 non Morton 1834 D66]

*Porpitella hayesiana (Desmoulins 1837) M89 [=Cassidulus hayesianus M89, Scutellina hayesiana D66; incl. S. supera Agassiz 1841 D66]

Rotula deciesdigitata (Leske 1778) M89 [=Echinodiscus deciesdigitatus M89; incl. R. multiloba Schumacher 1817 D66, *Echinotrochus multiloba D66, Echinodiscus octiesdigitatus Leske 1778 M89, *Rotula octiesdigitata M89]

*Scutellina lenticularis (Lamarck 1816) M89 [=Scutella lenticularis M89; incl. Scutella nummularia Defrance 1827 D66, Scutellina nummularia D66]

*Type species of generic name indicated

REFERENCES

[D66] Durham, J. D. 1966. Clypeasteroids. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt U. Echinodermata 3 vol. 2 pp. U450–U491. The Geological Society of America, Inc., and The University of Kansas Press.

[M89] Mooi, R. 1989. Living and fossil genera of the Clypeasteroida (Echinoidea: Echinodermata): an illustrated key and annotated checklist. Smithsonian Contributions to Zoology 488: 1–51.