Keyhole sand dollar Echinodiscus sp., copyright Ria Tan.

Belongs within: Irregularia.
Contains: Arachnoididae, Clypeaster, Fibulariidae, Laganidae, Neolaganidae, Mellitidae, Astriclypeidae, 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.

    |  i. s.: Runa Agassiz 1841M89
    |           `--*R. comptoni Agassiz 1841D66
    |         Tournoueraster Lambert 1914M89
    |           `--*T. decemfissus (Desmoulins 1835) [=Scutella decemfissus]D66
    |    |--ArachnoididaeD66
    |    |--ClypeasterD66
    |    `--FossulasteridaeSG93
    |         |--Fossulaster Lambert & Thiéry 1925 [incl. Prowillungaster Wang 1994]MM22
    |         |    |--*F. halli Lambert & Thiéry 1925M89 [incl. Scutellina patella Hall 1908 non Tate 1891D66]
    |         |    |--F. exiguusMM22
    |         |    `--F. susae McNamara & Martin 2022MM22
    |         |--Willungaster Philip & Foster 1971SG93, M89
    |         |    `--*W. scutellaris Philip & Foster 1971M89
    |         |--Scutellinoides Durham 1955SG93, D66
    |         |    `--*S. patella (Tate 1891) [=Scutellina patella]M89
    |         `--Philipaster Wang 1994 [incl. Orbispala Irwin 1995]MM22
    |--Laganina [Rotulina]M89
    |    |  i. s.: Pentedium Kier 1967M89
    |    |           `--*P. curator Kier 1967M89
    |    |         Leniechinus Kier 1968M89
    |    |           `--*L. herricki Kier 1968M89
    |    |         Tridium Tandon & Srinivasta 1980M89
    |    |           `--*T. kieri Tandon & Srivastava 1980M89
    |    |         Marginoproctus Budin 1980M89
    |    |           `--*M. djakonovi Budin 1980M89
    |    |         Proescutella Pomel 1883M89 [=Praescutella (l. c.)D66]
    |    |           `--*P. cailliaudi (Cotteau 1861) [=Scutella cailliaudi]M89
    |    |         Tetradiella Liao & Lin 1981M89
    |    |           `--*T. sinica Liao & Lin 1981M89
    |    |--FibulariidaeD66
    |    `--LaganideaSG93
    |         |--LaganidaeD66
    |         |--NeolaganidaeD66
    |         `--RotulidaeD66
    |              |--Rotula Schumacher 1817 nec Lour. 1790 (ICBN) nec Raf. 1815 (ICBN)M89 [=Echinotrochus Pomel 1883D66]
    |              |    `--R. deciesdigitata (Leske 1778)M89 (see below for synonymy)
    |              |--Rotuloidea Etheridge 1872D66
    |              |    |--*R. fimbriata Etheridge 1872M89
    |              |    `--R. vieirai Dartevelle 1953SG93
    |              `--Heliophora Agassiz 1840 [=Radiorotula Lambert & Thiéry 1921; incl. Hemiheliopsis Lambert 1906]D66
    |                   |--*H. orbiculus (Linnaeus 1758)M89 [=Echinus orbiculusM89, *Radiorotula orbiculusD66]
    |                   `--*Hemiheliopsis’ fonti Lambert 1906D66
    `--Scutellina [Scutellaria, Scutellidea]M89
         |  i. s.: Porpitella Pomel 1883M89
         |           |--*P. hayesiana (Desmoulins 1837)M89 (see below for synonymy)
         |           `--P. paleocenicaSG93
         |         Lenita Desor 1847M89
         |           `--L. patellaris (Leske 1778)M89 [=Echinites patellarisM89, Echinus patellarisD66]
         |         Eoscutum Lambert 1914M89
         |           `--E. doncieuxi (Lambert 1905) [=Porpitella doncieuxi]M89
         |         Amplaster Martínez 1985M89
         |           `--*A. coloniensis Martínez 1985M89
         |         Sinaechinocyamus Liao 1979M89
         |           `--*S. planus Liao 1979M89
         |         Taiwanaster Wang 1984M89
         |           `--*T. mai Wang 1984M89
         |         Allaster Nisiyama 1968M89
         |           `--*A. rotundatus Nisiyama 1968M89
         |         Faassia Schmidt 1971M89
         |           `--*F. globosa Schmidt in Schmidt & Sinel’nikova 1971M89
         |         Kieria Mihály 1985M89
         |           `--*K. semseyana Mihály 1985M89
         |         ‘Mennerella’ Schmidt 1971 non Egorov 1950M89
         |           `--*M. ovata Schmidt in Schmidt & Sinel’nikova 1971M89
         |         Samlandaster Lambert & Thiéry 1914M89
         |           `--*S. germanicus (von Beyrich 1847) [=Scutella germanica]M89
         |         Scutulum Tournouer 1869M89 [=Scutellum (l. c.) nec Pusch 1833 nec Speg. 1881 (ICBN)D66]
         |           `--*S. parisiense Tournouer 1869M89
         |         Scutellina Agassiz 1841M89
         |           |--*S. lenticularis (Lamarck 1816)M89 (see below for synonymy)
         |           `--S. obovataM89
         |  `--ProtoscutellidaeD66
         |       |--Protoscutella Stefanini 1924M89
         |       |    `--*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 1866D66
         |            |--*P. altus (Conrad 1865) [=Sismondia alta]M89
         |            `--P. lyelliM89
         |                 |--P. l. lyelliD66
         |                 `--P. l. pileussinensisD66
            |  `--+--ScutellidaeD66
            |     `--Abertella Conrad 1842M89 [AbertellidaeD66]
            |          `--*A. aberti (Conrad 1842) [=Scutella aberti]M89
            `--+--Eoscutella Grant & Hertlein 1938M89 [EoscutellidaeD66]
               |    |--*E. coosensis (Kew 1920) [=Scutella coosensis]M89
               |    `--E. vaquerosensis (Kew 1920) [=Scutella vaquerosensis]SG93
               |  |--DendrasteridaeD66
               |  `--Scutaster Pack 1909M89 [ScutasteridaeD66]
               |       |--*S. andersoni Pack 1909M89
               |       `--S. vaquerosensisD66
                    |--Monophoraster Lambert & Thiéry 1921M89 [incl. Monophora Deso 1847 non Bory de St Vincent 1804D66]
                    |    `--*M. darwini (Desor 1847)M89 [=*Monophora darwiniD66]
                    |--Iheringiella Berg 1898 (see below for synonymy)D66
                    |    `--*I. patagoniensis (Desor 1847)M89 (see below for synonymy)
                    `--Karlaster Marchesini Santos 1958D66
                         `--*K. pirabensis Marchesini Santos 1958M89

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

*Iheringiella patagoniensis (Desor 1847)M89 [=Scutella patagoniensisM89, *Iheringia patagoniensisD66, *Iheringiana patagoniensisD66, *Iheringina patagoniensisD66]

*Mortonella quinquefaria (Say 1825)M89 [=Scutella quinquefariaM89, Periarchus (Mortonella) quinquefariaSG93; incl. S. rogersi Agassiz 1841 non Morton 1834D66]

*Porpitella hayesiana (Desmoulins 1837)M89 [=Cassidulus hayesianusM89, Scutellina hayesianaD66; incl. S. supera Agassiz 1841D66]

Rotula deciesdigitata (Leske 1778)M89 [=Echinodiscus deciesdigitatusM89; incl. R. multiloba Schumacher 1817D66, *Echinotrochus multilobaD66, Echinodiscus octiesdigitatus Leske 1778M89, *Rotula octiesdigitataM89]

*Scutellina lenticularis (Lamarck 1816)M89 [=Scutella lenticularisM89; incl. Scutella nummularia Defrance 1827D66, Scutellina nummulariaD66]

*Type species of generic name indicated


[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.

[MM22] McNamara, K. J., & S. Martin. 2022. Middle Eocene echinoids from the western Eucla Basin, Western Australia. Records of the Western Australian Museum 37: 31–56.

[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.

[SG93] Simms, M. J., A. S. Gale, P. Gilliland, E. P. F. Rose & G. D. Sevastopulo. 1993. Echinodermata. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 491–528. Chapman & Hall: London.

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