Podosphaeraster sp., from Christopher Mah.

Belongs within: Valvatacea.
Contains: Stauranderasteridae, Goniasterinae, Anthenoidinae, Hippasteriinae.

The Goniasteroidea are a group of starfish with flat, plate-like abactinals (Blake 1987).

Characters (from Blake 1987, as Goniasteracea): Body shape usually more or less flattened with discs large, interbrachial arcs rounded; some species subspherical; multi-armed species lacking; most species moderate to large in size but some small. Abactinals, marginals, actinals almost always differentiated, body moderately stout with closely fitted ossicles, abactinal surface somewhat flexible unless body is subspherical; dermal and skeletal layer thickened in Asterodiscididae. Encrusting ossicles varied, mostly in the form of spinelets, granules, also spines, tubercles; pedicellariae either absent or simple, common; blades varied, sessile or alveolar. Abactinals in form of paxillae, tabulae or flattened plates; marginals enlarged, varied, intermarginals almost always lacking. Ambulacrals, adambulacrals varied, from thin to quite stout; spicules lacking from tube feet; superambulacrals present or absent, interbrachial septa almost always lacking ossicles.

Mystery animal for today
Published 15 February 2008

Take a close look at the photo above. What kind of animal do you think this is? [The photo comes from here, but don’t look there just yet, because that would be cheating.]

Some of the more observant among you may have noticed the five rays visible on the animal, and so you would have correctly decided that this is an echinoderm, seen from the underside. Echinoderms are the phylum of marine animals that includes crinoids (sea lilies and feather stars), asteroids (sea stars or starfish), ophiuroids (brittle stars), echinoids (sea urchins) and holothuroids (sea cucumbers). The five rays are the ambulacra—furrows lined with the tube feet that the echinoderm uses for walking on, or for passing food particles to the central mouth. Before I reveal exactly what kind of echinoderm this is, though, I’ll show you another photo of the same specimen (from the same site) seen from the side:

By now, it should be pretty obvious which of the five living classes of echinoderms this is. So if you guessed “starfish”*—you’re absolutely right. This specimen is, in fact, the type specimen of Podosphaeraster toyoshiomaruae Fujita & Rowe 2002. Podosphaeraster is an extremely unusual asteroid known from the western Pacific and north-east Atlantic that has abandoned the typical star-shape of most members of its class, and adopted a near-spherical form much more similar to that of an echinoid. If you were to look closely at the specimen, you would be able to see a difference from a typical echinoid in that the ambulacral furrows only go halfway up the side of the sphere, rather than all the way up as in echinoids.

*Kevin Zelnio is going to kill me for calling it a starfish instead of a sea star. Tough.

The way in which Podosphaeraster has evolved its unusual form is relatively simple. The development of the plates that normally form the dorsal (aboral) surface of the flattened star has been greatly reduced relative to those that form the ventral (oral) surface. The reasons why this unusual morphology has evolved in Podosphaeraster, however, are unknown. Though five species have been described to date, specimens of Podosphaeraster are few and far between. All species are small (the largest specimens are little over a centimetre in diameter) and there is evidence that they live in habitats that are not conducive to easy collecting—among sponges or rocky ground in depths of 85–615 m. It may be adapted to living in cracks or crevices in these habitats.

For all its unusualness, Podosphaeraster is not unique. A fossil family of asteroids, the Sphaerasteridae, also developed a similar globose form by the reduction of the aboral surface. Also, Smith (1997) suggested that echinoids could have also evolved from a star-like ancestor in just this way. If true, what might seem an interesting but inconsequential oddity in the asteroid world could actually be very significant in understanding how another of the major modern animal groups came into being.

Systematics of Goniasteroidea
<==Goniasteroidea [Goniasteracea]
    |  i. s.: Podosphaeraster Clark in Clark & Wright 1962 [Podosphaerasteridae]FR02
    |           |--*P. polyplax Clark in Clark & Wright 1962FR02
    |           |--P. gustavei Rowe 1985FR02
    |           |--P. pulvinatus Rowe & Nichols 1980FR02
    |           |--P. thalassae Cherbonnier 1970FR02
    |           `--P. toyoshiomaruae Fujita & Rowe 2002FR02
    |    |--StauranderasteridaeSW66
    |    |--Monaster Etheridge 1892BE03 [incl. Etheridgaster Gregory 1899SW66; MonasteridaeSW66]
    |    |    |--*M. clarkei (de Koninck 1878)BE03 [=Palaeaster (*Monaster) clarkeiF71, Etheridgaster clarkeiF71]
    |    |    `--M. stutchburii (Etheridge 1892) [=Palaeaster (Monaster) stutchburii]F71
    |    `--SphaerasteridaeB87
    |         |--Valettaster Lambert 1914FR02 [=Tholaster Spencer 1913 non Seunes 1890SW66; incl. Asteriaceros Valette 1934SW66]
    |         |    `--*V. ocellatus [=Oreaster ocellatus, *Tholaster ocellatus]SW66
    |         `--Sphaeraster Quenstedt 1875FR02 [=Sphaerites Quenstedt 1852 nec Duftschmid 1805 nec Unger 1850 (ICBN)SW66]
    |              |--*S. punctatus (Quenstedt 1852) [=*Sphaerites punctatus]SW66
    |              `--S. annulosusSG93
    `--+--AsterodiscidesMG-H11 [AsterodiscididaeB87]
       |    |--A. macroplax Rowe 1985MG-H11
       |    |--A. tessellatus Rowe 1977MG-H11
       |    `--A. truncatusB87
            |  i. s.: Lithosoma Fisher 1911SW66
            |           |--*L. actinometra Fisher 1911SW66
            |           `--L. penichra Fisher 1917MG-H11
            |         Milteliphaster Alcock 1893SW66
            |           |--*M. woodmasoni Alcock 1893SW66
            |           `--M. regenerator (Doderlein 1922)MG-H11
            |         Rosaster Perrier 1894 [incl. Nereidaster Verrill 1899]SW66
            |           `--*R. alexandri (Perrier 1881) [=Pentagonaster alexandri]SW66
            |         Codellaster Blake & Kues 2002BK02
            |           `--*C. keepersae Blake & Kues 2002BK02
            |         Comptonia Gray 1840E01
            |           |--*C. elegans Gray 1840SW66
            |           `--C. comptoni (Forbes 1848)E01
            |         Noviaster Vallette 1929E01
            |           `--*N. lissajousi Valette 1929SW66
            |         Mediaster Stimpson 1857 [incl. Isaster Verrill 1894 non Desor 1858; Mediasterinae]SW66
            |           |--*M. aequalis Stimpson 1857SW66
            |           |--M. australiensis Clark 1916MG-H11
            |           `--M. hayi Blake 1986BK02
            |         Nymphaster Sladen 1889SW66
            |           |--N. arenatus (Perrier 1881) [=Pentagonaster arenatus, *N. protentus Sladen 1889]SW66
            |           |--N. moebii Studer 1884MG-H11
            |           `--N. moluccanus Fisher 1913MG-H11
            |         Calliaster Gray 1840SW66
            |           `--*C. childreni Gray 1840SW66
            |         Calliderma Gray 1847 [incl. Tomidaster Sladen 1891]SW66
            |           |--*C. emma Gray 1847SW66
            |           `--C. smithiaeSW66
            |         Cenomanaster Wright 1951 (see below for synonymy)SW66
            |           `--*C. cenomanensis (Mercier 1935) [=*Jacobella cenomanensis]SW66
            |         Chomataster Spencer 1913 [incl. Huraeaster Valette 1915]SW66
            |           `--*C. acules Spencer 1913SW66
            |         Crateraster Spencer 1913 [incl. Austinaster Adkins 1928]SW66
            |           `--*C. quinqueloba (Goldfuss 1822) [=Asterias quinqueloba]SW66
            |         Forbesiaster de Loriol 1909SW66
            |           `--*F. wrighti de Loriol 1909SW66
            |         ‘Indiaster’ Rao 1957 non Lambert 1920SW66
            |           `--*I. krishna Rao 1957SW66
            |         Leptogonium Pomel 1887SW66
            |           `--*L. mauritanicum Pomel 1887SW66
            |         Mastaster Mercier 1935SW66
            |           `--*M. villersensis Mercier 1935SW66
            |         Miopentagonaster Mercier 1935SW66
            |           `--*M. calloviensis Mercier 1935SW66
            |         Ophryaster Spencer 1913SW66
            |           |--*O. oligoplax (Sladen 1891) [=Nymphaster oligoplax]SW66
            |           `--O. magnusSW66
            |         Pachyaster de Loriol 1909SW66
            |           `--*P. aegyptiacus de Loriol 1909SW66
            |         Spenceraster Lambert 1913 [=Trachyaster Spencer 1913 non Pomel 1883]SW66
            |           `--*S. rugosus (Spencer 1907) [=Nymphaster rugosus, *Trachyaster rugosus]SW66
            |         Teichaster Spencer 1913SW66
            |           `--*T. favosus Spencer 1913SW66
            |         Tylasteria Valette 1930 [=Tylaster Spencer 1913 non Danielsson & Koren 1881]SW66
            |           |--*T. jurensis (Goldfuss 1822) [=Asterias jurensis, *Tylaster jurensis]SW66
            |           `--T. berthandiSG93
            |         Amphiaster Verrill 1868SW66
            |           `--*A. insignis Verrill 1868SW66
            |         Astroceramus Fisher 1906SW66
            |           `--*A. callimorphus Fisher 1906SW66
            |         Astrothauma Fisher 1913SW66
            |           `--*A. euphylacteum Fisher 1913SW66
            |         Circeaster Koehler 1909SW66
            |           `--*C. marcelli Koehler 1909SW66
            |         Eugoniaster Verrill 1899SW66
            |           `--*E. investigatoris (Alcock 1893) [=Pentagonaster investigatoris]SW66
            |         Gigantaster Döderlein 1924SW66
            |           `--*G. weberi Döderlein 1924SW66
            |         Gilbertaster Fisher 1906SW66
            |           `--*G. anacanthus Fisher 1906SW66
            |         Johannaster Koehler 1909SW66
            |           `--*J. superbus Koehler 1909SW66
            |         Litonotaster Verrill 1899SW66
            |           `--*L. intermedius (Perrier 1884) [=Pentagonaster intermedius]SW66
            |         Lydiaster Koehler 1909SW66
            |           `--*L. johannae Koehler 1909SW66
            |         Mahabissaster Macan 1938SW66
            |           `--*M. zengi Macan 1938SW66
            |         Mariaster Clark 1916SW66
            |           `--*M. giganteus (Goto 1914) [=Johannaster giganteus]SW66
            |         Notioceramus Fisher 1940SW66
            |           `--*N. anomalus Fisher 1940SW66
            |         Peltaster Verrill 1899SW66
            |           `--P. nidarosiensis (Storm 1881) [=Goniaster nidarosiensis; incl. *P. hebes Verrill 1899]SW66
            |         Progoniaster Döderlein 1924SW66
            |           `--*P. atavus Döderlein 1924SW66
            |         Pseudogoniodiscaster Livingstone 1930SW66
            |           `--*P. wardi Livingstone 1930SW66
            |         Sibogaster Döderlein 1924SW66
            |           `--*S. digitatus Döderlein 1924SW66
            |         Styphlaster Clark 1938SW66
            |           `--*S. notabilis Clark 1938SW66
            |         Pentoplia Clark 1971 [Pentopliidae]B87
            |           `--*P. felli Clark 1971B87
            |         Gephyriaster Fisher 1910B87
            |           `--*G. swifti (Fisher 1905) [=Mimaster swifti]SW66
            |         Buterminaster Blake in Blake & Zinsmeister 1988BZ88
            |           `--*B. elegans Blake in Blake & Zinsmeister 1988BZ88
            |--Chitonaster Sladen 1889 [Chitonasterinae]SW66
            |    `--*C. cataphractus Sladen 1889SW66
                 |--Nectria Gray 1840SW66
                 |    `--*N. ocellifera (Lamarck 1816) [=Asterias ocellifera]SW66
                 `--Nectriaster Clark 1946SW66
                      `--*N. monacanthus (Clark 1916) [=Mediaster monacanthus]SW66

Cenomanaster Wright 1951 [=Jacobella Mercier 1935 nec Jeannet 1908 nec Patte 1926 nec Passendorfer 1930]SW66

*Type species of generic name indicated


[B87] Blake, D. B. 1987. A classification and phylogeny of post-Palaeozoic sea stars (Asteroidea: Echinodermata). Journal of Natural History 21 (2): 481–528.

[BE03] Blake, D. B., & D. R. Elliott. 2003. Ossicular homologies, systematics, and phylogenetic implications of certain North American Carboniferous asteroids (Echinodermata). Journal of Paleontology 77 (3): 476–489.

[BK02] Blake, D. B, & B. S. Kues. 2002. Homeomorphy in the Asteroidea (Echinodermata); a new late Cretaceous genus and species from Colorado. Journal of Paleontology 76 (6): 1007–1013.

[BZ88] Blake, D. B., & W. J. Zinsmeister. 1988. Eocene asteroids (Echinodermata) from Seymour Island, Antarctic Peninsula. Geological Society of America Memoir 169: 489–498.

[E01] Eagle, M. K. 2001. A new species of Cottreauaster (Asteroidea: Echinodermata) from the Middle Jurassic of New Zealand. Records of the Auckland Museum 37: 93–100.

[F71] Fletcher, H. O. 1971. Catalogue of type specimens of fossils in the Australian Museum, Sydney. Australian Museum Memoir 13: 1–167.

[FR02] Fujita, T., & F. W. E. Rowe. 2002. Podosphaerasteridae fam. nov. (Echinodermata: Asteroidea: Valvatida), with a new species, Podosphaeraster toyoshiomaruae, from southern Japan. Species Diversity 7: 317–332.

[MG-H11] McEnnulty, F. R., K. L. Gowlett-Holmes, A. Williams, F. Althaus, J. Fromont, G. C. B. Poore, T. D. O’Hara, L. Marsh, P. Kott, S. Slack-Smith, P. Alderslade & M. V. Kitahara. 2011. The deepwater megabenthic invertebrates on the western continental margin of Australia (100–1100 m depths): composition, distribution and novelty. Records of the Western Australian Museum Supplement 80: 1–191.

[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.

Smith, A. B. 1997. Echinoderm larvae and phylogeny. Annual Review of Ecology and Systematics 28: 219–241.

[SW66] Spencer, W. K., & C. W. Wright. 1966. Asterozoans. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt U. Echinodermata 3 vol. 1 pp. U4–U107. The Geological Society of America, Inc., and The University of Kansas Press.

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