Antedoninae

Antedon bifida, photographed by Bernard Picton.

Belongs within: Antedonacea.

The Antedoninae are a group of feather stars with a relatively large base to the central calyx, and relatively short cirri without dorsal spines. Most recognised genera are recent, with a single fossil genus Palaeantedon recognised from the Eocene to the Quaternary (Wienberg Rasmussen 1978).

The Antedoninae: (relatively) big-bellied feather stars
Published 2 September 2013

The feather stars and other crinoids are both the most divergent and least known of the modern echinoderms. This is the second post here at Variety of Life on modern feather stars; an earlier post gave a brief overview of some of the details of the feather star lifestyle and anatomy. The main subject of the earlier post was the family Charitometridae; this post will focus on a different group, the Antedoninae. Yes, Virginia, there are different varieties of feather star.

The Antedonidae and related families differ from most other feather stars in that the internal cavity of the centrodorsal, the plate that forms the base of the calyx (central cup) of the feather star, is relatively large compared to the centrodorsal’s diameter (in life, this cavity has organs nestled in it). When the antedonids were reviewed by the American echinodermatologist Austin H. Clark (Clark & Clark 1957*), he regarded this difference as significant enough to treat the antedonids and related families as a separate group, the Macrophreata, from other families in the Oligophreata with only a small centrodorsal cavity. However, later researchers have downplayed the significance of this distinction (e.g. Wienberg Rasmussen 1978), and even the monophyly of the Antedonidae has been questioned. Well-developed muscular articulations in the upper part of the calyx also indicate that antedonids are generally stronger swimmers than other feather stars (Meyer 1972). Clark & Clark (1967) divided the antedonids between six subfamilies, but Ailsa Clark commented that the distinctions between subfamilies were not always clear.

*Austin Clark’s epic revision of the living crinoids was left incomplete after his death in 1954, until it was taken up by the British researcher Ailsa Clark (no relation, as far as I’ve found). The section of Clark’s monograph on the ‘Macrophreata’ therefore made its debut under both researcher’s names.

Specimen of Dorometra photographed by Lyle Vail and Anne Hoggett. The page linked notes that this species swims actively when disturbed, before ‘holding their arms above the disk to form a shuttlecock shape and then plummeting towards the bottom’.

The Antedoninae generally differ from other antedonids in having rather short cirri (though the Philippine species Eumetra chamberlaini has exceptionally long cirri, up to about a third of the length of its arms). The cirri are also rounded dorsally, without dorsal spines or ridges, and most species lack ventral spines except one on the penultimate segment of the cirrus that opposes the terminal claw. The centrodorsal is low and rounded in the majority of species, though it may become raised and closer to conical. Antedonines include some of the shallowest-living of recent crinoids, with some species even found in tide pools; the deepest-living antedonines are known from 932 m. Clark and Clark (1967) recognised ten genera within the Antedoninae; a fossil genus Palaeantedon (from the Eocene to Quaternary) was listed in addition to the Recent genera by Wienberg Rasmussen (1978), and an eleventh Recent genus Ctenantedon was described by Meyer (1972).

The rosy feather star Antedon bifida and the Mediterranean feather star A. mediterranea are among the best-studied of all feather stars, primarily due to both being found in shallow waters around Europe. However, the greater diversity of antedonines is known from the Indo-Pacific. Apart from species of Antedon, the only Recent antedonine known from the Atlantic is the Caribbean Ctenantedon kinziei (the fossil species of Palaeantedon are also Atlantic). Characters used to distinguish genera include features of the pinnules, the slender side-branches of the arms. Antedon species, for instance, usually have the second and third pinnules on each arm similar in size to each other, and both distinctly shorter than the first pinnule. Ctenantedon kinziei is unusual in having a comb of ‘teeth’ developed in the distal part of the proximal pinnules. The function of these teeth is not entirely certain, though Meyer (1972) noted that he had observed the oral pinnules of comasterid feather stars (which also bear similar teeth) moving in and out from the central disk in a manner that suggested they were being used to remove undigested food and other waste material.

Systematics of Antedoninae

Characters (from Wienberg Rasmussen 1978): Centrodorsal discoidal to low hemispherical or rounded subconical, generally with a small cirrus-free, smooth, rugose or tuberculate dorsal area. Cirrus sockets closely placed, often small, forming two to three irregular circles on low centrodorsals, three or four regularly alternating circles in higher centrodorsals and up to six circles in conical centrodorsals; exceptionally up to 100 sockets including obsolete sockets of dorsal area. Cirri 10 to 40, rather short, generally with less than 20 cirrals, dorsally rounded without dorsal spines or processes and never carinate. Centrodorsal cavity moderate. Shallow, small radial pits may be present in specimens of Antedon bifida. Basal rosette, no rod-shaped basals. Radials generally follow edge of centrodorsal without free surface in midradial area, and may be further restricted, not covering radial margin of centrodorsal. Articular face of radial gently sloping, wider than high. Ventral muscular fossae moderate, slightly larger than interarticular ligament fossae, and broadly rounded, more or less four-sided, generally wider than high, separated by broad midradial ridge with median furrow, and shallow notch. Synarthrial articularton at brachials 1-2 flat or slightly embayed. In a few specimens of Antedon further division at secundibrachs 2 or secundibrachs 4 has been found in some of the arms.

<==Antedoninae
    |--Andrometra Clark 1917WR78
    |    `--*A. psyche (Clark 1908) [=Antedon psyche; incl. Toxometra aequipinna Gislén 1922]WR78
    |--Annametra Clark 1923WR78
    |    `--*A. occidentalis (Clark 1915) [=Cominia occidentalis]WR78
    |--Argyrometra Clark 1917WR78
    |    `--*A. crispa (Clark 1908) [=Iridometra crispa]WR78
    |--Euantedon Clark 1912WR78
    |    |--*E. moluccana (Clark 1912) [=Antedon moluccana]WR78
    |    `--E. polytes Clark 1936SM15
    |--Eumetra Clark 1908WR78
    |    `--*E. chamberlaini Clark 1908WR78
    |--Iridometra Clark 1908WR78
    |    `--*I. adrestine (Clark 1907) [=Antedon adrestine; incl. I. melpomene Clark 1911]WR78
    |--Mastigometra Clark 1908WR78
    |    `--*M. flagellifera Clark 1908WR78
    |--Dorometra Clark 1917WR78
    |    |--*D. nana (Hartlaub 1890) [=Antedon nana]WR78
    |    |--D. clymene Clark 1917MG-H11
    |    `--D. parvicirra (Carpenter 1888)SM15
    |--Toxometra Clark 1911 [incl. Monilimetra Clark 1938]WR78
    |    |--*T. paupera Clark 1911WR78
    |    |--T. leptaSM15
    |    |--T. nomima (Clark 1938)SM15 [=*Monilimetra nomimaWR78]
    |    `--T. poecilaSM15
    |--Palaeantedon Gislén 1924 [Palaeantedonidae]WR78
    |    |--*P. soluta (Pomel 1887) [=Antedon solutus]WR78
    |    |--P. ambiguaWR78
    |    |--P. carolinianaWR78
    |    `--P. pannoicaWR78
    `--Antedon de Freminville 1811 (nom. cons.) (see below for synonymy)WR78
         |--A. bifida (Pennant 1777)LR06 (see below for synonymy)
         |    |--A. b. bifidaBK77
         |    `--A. b. maroccanaBK77
         |--A. abyssorumD05
         |--A. adriaticaBK77
         |--*Repometra’ arabica Clark 1937WR78
         |--*Kallispongia’ archeri Wright 1877 [incl. Antedon loveni Bell 1882, *Compsometra loveni]WR78
         |--A. avenionensisWR78
         |    |--A. a. avenionensisWR78
         |    `--A. a. minor Nicolas 1898WR78
         |--‘Pentacrinus’ europaeus Thompson 1827 [=*Hibernula europaeus, *Phytocrinus europaeus]WR78
         |--A. exiguaD05
         |--A. hirsutaD05
         |--A. incommoda Bell 1888MG-H11
         |--A. mediterranea (Lamarck 1816)LR06 [=Comatula mediterraneaBK77]
         |--A. petasusBK77
         |--A. pinnulata [=Comatula pinnulata, Geocoma pinnulata, Pterocoma pinnulata]B89
         |--*Ganymeda’ pulchella Gray 1834WR78
         |--A. rhomboideaD05
         `--A. serrataGD00 [=Compsometra serrataF67]

Antedon de Freminville 1811 (nom. cons.) [=Cintedon (l. c.); incl. Compsometra Clark 1908, Decacnemos Linck ex Bronn 1825, Ganymeda Gray 1834, Hibernula Fleming 1828, Phytocrinus de Blainville 1830, Kallispongia Wright 1877, Repometra Clark 1937; Antedoninae]WR78

Antedon bifida (Pennant 1777)LR06 [=Asterias bifidaWR78; incl. Comatula decacnemosBK77, Alecto europaeaBK77, *Antedon gorgonia de Freminville 1811WR78]

*Type species of generic name indicated

References

[BK77] Barel, C. D. N., & P. G. N. Kramers. 1977. A survey of the echinoderm associates of the north-east Atlantic area. Zoologische Verhandelingen 156: 1–159.

[B89] Boehm, G. 1889. Ein Beitrag zur Kenntniss fossiler Ophiuren. Berichte der Naturforschenden Gesellschaft zu Freiburg I. B. 4: 232–287, pls 4–5.

Clark, A. H., & A. M. Clark. 1967. A monograph of the living crinoids. Volume 1. The comatulids. Part 5—suborders Oligophreata (concluded) and Macrophreata. Smithsonian Institution, United States National Museum, Bulletin 82.

[D05] Döderlein, L. 1905. Arktische Crinoiden. In: Römer, F., & F. Schaudinn (eds) Fauna Arctica. Eine Zusammenstellun der arktischen Tierformen, mit besonder Berücksichtigung des Spitzbergen-Gebietes auf Grund der Ergebnisse der Deutschen Expedition in das Nördliche Eismeer im Jahre 1898 vol. 4 pp. 395–406. Gustav Fischer: Jena.

[F67] Fell, H. B. 1967. Echinoderm ontogeny. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt S. Echinodermata 1. General characters. Homalozoa—Crinozoa (except Crinoidea) vol. 1 pp. S60–S85. The Geological Society of America, Inc., and The University of Kansas: Lawrence (Kansas).

[GD00] Giribet, G., D. L. Distel, M. Polz, W. Sterrer & W. C. Wheeler. 2000. Triploblastic relationships with emphasis on the acoelomates and the position of Gnathostomulida, Cycliophora, Plathelminthes, and Chaetognatha: a combined approach of 18S rDNA sequences and morphology. Systematic Biology 49: 539–562.

[LR06] Lanterbecq, D., G. W. Rouse, M. C. Milinkovitch & I. Eeckhaut. 2006. Molecular phylogenetic analyses indicate multiple independent emergences of parasitism in Myzostomida (Protostomia). Systematic Biology 55 (2): 208–227.

[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.

Meyer, D. L. 1972. Ctenantedon, a new antedonid crinoid convergent with comasterids. Bulletin of Marine Science 22 (1): 53–66.

[SM15] Sampey, A., & L. M. Marsh. 2015. Kimberley marine biota. Historical data: echinoderms. Records of the Western Australian Museum Supplement 84: 207–246.

[WR78] Wienberg Rasmussen, H. 1978. Articulata. In: Moore, R. C., & C. Teichert (eds) Treatise on Invertebrate Paleontology pt T. Echinodermata 2. Crinoidea vol. 3 pp. T813–T927. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).

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