Evolutionary and ecological significance of Lepidaster grayi, the earliest multiradiate starfish

Liam George Herringshaw, M. Paul Smith, Alan T. Thomas

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    Lepidaster grayi Forbes, 1850, from the Much Wenlock Limestone Formation (Silurian: Wenlock) of England, is the earliest species of starfish (Echinodermata: Asteroidea) to deviate from pentaradial symmetry, having 13 rays rather than five. Based on the patterns of supernumerary ray development seen in extant multiradiate asteroids, two possible models are evaluated for the origin of the eight additional rays seen in L. grayi. In the 'all-in-one' model, all rays were added in the same interradius, whereas in the 'quadrants' model generations of rays would have been added in each of four interradii. The smallest specimen of L. grayi, apparently having only nine rays, suggests that the,quadrants' model is most probable for the species. The presence of supernumerary rays in Silurian starfish, coupled with the existence of numerous other Palaeozoic multiradiate taxa, shows that asteroids have been able to deviate from pentamerism for most of their evolutionary history, and the variety of methods of supernumerary ray addition indicates that the multiradiate condition is homoplastic. The ecological significance of multiradiate Palaeozoic starfish is reviewed: the mouth frame of L. grayi had considerably greater flexibility than that of contemporaneous five-rayed species and, in combination with its supernumerary rays, enabled L. grayi to manipulate and consume larger food items. It is probable that Silurian starfish utilized a similar range of trophic guilds as those exploited by extant taxa.
    Original languageEnglish
    Pages (from-to)743-754
    Number of pages12
    JournalZoological Journal of the Linnean Society
    Volume150
    Issue number4
    DOIs
    Publication statusPublished - Aug 2007

      Fingerprint

    Keywords

    • asteroidea
    • palaeoecology
    • pentamerism
    • pentaradial
    • Silurian
    • supernumerary rays
    • Wenlock

    Cite this