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Article: A Laurentian Iocrinus Hall (Crinoidea, Disparida) in the Dapingian or Darriwilian (Middle Ordovician, Arenig) of Oman

Publication: Palaeontology
Volume: 54
Part: 3
Publication Date: May 2011
Page(s): 525 533
Author(s): Stephen K. Donovan, C. Giles Miller, Ivan J. Sansom, Alan P. Heward and Jan Schreurs
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How to Cite

DONOVAN, S. K., MILLER, C., SANSOM, I. J., HEWARD, A. P., SCHREURS, J. 2011. A Laurentian Iocrinus Hall (Crinoidea, Disparida) in the Dapingian or Darriwilian (Middle Ordovician, Arenig) of Oman. Palaeontology54, 3, 525–533.

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Abstract

Early and early Middle Ordovician crinoids are rare globally, and are best known from North America and the British Isles. The first Arenig crinoid from the Arabian Peninsula is Iocrinus sp. cf. I. subcrassus (Meek and Worthen), known from two near-complete individuals, and numerous fragmentary specimens and ossicles. These are the stratigraphically oldest Iocrinus specimens, and provide an unexpected extension of the palaeogeographical range of a genus known otherwise from slightly younger deposits in Laurentia (North America) and Avalonia (Wales). The Oman specimens differ from Gondwanan Heviacrinus melendezi Gil Cid et al., currently classified as a maennilicrinid, but morphologically close to Iocrinus, in having arms that branch at least seven times instead of four and in having columnals typical of Iocrinus. Three species from Wales and the Welsh Borders, previously placed in Iocrinus, but differing in having smooth, conical dorsal cups, are reclassified as Margoiocrinus Donovan gen. nov., type species Iocrinus shelvensis Ramsbottom.
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