Functional morphology and mode of life of Palaeozoic leiocope ostracodes

Abstract

Leiocopes differ from all other major ostracode groups (e.g. Palaeocopa. Binodicopa, Podocopa, Myodocopa) mainly in having a simple rounded/convex shape and a strong (dorsal and/or ventral) asymmetry. These morphological features are highly conservative in leiocopes through the Palaeozoic (lower Ordovician‐middle Devonian). Functional morphology and facies distribution suggest that typical ‘dome‐like’ leiocopes (e.g. aparchitids) may have lived off the bottom in relatively deep water environments, contrasting with most (inferred) benthic Palaeozoic ostracodes (e.g. heavily calcified dimorphic palaeocopes). Reversely, smaller sized and both dorsally and ventrally asymmetrical leiocopes (e.g. Ordovician jaanussoniids) are considered as possible benthic dwellers with reduced mobility on or within the substratum. □Ostracodes, Leiocopa, Aparchitidae, Jaanussoniidae. Palaeozoic. Ordovician, Silurian, Devonian, asymmetry, functional morphology.

Silurian Myodocopes: Pioneer pelagic ostracods and the chronology of an ecological shift

“…The shape, centre of gravity and ventral structures of typical Ordovician palaeocope and binodicope ostracods suggests that they were mostly benthic crawlers or maybe bottom swimmers (Schallreuter & Siveter 1985;Vannier et al 1989). A cursory investigation would probably identify forms such as certain leiocopes (see Vannier 1990) to be amongst possible contenders for the title of pelagic ostracods in the Ordovician, but even then the evidence would not be as clear cut as if it had the added bonus of involving myodocope-like morphology.…”

Upper Ordovician ostracods from the Cautley district, northern England: Baltic and Laurentian affinities

“…Although some Ordovician ostracod carapace morphologies suggest a more mobile mode of life, spent largely off the sea-bottom (see some of the leiocopes detailed by Vannier, 1990), no Ordovician ostracods have shell morphologies that resemble the typically 'thin-shelled' (weakly mineralized) carapaces of the pelagic Silurian myodocopids or Devonian entomozoaceans (see Siveter, 1984;Siveter, Vannier & Palmer, 1991;Gooday, 1978). Furthermore, ostracods are absent from typically pelagic biofacies of the Ordovician, such as those represented in the Hartfell Shale Formation (Moffat Shale Group) of southern Scotland, and which are characterized by graptolites and rare pelagic brachiopods.…”