Subclass MYODOCOPA Sars, 1866

© Copyright Anna Syme

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Introduction

Ostracods of the subclass Myodocopa are marine, living in benthic, planktonic and demersal habitats. These ostracods include scavengers, detritus feeders, suspension feeders, and some predators. Myodocopa are defined by the eight or nine articles in the exopod of the second antenna (compared to a maximum of two in Podocopa). Vannier and Abe (1995) suggested that Myodocopa have a body well suited to swimming or moving through sediment – it is bilaterally symmetrical, ellipsoid and has a circulatory system. In contrast, Podocopa have a body adapted for crawling or resting – it is asymmetrical (so one valve can slot into the other), has no circulation and the carapace is well-calcified. The Myodocopa is divided into two orders: Myodocopida and Halocyprida (Kornicker and Sohn 2000).

Diagnosis

Valves with or without anterior rostrum and incisure (if incisure lacking, valves usually rather oval or circular), ventral margin never concave. Valve overlap minimal. Valve marginal zone narrow, or occasionally broad, infold. Between 5 and 7 pairs of limb and well-developed, sclerotised, flat furca with marginal claws; female additionally with general apparatus, male additionally with copulatory limb(s). Antenna biramous, endopod reduced (1–3 articulated podomeres), exopod strongly developed (usually articulated segments); usually a swimming appendage with long feathery setae. Mandibula usually coxal endopod, basis with or without an endite; short unsegmented exopod often inserted adjacent to long, segmented endopod. Maxillula without branchial plate (but sometimes with bare lobe, possibly epipod); with segmented endopod and often adjacent unsegmented exopod. Fifth limb with large bronchial plate (epipod), endopod and sometimes adjacent unsegmented exopod. Eighth limb represented by copulatory limb. Furca posterior to anus. With or without paired lateral compound eyes, medial naupliar eye and Bellonci organ.

ID Keys

A tabular key is presented in Cohen et. al., 2007.

Diagnosis References

Cohen, A.C., Peterson, D.E., & Maddocks, R.F. 2007. Ostracoda. pp. 417-446 in Carlton, J.T. The Light & Smith Manual: Intertidal Invertebrates from Central California to Oregon. Berkeley & Los Angeles : University of California Press 4.

Horne, D.J., Cohen, A. & Martens, K. 2002. Taxonomy, morphology and biology of Quaternary and living Ostracoda. Geophysical Monograph 131: 5-36 [29]

General References

Kornicker, L.S. & Sohn, I.G. 2000. Myodocopid Ostracoda from the late Permian of Greece and a basic classification for Paleozoic and Mesozoic Myodocopida. Smithsonian Contributions to Paleobiology 91: 1-33

Vannier, J. & Abe, K. 1995. Size, body plan and respiration in the Ostracoda. Palaeontology 38: 843-873

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