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Obtusoecia (Halocyprida: Myodocopa: Ostracoda) a bipolar planktonic oceanic genus. Taxonomy, bathymetry and zoogeographical distribution

100%

Angel M. V., Blachowiak-Samolyk K.

Annales Zoologici

2006

tom 56

nr 1

Full detailed descriptions of the two species of Obtusoecia, one of two planktonic halocyprid ostracod genera that are bipolar, demonstrate that the taxonomic separation of these two forms formerly considered to be conspecific, is valid. The segregation of the genus from Porroecia is also validated. The value of characters of limbs other than the first and second antennae particularly in defining halocyprid genera is emphasised. Zoogeographical distributions of the two species based on comprehensive compilations of both published and unpublished data show that O. obtusata is confined to the North Atlantic, whereas O. antarctica has an Antarctic circumpolar distribution. Detailed bathymetric profiles show that O. obtusata is a shallow mesopelagic species that is overwhelmingly dominant at depths of 50-200 m in subpolar seas, and shows limited ability to submerge at lower depths, so that it is restricted to seas that have a marked seasonal cycle of turn-over and stratification. It is postulated that the bathymetric distributions of the two species are similar, also that O. antarctica is more likely to be ancestral to O. obtusata than vice versa.

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An atypical Silurian myodocope ostracod from the Armorican Massif, France

80%

Perrier V.

Acta Palaeontologica Polonica

2012

tom 57

nr 2

A new myodocope ostracod Sineruga insolita gen. et sp. nov. is herein described from the Armorican Massif (France). Sineruga resembles Silurian myodocopes (i.e., bolbozoids and cypridinids) in having anterior features (thinner carapace) possibly related to vision. On the other hand, it resembles entomozoid ostracods in having a bean−shaped outline along with a deep adductorial sulcus and a simple muscle spot, but lacks their characteristic ribbed ornament. The data available suggest that Sineruga insolita was probably an atypical, non−ribbed member of the entomozoids thus indicating that early entomozoids may have had smooth representatives. Comparisons with other Recent and fossils ostracods show that the presence of a rostrum and/or symmetrical vision related carapace features (i.e., indicating lateral eyes) can be used as diagnostic characters for myodocope ostracods. The position and shape of the dorsal connection and to a lesser extent that of the sulcus and the adductorial muscle scar can be used to discriminate the higher groups of Silurian myodocopes (bolbozoids, cypridinids, and entomozoids).

Ograniczanie wyników

1 Acta Palaeontologica Polonica

1 Annales Zoologici

1 Angel M. V.

1 Blachowiak-Samolyk K.

1 Perrier V.

1 2012

1 2006

Wyniki wyszukiwania

Obtusoecia (Halocyprida: Myodocopa: Ostracoda) a bipolar planktonic oceanic genus. Taxonomy, bathymetry and zoogeographical distribution

An atypical Silurian myodocope ostracod from the Armorican Massif, France