Lipostraca

''Lepidocaris rhyniensis'' is an extinct species of crustacean. It is the only species known from the order Lipostraca, and is the only abundant animal in the Pragian-aged Rhynie chert deposits. It resembles modern Anostraca, to which it is probably closely related, although its relationships to other orders remain unclear. The body is long, with 23 body segments and 19 pairs of appendages, but no carapace. It occurred chiefly among charophytes, probably in alkaline temporary pools.

Biostratigraphy and taxonomy

All the known specimens of ''Lepidocaris rhyniensis'' have been excavated from the Rhynie chert deposits in Aberdeenshire, Scotland, which is a famous ', or site of exceptional preservation. ''Lepidocaris'' is the only abundant animal in the deposits, and is likely to be responsible for many of the frequent coprolites found in the rocks.

''Lepidocaris'' was first described by D. J. Scourfield in a 1926 paper in the ''Philosophical Transactions of the Royal Society B''. Scourfield could not accommodate his new genus in the same order as its closest relatives – the Anostraca – so he erected a new family and order for ''Lepidocaris'' alone: Lepidocarididae and Lipostraca, respectively. Until 2003, when '' Castracollis'' was described, ''Lepidocaris'' was the only crustacean known from the Rhynie chert.

Description

''Lepidocaris rhyniensis'' is a segmented animal with 23 body segments. The whole body measures around long. The head has two pairs of antennae, the second of which is used for swimming. As in Anostraca, there is no carapace. There are eleven pairs of appendages on the thorax and abdomen, of which the first three pairs are ''phyllopodia'', or leaf-like limbs, as seen in other branchiopods such as ''Triops'', while the last eight pairs are similar to the swimming limbs of copepods. The tail ends in a pair of caudal furcae.

Ecology

''Lepidocaris'' is one of the earliest preserved freshwater crustaceans. It is frequently found in association with the charophyte '' Palaeonitella'' (Characeae); if the ecology of ''Palaeonitella'' resembled that of its modern relatives, the water would have been alkaline. Similarly, ''Lepidocaris'' is thought to have had a similar ecology to extant members of the Anostraca and the Notostraca such as ''Artemia'' and ''Triops'', inhabiting shallow, temporary pools.

Relationships

The phylogenetic position of ''Lepidocaris'' in relation to other orders of crustaceans is uncertain. In his original description of the species, Scourfield noted that ''Lepidocaris'' could not be accommodated in the existing order Anostraca, and even suggested that a position outside the Branchiopoda was not unthinkable. In 1986, Frederick Schram considered Lipostraca to be the sister group to Brachypoda, with the two orders together making up the Cephalocarida. In 1997, Dieter Walossek considered ''Lepidocaris'' and '' Rehbachiella'' to be stem-group anostracans, outside the extant Euanostraca. In 2001, Schram and Koenemann considered ''Lepidocaris'' and ''Rehbachiella'' to be stem-group lineages basal to the whole Branchiopoda.

References

Further reading

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{{Taxonbar, from=Q6527441

Branchiopoda genera
Prehistoric crustacean genera
Monotypic arthropod genera
Devonian animals of Europe
Fossil taxa described in 1926