Leptostraca
| Leptostraca Temporal range:
| |
|---|---|
| Nebalia bipes | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Subclass: | Phyllocarida |
| Order: | Leptostraca Claus, 1880 [1] |
| Families [2] | |
Leptostraca (from the Greek words for thin and shell)[3] is an order of small, marine crustaceans. Its members, including the well-studied Nebalia, occur throughout the world's oceans and are usually considered to be filter-feeders.[4] It is the only extant order in the subclass Phyllocarida. They are believed to represent the most primitive members of their class, the Malacostraca, and first appear in the fossil record during the Cambrian period.[5]
Description
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Leptostracans are usually small, typically 5 to 15 millimetres (0.2 to 0.6 in) long,[7] but the largest species (Nebaliopsis typica) can reach 4 cm, and the Silurian Ceratiocaris could grow to 75 cm.[8] They are distinguished from all other members of their class in having seven abdominal segments, instead of six. Their head has stalked compound eyes, two pairs of antennae (one biramous, one uniramous), and a pair of mandibles but no maxillipeds.[4] They are the only malacostracans with a carapace that comprises two valves. It covers the head and the thorax, including most of the thoracic appendages, and serves as a brood pouch for the developing embryos. Its anterior tip bears a movable rostrum. Also unique among malacostracans is their eight pairs of thoracic appendages which have been specialized into leaf-like filter feeding organs, and are not used for locomotion. The first six abdominal segments bear pleopods, while the seventh bears a pair of caudal furcae, which may be homologous to uropods of other crustaceans.[9][10][11]
Leptostracans have gills on their thoracic limbs, but also breathe through a respiratory membrane on the inside of the carapace. The eggs hatch as a postlarval, or "manca" stage, which lacks a fully developed carapace, but otherwise resembles the adult.[5]
Classification
[edit | edit source]It is now accepted that leptostracans belong to the Malacostraca,[12] and the sister crown group to Leptostraca is Eumalacostraca.[13]
The order Leptostraca is divided into three families, with ten genera containing a total of around 40 validly described extant species:[14]
References
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- ^ Leptostraca (Crustacea: Phyllocarida: Nebaliidae) from French coastal waters: new records and new data on their ecology and distribution
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Invertebrate Palaeontology and Evolution
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ A phylogeny of the Leptostraca (Crustacea) with keys to families and genera
- ^ Multicellular Animals: Volume II: The Phylogenetic System of the Metazoa
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External links
[edit | edit source]- Error creating thumbnail: File missing Media related to Lua error in Module:Commons_link at line 62: attempt to index field 'wikibase' (a nil value). at Wikimedia Commons
Data related to Leptostraca at Wikispecies
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