Belongs within: Branchiopoda.
Contains: Eosestheria, Spinicaudata, Cladoceromorpha.
The Diplostraca is a clade of freshwater crustaceans with the body enclosed within a bivalved carapace. They have a fossil record extending back to the early Devonian (Briggs et al. 1993). The diplostracans have been divided in the past between the Cladocera (water fleas) and ‘Conchostraca’ (clam shrimps) with the Conchostraca having a more expansive carapace and retaining posterior appendages. However, current indications are that the clam shrimps are paraphyletic with the Spinicaudata being more closely related to the Cladocera than to the Lynceidae.
The clam shrimps of the Lynceidae have a smooth carapace without growth lines, and a greatly reduced telson lacking a furca. They are most commonly found in ephemeral pools and streams. Lynceids have a less extensive fossil record than the Spinicaudata, going back only to the Cretaceous (Briggs et al. 1993), suggesting the existence of a long ghost lineage. The largest lynceids in the genus Lynceus reach twelve millimetres in length.
Synapomorphies (from Ax 1999): Median placement of compound eyes in close proximity; second antenna biramous, strongly developed with locomotory function; first thoracopod of male with hooks for copulation, movable finger differentiated from endopodite; eggs deposited in dorsal shell space between carapace and back of thorax, eggs attached onto dorsal structures of endopodite; abdomen short, legless, folded downwards; dorsal telson with pair of long setae; branches of furca differentiated into backward-directed claws.
<==Diplostraca [Conchostraca, Onychura] |--+--SpinicaudataLSE13 | `--CladoceromorphaLSE13 `--Lynceidae [Laevicauda, Laevicaudata, Laeviscaudata, Lyncaeidae]RS10 |--Camptocercus lilljeborgiiD01 |--Acroperus leucocephalusD01 |--Duvenhedia setigeraD01 |--PleuroxusD01 | |--P. aduncusD01 | |--P. csikii Daday 1901D01 | |--P. excisusD01 | |--P. hastatusD01 | |--P. personatusD01 | |--P. trigonellusD01 | `--P. truncatusD01 `--LynceusLSE13 |--L. brachyurusR26 [=Monoculus brachyurusL02] |--L. lamellatus [=Monoculus lamellatus]L02 |--L. longirostris [=Monoculus longirostris]L02 |--L. macleayanusT06 |--L. macrourus [=Monoculus macrourus]L02 |--L. quadrangularis [=Monoculus quadrangularis]L02 |--L. socors [=Monoculus socors]L02 |--L. sphaericus [=Monoculus sphaericus]L02 |--L. stschukini Chernyshev 1940BWW93 |--L. trigonellus [=Monoculus trigonellus]L02 `--L. truncatus [=Monoculus truncatus]L02 Diplostraca incertae sedis: BairdestheriaS02 EosestheriaS81 DiestheriaS81 |--D. gansuensisS81 |--D. jiayuguanensisS81 |--D. ovalisS81 |--D. xiagouensisS81 |--D. yixianensisS81 `--D. zhoulangensisS81 GansulimnadiaS81 |--G. ovataS81 `--G. quadrataS81 Pseudestherites qinghemensisS81 YanjiestheriaS81 |--Y. fusiformisS81 |--Y. hanhsiaensisS81 |--Y. minorS81 |--Y. sinensisS81 |--Y. venulosaS81 `--Y. yumenensisS81 NeodiestheriaS81 |--N. changmaensisS81 `--N. dalaziensisS81 Orthesteriopsis liupanshanensisS81 Lepidilla Matthew 1886BB61 `--*L. anomala Matthew 1886BB61 Lepiditta Matthew 1886BB61 `--*L. alata Matthew 1886BB61 Laxitextella laxitexta (Jones 1890)DS16
*Type species of generic name indicated
References
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