Editing Notostraca (section)

==Evolution and fossil record==
The [[fossil record]] of Notostraca is extensive, occurring in a wide range of geological deposits.<ref>{{cite book |author1=Atte Korhola  |author2=Milla Rautio  |name-list-style=amp |year=2001 |chapter=Cladocera and other branchiopod crustaceans |pages=5–41 |editor1=John P. Smol |editor2=Harry John Betteley Birks |editor3=William M. Last |title=Tracking Environmental Change Using Lake Sediments. Volume 4: Zoological Indicators |publisher=[[Kluwer Academic Publishers]] |isbn=978-1-4020-0658-6 |chapter-url=https://books.google.com/books?id=p-bwPq3P1YwC&pg=PA30}}</ref> The oldest known notostracan is the species ''[[Strudops|Strudops goldenbergi]]'' from the Late [[Devonian]] ([[Famennian]] ~ 365 million years ago) of Belgium.<ref>{{Cite journal|last1=Lagebro|first1=Linda|last2=Gueriau|first2=Pierre|last3=Hegna|first3=Thomas A.|last4=Rabet|first4=Nicolas|last5=Butler|first5=Aodhán D.|last6=Budd|first6=Graham E.|date=May 2015|editor-last=Korn|editor-first=Dieter|title=The oldest notostracan (Upper Devonian Strud locality, Belgium)|journal=Palaeontology|language=en|volume=58|issue=3|pages=497–509|doi=10.1111/pala.12155|s2cid=129231634|issn=0031-0239|doi-access=free|bibcode=2015Palgy..58..497L }}</ref> The lack of major morphological change since {{Ma|250}} has led to Notostraca being described as [[living fossil]]s.<ref name="Diversity"/> [[Kazacharthra]], a group known only from [[Triassic]] and [[Jurassic]] fossils from [[Kazakhstan]] and Western [[China]],<ref name=Liu>{{cite journal|last=Liu|first=Hongfu|journal=Acta Palaeontologica Sinica|year=1996|volume=4|issue=35|pages=490–494|url=http://europepmc.org/abstract/CBA/295478/reload=0;jsessionid=ZLmTAb0szp8TXnYtpqjL.4|archive-url=https://archive.today/20130414172059/http://europepmc.org/abstract/CBA/295478/reload=0;jsessionid=ZLmTAb0szp8TXnYtpqjL.4|url-status=dead|archive-date=2013-04-14|title=New materials of Late Triassic Kazacharthra from Xinjaing}}</ref> are closely related to notostracans, and may belong within the order Notostraca,<ref>{{cite book |author=Marjorie L. Reaka-Kudla |year=2002 |chapter=Habitat specialization and its relation to conservation policy in Crustacea |pages=211–221 |editor=Elva Escobar-Briones |editor2=Fernando Alvarez |title=Modern Approaches to the Study of Crustacea |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-0-306-47366-1}}</ref> or alternatively are placed as their sister group within the clade Calmanostraca.

The "central autapomorphy" of the Notostraca is the abandonment of [[filter feeder|filter feeding]] in open water, and the development of a benthic lifestyle in muddy waters, taking up food from particles of sediment and preying on small animals.<ref name="Ax">{{cite book |author=Peter Ax |year=2000 |title=Multicellular Animals. The Phylogenetic System of the Metazoa. Volume II |publisher=[[Springer Science+Business Media|Springer]] |isbn=978-3-540-67406-1|chapter=Notostraca |pages=158–159 |chapter-url=https://books.google.com/books?id=FweHI7uZ198C&pg=PA158}}</ref> A number of other characteristics are correlated with this change, including the increased size of the animal compared to its relatives, and the loss of the ability to hinge the carapace; although a central keel marks the former separation into two valves, the [[Adduction|adductor muscle]] is missing.<ref name="Ax"/> Notostracans retain the [[plesiomorphy|plesiomorphic]] condition of having two separate compound eyes, which abut, but have not become united, as seen in other groups of Branchiopoda.<ref name="Ax"/>
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The metamerism of the trunk of Notostraca is unique. Whereas each of the first eleven thoracic segments in them has one pair of limbs, the next 16 to 20 segments have several pairs each - from two to six pairs on each segment, the number of pairs per segment increasing rearward while the size of the limbs decreases. Such polypody is a unique phenomenon. It is usually attributed to fusion of segments or to their failure to develop. F. Linder states that in the postembryonic development of Conchostraca the individualisation of each new segment begins on the ventral side, and in some cases is not completed: the author attributed the polypody of Notostraca to that process. In fact, not only the limbs of Notostraca but also other metameric organs on their ventral side are subject to 'multiplication': the metamerism of the ventral nerve chain and the ventral muscles agrees with the metamerism of the limbs, and not with that of the cuticle and of the longitudinal musculature of the dorsal side of the body. Apart from their polypody, the postgenital thoracic segments of Notostraca differ considerably from the pregenital segments, in both the structure of their musculature and that of the peripheral nerves innervating it. Because of all these differences, carcinologists often regard only the pregenital segments of Notostraca and Conchostraca as thoracic, and classify all the rest as abdominal. The last four to fifteen segments of the body of Notostraca have no limbs ..., which ends in the anal lobe, with paired filamentous cerci. The separate species of Notostraca differ among themselves in the number of postgenital (polypodous) segments, the number of limbs, and the number of limbless abdominal segments; these numbers vary even within each separate species. Inconstancy of numbers of body segments within a species is a very primitive feature, and very rare among arthropods; except for Notostraca and Conchostraca, such inconstancy is known only among some trilobites and myriapods.
<ref>{{cite book |author=D. R. Khanna |year=2004 |title=Biology of Arthropoda |publisher=[[Discovery Publishing House]] |isbn=978-81-7141-897-8 |chapter=Segmentation in arthropods |pages=316–394 |url=https://books.google.com/books?id=Hd4OEDo4gbwC&pg=PA349}}</ref>
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