Palaeocambarus

{{Short description|Extinct genus of crustaceans}} {{Use dmy dates|date=August 2021}} {{Italic title}} {{Taxobox | fossil_range = Early Cretaceous, {{fossilrange|Barremian|Aptian}} | image = 奇异环足虾 Cricoidoscelosus aethus;弓鳍鱼 Sinamia (cropped).jpg | image_caption = Specimen from the Yixian Formation of China | regnum = Animalia | phylum = Arthropoda | subphylum = Crustacea | classis = Malacostraca | ordo = Decapoda | familia = Cambaroididae | genus = {{extinct}}'''''Palaeocambarus''''' | genus_authority = Taylor, Schram & Shen, 1999 | species = {{extinct}}'''''P. licenti''''' | binomial = {{extinct}}''Palaeocambarus licenti'' | binomial_authority = (Van Straelen, 1928) | synonyms = *''Cricoidoscelus aethus'' Taylor ''et al.'', 1999 *''Astacus spinirostrius'' Imaizumi, 1938 *''Mongolarachne chaoyangensis'' <small>Cheng ''et al.'', 2019</small> | type_species = ''Astacus licenti'' | type_species_authority = Van Straelen, 1928 }}

'''''Palaeocambarus''''' is an extinct genus of crayfish discovered in the Yixian Formation in China, with only a single species, '''''Palaeocambarus licenti.''''' It is one of the oldest known fossil crayfish.<ref name=":0" /><ref name="Two19">{{cite journal |author1=Paul A. Selden |author2=Alison N. Olcott |author3=Matt R. Downen |author4=Dong Ren |author5=Chungkun Shih |author6=Xiaodong Cheng |year=2019 |title=The supposed giant spider ''Mongolarachne chaoyangensis'', from the Cretaceous Yixian Formation of China, is a crayfish |url=http://www.paulselden.net/uploads/7/5/3/2/7532217/yixiancrayfish2019.pdf |journal=Palaeoentomology |volume=2 |issue=5 |pages=515–522 |doi=10.11646/palaeoentomology.2.5.15|s2cid=208124459 }}</ref><ref name=Taylor99>Taylor, R.S., Schram, F.R. & Shen, Y.B. (1999) A new crayfish family (Decapoda: Astacida) from the Upper Jurassic of China, with a reinterpretation of other Chinese crayfish taxa, ''Paleontological Research'', 3, 121–136.</ref>

The genus ''Cricoidoscelosus'' is now considered to be a junior synonym.<ref name=":0">{{Cite journal |date=2023 |title=Crayfishes from the Jehol biota |url=https://sciencepress.mnhn.fr/en/periodiques/geodiversitas/45/24 |journal=Geodiversitas |language=en |volume=45 |issue=24 |pages=689–719}}</ref> It was initially believed to be Late Jurassic (Tithonian) in age,<ref name=Taylor99 /> but it is now confirmed to have been Early Cretaceous (Barremian-Aptian) in age.<ref name=Two19 />

== Taxonomy == The species was first named by Van Straelen in 1928 as ''Astacus licenti''. In 1999, the species was assigned to the new genus ''Palaeocambarus,'' and was placed in the family Cambaridae. In the same publication, the genus and species ''Cricoidoscelosus aethus'' was described, and was placed into the monotypic family Cricoidoscelosidae.<ref name=":0" /> In 2019, a supposed new species of the spider ''Mongolarachne, "Mongolarachne" chaoyangensis'' was described from the Yixian Formation in China.<ref>{{Cite journal |author1=Xiaodong Cheng |author2=Sizhao Liu |author3=Wenjuan Huang |author4=Li Liu |author5=Hongming Li |author6=Yinxian Li |year=2019 |title=A new species of Mongolarachnidae from the Yixian Formation of western Liaoning, China |url=http://www.geojournals.cn/dzxben/ch/reader/create_pdf.aspx?file_no=2019endzxb01016&flag=1&journal_id=dzxben&year_id=2019 |journal=Acta Geologica Sinica (English Edition) |volume=93 |issue=1 |pages=227–228 |doi=10.1111/1755-6724.13780 |archive-url=https://web.archive.org/web/20190429172620/http://www.geojournals.cn/dzxben/ch/reader/create_pdf.aspx?file_no=2019endzxb01016&flag=1&journal_id=dzxben&year_id=2019 |archive-date=2019-04-29 |doi-access=|bibcode=2019AcGlS..93..227C |url-access=subscription }}{{Retracted|doi=10.1111/1755-6724.14580|intentional=yes}}</ref> However, in a later publication that same year, when the specimen was subject to fluorescence microscopy, it was shown that the specimen was a forgery using specimen D3088, a specimen of ''Cricoidoscelosus'', as a base, that had been painted to look like a spider, and as such the species was a junior synonym of ''Cricoidoscelosus.<ref name="Two19" />'' In 2023, a re-evalutation of crayfish from the Yixian Formation found that ''Cricoidoscelosus'' was a synonym of ''Palaeocambarus'' and that ''Palaeocambarus'' could be confidently placed in Cambaroididae, which includes modern East Asian crayfish (''Cambaroides'').<ref name=":0" />

== References == {{reflist}}

Category:Fossil taxa described in 1999 Category:Crayfish Category:Barremian genus first appearances