''Cricoidoscelosus'' is an extinct
genus of
crayfish
Crayfish are freshwater crustaceans belonging to the clade Astacidea, which also contains lobsters. In some locations, they are also known as crawfish, craydids, crawdaddies, crawdads, freshwater lobsters, mountain lobsters, rock lobsters, mu ...
discovered in the
Yixian Formation in
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
, with only the type species, ''C. aethus'', known, that may be one of, if not, the oldest known fossil crayfish to date.
[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.]
''Cricoidoscelosus'' was initially believed to be
Late Jurassic (
Tithonian
In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...
) in age,
but it is now confirmed to have been
Early Cretaceous
The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.
Geology
Pro ...
(
Barremian-
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...
) in age.
Taxonomy
"''Mongolarachne''" ''chaoyangensis''
In 2019, a supposed new species of the spider ''
Mongolarachne
''Mongolarachne'' is an extinct genus of spiders placed in the monogeneric family Mongolarachnidae. The genus contains only one species, ''Mongolarachne jurassica'', described in 2013, which is presently the largest fossilized spider on record ...
, "Mongolarachne" chaoyangensis'' was described from the Yixian Formation in China.
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
Forgery is a white-collar crime that generally refers to the false making or material alteration of a legal instrument with the specific intent to defraud anyone (other than themself). Tampering with a certain legal instrument may be forbidd ...
using a fossil of ''Cricoidoscelosus'' as a base, that had been painted to look like a spider, and as such the species was a
junior synonym
The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently.
* In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...
of ''Cricoidoscelosus.
''
References
Fossil taxa described in 1999
Crayfish
Barremian genus first appearances
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