Asiamericana

Asiamericana (AY-zha-MER-i-KAHN-a – (Greek: Asia meaning Asia and New Latin Americas meaning Americas) is a dubious fossil fish genus known only from isolated teeth. It was named to recognize the occurrence of similar fossil teeth in Central Asia and North America. These regions once formed a connected land mass, during the Cretaceous period and were referred to as Asiamerica.

Asiamericana
Temporal range: Late Cretaceous, 90 Ma
↓
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Ichthyodectiformes
Family: †Ichthyodectidae
Genus: †Asiamericana
Nesov, 1995
Species:
†A. asiatica
Binomial name
†Asiamericana asiatica
Nesov, 1995

The teeth were discovered by L. A. Nesov in 1995. The findings were based on three teeth found in the central Kyzylkum desert, Uzbekistan, in deposits of the Bissekty Formation, dated to the mid-late Turonian age of the Late Cretaceous, about 90 million years ago. They are comparable to other teeth found in Kazakhstan and North America, which have been illustrated but not formally described. The type species is A. asiaticus.

The teeth themselves are straight, lack a constriction at the base, and lack serrations.[1]

Classification

In his initial description of the unusual teeth, Nesov speculated that they may belong to either saurodont fish or to spinosaurid dinosaurs.[1] He later changed his opinion, deciding that they definitely represented fish remains,[2] and this opinion was followed by most later researchers who excluded them from reviews of spinosaurid teeth for this reason.[3]

However, in 2013 a study concluded that the teeth were identical to those of the possibly dromaeosaurid Richardoestesia isocles Sankey 2001, and renamed the species into Richardoestesia asiatica.[4] A subsequent study confirmed this in 2019.[5]

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References
  1. Nessov, 1995. Dinozavri severnoi Yevrasii: Novye dannye o sostave kompleksov, ekologii i paleobiogeografii [Dinosaurs of Northern Eurasia: new data about assemblages, ecology and paleobiogeography], Scientific Research Institute of the Earth's Crust, St. Petersburg State University, St. Petersburg, Russia: 156 pp. + 14 pl. [in Russian with short English, German, and French abstracts].
  2. Nessov, L.A. (1997). Cretaceous nonmarine vertebrates of northern Eurasia. Saint Petersburg: University of Saint Petersburg Institute of Earth Crust, 218 pp. [in Russian].
  3. Buffetaut, Suteethorn, Tong and Amiot (2008). "An Early Cretaceous spinosaurid theropod from southern China." Geological Magazine, 145(5): 745–748.
  4. Sues H.D. and Averianov, A. 2013. "Enigmatic teeth of small theropod dinosaurs from the Upper Cretaceous (Cenomanian–Turonian) of Uzbekistan". Canadian Journal of Earth Sciences. 50: 306-314
  5. Alexander Averianov & Hans-Dieter Sues. 2019. "Morphometric analysis of the teeth and taxonomy of the enigmatic theropod Richardoestesia from the Upper Cretaceous of Uzbekistan". Journal of Vertebrate Paleontology: e1614941


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