| Richardoestesia | |
|---|---|
 | |
| Tooth of cf.R. gilmorei with close up of denticles | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Coelurosauria |
| Genus: | †Richardoestesia Currie, Rigby & Sloan, 1990 |
| Type species | |
| †Richardoestesia gilmorei Currie, Rigby & Sloan, 1990 | |
| Other species | |
| Synonyms | |
| |
Richardoestesia is amorphogenus oftheropoddinosaur teeth, originally described from theLate Cretaceous of what is nowCanada, theUnited States, and possibly alsoUzbekistan. It currently contains two species,R. gilmorei andR. isosceles, and a possible third,R. asiatica, although it has been classified in its own genusAsiamericana. It has been used as a morphotaxon to describe other theropod teeth widely displaced in time and space from the type species. If all teeth assigned to the genus are truly reflective of the animals biology and taxonomic state (as some teeth go as far back as the Late Jurassic), it would have been one of the longest lasting dinosaur genera, perhaps also being the most widely distributed.
The jaws were found in 1917 byCharles Hazelius Sternberg and sons in theDinosaur Provincial Park inAlberta at theLittle Sandhill Creek site. In 1924Charles Whitney Gilmore namedChirostenotes pergracilis and referred the jaws to this species.[2] In the 1980s it became clear thatChirostenotes was anoviraptorosaur to which the long jaws could not have belonged. Therefore, in 1990Phillip Currie,John Keith Rigby andRobert Evan Sloan named a separate species:Richardoestesia gilmorei.[3]
The genus is named forRichard Estes, to honor his important work[4] on small vertebrates and especially theropod teeth of the Late Cretaceous. The naming authors actually intended to use the spellingRicardoestesia,Ricardus being the normal latinisation of "Richard". However, except in one overlooked figure caption, the editors of the paper altered the spelling to include the 'h'.[5] Ironically, in 1991 George Olshevsky in a species list also used the spellingRichardoestesia, and indicatedRicardoestesia to be the misspelling, unaware that the original authors actually intended the name to be spelled this way. As a result, underICZN rules, he acted as "first revisor" choosing between the two spelling variants of the original publication and inadvertently made the misspelt name official. Subsequently, the original authors have adopted the spellingRichardoestesia. Thespecific name honors Gilmore.[citation needed]
Theholotype specimen ofRichardoestesia gilmorei (NMC 343) consists of a pair of lower jaws found in the upperJudith River Group, dating from theCampanian age, about 75 million years ago. The jaws are slender and rather long, 193 millimeters, but the teeth are small and very finely serrated with five to six denticles per millimeter. The serration density is a distinctive trait of the species.
In 2001,Julia Sankey named a second species:Richardoestesia isosceles, based on a tooth, LSUMGS 489:6238, from the TexanAguja Formation, which is of a longer and less recurved type.[6] The teeth ofR. isosceles have also been identified ascrocodyliform in shape, possibly belonging to asebecosuchian.[7]
In 2013 a study assumed that the teeth of thecoelurosaurAsiamericana asiatica, from the CBI-14 site of theBissekty Formation inUzbekistan,[8][page needed] were identical to those ofRichardoestesia isosceles, and renamed the species intoRichardoestesia asiatica.[9] A subsequent study confirmed this in 2019.[10] The holotype ofR. asiatica is CCMGE 460/12457,[8][page needed] and two other teeth (ZIN PH 1110/ 16 and ZIN PH 1129/16) are also known.[10]
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Richardoestesia-like teeth have been found in many Late Cretaceous geological formations, including theHorseshoe Canyon Formation, theScollard Formation,Hell Creek Formation,Ferris Formation, and theLance Formation (dated to about 66 million years ago). Similar teeth have been referred to this genus from as early as theBarremian age (Cedar Mountain Formation, 125 million years ago).[1]
Because of the disparity in location and time of the many referred teeth, researchers have cast doubt on the idea that they all belong to the same genus or species, and the genus is best considered aform taxon. A comparative study of the teeth published in 2013 demonstrated that bothR. gilmorei andR. isosceles were only definitively present in theDinosaur Park Formation, dated to between 76.5 and 75 million years ago.R. isosceles was also present in theAguja Formation, roughly the same age. All other referred teeth most likely belong to different species, which have not been named due to the lack of body fossils for comparison.[11]
Fossils ofRichardoestesia have also been found in theTremp Formation of northeastern Spain (Blasi 2 member).[12] The oldest fossils that have been referred toRichardoestesia come from the Jurassic of Portugal.[13]
At least a few studies have speculated a piscivorous lifestyle forRichardoestesia, due to its vast distribution as well as predominance in marine sites.[14][15]
Media related toRichardoestesia at Wikimedia Commons.jpg)
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