Richardoestesia

Richardoestesia is a special group of theropod dinosaur teeth that scientists study. These teeth were first found in rocks from the Late Cretaceous period in places that are now Canada, the United States, and maybe even Uzbekistan. Scientists gave this group two names: R. gilmorei and R. isosceles. There might be a third kind called R. asiatica, but some scientists think it should have its own special name, Asiamericana.

This group of teeth is interesting because it has been found in many different places and times. If all the teeth that scientists have linked to Richardoestesia really belong to the same kind of dinosaur, it might have been one of the longest-living dinosaur groups. It could also be one of the groups that lived in many different places around the world. Studying these teeth helps scientists learn more about how these dinosaurs lived and spread across the Earth.

History

The jaws of Richardoestesia were found in 1917 by Charles Hazelius Sternberg and his sons in Dinosaur Provincial Park in Alberta. In 1924, Charles Whitney Gilmore named a species called Chirostenotes pergracilis and included these jaws, but later it was clear they did not belong to that species. In 1990, Phillip Currie, John Keith Rigby, and Robert Evan Sloan named a new species: Richardoestesia gilmorei.

The genus name honors Richard Estes for his work on small vertebrates, especially theropod teeth from the Late Cretaceous. There was some confusion about the spelling of the name, but it was settled as Richardoestesia. The species name honors Gilmore.

Species

The main specimen of Richardoestesia gilmorei is a pair of lower jaws from the upper Judith River Group, dating back about 75 million years. The jaws are long and slender, with small, finely serrated teeth.

In 2001, a second species, Richardoestesia isosceles, was named from a tooth found in the Aguja Formation in Texas. In 2013, a study suggested that teeth from Uzbekistan belonged to this species and renamed them Richardoestesia asiatica. This was confirmed in 2019.

Classification

Richardoestesia-like teeth have been found in many Late Cretaceous geological formations, including the Horseshoe Canyon Formation, the Scollard Formation, Hell Creek Formation, Ferris Formation, and the Lance Formation (dated to about 66 million years ago). Similar teeth have been referred to this genus from as early as the Barremian age (Cedar Mountain Formation, 125 million years ago).

Because of the different locations and times when these teeth were found, researchers question if they all belong to the same group. A study in 2013 showed that both R. gilmorei and R. isosceles were only definitely present in the Dinosaur Park Formation, dated to between 76.5 and 75 million years ago. R. isosceles was also present in the Aguja Formation, roughly the same age. Other teeth likely belong to different species, but they have not been named because we lack body fossils for comparison.

Fossils of Richardoestesia have also been found in the Tremp Formation of northeastern Spain (Blasi 2 member). The oldest fossils referred to Richardoestesia come from the Jurassic of Portugal.

Paleobiology

Some studies suggest that Richardoestesia might have eaten fish. This idea comes from the wide area where its teeth have been found, including many places near water.