Richardoestesia

Richardoestesia is a special group of theropod dinosaur teeth that scientists study. These teeth were 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 and included these jaws, but later found they did not belong there. 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. There was some confusion about the spelling, 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 places from the Late Cretaceous period, about 66 million years ago. These places include the Horseshoe Canyon Formation, the Scollard Formation, Hell Creek Formation, Ferris Formation, and the Lance Formation. Similar teeth have also been found as far back as 125 million years ago in the Cedar Mountain Formation from the Barremian age.

Because these teeth were found in different places and times, scientists are not sure if they all belong to the same group. A study in 2013 showed that R. gilmorei and R. isosceles were definitely found in the Dinosaur Park Formation, which is between 76.5 and 75 million years old. R. isosceles was also found in the Aguja Formation, about the same age. Other teeth might belong to different species, but they have not been named because we do not have full body fossils to compare them to.

Fossils of Richardoestesia have also been found in the Tremp Formation in northeastern Spain. The oldest fossils thought to be Richardoestesia come from the Jurassic period in 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.