An article published in the journal “Acta Palaeontologica Polonica” reports the identification of two new species of dinosaurs that lived in present-day Thailand, in the Sao Khua Formation, in the Lower Cretaceous period, about 125 million years ago. A team of researchers named the two species Phuwiangvenator yaemniyomi and Vayuraptor nongbualamphuensis, classified in the group of coelurosaurs, distant relatives of the T.rex even if with more primitive physical structures but good enough to make them efficient predators too.
Coelurosaurs (Coelurosauria) were a group of theropod dinosaurs that have been the subject of a number of revisions over time with the re-evaluation of the inclusion of various subgroups including birds and relationshipss among the included species. Among the discussions there are those on the relationships with the megaraptor (Megaraptora) group and the authors of this research consider it part of the larger coelurosaur group.
The identification of two new species of coelurosaurs was made by studying old fossils discovered in the past decades in the Sao Kuha Formation, famous for the many dinosaur discoveries. Scattered bones were found of both specimens, as shown in the bottom image (Courtesy Adun Samathi/Uni of Bonn. All rights reserved) which shows them in white. This is a common problem in the field of paleontology which in the past made it very difficult to identify fossils. The knowledge accumulated over the decades is of great help and allows to offer new answers to the examinations of old fossils set aside long ago.
The specimen now identified as Phuwiangvenator yaemniyomi was discovered in 1993 and had an estimated length around 6 meters, about half of its famous cousin T.rex but older. The specimen now identified as Vayuraptor nongbualamphuensis was discovered in 1988 and had an estimated length around 4.5 meters. It too shows primitive characteristics but the limits due to the few bones available make it difficult to evaluate its relationships with other coelurosaurs. The top image (Courtesy Adun Samathi/Uni of Bonn. All rights reserved) shows an artistic reconstruction of these two dinosaurs. Both were bipeds but unlike the T.rex they had strong arms with long claws.
Various features of Phuwiangvenator yaemniyomi indicate that it was a fast runner and one of the first representatives of the Megaraptora group. This is interesting because dinosaur fossils belonging to this group have been discovered mainly in South America and Australia but it’s possible that actually their origin was in south-eastern Asia and then spread to other continents.
This study is based on a few bones but it’s still useful to offer new information on coelurosaurs. Actually it will probably take much more to clarify the relationships within such a diverse group and their origins, which could even date back to the Triassic period with a development in the Jurassic and the peak of diversification in the Cretaceous up to the great extinction at the end of that period.