St Petersburg University palaeontologists discover that dinosaur remains found more than 20 years ago in Mongolia belong
Scientists from St Petersburg University have conducted a palaeohistological analysis, that is, they have studied the microanatomical structure of the bones of Parvicursor remotus, found in Mongolia in 1996. As a result of the study of the Parvicursor specimen, palaeontologists revealed its juvenile age and made a conclusion about the main ways of evolution of the size of alvarezsaurids.
The Alvarezsauridae family, whose representatives lived at the end of the Cretaceous period (99.6 to 66.0 million years ago), are theropod dinosaurs whose forelimbs were reduced to one finger. There is an ongoing debate in the scientific community about the reasons for the decrease in the forelimbs of these dinosaurs and whether that happened in all members of the family. At some point, there was even an assumption that the forelimbs of these dinosaurs had decreased due to the fact that they made it easier for them to feed on social insects.
The research findings are published in Biological Communications, a journal published by St Petersburg University.
It has been scientifically proven that some species of theropod dinosaurs in the course of their evolution went through miniaturisation, i.e. became smaller, which enabled them to avoid competition among their larger relatives and occupy free ecological niches. Birds are an example of such evolution. They are a group of dinosaurs that emerged due to miniaturisation. Miniaturisation was an element of the evolution of many theropod dinosaurs, including alvarezsaurids.
St Petersburg University scientists are major experts in palaeontology. Thus, at the end of 2022, together with their colleagues from the UK, they discovered and described the oldest complete skeleton of a tailed amphibian 'superhero'. And in 2023, dinosaur bones helped St Petersburg University palaeontologists confirm that in ancient times Chukotka had a milder climate.
In addition, the University specialists have prepared a unique online course titled 'The evolutionary history of vertebrates: from fish to dinosaurs and humans' on the Open Education platform. Students will be able to 'travel' along the evolutionary path of vertebrates, from long-extinct groups of dinosaurs to modern representatives of the fauna.
The smallest representative of the alvarezsaurids, Parvicursor remotus, lived at the end of the Cretaceous period on the territory of modern Mongolia. Its remains were first described in 1996 by scientists from the Borissiak Palaeontological Institute of the Russian Academy of Sciences. For a long time, it was believed that the remains of Parvicursor belonged to a very small adult, about 40 cm long. However, St Petersburg University palaeontologists, together with their colleagues from the Palaeontological Institute, conducted a detailed study of the remains of this species and made an opposite conclusion.
'We took the remains of a Parvicursor holotype specimen, which are kept at the Palaeontological Institute of the Russian Academy of Sciences, and applied palaeohistological methods to study them. We believe that if this dinosaur were an adult one, the bones would have annual rings similar to the rings of trees, but they were not found in the sample studied. In addition, if that dinosaur were an adult, dense bone tissue with a small number of vessels would pass along the outer side of the bones, because bones must have blood supply for their growth, and it is this "nutrition" that vessels carry,' reported Pavel Skutschas, Head of the Department of Vertebrate Zoology at St Petersburg University.
More information:
biocomm.spbu.ru/article/view/15305 Alexander Averianov et al, Ontogeny and miniaturization of Alvarezsauridae (Dinosauria, Theropoda), Biological Communications (2023). DOI: 10.21638/spbu03.2023.201
Provided by St. Petersburg State University