The journal Nature has published a study analysing the lines of arrested growth (LAG) in the bones of around a hundred ruminants, representative of the specific and ecological diversity of that group of mammals. The results show that the presence of these lines is not an indicator of an ectothermic physiology (does not generate internal heat), as had previously been thought, since all warm-blooded mammals have them. The study therefore dismantles the key argument of the hypothesis that dinosaurs could have been cold-blooded reptiles. The work was carried out by researchers from the Institut Catal de Paleontologia Miquel Crusafont (ICP), in collaboration with a researcher from the Norwegian Polar Institute.
LAGs are seen in bone sections as dark rings, similar to those seen in tree trunks. The rings are formed, both in the studied mammals and in trees, during the unfavourable seasons (winter or dry season) when the growth of the organism is arrested as a result of a lack of resources. The presence of LAGs in bones was, until now, considered to be the clearest indicator of ectothermy since the seasonal arrest of growth was related to the animal's inability to maintain a more or less constant body temperature (endothermy) during the season of scarce resources.
As the ICREA researcher and ICP palaeontologist Meike Khler explains: The study we have carried out is very powerful, both in terms of the amount of material and the diversity of species with which we worked, but we did not design it to find a response to the thermophysiology of dinosaurs. We sought to better understand the physiology of extant mammals and how the environment affects them how their growth changes as a result of external temperatures, rain and the availability of food and water".
Understanding this was the first step to establishing discussions in paleontological research about the physiology of animals that lived several million years ago.
|Contact: Maria Jesus Delgado|
Universitat Autonoma de Barcelona