New species of carnivorous dinosaur from 83 million years ago

A species of carnivorous dinosaur that lived about 83 million years ago has been discovered in what is now the Argentine province of Neuquén. The new species has been given the name Diuqin lechiguanae. The new dinosaur belongs to the group of theropods, a clade of bipedal and mostly carnivorous dinosaurs. In turn, and more specifically, it has been classified within the group of unenlagines, which are theropod dinosaurs that are closely related to the ancestors of birds.

The international team that carried out the study highlights that this discovery is important for several reasons. Firstly, the discovery of theropod dinosaurs is not very common, and in particular those of this type of theropod, small to medium-sized and with more slender and fragile bones, are even more difficult to discover. On the other hand, unenlaginians are very rare, so any new fossil remains that can be assigned to this group provide a great deal of information both anatomically and about the diversity of this group of theropods.

“This helps us understand a little more about the kinship relationships between unenlaginians and other theropod groups. In the particular case of Diuqin, its age is also important, because until now no other unenlaginian of that age had been found. The others that have been found are older or more recent in time, so this new species would have an intermediate temporal position. The latter is consistent with the size and some anatomical characteristics that can be interpreted as transitional between the oldest and most recent species. This discovery also enriches our dinosaur record in particular and our paleontological heritage in general,” says Federico Gianechini, a CONICET researcher at the Multidisciplinary Institute of Biological Research of San Luis (IMIBIO-SL, CONICET-UNSL) who participated in the study.

The fossil remains were found by Juan Porfiri, a paleontologist at the National University of Comahue in Argentina, and Gastón Garat, in an area near Lake Barreales, specifically on an isthmus that separates it from Lake Mari Menuco, in the central-eastern part of the province of Neuquén. The fossils were found during an exploration in the aforementioned area. First, bone chips from a sauropod dinosaur were found. Then, very close by, the remains of the Diuqin lechiguanae appeared, all in a relatively small area.

The name Diuqin comes from a Mapuzungun term, the language of the Mapuche people native to the region, which means “bird of prey” in Spanish. On the other hand, the second part of the name, lechiguanae, comes from “Lechiguana”, which was the name of the witch in the 1975 Argentine film “Nazareno Cruz y el lobo”, directed by Leonardo Favio. Therefore, the full name of this new species means “the Lechiguana bird of prey.”

“The work process on this new species of dinosaur had different stages, first a detailed anatomical study of the bones was carried out. This is done based on general observations and with a binocular magnifying glass to be able to visualize specific details and take measurements. The material was also scanned with a 3D scanner, and from the images obtained, three-dimensional models of the bones could be made. The anatomy is always compared to that of other species, to see similarities and differences. These anatomical studies are the basis for all subsequent studies, because they are what allow us to identify which group of dinosaur the remains belong to and to be able to see what particular characteristics the new species has that differentiate it from others. On the other hand, what is called a phylogenetic analysis was carried out, which allows us to see the kinship relationships with other species of theropods,” explains Gianechini.

The work also included a study of some marks observed on the humerus, one of the preserved bones. This had circular depressions at one end. Sometimes it happens that marks produced by other animals are preserved on fossil bones, such as those generated by teeth during bites. This happens in modern animals that were eaten by predators or scavengers after death, but these events also occurred in the past and sometimes this evidence is preserved on the surface of the bones.

“Through studies on the shape, its location and other characteristics, it is possible to infer what type of animal produced the mark and this gives us information on the interactions that may have occurred between predators and prey or with scavengers, giving us a greater picture. about what the ecosystem was like at that time and the relationships between the different animals that inhabited it. In the particular case of the marks observed in Diuqin, it is likely that they were generated by bites from another predator and even by another member of the same species, which would indicate a possible example of cannibalism,” indicates the researcher.

Reconstruction of Diuqin lechiguanae. (Image: Hannah Jones and Andrew McAfee)

Characteristics of Diuqin lechiguanae

“Some characteristics are very difficult to infer, because the bones found are too scarce to make a complete reconstruction of the animal or to find out its living habits and feeding habits. Despite this, as it has been classified as an unenlagine, it can be said that it would have had a body shape and a way of feeding similar to that of other unenlagines, that is, it is very likely that it was a predatory carnivore and a agile runner. On the other hand, based on the size of the bones, it can be said that it had a similar size to another unenlagino from Patagonia, called Unenlagia, with a body length estimated at more than 2 meters,” indicates the researcher.

Unenlagines are a group of predatory theropod dinosaurs that, until now, have only been found in the southern hemisphere, mainly in South America. Argentina is where most of the species were found, with six recognized until the publication of Diuqin lechiguanae, all from Patagonia. But not only do most of the unenlaginos come from Argentina, but also those that have an almost complete and very well preserved skeleton. In general, unenlagines have been closely related to other theropod dinosaurs such as Velociraptor. These dinosaurs are characterized, among other things, by having a claw on the second toe that is much larger than those on the other fingers, shaped like a curved blade, like a sickle, which was used by the animal during hunting. their prey.

“Unlike Velociraptor, unenlagini had a more graceful or slender body, long legs, and a head with an elongated snout and small teeth. They would have been agile runners and could have pursued and hunted their prey in the manner of modern birds such as chunas, although it has also been postulated that they could have fed on fish, in a similar way to modern aquatic birds such as herons or storks,” says Gianechini, and continues, “Both Velociraptor and many other theropods closely related to unenlagini had feathers on most of their bodies, including their arms and legs. Thus, although unenlagini with feathers have not yet been found, it is very likely that they also had them. Unenlagini have also been proposed as being very closely related to the first birds.”

The study is titled “Diuqin lechiguanae gen. et sp. nov., a new unenlagiine (Theropoda: Paraves) from the Bajo de la Carpa Formation (Neuquén Group, Upper Cretaceous) of Neuquén Province, Patagonia, Argentina.” And it has been published in the academic journal BMC Ecology and Evolution. (Source: Nahuel Aldir / Research Institute in Paleobiology and Geology (IIPG) / CONICET / National University of Río Negro (UNRN). CC BY 2.5 AR)