The 'rhino' of the Triassic: the first giant terrestrial mammals of about 250 million years ago

Site of Lisowice in Poland. SCIENCE Among these animals Niedzwiedzki advances the "exciting" presence of "our cousins" stakeholders", the morganucodóntido

The 'rhino' of the Triassic: the first giant terrestrial mammals of about 250 million years ago
Makes about 237 million years ago, in a period known as the Triassic Upper, an animal the size of an elephant and nine tons of weight inhabited the earth. Her manner and walk are reminiscent of the current rhino. Also it fed on plants and drank in small pools. But its mammoth size, its age and the place where they have found his remains has surprised the scientific community.

it is Not a mammal, but a dicinodonte, a to be extinct known as protomamífero or reptile mamiferoide. In addition, their bones are huge for their age and have been found in Poland, not in Africa, Asia, or America, where the fossil record is abundant in this type of fauna. It is a new species and a most unusual puzzle evolutionary scientists now have to interpret. Your name: Lisowicia bojani, by the local Polish Lisowice where there has been the discovery, and in honor of the anatomist and paleontologist, alsatian-Ludwig Heinrich Bojanus (1776-1827).

"The discovery of Lisowicia provides the first evidence he had dicinodontes the size of an elephant similar to a mammal and at the same time that the famous dinosaur sauropodomorfos long neck," he says to THE Grzegorz Niedzwiedzki, a paleontologist from the University of Uppsala (Sweden) and principal author (together with researcher of the Academy of Sciences of Poland, Tomasz Sulej) of the research that this Thursday has been made public in the journal Science.

A new species

The site in which you have excavated the fossil of "this giant beast", as described by Niedzwiedzki in an email, was discovered in 2005 by an amateur geologist named Robert Borzcki. From the first bone fragment found this year and until 2017, we have extracted the remains of different sizes. A femur of 80 cm long and a blade of more than 1 metre in length has stunned the scientists themselves. "It is not a dicinodonte typical," he stresses, "is a kind giant and unknown".

To understand the evolutionary relationships of this species dates back 270 million years ago, when the subclass of mammals and within the order of the therapsids was divided into two lineages, one mammal and not another mammal. It is not a mammal, commonly known as protomamífero or reptile mamiferoide (but that is neither the one nor the other) which includes the dicinodontes, the parvorder in the who has classified the new species (and new genus) Lisowicia bojani, an animal that could be baptized, but only by its likeness, as the rhinoceros of the Triassic.

Lisowicia has the skull typical of a reptile mamiferoide, that is not a reptile precisely having a fenestra temporary feature, that is, an opening in the roof of the skull behind each eye, and is a unique character of mammals. In addition, it presents the progress of the reptiles, since the shape of its front legs allow them to an upright posture, such as large mammals present, the rhino or the hippo. For Niedzwiedzki, their characteristics of bone make it "more like a rhinoceros".

A growth and unusual size

With a height of 2.6 meters, a length of over 4.5 meters and a body mass of 9 tons, "Lisowicia is the largest sinápsido of the Triassic and is even larger than some of the largest mammals in the Permian," says Niedzwiedzki. Against what was believed before, this prehistoric animal provides the first evidence that large dicinodontes, the size of an elephant, coexisted with the dinosaurs sauropodomorfos long neck. In addition fills a gap in the fossil record, because of the shape and size of their limbs no longer can be said that large mammals or dinosaurs are the only ones who have them.

Site of Lisowice in Poland. SCIENCE

Among these animals Niedzwiedzki advances the "exciting" presence of "our cousins" stakeholders", the morganucodóntidos, a small mammal similar to a shrew, and that they lived "at the foot of the gigantic dicinodontes", a conclusion that arises from the findings of teeth morganucodóntidos in the same bed in which were found the bones of Lisowicia.

Large animals in the evolution

To date, it was believed that only large herbivores of the Triassic were the dinosaurs. The new species Lisowicia bojani found in Poland, a dicinodonte that reached a body size with a gigantic strip by land the previous statement, and opens the door to new theories. On the one hand, its expansion was greater than what was believed, and on the other, the large size of some terrestrial animals, because it is not only in the evolution of dinosaurs.

If we look at the current species, animals of larger sizes are herbivores, terrestrial or marine mammals. In the past, and for what who sheds this research, this was not the case. With the dinosaurs, and now with the dicinodontos, it is known that lived on dry land species tetrápodas of large carnivorous and herbivorous, but not just dinosaurs. This raises new questions that many scientists relate to a balance between the energy cost, sustainability, mobility and defense.

But, what has favored the evolution of herbivores have large sizes? "Definitely, the marine mammals of today are enormous. We have large terrestrial mammals such as elephants, which are not as large as the aquatic animals. Scientists still don't have a good explanation of why forms appear gigantic in certain storylines", it indicates Niedzwiedzki. It is difficult to determine, therefore, "the why of these large sizes, and I'm afraid that in the process of evolution, there are more phenomena probabilistic than we ever imagined," he adds.

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Updated Date: 26 November 2018, 08:00

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