The outer parts of long-dead creatures do not easily enter the fossil record. That’s why this incredibly well-preserved skin of an iconic carnivorous dinosaur is a delight: a new analysis reveals a complex layer of scales, tacos, spines, bumps and wrinkles.
The remains of this bizarre-looking predator, known as the horned bee-eater (Carnotaurus sastrei), first discovered in Patagonia in 1984. At the time, it was the first meat-eating dinosaur ever found with fossilized skin, and exquisite prints covered almost every part of the predator, from head to tail. .
At times, the toothed surface almost resembles the spiny devil of Australia (Moloch horridus), and yet the ridges of some other scales remind scientists of an elephant skin. Nowhere is there even a touch of pen.
All that was missing was the fossilized skin of the bathed head of the abelisaurid; now, scientists have properly analyzed and described the discovery in great detail.
Unlike other brief descriptions of skin footprints, new analyzes have found no evidence that dinosaur scales were arranged in irregular rows or had different sizes depending on where they were in the body (as we see in some modern lizards, for example).
For example, the scales do not become smaller as they extend below the tail and move away from the core of the dinosaur’s body. In contrast, the larger scales appear randomly distributed throughout the thorax and tail.
Reconstruction of Carnotaurus by a new artist, with scaly skin. (Jake Baardse)
“Looking at the skin from the shoulder, belly, and tail regions, we discovered that the skin of this dinosaur was more diverse than previously thought, consisting of large, tapered tacos distributed randomly surrounded by a web. of small elongated, diamond-shaped or subcircular scales, “describes paleontologist Christophe Hendrickx of the Lillo Execution Unit in San Miguel de Tucumán.
Although feathered dinosaurs are more common than we once assumed, not all of these prehistoric creatures developed such striking decorations.
Even dinosaurs that came from the same branch as modern birds did not necessarily possess feathers. Large, terrestrial carnivores, such as the T. rex and the bathed abelisaurids, indeed, seemed to have a scaly, lizard-like skin.
Both iconic predators belonged to a branch of two-legged dinosaurs with hollow bones known as theropods, from which modern birds later branched out.
But this copy of C. sastrei it has the best-preserved skin of any non-avian theropod, the researchers say. In total, it includes six fragments of skin extracted from the neck, shoulder girdle, chest and tail.
Location of skin specimens. (Jake Baardse)
The largest patch comes from the front of the tail. Here, the smallest scale measures only 20 millimeters in diameter, and yet sometimes these small flakes of smooth skin can be found among other flakes twice as large.
These much larger feature scales have an almost dome-like appearance, similar to the dome scales found in Diplodocus – a long-necked herbivorous dinosaur. Others are more diamond-shaped, with much longer lengths than widths; these resemble the scales seen in tyrannosaurids that also lived in the late Cretaceous, about 70 million years ago.
Why horned abelisaurids once possessed such a wide range of large and small scales is another mystery.
In 1997, scientists suggested the large conical scales found Carnotaurus it existed for “a certain degree of protection during the confrontation,” but the authors of this new analysis say that these scales would serve little against the teeth.
“Alternatively, a Carnotaurus and, more broadly, among dinosaurs, feature scales may have simply had a visualization / coloring function, ”they suggest.
This is similar to the feathers of modern birds, which can serve as simple displays or for flying. Given that feathers are believed to have evolved from scales, this similar diversity may not be a coincidence.
The stairs of C. sastrei (AE) compared to other dinosaurs. (Hendrick and Bell, Cretaceous Research, 2021)
However, other similarities are more difficult to pinpoint. Some of the most intriguing scales of the horned abelisaurid, for example, come from its tail, where certain flakes contain an arrangement of ridges or vertical grooves.
The authors say that these parallel lines almost resemble the wrinkles of elephant skin, and given that both the theropod and the African elephant are large terrestrial animals without sweat glands that live in warmer climates, the authors suspect that these mountain ranges may have similar functions. (African elephants have wrinkles on their skin to increase the surface area and more effectively release excess heat by evaporation).
“Although we do not claim this Carnotaurus and elephants necessarily thermoregulated in the same ways (i.e. by evaporative cooling), we observe here that they share distinct gross morphological similarities in their integument, although one has scales and the other has a highly modified mammalian epidermis. ” , write the authors.
Regardless of the details, they maintain, it is likely that theropod skin has played at least some role in thermoregulation. Future research into the scaly skin of early dinosaurs may reveal much more than just their appearance. He can also tell us how they lived.
The study was published in Cretaceous research.