Careful analysis of skulls thousands of years old has helped reveal the true dimensions of a South American Ice Age giant: the deer. antifer ensenadensis, which became extinct about 10,000 years ago. A new estimate indicates that the animal could exceed 200 kg — therefore weighing almost twice as much as its largest living relative in the region, the marsh deer.
Only the animal’s antlers, with beautiful symmetrical branches and roughness that make it unmistakable, could reach 1 meter in length — it is one of the most imposing in the evolutionary history of its group.
The new portrait of the species, which includes the first virtual reconstruction of its brain, is the result of a master’s research by paleontologist Emmanuelle Fontoura, from UFSM (Federal University of Santa Maria, in Rio Grande do Sul). Along with her advisor Leonardo Kerber and other colleagues, the researcher submitted two skulls from the A. ensenadensis to computed tomography sessions.
The team also compared the animal’s cranial characteristics and brain structure with that of its current relatives in South America (such as the pampas deer and the bororó deer) and in the northern hemisphere (the case of the noble deer, common in Europe and In the USA).
Fontoura explains that skull measurements usually provide relatively reliable estimates of a species’ body size. Another bone structure often used for this is the femur (thigh bone), but the problem is the difficulty of knowing who is who among fossil deer by examining only the skeleton below the neck. “In their case, the skull and antlers turn out to be more characteristic and easier to identify,” she says.
In part, it makes sense that the antifer was so large when you consider that the geological epoch in which he lived, the Pleistocene, was the heyday of large mammals in South America. Giant sloths, gomphotheres (extinct relatives of elephants), super armadillos, saber-toothed bears, llamas, and horses populated the mainland’s open vegetation areas.
It is conceivable that the deer would have acquired a larger size both to compete with other herbivores and to defend itself from large predators. In addition, the researcher recalls, the cooler climate of the Pleistocene also favored the evolution of larger body structures (in general, the larger the body of an animal, the easier it is to minimize the loss of body heat).
In fact, the A. ensenadensis it is usually found in colder regions, such as southern Brazil, and associated with environments with a lot of water, such as swamps — another factor in common it has with today’s marsh deer.
However, it is not possible to say that the Pantanal deer is the closest living relative of the extinct animal. “The phylogeny [“árvore genealógica” evolutiva] of these animals is still poorly understood, partly because it is a group that evolved very quickly”, says the paleontologist.
Even so, it is possible to make some inferences about the behavior of the Pleistocene species, taking into account what is known about the antlers of other deer. According to Fontoura, two factors complement each other to explain the evolution of large antlers: they can be a factor in attracting mates, signaling health and other genetic qualities in males, and they are also used as weapons in combats between male members (involving , again, the dispute over females).
“Of course, a balance is needed in the development of the animal, otherwise it could develop antlers whose weight it would not even be able to bear”, he explains. In case of antiferthis process was close to reaching its apex.
The animal’s brain wasn’t exactly enviable. The relationship between organ size and species body size is more or less within what is seen in similar deer. In general, larger animals within the group tend to carry proportionately smaller brains, while the brain size of more modest deer is proportionately larger.
The most likely explanation is that smaller species suffer more threats from predators and competition with other herbivores, which would lead to the evolution of a larger brain.
Fontoura and his colleagues’ work on the extinct deer brain was published in the Journal of Morphology.
