ELIZETE HOLANDAFossil of Tapirus rondoniensis: sagittal crest and premolar cusp different ELIZETE HOLANDA
Brazil currently harbors one of only four living tapir species, Tapirus terrestris, which at 2 meters in length and weighing up to 300 kilograms, is considered the largest land mammal in South America. But 40,000 years ago, during the Pleistocene epoch, a distinct form of this large herbivore may have existed in the western portion of the northern region of Brazil, near the border with Bolivia, in what is now the state of Rondônia. A new fossil of an extinct species of mammal has recently been described by Brazilian researchers in an article published in the February issue of the American Journal of Mammalogy. Collected in a former mining area of the Madeira River, the newly discovered Amazonian tapir was named Tapirus rondoniensis in honor of the unity of the federation in which the only known exemplar was found.
Generally speaking, this probable new species has many anatomical similarities to T. terrestris, commonly known as the Brazilian tapir, which is now present in nearly all of Brazil and at least part of every other country in South America, except for Uruguay. “It must have been very similar to our living tapir,” says paleontologist Ana Maria Ribeiro, of the Zoobotânica Foundation in Rio Grande do Sul, and one of the authors of the paper. The new fossil exhibits primitive traits of the teeth and skull that are also characteristic of T. pinchaque, the smallest living species of tapir and the only one to live outside of forested areas, specifically in the Andes Mountains in parts of Colombia, Ecuador and Peru. T. rondoniensis had a wider forehead and a smaller sagittal crest than the Brazilian tapir, as well as a second maxillary premolar with a reduced cusp. “In the past, the Brazilian tapir and this new fossil species must have coexisted in parts of the Amazon,” says Professor Elizete Holland, of the Department of Geology at the Federal University of Roraima (UFRR), and one of the collaborators in the current study.
Consisting of a nearly complete and well-preserved skull, the fossil remains of this newly discovered extinct species of tapir are now a part of the paleontological collection of the Federal University of Rondônia (Unir). The remains of the ancient herbivore were discovered in 1970 by miners seeking gold in the area of Araras, in the municipality of Nova Mamoré, on the right bank of the Madeira River. This region has rich deposits of fossil vertebrates and plants, which usually occur in a layer of sedimentary rock that is rich in sand and limestone, and located about 10 meters below the surface. This sedimentary layer also contains the gold that was being sought by the miners. According to Elizete, who graduated from Unir at the beginning of the last decade, when she had her first contact with the skull of T.rondoniensis, fossils that were not destroyed by the mining process fell into the hands of private collectors or universities. Luckily, the skull of this Amazonian tapir ended up going to the second destination.
Biologist Mário de Vivo, curator of mammals at the University of São Paulo (USP) Museum of Zoology, is not convinced that the fossil tapir from Rondônia represents a new, even extinct, species of herbivore. Although the differences between T. rondoniensis and T. terrestris are real and may indicate that these actually are two distinct forms of tapir, the researcher argues that the description of only a single exemplar fossil of the supposed new species does not allow for a good evaluation of the morphological variation present in the skull of this Rondônian tapir. For him, the differences in the dentition and size of the sagittal crest of the ancient herbivore fossil rescued from the banks of the Madeira River may just represent normal anatomical variation that is intrinsic to the population of T.terrestris in this remote region.”It’s not impossible that this fossil from Rondônia represents a new species of tapir, but I would like to see more skeletons with these same characteristics”, reflects de Vivo. According to paleontologist Jorge Ferigolo, of the Zoobotânica Foundation in Rio Grande do Sul, and also one of the authors of the Journal of Mammalogy publication, this ancient Amazonian tapir is sufficiently distinct from the Brazilian tapir. “Small details can distinguish one species from another,” affirms Ferigolo.
The taxonomic classification of living beings in families, genera and species is an activity that is always subject to debate. Consensus is often slow to take shape and taxonomic revisions are frequent and necessary in many groups. Further to the proposal that there was a prehistoric species of tapir particular to the Amazon region, Elizete also defends the possibility that another extinct species of herbivore, T.cristatellus, lived in a transition zone between the South and Northeastern regions of Brazil at more or less the same time. New exemplars of this form of tapir, which had a very low sagittal crest, were recently found in caves in Bahia. Until then, skulls of T. cristatellus – still not recognized as a valid species by many experts, who prefer to treat it as a variant of the Brazilian tapir – had been found only in the Lagoa Santa region of Minas Gerais near the capital city of Belo Horizonte. If this hypothesis is correct, Brazil may have harbored three different and concomitant species of tapir 40,000 years ago: the Brazilian tapir, which is still alive, and those from Amazon and the Southeast-Northeast regions, which are both extinct.
Scientific article
HOLLAND, EC et al. New Tapirus species (Mammalia: Perissodactyla: Tapiridae) from the upper Pleistocene of Amazonia, Brazil. Journal of Mammalogy.v. 92, n. 10, p. 111-20. February 2011.
