South American tapir

With an estimated mass of only 110 kg (240 lb), T. kabomani is the smallest living tapir.[6] For comparison, the mountain tapir has a mass between 136 and 250 kg (300 and 551 lb).[11][12][13][14] Tapirus kabomani is roughly 130 centimetres (51 in) long and 90 centimetres (35 in) in shoulder height.[6]

It has a distinct phenotype from other members of the species. It can be differentiated by its coloration: it is a range of darker grey to brown than other T. terrestris strains.[6] This species also features relatively short legs for a tapir caused by a femur length that is shorter than dentary length.[6] The crest is smaller and less prominent.[7] T. kabomani also seems to exhibit some level of sexual dimorphism as females tend to be larger than males and possess a characteristic patch of light hair on their throats. The patch extends from the chin up to the ear and down to the base of the neck.[6]

Head and skull attributes are also important in identification of this species. This tapir possesses a single, narrow, low and gently inclined sagittal crest that rises posteriorly from the toothrow.[6] T. kabomani skulls also lack both a nasal septum and dorsal maxillary flanges.[6] The skull possesses a meatal diverticulum fossa that is shallower and less dorsally extended than those of the other four extant species of tapir.[6]

The species may be relatively common in forest-savanna mosaic habitat (relicts of former cerrado). Nevertheless, the species is threatened by prospects of future habitat loss related to deforestation, development and expanding human populations.[6]

While this tapir does not seem to be rare in the upper Madeira River region of the southwestern Brazilian Amazon,[6] its precise conservation status is unknown. T. kabomani is limited by its habitat preference and tends not to be found where its preferred mosaic gives way to either pure savannah or forest.[6] This, in combination with the fact that other less restricted tapir species within the area are already classified as endangered, has led scientists to hypothesize that the new species is likely to prove more endangered than other members of its genus.[7] Human population growth and deforestation within southwestern Amazonia threaten T. kabomani through habitat destruction.[6] The creation of infrastructure such as roads as well as two dams planned for the area as of December 2013 further threaten to considerably alter the home range.[7] Hunting is also a concern. The Karitiana tribe, a group of people indigenous to the area, regularly hunt the tapir.[7] Additional threats exist from crocodilians and jaguars, natural predators of tapirs within the area.[21]

Humans aside, the region of the Amazon in which T. kabomani is found has also been highlighted as an area that is likely to be particularly susceptible to global warming and the ecosystem changes it brings.[6]

In both morphological and molecular phylogenetic analyses,[6] T. kabomani was recovered as the first diverging of the three tapirs restricted to South America. Morphological analysis suggested that the closest relative of T. kabomani may be the extinct species T. rondoniensis.[6] Molecular dating methods based on three mitochondrial cytochrome genes gave an approximate divergence time of 0.5 Ma for T. kabomani and the T. terrestris–T. pinchaque clade, while T. pinchaque was found to have arisen within a paraphyletic T. terrestris complex much more recently (in comparison, the split between T. bairdii and the tapirs restricted to South America took place around 5 Ma ago).[6]

The validity of the species, and whether or not it can be reliably distinguished from the South American tapir, has subsequently been questioned on both morphological and genetic grounds. Morphological differences between the two species of tapir are noted to be especially difficult to discern in photographs allegedly depicting T. kabomani and noted to be only qualitatively described in the original literature.[26] Morphologically, lack of published numerical ranges for diagnostic differences make it incredibly difficult for individuals to be identified in the field as little black tapirs instead of South American tapirs. A heavy reliance upon the indigenous people for identification of T. kabomani was also noted in the major dissenting article. Concerns were cited regarding the reliability of information when it is gathered from locals as, while they are frequently aware of many more species in an area, they can sometimes describe haplotypes of culturally important species to be entirely different species.[26]

Genetic evidence has been questioned on similar grounds. Several examined genetic sequences said to be characteristic for the species, most notably the Cyth sequence of cytochrome b, have been described as minimally divergent from those of other South American tapirs.[26] Further analyses of cytochrome b sequences did reveal a clade allegedly belonging to T. kabomani, however, it was described to be only as divergent as some haplotype found in other species.[26] Mitochondrial DNA originally connected to morphological traits and used to describe the species has also been called into question. Although several samples of T. kabomani have been obtained, only the two samples from southwestern Amazonia were analysed while those obtained in the northwest were not.[26] The connection between the morphology and DNA of supposed T. kabomani in northwestern areas is unknown and there is the possibility that the correlation between mtDNA and morphology is insufficiently supported.[26]

However, besides cytochrome b, two other mitochondrial genes were analyzed, COI and COII, both showing the same pattern found for cytochrome b.[27] Several other objections raised against the distinction of T. kabomani from T. terrestris, including external and internal morphological characters, statistical analysis, distribution and use of folk taxonomy, were addressed in Cozzuol et al (2014).[27]

Further genetic evidence invalidating T. kabomani as a new species was published by Ruiz-Garcia et al. (2016).[8] Ruiz-Garcia et al. found and sampled tapirs that fit the morphological description provided by Cozzuol et al. (2013) for T. kabomani but they only showed haplotypes of other T. terrestris haplogroups.[8] In addition, the morphological evidence for T. kabomani has been contradicted by further research.[28] Dumbá et al. reevaluated skull shape variation among tapir species and found that T. kabomani and T. terrestris exhibit considerable overlap in skull morphology, though it could still be distinguished by its broad forehead.[28]