Ontogenetic skull variation in an Amazonian population of lowland tapir, Tapirus terrestris (Mammalia: Perissodactyla) in the department of Loreto, Peru

Abstract

The skulls of 54 specimens of the South American tapir, Tapirus terrestris collected in the department of Loreto, Peru were measured, analyzed and compared to investigate skull development of this species. Univariate, multivariate and allometric analyses were performed using 32 skull variables through traditional morphometrics. Significant skull shape variation was detected among ontogenetic classes. Young individuals (class I, n = 22) showed higher variation than subadults and adults (class II, n = 23 and class III, n = 9), without evidence of sexual dimorphism (males = 35, females = 19). Principal component analyses and discriminant function analysis showed almost complete separation of the age classes. Allometric analysis indicated a tendency of unproportioned cranial growth. All our samples come from the same population living under the same ecological condition, which eliminates the effect of confounding variables related to habitat on the pattern of ontogenetic variation of this anatomical structure.

Sagittal crest morphology decoupled from relative bite performance in Pleistocene tapirs (Perissodactyla: Tapiridae)

“…Specimens were sought to have at least M2 erupted/erupting to minimize the influence of age. No sexual dimorphism has been found in tapir crania (Rojas et al 2021), thus we do not account for this.…”

“…No sexual dimorphism has been found in tapir crania (Rojas et al . 2021), thus we do not account for this.…”

“…These components are known to be consumed to different degrees in different modern tapir species (Janzen 1982;Henry et al 2000;Downer 2001;DeSantis 2011;O'Farrill et al 2013). Tapir skulls exhibit a great deal of variation in the attachment sites of the temporalis musculature, that is, the sagittal crest (Hulbert et al 2009;Dumbá et al 2018;DeSantis et al 2020); with no observed sexual dimorphism (Rojas et al 2021). A good example of this variation is the different crest morphologies exhibited by extant tapirs (Fig.…”

“…2020); with no observed sexual dimorphism (Rojas et al . 2021). A good example of this variation is the different crest morphologies exhibited by extant tapirs (Fig.…”