Establishing A Cohesive Ontogenetic Framework for Tapirus spp. (Ceratomorpha, Perissodactyla)
Abstract
Tapirus spp. are perissodactyl ungulates from Europe, Asia, North America, and South America, with an extensive fossil record spanning ~50 million years and into the modern day. Tapirus spp. are known to be persistent browsers of leafy material throughout their natural history, yet the varying morphology of the Tapirus cranium and forelimb implies adaptive morphology. Despite this variation found in Tapirus anatomy, the postcranium during ontogeny and growth in relation to the cranium is poorly understood. Here, 247 bones encompassing humeri, radii, ulnae, femora, tibiae, astragali, and third metatarsi of Tapirus polkensis from the Gray Fossil Site were sampled across various life stages. Four measurements were taken: diaphyseal midpoint, proximal total width, distal total width, and total length. Ontogenetic stage data based on tooth eruption and wear were recorded, though isolated elements with no ontogenetic data were also measured. To simplify the wear and eruption timing of individuals, integrate shifts in the skull bones across ontogeny, and account for natal/fetal individuals, four ontogenetic stages were established: natal, juvenile, subadult, and adult. Bivariate scatter plots were then created to identify the strongest correlation for the four ontogenetic stages via measurement data. Total length and diaphyseal midpoint of the third metatarsal and humerus, as well as proximal width and total dorsoventral length of the femur, are good predictors of ontogenetic stages. Tibiae, astragali, and radii are not good predictors of ontogenetic stages. Regardless, this work demonstrates that T. polkensis postcrania can be used to understand the ontogeny and growth of tapirs as a cohesive whole. However, caveats of select highly variable limb bones, timing of radius and ulna fusion into the radioulnae, and preservation bias currently obfuscate research efforts. Future research will expand taxonomic sampling of growth with the methods outlined herein, in addition to quantifying bone shape throughout ontogeny.
Start Time
15-4-2026 9:00 AM
End Time
15-4-2026 12:00 PM
Room Number
Culp Ballroom 316
Poster Number
54
Presentation Type
Poster
Presentation Subtype
Posters - Competitive
Presentation Category
Science, Technology, and Engineering
Student Type
Graduate and Professional Degree Students, Residents, Fellows
Faculty Mentor
Steven Wallace
Establishing A Cohesive Ontogenetic Framework for Tapirus spp. (Ceratomorpha, Perissodactyla)
Culp Ballroom 316
Tapirus spp. are perissodactyl ungulates from Europe, Asia, North America, and South America, with an extensive fossil record spanning ~50 million years and into the modern day. Tapirus spp. are known to be persistent browsers of leafy material throughout their natural history, yet the varying morphology of the Tapirus cranium and forelimb implies adaptive morphology. Despite this variation found in Tapirus anatomy, the postcranium during ontogeny and growth in relation to the cranium is poorly understood. Here, 247 bones encompassing humeri, radii, ulnae, femora, tibiae, astragali, and third metatarsi of Tapirus polkensis from the Gray Fossil Site were sampled across various life stages. Four measurements were taken: diaphyseal midpoint, proximal total width, distal total width, and total length. Ontogenetic stage data based on tooth eruption and wear were recorded, though isolated elements with no ontogenetic data were also measured. To simplify the wear and eruption timing of individuals, integrate shifts in the skull bones across ontogeny, and account for natal/fetal individuals, four ontogenetic stages were established: natal, juvenile, subadult, and adult. Bivariate scatter plots were then created to identify the strongest correlation for the four ontogenetic stages via measurement data. Total length and diaphyseal midpoint of the third metatarsal and humerus, as well as proximal width and total dorsoventral length of the femur, are good predictors of ontogenetic stages. Tibiae, astragali, and radii are not good predictors of ontogenetic stages. Regardless, this work demonstrates that T. polkensis postcrania can be used to understand the ontogeny and growth of tapirs as a cohesive whole. However, caveats of select highly variable limb bones, timing of radius and ulna fusion into the radioulnae, and preservation bias currently obfuscate research efforts. Future research will expand taxonomic sampling of growth with the methods outlined herein, in addition to quantifying bone shape throughout ontogeny.
