Taxonomic and palaeobiological implications of a large, pathological sabretooth (Carnivora, Felidae, Machairodontinae) from the Lower Pliocene of South Africa

Abstract

We describe the most complete postcranial remains of a pathological, large-bodied sabretooth from the Lower Pliocene site of Langebaanweg 'E' Quarry (South Africa). The skeleton consists of hind limb and vertebral elements that exhibit distinctive exostoses, osteophytes and eburnation. We performed a quantitative morphological comparison of the new postcranial remains found in Langebaanweg, with other Neogene and Quaternary sabretooth and non-sabretooth felids, consisting of the genera Amphimachairodus, Machairodus, Lokotunjailurus, Dinofelis, Panthera, Homotherium and Smilodon from several sites in Africa, Europe and North America, using principal component analysis and Mosimann transformations. Although the pathological deformation of the remains distorted some of the linear measurements, most of the analysed variables do not contain pathological features, and strongly indicate that the Langebaanweg sabretooth is morphologically closer to Machairodus aphanistus and Lokotunjailurus emageritus than it is to Amphimachairodus giganteus. This indicates that the remains could belong to an undetermined sabretooth species from the Langebaanweg locality. The observed pathologies in the foot and lumbar spine are consistent with diagnostic criteria for severe osteoarthritis (due to maturity), which would have limited limb mobility with severe consequences for hunting success.

Langebaanweg’s sabertooth guild reveals an African Pliocene evolutionary hotspot for sabertooths (Carnivora; Felidae)

“…The potential presence of species belonging to or closely related to Lokotunjailurus in Langebaanweg has recently been proposed based on postcranial bone morphology and limb proportions. 52 This is in accordance with our study on craniodental material. The original and the new material of Machairodus sp.…”

“…SAM-PQL-22193, six thoracic vertebrae, three lumbar vertebrae, two femora, two tibiae, the left fibula, the right astragalus, the left calcaneum and the second, third and fourth metatarsals; and SAM-PQL-52061, complete left calcaneum described in Rabe et al. 52 The large size, and its relatively high femur greater trochanter indicate a large felid affinity. Moreover, its morphology does not fit with Amphimachairodus (and presumably Adeilosmilus ), but is closer to Lokotunjailurus , as has been discussed in Rabe et al., 52 and here assigned to L. chinsamyae sp.…”

“… 52 The large size, and its relatively high femur greater trochanter indicate a large felid affinity. Moreover, its morphology does not fit with Amphimachairodus (and presumably Adeilosmilus ), but is closer to Lokotunjailurus , as has been discussed in Rabe et al., 52 and here assigned to L. chinsamyae sp. nov.…”

Palaeoecological deductions from osteohistology

“…However, there are many studies that have documented other types of skeletal pathologies in extant and extinct animals based on morphological observations (figure 2a-c), e.g. [129][130][131][132][133]. Indeed, some diseases simply do not manifest on the bone surface or the animal had not lived long enough for the condition to alter the exterior bone morphology, but histological examination sometimes can suggest a pathology.…”

Osteohistology and palaeobiology of giraffids from the Mio‐Pliocene Langebaanweg (South Africa)

“…Langebaanweg ranks as one of the richest Neogene fossil vertebrate sites in Africa and comprises of a diverse range of vertebrates (e.g. Hendey, 1981, 1989; Rabe et al, 2022; Valenciano et al, 2022; Woolley et al, 2019). The contemporaneous extinct giraffe taxa are well represented in the faunal composition of this Pliocene locality, where they have been recovered from the ‘Varswater Formation’ (Harris, 1976).…”