New insights into the giant mustelids (Mammalia, Carnivora, Mustelidae) from Langebaanweg fossil site (West Coast Fossil Park, South Africa, early Pliocene)

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

Here, we describe and revise craniodental material from Langebaanweg 'E' Quarry (South Africa, early Pliocene, ∼5.2 Ma), which represents one of the largest and best-preserved collections of sabertooth felids from Mio-Pliocene deposits of Africa. Four taxa, including two new species, are recognized: Lokotunjailurus chinsamyae sp. nov., Adeilosmilus aff. kabir, Yoshi obscura, and Dinofelis werdelini sp. nov. The felid guild composition analyzed herein suggests the presence of a mosaic environment with open components in the region, and shows a potential relationship with that of Yuanmou, suggesting a similar environment and/or dispersal route/event. The reassessment of the rich early Pliocene felids from Langebaanweg is a step toward understanding the transition and evolution of the felids in the southern hemisphere during the late Miocene to early Pliocene.

Mineralized-tissue histology reveals protracted life history in the Pliocene three-toed horse from Langebaanweg (South Africa)

We studied the bone and dental histology of the tri-dactyl equid Eurygnathohippus hooijeri, one of the most iconic mammals found at the world-renowned Pliocene site of Langebaanweg, South Africa, to reconstruct important features of its life history. Our results show that key life-history events, such as weaning, skeletal maturity and reproductive maturity, occurred later in this African hipparionine compared with European three-toed equids and several extant Equus. Its late life-history schedule agrees with an ecological context of low adult extrinsic mortality and low juvenile survival rates. We also observed high rates of bone growth in Eu. hooijeri that were probably achieved through a high-quality diet and plentiful available water. Our research highlights the significance of combining bone and dental histology in the same taxon to obtain refined palaeobiological information about extinct vertebrates.

Eucyon khoikhoi sp. nov. (Carnivora: Canidae) from Langebaanweg ‘E’ Quarry (early Pliocene, South Africa): the most complete African canini from the Mio-Pliocene

A new medium-sized canid, Eucyon khoikhoi sp. nov., is described from the early Pliocene site of Langebaanweg ‘E’ Quarry (South Africa). It possesses a robust dentition with large upper- and lower-second molars, an m1 talonid without a transverse cristid between the entoconid and the hypoconid, and a well-developed hypoconulid shelf. Our cladistic analysis of the earliest better-known African canini, places E. khoikhoi as the most basal taxon of an African clade composed of E. wokari, ?Nyctereutes barryi, ?Schaeffia mohibi and Schaeffia adusta (living side-striped jackal). We suggest an alternative arrangement for the poorly known East African E. intrepidus from the Late Miocene and E. kuta from the Middle Pliocene. Eucyon intrepidus could belong to the same clade as E. khoikhoi, unlike E. kuta, whose dentition suggests a closer relation with the Lupulella group. Thus, these results support the paraphyly of Eucyon, demonstrating the need for an in-depth review of the genus. Eucyon khoikhoi has a body mass comparable to E. kuta and the European E. debonisi and E. monticinensis. We conclude that E. khoikhoi may have had a comparable role in the ecosystem to the extant hypocarnivorous S. adusta.

Differing limb functions and their potential influence upon the diversification of the mustelid hindlimb skeleton

Though form-function relationships of the mammalian locomotor system have been investigated for over a century, recent models of trait evolution have hitherto been seldom used to identify likely evolutionary processes underlying the locomotor system’s morphological diversity. Using mustelids, an ecologically diverse carnivoran lineage, I investigated whether variation in hindlimb skeletal morphology functionally coincides with climbing, digging, swimming and generalized locomotor habits by using 15 linear traits of the femur, tibia, fibula, calcaneum and metatarsal III across 44 species in a principal component analysis. I subsequently fit different models of Brownian motion and adaptive trait diversification individually to each trait. Climbing, digging and swimming mustelids occupy distinct regions of phenotypic space characterized by differences in bone robustness. Models of adaptive and neutral evolution are, respectively, the best fits for long bone lengths and muscle in-levers, suggesting that different kinds of traits may be associated with different evolutionary processes. However, simulations based upon models of best fit reveal low statistical power to rank the models. Though differences in mustelid hindlimb skeletal morphology appear to coincide with locomotor habits, further study, with sampling expanded beyond the Mustelidae, is necessary to better understand to what degree adaptive evolution shapes morphological diversity of the locomotor system.