Morphological and Functional Divergence of the Lower Jaw Between Native and Invasive Red Foxes

Variability of jaw muscles in Tunisian street dogs and adaptation to skull shape

The impact of artificial selection on the masticatory apparatus of dogs has been poorly studied, and comparative data with dogs subjected to more natural constraints are lacking. This study explores the jaw musculature of Tunisian street dogs, which are largely free from the influence of breed-specific selection. The masticatory muscles (digastric, masseter, temporalis, and pterygoid) of 27 adult dogs were dissected and muscle mass and physiological cross-sectional area (PCSA) were quantified, providing a baseline for comparisons between dogs from more natural versus more controlled environments. Our findings reveal that the morphology of the jaw adductor muscles is remarkably conserved among dogs, despite significant variation in skull shape. Additionally, all masticatory muscles scale isometrically with body mass. Notably, females exhibit functional adaptations that optimize muscle strength, particularly in the temporalis muscle, despite showing smaller overall muscle volumes compared to males. This could be linked to differences in predation, competition for food, or factors related to sexual behavior. Preliminary evidence suggests that captivity may limit the development of muscle mass and PCSA in the temporalis muscle, likely due to changes in lifestyle and diet. Significant relationships were also observed between skull shape and muscle data, particularly in the mandible, indicating that skull variability reflects jaw adductor muscle anatomy to some degree. This study enhances our understanding of jaw muscle morphology and function in feral dog populations and offers insights into the adaptation of the masticatory apparatus in dogs.

Morphometric classification of kangaroo bones reveals paleoecological change in northwest Australia during the terminal Pleistocene

Specimen identification is the backbone of archeozoological research. The challenge of differentiating postcranial skeletal elements of closely related wild animals in biodiverse regions can prove a barrier to understanding past human foraging behaviours. Morphometrics are increasingly being employed to classify paleozoological animal remains, however, the potential of these methods to discriminate between wild animal groups has yet to be fully realised. Here we demonstrate the applicability of a traditional morphometric approach to taxonomically classify foot and ankle bones of kangaroos, a large and highly diverse marsupial family. Using multiple discriminant analysis, we classify archaeological specimens from Boodie Cave, in northwest Australia and identify the presence of two locally extinct macropod species during the terminal Pleistocene. The appearance of the banded hare-wallaby and northern nail-tail wallaby in the Pilbara region at this time provides independent evidence of the ecological and human responses to a changing climate at the end of the last Ice Age. Traditional morphometrics provides an accessible, inexpensive, and non-destructive tool for paleozoological specimen classification and has substantial potential for applications to other diverse wild faunas.