Insights from the skull and postcranial osteometry of the Sardinian pine marten (Martes martes latinorum). Does it obey the island rule?

Abstract This study investigates the osteometric differences between the Sardinian pine marten ( Martes martes latinorum ) and its continental counterpart ( Martes martes martes ), focusing on both cranial and postcranial skeletal elements. According to the island rule, small mammals on islands tend to increase in size. The Sardinian pine marten exhibits an increase in skull size (+12% in both sexes) compared to European subspecies, while its overall body mass shows a smaller increase (+9%). Analysis of the masticatory apparatus suggests hypertrophy of the temporalis and masseter muscles, reflected in a more robust zygomatic arch and a narrower postorbital constriction (−3.5% in males, −2.9% in females), suggesting a dietary shift toward increased meat consumption. The cranial capacity of Sardinian pine martens (22.85 cm 3 in males, 21.48 cm 3 in females) remains relatively large, possibly due to the cognitive demands associated with predation. Limb bones are longer in Sardinian females (+5.8%) but show negligible difference in males (< 1%) compared to the European subspecies. This study provides the first comprehensive osteological analysis of M. m. latinorum , demonstrating that the Sardinian marten population forms a distinct insular cluster, as also confirmed by genetic data. Historical and archeological evidence suggests that the Sardinian pine marten was introduced during the Neolithic (approximately 8,000 years ago). Therefore, the observed skeletal modifications, including the increased size of the skull, occurred in a relatively short evolutionary timescale.