Comparative Craniodental Morphology of Two Endemic Fossil Sus Species (Suidae, Mammalia) From the Middle Pleistocene of Java (Indonesia)

Abstract

Over a century ago, Dutch anatomist and geologist Eugène Dubois discovered the famous “Java man” and associated mammals in Java. His collection continues to be widely recognised for its significance to palaeontology and palaeoanthropology. Mammal fossil remains from Dubois’ collections have been essential for understanding faunal migrations driven by Quaternary glacial cycles from Southeast Asia to the Sunda Shelf and beyond, and thus the evolution and present distribution of mammals across Island Southeast Asia (ISEA). An important group are the Suinae (pigs). Most extant Eurasian Suinae species belonging to the genus Sus, except the widely distributed Sus scrofa, are mostly found in ISEA, and represent an example of species radiation. Knowledge of the origin, migration, and evolution of the genus Sus is limited, and studies on ecomorphological disparity and phylogeny of fossil Suinae are scarce. Considering the importance of ISEA in the evolutionary history of the genus, a detailed understanding of the fossil Sus species from the region is key to understanding the origin, dispersal, and evolution of Sus. Here, I focus on the anatomy of two endemic species from the Middle Pleistocene of Java (Indonesia), S. brachygnathus and S. macrognathus. A detailed anatomical description and morphological comparison between these species and extant and fossil suids are provided, including hitherto undescribed features of two species in the context of ecomorphology. Finally, aspects of the phylogenetic relationships of both species are discussed in relation to insular evolutionary trends. The importance of these fossil Sus remains from Java lies not only in their key role to understanding the evolutionary history and diversification of Sus, but also in providing insights into the evolutionary trends of insular pigs.