Synapsiga

synapsiga is a recently described genus of small, burrowing marsupials from the late Miocene strata of the Central Chile Basin. First identified by Rivera and colleagues in 2024, the genus is distinguished by its elongated snout, reduced pigmentation, and a dentition pattern that combines traits seen in both Australasian phyllodromine marsupials and South American diprotodontids. The type species, synapsiga chilensis, exhibits a cranial morphology that suggests an adaptation to a specialist diet of subterranean tubers and small invertebrates. Fossil evidence indicates a body length of approximately 30 centimeters and a weight of around 250 grams.

Phylogenetic analyses place synapsiga within the order Diprotodontia, using both morphological characteristics and limited collagen sequencing. The genus shows convergent evolutionary patterns with the family Macropodidae, particularly in the configuration of the auditory bullae. The discovery of synapsiga extends the known geographic range of Diprotodontia into the high‑altitude continental interiors of South America, offering new insights into the biogeographic dispersal of marsupials during the Neogene.

Ecological reconstructions suggest that synapsiga occupied a niche analogous to the modern-day potoroo, living in dense shrubland and playing a role in seed dispersal through its diet. The extinction of the genus is linked to climatic shifts at the end of the Miocene, which led to habitat fragmentation. Comparative studies of synapsiga dental microwear provide evidence for a predominantly herbivorous diet, although isotopic analysis indicates occasional opportunistic consumption of carrion. In summary, synapsiga represents a key taxon for understanding marsupial diversification in the Southern Hemisphere, illustrating both adaptive radiation and the impacts of late Miocene environmental change.