Paucituberculata – South American marsupials

The shrew opossums, more formally known as “caenolestids,” are indeed fascinating creatures that inhabit the misty elevations of the Andes mountains. These diminutive marsupials, which are often compared to shrews or rats due to their elongated snouts and slender bodies, represent a lineage that has largely remained enigmatic to science. Their secluded mountainous territories, coupled with nocturnal predispositions, render them elusive subjects for study, and thus, much of their ecology and behavior remain shrouded in mystery.

Their eyes, while suited to their twilight existence, are not the primary tools for navigating the complex Andean landscapes. Instead, these creatures are heavily reliant on their acute auditory senses and tactile feedback from their vibrissae, or whiskers, which are incredibly sensitive to environmental stimuli. This sensory adaptation is pivotal for foraging in the darkness, allowing them to detect the minute movements of insects and other small prey that constitute their diet.

One of the most peculiar and rarely discussed aspects of caenolestids is their reproductive biology. Like their distant North American relatives, the opossums, caenolestids exhibit the phenomenon of paired spermatozoa. This unique form of sperm pairing is theorized to enhance the motility and competitiveness of sperm, thereby increasing the chances of successful fertilization.

The order to which these South American marsupials belong, Paucituberculata, once flourished with a diverse array of species, painting a picture of a once-rich tapestry of marsupial biodiversity across the ancient landscapes of South America. However, this group has suffered extensive losses through time, with only six extant species remaining across three genera—Caenolestes, Lestoros, and Rhyncholestes. Each of these surviving species is a testament to the resilience and adaptability of life, having weathered drastic climatic changes and the rise of competing faunas.