The confusion surrounding the terms “possum” and “opossum” stems from a linguistic shortening, but the animals they refer to are distinct biological groups. The North American animal is properly called an opossum, though “possum” is frequently used in common speech. Zoologically, these two groups belong to separate families and have evolved independently for millions of years, despite sharing a common ancient ancestry. Understanding their differences requires examining their geographical origins, unique physical traits, and taxonomic classifications.
The Definitive Geographical Distinction
The difference between the names is rooted in geography and historical naming conventions. The original term “opossum” (derived from the Algonquian word apassoum, meaning “white animal”) was first applied to the marsupial found in the Americas by English colonists in the early 17th century. In North America, the initial “O” is often dropped in colloquial language, leading to the nickname “possum.”
The term “possum” without the “O” is scientifically reserved for species native to Australia, New Guinea, and surrounding islands. This Australian animal was named later, when 18th-century explorer Sir Joseph Banks noted a superficial resemblance to the American opossum.
Characteristics of the American Opossum
The American opossum, exemplified by the Virginia opossum (Didelphis virginiana), is the only marsupial found in North America north of Mexico. It is characterized by its pointed snout, grayish body fur, and a long, scaly, hairless prehensile tail used for grasping branches. This species also possesses opposable, clawless big toes, known as the hallux, that function like thumbs to aid in climbing.
Perhaps the most famous trait is its involuntary defense mechanism known as thanatosis, or “playing dead.” When severely threatened, the animal enters a comatose-like state, accompanied by a lowered heart rate and the secretion of a foul-smelling fluid to mimic decomposition.
Characteristics of the Australian Possums
Australian possums, such as the Common Brushtail Possum (Trichosurus vulpecula), differ noticeably in appearance from their American counterparts. These species typically feature much thicker, softer fur, large ears, and a distinctively bushy tail. The Brushtail Possum often has a dense coat of silver-grey or brown fur and a black band across its snout.
Many Australian possums are highly specialized arboreal creatures, with adaptations like a prehensile tail and sharp claws for navigating the canopy. These animals are primarily nocturnal, feeding on a varied diet of leaves, flowers, fruits, and insects.
Shared Marsupial Lineage
Despite geographical separation and physical differences, opossums and possums share a distant biological tie as they are both marsupials, belonging to the infraclass Marsupialia. Both groups share the reproductive strategy of giving birth to underdeveloped young that complete their growth in a pouch. However, their evolutionary paths diverged long ago, placing them in completely different taxonomic orders.
The American opossums belong to the Order Didelphimorphia, the largest group of marsupials in the Western Hemisphere. In contrast, the Australian possums belong to the Order Diprotodontia, a diverse group that also includes kangaroos, koalas, and wombats. This taxonomic separation confirms they are only related through ancient marsupial ancestry.