Not too long ago, I heard a zookeeper speak of our Virginia opossum as either "the only species of opossum" or "the only North American species of opossum."
Either way, I silently disagreed. I immediately thought of the yapok, or water opossum of Mexico.
This zookeeper had some justification for her statement, if it was the North American question. Many people do not consider mesoamerica or the Caribbean to be part of North America. Further, the information online (plus my own observations) is misleading at best. Many websites make it a firm statement that the opossum is "North America's only marsupial." That is correct, but there at least 3 species of North American opossums (when you include Mesoamerica). Even wikipedia seems to have trouble with this, saying the Virginia opossum is the only marsupial found in North America north of Mexico".
Yet, from doing a little research, there seem to be 103 species of true opossums (of the American genetic background, as opposed to the "possums" of the Austrailian region which look unrelated, because they very much are.)
That's more than I had supposed, and while most are South American, some are native to the Caribbean islands, which I would consider North American.
But it occurs to me that this is really part of a larger debate on understanding:
Is Central America a part of North America?
The continent is delimited on the southeast by most geographers at the Darién watershed along the Colombia-Panama border, placing all of Panama within North America. Alternatively, less common views would end North America at the man-made Panama Canal, and some geologists physiographically locate its southern limit at the Isthmus of Tehuantepec, Mexico, with Central America extending southeastward to South America from this point.
Back to opossums: I recently read that Virginia opoosums have their furthest southernly range is in Costa Rica. Did you know Costa Rica has white-tailed deer? racoons? cougars? North American porcupines?