Opossum Skull: 50 Teeth and How to Tell It From a Raccoon or Cat

The University of Texas DigiMorph project, based at the Texas Memorial Museum, describes the Virginia opossum skull as having a long snout, a small braincase and a pronounced sagittal crest along the top. The sagittal crest is a ridge of bone running from front to back over the skull, where the jaw muscles attach. In an opossum it stands out clearly, a raised line you can feel with a fingertip.

The Maryland Department of Natural Resources key to mammal skulls, published in 2022 by wildlife specialist Kerry Wixted, picks out the opossum by the same combination: 50 teeth, a large sagittal crest and a small braincase. Check all three, because together they make a far stronger case than any one of them alone.

Size is less help than you might think. The Virginia opossum is about the size of a small cat, and the Santa Barbara Museum of Natural History gives adult skull lengths of roughly 77.9 to 145.8 millimeters. That is a wide range, and its lower end overlaps with a house cat's, so the teeth and the crest tell you more than the ruler does.

The formula I 5/4, C 1/1, P 3/3, M 4/4 reads like this. On each side of the upper jaw there are five incisors, one canine, three premolars and four molars. On each side of the lower jaw there are four incisors, one canine, three premolars and four molars. That makes 13 above and 12 below on each side, 25 per side and 50 in all.

The quickest single clue is at the very front. Five small upper incisors on each side, ten across the top of the mouth, is something no raccoon, cat or fox has. If you count only one thing, count those.

Old skulls lose teeth, so count the empty sockets along with the teeth that remain. A young opossum's skull may not show the full adult set yet, so a low count on a small skull is not enough on its own to rule out an opossum. The crest and the shape of the snout still help.

Opossums are marsupials, and the National Park Service calls the Virginia opossum North America's only marsupial. The 50 teeth come with the family. The University of Michigan Museum of Zoology's account of the Didelphidae, the family of American opossums, gives the same formula, five over four incisors, one over one canines, three over three premolars and four over four molars, for 50 teeth across the family.

That pattern is a generalized one, shared by didelphid opossums and associated with early mammals. It is not a set of tools built for one particular food. Opossums are omnivores that eat insects, carrion, fruits and seeds, and their mouths carry small conical incisors, large canines and a long run of cheek teeth that can handle all of it.

What is known, then, is the pattern and the diet. Exactly why the Virginia opossum has kept all 50 is a question the tooth count alone does not answer.

The raccoon is the usual look-alike, and the count settles it fast. A raccoon, *Procyon lotor*, has about 40 to 42 teeth in Maryland's key, along with a short nose, a larger braincase and broad molars made for crushing. The Smithsonian National Museum of Natural History notes that raccoon molars are wide and suited to both crushing and shearing, and the University of Florida IFAS account of the northern raccoon shows the raccoon skull for comparison.

Count the teeth first, then compare the snout and the cheek teeth. A long, narrow snout with a small braincase and a tall crest points to opossum; a shorter, broader face with a roomy braincase and wide molars points to raccoon. Our raccoon skull story has the full side-by-side from the raccoon's end.

A domestic cat, *Felis catus*, has about 30 adult teeth and a much shorter face. Maryland's key adds a small, peg-like upper premolar behind each canine, a tooth that can fall out of a cleaned skull and leave a visible socket. The same key gives an adult house cat skull a length of 77 to 101 millimeters, which overlaps with a small opossum, so here too the teeth decide. Twenty extra teeth and a long snout are hard to miss. The cat skull story goes through the cat in detail.

And if your skull is long and narrow but has only 42 teeth and sharp, blade-like cheek teeth, you may be holding a fox. How to identify a fox skull takes it from there.

In Mexico, tlacuache is a common name for the opossum, and zarigüeya is another. The animal is also a hero of old stories, and the Museo Nacional de Antropología, run by INAH, Mexico's National Institute of Anthropology and History, keeps one in its collection. It presents a Pame figure from Santa María Acapulco, Santa Catarina, San Luis Potosí, as the tlacuache who first found and created fire. In that story the animal's tail catches fire from friction between rocks, and the tlacuache shows how fire is made with flint.

INAH's publication *El Tlacuache* describes related Mesoamerican versions in which the tlacuache steals fire from the beings who guard it and carries it to people. In those tellings, the opossum's bare tail is the mark it earned by carrying the flame.

These are traditional narratives with several versions, told by particular peoples, the Pame among them, and they are not a single story for all of Mexico. They are also not zoology. They are a good reason to look at that long, hairless tail a little differently.

Opossum skulls turn up in contemporary decor, artwork and tattoos. Their meaning is the one the artist, tattooist or wearer gives them, so if a design speaks to you, ask its maker what it stands for. For more on skulls as decoration, see skull home decor, and for skulls in ink, skull tattoo meaning.

None of this is legal advice. Opossum rules depend on where you are, and wildlife agencies change them from time to time.

Before you keep, transport, sell or display an opossum skull, check the wildlife agency rules for the state or country where it turned up, and ask the owner or manager of the land. Our story on what to do when you find an animal skull covers the federal and state rules that can apply and who to ask, and how to clean an animal skull goes through cleaning once you know it is yours to handle. Real skulls are not something we buy or sell.

A few more points about the skull on your table.

If your skull turns out to be a raccoon, a cat or a fox, the raccoon skull, cat skull and fox skull stories each pick up the comparison. Before any skull goes on a shelf, what to do when you find an animal skull is the place to start.

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