This year, I’m devoting my annual Halloween essay to fangs, those scary anatomical structures that have evolved independently among many unrelated groups of ambush predators. Some of the earliest placental mammals to evolve fangs were the nimravids and barbourofelids. These 2 families of carnivores were formerly thought to be closely related, and some scientists still classify them as such. There are 9 known species of nimravids and 7 known species of barbourofelids. Both families had representative species that lived from the late Eocene (~40 million BP) to the late Miocene (~9 million BP).
Illustration of Barbourofelis fricki, also known as the false saber-tooth. It was a very large carnivore that may have preyed upon rhinos, the most abundant large prey species of the Miocene. The background environment of this illustration is likely not accurate. Forested environments predominated during the Miocene.
Illustration of Hoplophoneus, a nimravid that grew to about 320 pounds.
The nimravids and the barbourofelids were formerly thought to have been ancestral to the cat family–they have similar builds and likely occupied similar ecological niches. However, fundamental differerences in the auditory bulla (an inner ear bone) distinguish cats from nimravids and strongly sugggest nimravids could not be of ancestral lineage to cats. NImravids and barbourofelids also walked flat on their feet, like bears, whereas cats walk on their toes.
Click to enlarge the image. Cats have multi-chambered auditory bulla. Nimravids had a single chamber in some species, and in others the structure was made out of cartilage. This is evidence that nimravids were not ancestral to cats, despite the similarity in appearance. Click to enlarge. This illustration is from a page in the book The Big Cats and their Fossil Relatives by Alan Turner and illustrated by Mauricio Anton.
Cats ecologically replaced nimravids. Whether they outcompeted them or took advantage of their extinction due to other causes is unknown. There were 2 species of fanged cats during the late Pleistocene of North America–the famous saber-tooth (Smilodon fatalis) and the lesser known scimitar-tooth (Dinobastis serus).
Illustration of Smilodon fatalis.
An extinct species of vampire bat (Desmodus stocki) fed upon the blood of megafauna during the Pleistocene. It ranged all across the continent of North America. See (http://markgelbart.wordpress.com/2011/10/24/the-pleistocene-vampire-bat-desmodus-stocki/)
Photo of 1 of the 3 species of extant vampire bats which live in South America.
A person doesn’t have to go far to find a creature with fangs. Most suburban yards host a plethora of wolf spider species. Venomous fangs help subdue dangerous prey, such as bees and wasps, quickly. Wolf spider venom is not hazardous to people. Venom also helps protect rattlesnakes. Venomous snakes withdraw after injecting their venom with a quick strike, so they avoid injury while the victim struggles in its death throes. They don’t begin swallowing prey until it has been immobilized by venom.
Illustration showing how snake fangs work.
Wolf spider (Lycosidae) fangs.
There was even a family of saber-toothed salmon swimming in the Western Interior Seaway that separated Eastern and Western North America during the Cretacous age of the dinosaurs.
Illustration of the extinct saber-toothed salmon (Enchodus sp.) that swam in the seas when dinosaurs roamed the earth.
There is a clear evolutionary advantage in the repeated occurrence of fangs in the animal world. Individuals that carry the mutation for fangs are more likely to be able to subdue their prey without sustaining injury, and therefore are more likely to pass that gene mutation to their offspring. Although there are no large mammalian predators with fangs today, it’s possible and likely a big cat with fangs could evolve again…if man allows enough of the natural world to exist.