I HAD PLANNED on writing about protostomes and deuterostomes today, but Christopher Taylor of Catalogue of Organisms mentioned some people think protostomes evolved from deuterostomes, which I had not heard before. So the deuterostomes are on hold until I can read about this idea, probably Monday. Which is fine with me because the alternative topic is the Barbourofelidae!
We are dependent on paleontologists for an accurate reconstruction of a fossil skeleton, but even once that is done it can be hard for us to imagine what the animal really looked like unless an expert steps in and reconstructs the details. From looking at the skulls of the saber-toothed nimravids, barbourifelids, and true cat machairodontids, we know that they were predators with really long canines. But what did they really look like?
I was lucky enough to find a paper which attempts to reconstruct Barbourofelid fricki‘s face.1 To do this the authors used skull structure and muscle attachment scars, with reference to modern cats. While the barbourofelids are not felids, the two groups had superficially similar body plans allowing some comparisons to be made. Many of the conclusions from modeling this species can probably be generalized to other dirk-toothed predators.
As mentioned before, the barbourofelids were recently exiled from the Nimravidae.2 After exclusion from Felidae, they were placed in their own family, Barbourofelidae. These decisions were made based upon dental, auditory, and cranial characteristics. Barbourofelids were actually easier to exclude from Nimravidae based upon dentition than Felidae, an examination of the basicranium excluded them from Felidae. The validity of categorizing the barbourofelids with the nimravids or even placing them as a sister clade to Nimravidae were doubted because the barbourofelids did not appear until several million years after the last nimravids in the fossil record. The barbourofelids are believed to have evolved in Africa and later colonized Europe and then North America until becoming extinct 7 million years ago.
The barbourofelid chosen for modeling was Barbourofelid fricki, which is one of the most derived (with features changed from their ancestral state) barbourofelids and the last to become extinct. All barbourofelids were dirk-toothed, with long saber-teeth and stocky, muscular bodies. Barbourofelid fricki took these characteristics to the extreme. Its teeth were very long, and it opened its mouth to a gape of 115°, almost twice as wide as the gapes of modern cone-toothed big cats. This clay reconstruction of Barbourofelid shows it to have a blocky head with low-set ears.
An additional drawing shows the massive gape of Barbourofelid fricki.
Some notable features are a broadening of the muzzle due to the very large saber-tooth roots, the shortening and deepening of the skull, lowering of the ears, and divergence of the eyes resulting in a decreased zone of stereoscopic vision. Most of these changes probably resulted from accommodation to increasing saber-tooth size and gape. To open the mouth widely, barbourofelids would have had looser lips, and possibly flews. To protect their lips from laceration, muscles retracted the lips while the jaw was open. This would bunch up the skin around the eyes and possibly obscure vision, but it appears Barbourofelid fricki was not very dependent on stereoscopic vision in hunting. Moving the eyes more laterally decreased stereoscopic vision, but gave it a larger field of peripheral vision than the structurally similar modern cats. It would have been able to lie in wait unmoving while monitoring activity in a large field of vision, and its short-range ambush would not require the depth perception needed by carnivores engaging in pursuits over distance. This is consistent with previous findings suggesting dirk-toothed carnivores ambushed their prey, immobilized it by pinning, and killed with a single stabbing bite.3
- Naples, V. L; Martin, L. D. “Restoration of the superficial facial musculature in nimravids.” Zoological Journal of the Linnean Society 2000, 130, 55-81. DOI:10.1006/zjls.1999.0210
- Morlo, M.; Peigné, S.; Nagel, D. “A new species of Prosansanosmilus: implications for the systematic relationships of the family Barbourofelidae new rank (Carnivora, Mammalia).” Zoological Journal of the Linnean Society 2004, 140, 43-61. DOI:10.1111/j.1096-3642.2004.00087.x
- Therrien, F. “Feeding behavior and bite force of sabretoothed predators.” Zoological Journal of the Linnean Society 2005, 145, 393-426. DOI:10.1111/j.1096-3642.2005.00194.x