Smilodon The Iconic Sabertooth

When it comes to Ice Age fame, sabertooth cats are right up there with mammoths. And within the sabertooth cats, the best-known group is the genus Smilodon. Even if you have not heard that name, you will very likely have seen it depicted. Rather than a pop-science book, this edited collection brings together the who-is-who of sabertooth palaeontology to provide a thorough and technical overview of the current state of the field. And if I did not know any better, I would say that the research community has developed an almost unhealthy obsession with this cat’s large canine teeth.

Smilodon: The Iconic Sabertooth consists of twelve mostly technical chapters covering a range of topics. Editor H. Gregory McDonald kicks off with the long and convoluted history of the name of the species, with different authorities suggesting different names and affiliations since its initial description in 1842. Nowadays, the consensus is that three species can be recognised, Smilodon fatalis, S. gracilis, and S. populator. There is also a chapter putting Smilodon in a phylogenetic context, suggesting some very tentative hypotheses as to how it related to other saber-toothed cat groups. Further chapters give detailed description of Peruvian S. fatalis and Chilean S. populator fossils, as well as fossil material from South Carolina. That last chapter argues for reinstating an older species name, going against the consensus I just mentioned.

There is a very readable review of palaeopathological research (i.e. research on fossil traces of injury and disease), and a technical review of its postcranial morphology (i.e. the skeleton minus the skull). This leaves five chapters on those teeth and what they tell us. There are two good reasons for this dental fixation. One, you cannot go around as a cat sporting vampire-like fangs and not expect a bunch of biologists to go crazy (trust me, I’m a biologist). Two, we have an awful lot of fossil skull material from this group, and skulls, in general, can tell us a lot about the biology of a species. There is one site, in particular, that has contributed disproportionately to our knowledge of Smilodon: the La Brea Tar Pits in Los Angeles.

Allow me a minor tangent, as I found this bit really interesting. Tar pits are areas where crude oil spontaneously seeps from the earth, forming pools. As lighter fractions of the oil degrade and evaporate, these pools turn into sticky asphalt that can easily trap animals. Trapped animals attract predators and scavengers looking for an easy meal, which in turn run the risk of also becoming trapped. The seepage at La Brea has been happening for tens of thousands of years (side-note: interestingly for such a legendary fossil site, there does not seem to be a good recent book describing it for a general audience as far as I am aware. I am similarly also not 100% clear if these pits are still “active”, but my impression is that they are). Due to their age, the pits have ensnared tens of thousands of animals and in more than a century of excavations, some 5 million (!) fossil specimens large and small have been recovered, including enough fossil bones to, possibly maybe, make up an estimated 3000 S. fatalis individuals.

Point of above little tangent is that La Brea has yielded a huge number of skulls and teeth, but very few articulated fossil skeletons (i.e. fossils where all the bones in the body are still neatly lying in the same orientation as they would have when the animal just died). Instead, La Brea has yielded an enormous unorganised jumble of bones belonging to the rest of the body, explaining the research focus on skulls. Well, that and those teeth of course.

As such, there are chapters here employing fancy new techniques such as computational biomechanics (finite element analysis, since you are asking) to model mechanical stress on the skull and teeth during bites, or steampunk-esque engineering experiments using Robocat (alas, pictures not included!) to do real-life bite tests on carcasses so as to test a proposed hypothesis for how Smilodon might have used those large canine teeth. There are review chapters on tooth development in life – yes, there is enough fossil material to make series of younger to older individuals to see how teeth erupted! And chapters on diet as revealed by dental microwear and isotope analysis of fossil teeth (see also my review of Evolution’s Bite), or changes in feeding ecology over thousands of years as revealed by changes in both tooth breakage and wear, and shape and size of the lower jaw bone.

The presentation of the book is neat and the reproduction of black-and-white photos and drawings usually excellent. Some tables seem to omit units used for measurements, and do not include explanations of all abbrevations (notably chapter 3 where table footers tell the reader that "N" stands for sample size, but do not add that "MT" stands for metatarsal, for example). Referring to the text will clarify these points, so overall these are minor niggles.

As happens quite often with edited collections of this kind, much of the material presented in Smilodon is of a highly technical nature, aimed at peers. Most chapters assume a detailed knowledge of, in this case, skeletal morphology and dentition and will not clarify jargon, assuming it understood. Next to review chapters, several chapters here are effectively journal articles presenting new research. As such, academic exactitude rather than readability is the prime directive. To give you just one example of what to expect, this from the chapter describing skeletal morphology: “Berta (1987, 1995) noted that S. gracilis has a tuberosity on the anterior margin of the intertrochanteric fossa that is characteristic of Smilodontini and lacking in P. onca” (p. 179). And this goes on for a good ten pages.

Now, to fault the book for this would be completely missing the point. The only reason I am highlighting this is for the reader to know what to expect going in. If you want a popular science book for a general audience, then this is not the book for you – instead, I refer you to Antón’s splendidly illustrated book Sabertooth and, more generally, The Big Cats and their Fossil Relatives. However, for practising palaeontologists and mammalogists, and tenacious readers who do not flinch at a journal article or two, this book is a treasure trove collecting review articles and new research on Smilodon. And it very neatly complements Naples et al.'s 2011 book The Other Saber-Tooths, also published by Johns Hopkins University Press, which is a comparable edited collection on Smilodon‘s close relatives.