Sabertooth

I recently read “Sabertooth” by Mauricio Anton. Obviously given my interests, this was one book I had to treat myself to. Anton and Turner’s “Big cats and their fossil relatives” was the first “technical” text I bought at the start of my D.Phil and has a special place in my heart (and bookshelf). That well thumbed volume was an invaluable help to getting a handle on the often confusing and complicated history of felid taxonomy and fossil description. I always get the feeling that the Felidae must be the most abstruse taxonomic family, outside the Hominidae, beset by lumpers and splitters all over the place. A favourite example comes from the history of two cat-like genera. Nimravides and Eofelis. It used to be thought that the family of carnivores now known as the Nimravidae were part of the Felidae. This lasted well into the twentieth century until a detailed examination of skulls (in particular the auditory bulla) showed that there was a great degree of separation between the two families. Unfortunately, this splitting led to species being moved from one family to another despite being named under the assumption that nimravids were cats and cats were nimravids. The genus Eofelis (literally “dawn cat”) moved to the nimravid side. The genus Nimravides moved to the felid side. Ugh!

Anyway, the new book is a beauty. Mauricio has, I think wisely, broadened the scope from just the more familiar machairodont sabertooths (e.g. Smilodon, Homotherium) to include also the marsupial sabertooths and creodont sabertooths, on top of the sabre-toothed nimravids and barbourofelids. This meant that personally, I found a lot more new information on mammal groups I was generally unfamiliar with. The writing is lucid and clear throughout, without being overly technical where it is not needed. In a book like this it can be very difficult to pitch the right tone- appealing to specialists and laypeople alike. I think Mauricio managed to get it almost right in this book. 

The main draw for many will be the unparalleled beauty of Mauricio’s art. Almost nobody can match him for the lithe grace and exoticism of his paleontological reconstructions of extinct felids. That Mauricio has spent countless hours observing wild felids in their natural environment and hours more dissecting every muscle and tendon shows in his work, produced with the eye of a field naturalist and a palaeontologist combined in one. A minor niggle is that some of the artwork has been recycled from “Big cats and their fossil relatives” but given the overlap between the two books and the obvious effort that must have gone into the paintings and drawings this can be more than forgiven.

I have been lucky enough to have had a small amount of professional interaction with Mauricio. He was extremely generous in allowing us to use his wonderful images of Smilodon fatalis and Miracinonyx trumani in our paper on their evolution. For that I am hugely appreciative.

The American Lion

Panthera atrox image by Sergiodlarosa

I’ve spent most of my professional life looking at questions to do with the evolution and spread of the lion (Panthera leo). One of my most cited papers looked at the DNA from recent and Pleistocene lions and sorted them into three “types”.

1. The African and South Asian maned lion that we all know (Panthera leo ssp.).

2. The Cave lion (Panthera leo spelaea) from Pleistocene Eurasia (including Alaska and the Yukon Territory, which was connected by the Bering land bridge to Siberia at the time).

3. The American lion (Panthera leo atrox) which was found from Southern Canada down to Mexico

Of the three, we are left with the veritable runt of the litter. The Cave lion and American lion were enormous cats. Probably the biggest felids ever to evolve, with spelaea commonly cited as 20-30% bigger than modern lions. Atrox may have ranged up to 350kg, exceeded only (perhaps) by the South American Smilodon populator. The American lion is most famously known from the LA tarpit site of Rancho La Brea. It is also known from many sites ranging from Florida to Wyoming, and even Edmonton. It used to be thought that the American lion was found as far south as Peru, but these remains are probably from a large form of Jaguar which was around at that time. It’s notoriously difficult to separate the Panthera cats, once their skins are off. It has definitely been found in Mexico, at the site of  Chiapas, and this is probably as far south as they got. The heavily forested isthmus of Panama would have acted as an efficient barrier to what is and was, essentially, a cat of the open plain.

So what was atrox like? Can we make some general assumptions about the biology of this extinct cat? Based on the phylogeny, the American lion is simply an isolated and distinctive population of the Cave lion. Therefore, deductions about the Cave lion should probably apply to the American lion as well. We know that the Cave lion probably lived in prides like modern lions do. Most of the Pleistocene art from places like Chauvet cave and Lascaux cave show multiple lions interacting with each other. Cave art is probably a good indicator of life habits as behaviours we know about from observing modern lions are also found in depictions of Panthera spelaea. For example this image:

Shows what appears to be a male Cave lion (note prominent testicles under the base of tail) “hunkering down” to a female as a courtship gesture. Also note that the mature male does not have a mane- there are no depictions of maned lions in European Pleistocene art. The mane is probably a recent evolutionary innovation unique to the modern African/Asian lineage. So, American lions were probably maneless, pride dwelling cats too.

The last radiocarbon dates for this species overlaps with the first humans in the Americas. As well as dodging Sabretooths like Smilodon fatalis and Homotherium serum, and the giant bear Arctodus simus, you would also have to outwit super sized, cooperatively hunting, smart lions.

Paleopoems

It seems today is national poetry day here in the UK. This got me thinking about poetry that intersects with or has as a theme paleontology and archaeology- the deep time sciences. Given my interest in extinct felids and other carnivores I immediately thought of The Innocent Assassins by Loren C Eiseley. This is the only poem (to the best of my knowledge) that takes its theme and subject as the fossil of a sabre tooth cat. The fossil in question can be viewed here. I first came across the poem and the fossil when I was researching my D.Phil on the molecular evolution of extinct felidae- an excerpt nearly ended up as the preface to my chapter on ancient DNA from Smilodon and Homotherium. (In the end I went with a quote from a contemporary of Eiseley’s, GG Simpson “If, as claimed, the large sabers made it very difficult to eat, the animals took 40 million years to starve to death”.) The innocent assassins that so beguiled Eiseley are not in fact sabre tooth cats in the taxonomic sense. True cats (family felidae) are split into the subfamilies machairodontinae (sabretooths) and felinae (modern conical-toothed cats), whereas the assassins fossil is of a nimravid: Nimravus brachyops. The Nimravidae are sometimes known as the false sabertooths or the palaeofelids. (An excellent publication on the species of Nimravus is available here by the palaeontologist Loren Toohey, including photos of the famous specimen.) One of the first facts you come across while researching sabretooths is that the laterally compressed canines are extremely fragile, and that contact with bone would have been avoided in life to prevent shattering or damage to the tooth. This specimens seems to contravene this accepted wisdom. The Nimravus canine has gone straight through the right humerus it is now bound to for eternity. And apparently without shattering. Toohey suggests that the penetration of the humerus may have been post-mortem and caused by the weight of the overlying sediment, but this seems unlikely to me. Was it caused by intraspecific fighting? Scavenging? Was contact between canine and bone a regular occurrence for this species and can we extrapolate to other sabretooths? I remember reading about a dire wolf (Canis dirus) skull from Rancho la Brea that supposedly was excavated with a Smilodon canine inserted in the braincase. But again whether this was pre or post-mortem is debated.

My other favourite paleopoem is by the incomparable Ogden Nash. His poem fossils, inspired by the playful music of Saint-Saëns, is tremendous fun-

At midnight in the museum hall

The fossils gathered for a ball

There were no drums or saxophones,

But just the clatter of their bones,

A rolling, rattling, carefree circus

Of mammoth polkas and mazurkas.

Pterodactyls and brontosauruses

Sang ghostly prehistoric choruses.

Amid the mastodontic wassail

I caught the eye of one small fossil.

“Cheer up, sad world,” he said, and winked—

“It’s kind of fun to be extinct.”

You can listen to the poem and music here. We had “fossils” playing at our wedding, before the bride entered for the ceremony. It gave a few of our friends a good laugh.