As much as I like The Police, Sting unfortunately got it wrong when singing about our paleontological past:
Hey mighty Brontosaurus, don’t you have a lesson for us? Thought your rule would always last, there were no lessons in your past … — from the song, “Walking in Your Footsteps”
For the general public, the view of the deep past is rather skewed towards dinosaurs and Ice Age mammals. One gets the impression that the first life was bacteria, then bugs, then some fishy things, and then dinosaurs came around and changed the world. To be fair, dinosaurs were an important and significant part of vertebrate history, but in many cases they were re-inventing ecosystems already established by our own distant ancestors, the Synapsids or, as the olde-timey paleontologists used to call them, the “mammal-like reptiles.”
Dinosaurs lived during the Mesozoic Era (~245-65 million years ago), but our distant ancestors appeared during the previous Paleozoic Era, sometime around 300 million years ago. In the public eye, the Paleozoic is unfortunately a forgotten Era, but it is possibly the most important time for vertebrate evolution: during this time period (~540-245 million years ago) the first vertebrates, all the major “fish” groups, the first tetrapods, and the ancestors of modern amphibians and modern amniotes (“reptiles,” birds, and mammal) all appear. Remember, this is coming from a dinosaur-o-phile here, so you know this must be very significant! And during this time, the first major vertebrate terrestrial ecosystems comprised of herbivores and carnivores appeared. The earliest representatives of these ecosystems were the aforementioned Synapsids and a group we will call the Parareptiles.
Many people have never heard of the Parareptiles, a totally extinct group (well, maybe — there is disagreement over whether turtles are living descendants, but that will have to wait for another post) that includes odd herbivores called Procolophonids, stocky animals about 1 to 2 feet in length. When I was doing fieldwork in South Africa, I worked side by side in the field with paleontologist Juan Cisneros who has traveled the world to study and unravel the evolutionary history of these peculiar parareptiles. We were digging in the Elliot Formation which is right on the cusp of the Triassic-Jurassic boundary, and Juan was hopeful he would find a very early Jurassic or very late Triassic procolophonid amongst the dinosaur bones. Alas, the only thing we found out about procolophonids on our dig was my inability to pronounce “procolophonid” effectively.
I was therefore ecstatic to open my new copy of National Geographic magazine and find a nice, illustrated comment about a South American fossil vertebrate discovered by Juan and colleagues last year. The cool part is, this was not a dinosaur or Ice Age mammal. Instead, Juan discovered the totally weird and surprisingly cool synapsid named Tiarajudens eccentricus, an herbivore with — get this — huge sabertooth incisors! As Juan explained, finding Tiarajudens was “like finding a unicorn.” Here is an animal with huge saber teeth, which at first glance would lead to you to think it was carnivorous. However, when Cisneros and his colleagues (one of which is Fernando Abdala, a name you might recognize from the Arcusaurus discovery) examined the rest of the teeth, especially the ones towards the back of the jaws and the palate they discovered wear on the crowns indicative of grinding. This was no carnivore — it was an herbivore! Not only that, but apparently Tiarajudens was capable of grinding up vegetation in a way that modern ruminants do today — only 265 million years ago! Moreover, saber-toothed herbivores are not as uncommon as you may think — see Brian Switek’s excellent post on the evolutionary history of saber-toothed vegetarians.
Juan has also discovered another exciting South American synapsid, one I plan to detail in another post. Suffice it to say, I am happy for Juan and his colleagues that the synapsids are getting their fair-share of public attention. I hope this highlights the fact that dinosaurs, while important, were not the first nor last vertebrate animals to have herbivore/carnivore ecosystems, and were certainly not the first terrestrial vertebrates to flourish and diversify across the globe.
Perhaps Sting should have sang, “Hey nifty Tiarajudens, what were those giant canines doin’?” Then again, this is why I will never be a rock star.