There is a whiteboard on the wall of the kitchen at the house where I live now, so I’ve been drawing a dino-a-day on it with some basic info (size, diet, when and where it lived), partially to get my housemates excited about the immense diversity of dinosaurs, and partially to better acquaint myself with some of the more obscure species of which I only have the most basic knowledge. The dino of the day a few days ago was Deltadromeus, a lanky African theropod which I had hardly paid much attention because I only became aware of it when it was publicized along side Paul Sereno’s discovery of a massive Carcharodontosaur specimen that outsized T-rex. At the time, the discovery of a predator that was bigger than T-rex overshadowed delicate Deltadromeus.
I could only find some very basic information on Deltadromeus on the web, but I was able to find some pretty decent images of a skeletal mount. Upon close inspection I was struck by the cool spiky display structures on its skull, and I thought it would be an interesting species to do a head reconstruction of, so I did a pretty quick one, which you can see above. The coloration was inspired by whiptail lizards (Cnemidophorus sp.) which are very speedy lizards and have very nice colors.
As I was drawing, I began wondering how this peculiar long legged theropod survived along side its much more heavily built predatory counterparts. Clearly it would’ve been a faster runner, but why did it take the evolutionary route towards speed over power? My first thought was that perhaps Deltadromeus used its speed and long arms to sprint in close to a larger predator’s kill, grab a hunk of meat and sprint off, but after a bit of imagining, this didn’t seem quite right to me. The hardest part of a relay race is the reversal of direction, and it would seem to me that this would be a very dangerous maneuver to try and pull in close proximity to a much more powerfully built predator. Certainly lions and hyenas steal meals from each other, but from what I’ve seen in nature documentaries, this has much more to do with group coordination than it does with either species being quicker than the other. What you never see, on the other hand, is the lighter built predators, the leopards, wild dogs and cheetahs, stealing from the bulkier predators. They may get scraps after the larger guys have finished eating, but it’s just not worth the risk to put yourself in sprint range of an animal that can crush you if it catches you. Furthermore, this type of incidental scavenging doesn’t seem to be the type of behavior that sculpts a creature’s physique to the degree that Deltadromeus has been trimmed up for running.
It was in thinking about how I have never seen footage, or read report of, cheetahs stealing meals from lions that I began to wonder if Deltadromeus was the cheetah of its time. Perhaps Deltadromeus specialized in hunting prey too quick for the slower Carcharodontosaurs and Afrovenators to hunt, just as modern cheetahs tend to hunt smaller quicker prey, while lions tend to hunt bigger/slower/tougher prey. Until more fossils are discovered and we develop a more complete picture of the ecology of Late Cretaceous Africa I can only wildly speculate… which is just fine - that’s one of my favourite things to do!
