Forelimb Evolution in Predatory Dinosaurs
Professor Sara Burch of the Biology Department at SUNY Geneseo gave a guest presentation on April 9th about the forelimb evolution in predatory dinosaurs and how that shapes our knowledge of their lives and evolutionary patterns. Throughout her presentation, Professor Burch showed us the research she and her students have been conducting to pursue this matter further and try and make more connections between more and more lines of Dinosaurs.
Professor Burch wanting to pursue this subject stemmed from her specificity in her research when she was in university, and has now continued to her tenure at SUNY Geneseo. Through her research, she has examined multiple species of dinosaurs along the 230-million long evolution of theropods. Though she has come to certain conclusions that have not only changed, but has also continue to expand our understanding the old occupants of our planet.
When conducting experiments into the development of various limb growths, she spit the theropods into two different sections to ease the study of them. These two categories were determined mostly by body size. So basically, the smaller the dinosaur the longer the forelimbs and the larger the dinosaur the smaller the forelimbs. The next step was to find out how these certain dinos lived. So she, and her fellow students inferred the behaviour of these creatures, due to the fact that dinosaurs have been extinct for millions of years.
Now the first group is the smaller-long forearmed group. This group consists more of the dinosaurs closely related to birds. These types have a lighter bone structure and have, of course a longer forelimb length, directional motion, a more advanced flexion (movement at wrist) movement, and has more holes in their bones so they can allow more air to flow through them. The dinosaurs you might see with these are the dilophosaurus, archaeopteryx, coelophysis, and the liliensternus. These dinosaurs had fairly weaker and lighter bones compared to the smaller forearmed cousins. These dinosaurs hunted smaller prey like small early mammals, smaller dinosaurs and small pterosaurs. There are though the dromaeosaurs like the velociraptor and the deinonychus who hunted bigger prey and their forearms were designed to grip onto and scar their prey. They do however hunt in packs like wolves and their bones are the same as the same as the group. This is just one difference in the long-forearmed group.
The next type was the ones with smaller forearms. These are yours tyrannosaurus, carnosaurs, and your ceratosaurs. These dinosaurs had as previously stated have short forearms. Now when we mean short, we mean short forearms to little rump claws protruding from their body. These arms, can seem from somewhat useful to literally not at all. Now however, professor Burch explained that these forearms have more of a use than expected. The more runt-like forearms could be used for many things actually. Studies have shown that these forearms were used for gripping and scarring onto their prey, for balancing their bodies, and for use as a way to attract a mate. Which, we didn’t expect that.
Now, when we asked about certain dinosaurs that seem to be sort of in the middle between long and short forearms if there was any leeway between the two. She stated that, “There isn’t really any leeway in a word but there are just some dinosaurs that are still being researched and being classified into the two groups.” We then asked if there was any specific dinosaurs, through her research throughout her career in university and now that she found sort of difficult to classify, “The dromaeosaurs are a little difficult. Due to the fact that this species is sort of a split between certain raptors and it has been difficult to decide which one goes where”.
Most will say that research to these ancient reptiles is useless and that we already know all we want to know and we don’t need to waste time with this. The research that Professor Burch is helping continue our understanding about the former occupiers of this planet. The research she’s doing is helping us know how these creatures evolved and changed with through the millions of years. It might also hold keys into how humanity might evolve in the future.