I discovered that theropods ranged in many sizes and had many different body design variations. After spending most of my free time over the past two years focusing on T. rex, I also decided to take a look at a few other theropod species. I was curious to see if the Treeosaur theory could be applied to theropods other than Tyrannosaurs.
The first species I looked at was Giganotosaurus: a large theropod that lived in South America in the late Cretaceous period. Giganotosaurus had a similar body design to T. rex, but with a few noticeable differences. It had a proportionately longer head, neck, arms, and overall body length than T. rex.
I found out that Giganotosaurus lived along side the largest know sauropod: Argentinosaurus. Most paleontologists believe a Giganotosaurus could not have possible brought down a massive adult Argentinosaurus by itself. Some paleontologists believe Giganotosaurus hunted in packs to overcome this problem. I definitely agree that Giganotosaurus hunted in packs, but I don’t believe packs of Giganotosauruses would have randomly attacked herds of Argentinosauruses. I believe packs of Giganotosauruses stealthily used the stand hunting from a tree strategy to effectively bring down Argentinosaurus.
I believe Giganotosaurus was capable of stand hunting from trees inside forests like T. rex, but probably spent most of its time hunting edge habitat. The reason I think Giganotosaurus was more of an edge habitat hunter was because of its pubis boot design and because of its prey, Argentinosaurus. Giganotosaurus’ pubis boot was proportionately smaller and less robust than T. rex’s pubis boot. This suggests to me that Giganotosaurus would not have been able to perform major Treeosaur maneuvering around a tree inside a forest like T. rex. Giganotosaurus’s pubis boot design seemed perfect to have made minor Treeosaur maneuvering around a tree at edge habitat. Most Paleontologists believe that large, mature sauropods were too big to have ventured deep into forests and probably spent most of their time feeding out in open country or on the edges of forests. It seems reasonable to believe that packs of Giganotosauruses may have stand hunted from trees on the forest’s edge and waited to ambush Argentinosaurus.
I can imagine a pack of Giganotosauruses strung along the edge of a forest in a high Treeosaur posture (same posture as T. rex) facing out into open country. Once the pack had detected an incoming herd of Argentinosaurus with its auditory, visual and possible vibration senses, the pack would have made minor Treeosaur sideways maneuvering and waited for the incoming prey. The pack’s only chance of success would have been if one of the Argentinosaurus had fed too close to one of the trees concealing a Giganotosaurus. Once this occurred, that single Giganotosaurus would have exploded off the tree to attack the Argentinosaurus’ exposed weak spots: its vulnerable head and neck, which were low to the ground for feeding.
I believe that Giganotosaurus’s attack zone was a small circular area that surrounded the tree, not a straight line attack zone like T. rex. The Giganotosaurus would have had to quickly attack the Argentinosaurus at very close-range to ensure the Argentinosaurus wouldn’t have had time to lift its head up and out of Giganotosaurus’s attack height. This meant a very short and very low attack zone for Giganotosaurus: a much shorter attack zone than T. rex’s attack zone. The Giganotosaurus’s best bet would have been to bite down hard on top of and directly behind Argentinosaurus’s head and then to grab underneath Argentinosaurus’s neck with its strong, powerful arms. This would have ensured a solid, firm hold for Giganotosaurus. If the Argentinosaurus were small and young, then the single Giganotosaurus may have been able to kill the Argentinosaurus quickly with its jaws. If the Argentinosaurus were large and mature, then the Giganotosaurus would have held on with its jaws and arms and used its strong neck and body weight to keep Argentinosaurus’s head from rising up. Though a very massive animal, the Argentinosaurus would probably not have been able to lift up its head and long neck because of the Giganotosaurus’s body weight bearing down from on top. Giganotosaurus would not have been able to stop the massive Argentinosaurus from walking away, but it could have used its powerful legs to maneuver along with the slow walking Argentinosaurus.
The only chance Argentinosaurus would have to shake off Giganotosaurus would be to spin its body around and try to use centrifugal force to throw off the attached predator. More than likely, Argentinosaurus would not have been able to do this in its current position because of the many trees at its flank sides. Argentinosaurus would have to try to clear these trees or risk injuring its neck during its defensive maneuver. The only chance Argentinosaurus had would have been to walk backwards and pull Giganotosaurus out of the tree line and then attempt to spin its body around. Argentinosaurus would have had to clear the tree line as quickly as possible. Giganotosaurus’s legs and feet would have had to work very hard to slow down the Argentinosaurus as much as possible as it attempted to reverse out of the tree line. I think this resistance would have automatically repositioned Giganotosaurus’s body up against Argentinosaurus and probably forced Giganotosaurus’s arms out from underneath Argentinosaurus’s neck. Giganotosaurus’s powerful jaws and long, strong, flexible neck would have been major advantages in this situation. Giganotosaurus’s strong jaws would have stayed firmly attached to Argentinosaurus as Giganotosaurus’s body was dragged up over and on top of the reversing giant’s head. Now Giganotosaurus could have re-embraced Argentinosaurus’s trunk-shaped head with its long, powerful arms. This new position would have given Giganotosaurus an even stronger grip, more leverage, and more maneuverability than if it had stayed positioned to the side of the Argentinosaurus.
Timing was everything for these battling giants. If Argentinosaurus had managed to quickly pull Giganotosaurus out of the tree line, it would have had a good chance to spin and throw off Giganotosaurus. Argentinosaurus would have then been able to raise its head and neck up to safety and then had plenty of room to defend itself. If Argentinosaurus had been too slow in pulling Giganotosaurus out of the tree line, then the results would have been disastrous for the Sauropod. The rest of Giganotosaurus’s nearby pack would have quickly arrived and attacked the vulnerable neck of Argentinosaurus, which would have been held down low by the attached Giganotosaurus. Like lions, I imagine the first few had arrived to assist with holding down and securing the prey animal while the rest of the pack tore into its flesh. I don’t think it would have taken long for the Giganotosauruses to bite deep into Argentinosaurus’s vulnerable neck and sever major arteries or its airway to bring the giant crashing to the ground.
I believe Giganotosaurus’s arms had all the same Treeosaur functions as T. rex’s arms, but that Giganotosaurus’s arms had one additional important function for dealing with the type of prey it hunted. Giganotosaurus had evolved longer and more powerful arms than T. rex simply because it needed them to assist its jaws in holding onto the head and long necks of large sauropods. If Giganotosaurus had spent most of its time hunting a more compact prey like Hadrosaurs, it probably would have depended mostly on its jaws for attacking and not have evolved long, powerful arms. If this were the case, Giganotosaurus would have evolved smaller arms, like T. rex. These arms would have been just strong enough to help the dinosaur perform its many Treeosaur tree tasks.
There are many other large theropod species that lived among other large sauropod species. One example of a possible predator/prey relationship could be the Allosaurus (theropod) and Diplodocus (sauropod). A lot of these other theropod species had proportionately similar body designs as Giganotosaurus: long necks, long arms, and a decent sized pubis boot. I believe these theropods may have evolved this body design to specialize in hunting sauropods by stand hunting from trees on the edges of forests.
After looking at a few other theropod species similar to Giganotosaurus, a very strange looking theropod caught my eye: Carnotaurus. This medium-sized theropod had also lived in South America in the late Cretaceous period. Carnotaurus had a very different body design than T. rex. Compared with T. rex, Carnotaurus had a smaller head, a shorter muzzle, tinier arms, a smaller pubis, and a thinner overall body profile. Carnotaurus also sported two horns over its eyes. Even though I was doubtful that the Treeosaur theory would work with Carnotaurus, I decided to analyze this theropod further.
I spent a few weeks scratching my head over Carnotaurus. I couldn’t see anything to suggest that this theropod’s biomechanics would have allowed it to sustain the Treeosaur posture against a tree like T. rex. Carnotaurus’s body didn’t seem designed to perform this task. I was about to give up when something finally occurred to me. I realized that the tree I used in my original Treeosaur T. rex model had a large, round trunk design. This tree design seemed reasonable to use since large coniferous and deciduous trees with round trunks had existed in T. rex’s environment. Perhaps trees of other sizes, widths and shapes had existed in Carnotaurus’s environment. Maybe a different type of trunk design would have allowed Carnotaurus to stand hunt from a tree.
I jumped online and started searching prehistoric trees, cretaceous trees, dinosaur trees, etc. Of course there were thousands of hits, but I couldn’t find any definitive website dedicated to prehistoric trees. Carnotaurus is from South America, so I ran a search under “South American trees.” Once again the search produced a countless number of hits. Even though there are hundreds of species trees in South America, I started browsing through photos. I stumbled onto a picture of an amazing tree. “Jackpot!” I think I had found exactly what I was looking for; I literally had goose bumps! On my computer screen was a photo of a modern day ceiba tree.
I didn’t know much about ceiba trees because they don’t exist in North America. However, they did look somewhat familiar to me. Maybe I recognized them from my scuba diving trips to the Caribbean. After reading up on ceiba trees, I found out that my hunch was correct: ceiba trees do exist in the Caribbean. There are about fifteen species of this tree found in tropical regions around the world.
Ceiba trees are very strange looking as far as trees go. Most trees widen slightly at the base, but ceiba trees take this widening to an extreme. Ceiba trees have buttress roots. This unique, wall-like root system can spider far out from the tree’s base. The roots gradually taper up into the trunk of the tree, many feet above ground level. Most of the ceiba tree pictures posted on the web show people standing in between the large crevasses of the buttress roots. There is a good chance that some prehistoric form of the ceiba tree had existed in Carnotaurus’s environment. Maybe Carnotaurus positioned itself in a crevasse of the buttress roots for concealment while stand hunting from a tree.
Carnotaurus, with its small head and thin body profile, may have had a “wedge” technique in contrast to T. rex’s “hug” technique while stand hunting from a tree. Instead of positioning itself more vertically high against a round tree, Carnotaurus may have positioned itself more horizontally low, onto its thick chest, in the crevasse of a buttress root tree. I think the design of Carnotaurus’s pelvis helps support this idea. Carnotaurus’s pubis and ischium were about the same size and both had a small boot. Carnotaurus’s ilium was practically horizontal when its pubis and ischium were resting on the ground. This suggests a more equal weight distribution on Carnotaurus’s pelvis while its body was cradled in a tree crevasse during a low Treeosaur posture.
T. rex’s ilium was positioned at more of an upward angle when its pubis and ischium were resting on the ground. This suggests T. rex had unequal weight distribution on its pelvis. While in a high Treeosaur posture, most of T. rex’s body weight would have been bearing down at the point directly below its upper body mass: the pubis. I believe that was why T. rex had a massive pubis boot and a smaller ischium.