Sunday, May 31, 2009
Carcharadontosaurus, a relative of Mapusaurs from Africa.
The last week or so I've been engaged in a discussion about theropods living in groups with a fellow blogger and Paleontologist. Basically it boils down to this. Since birds and crocs are dinosaurs closest relatives we should only use them it infer any behavior and biology. I disagreed and lots of comments and emails were exchanged. I was given a copy of the 2007 Deinonychus paper. A paper which is supposed to explain the feeding habits of Deinonychus. In it, the paper basically uses the ora, or what we in the west called the Komodo Dragon, as a comparison to the kill site were the 'raptors' were discovered. 4 raptors were found along with the carcase of a juvenile Tenontosaurus. The original idea being that the tenontosaurus either fell on or killed the 4 in the attack that cost it it's life. The fell on thing is kind of strange but the site is odd in itself. It appears that one fo the raptors 'killing' claws was imbeded in the tail tendons of another raptor. There were lots of shed teeth so we kow more than the 4 raptors were present. The paper argues that this site is simiar to ora kill sites, as the ora is know to be canibalistic and they explain the site as a single raptor killing the Tenontosaurus and then the others coming in and a sort of feeding frenzy ensued, during which things got out of hand and 4 of the raptors were also killed. We are told from this we can assume that this is how EVERY theropod dinosaur should now be interpreted as acting, single hunter and then a group comes in and they fight over and eat the kill, just like oras. It should be the 'fall back' position. I disagree. While the site is strange an equally plausible postion is a rival group of raptors showed up and a fight ensued. It explains the shed teeth, the claw in the other raptors tail, and the 4 dead animals. Am I sure of this..? No, but it's just as likely. The point is we don't actually know. It's a guess, an educated one but it's still a guess. But to claim that EVERY theropod should be cast as having the same exact behavior is just at odds with ALL other animals. No predators, even closely realted ones, act exactly the same way. Most birds hunt alone, but some hunt in groups. Some live alone, others in groups.
The Ora is a strange animal, it's the heaviest lizard, it lives on a small island (or group of islands) with very limited resources, it's now found to be venomus. It's cold blooded. Not very similar to theropods, who had much greater resources, continents to roam around on. Were most likely warm blooded, and not venomous (that we know of.) To just use the one lizard is just wrong. Other veranids don't behave that way, even ones closely related to the Ora. I fail to see how this should be the fall back position and how this is good science. Good science should say we don't know... We have some evidence for some theropds living together, but it's open to interpretation.
Case in point the Mapusaurs site. 7 individuals of various ages. were found burried together. I was told this shows a predator trap, but in every other predator trap (similar to the Le Brae tar pitts, but no tar) there are more than one speices of predator. In fact we have traps like this in the US, one in Utah with LOTS of Allosaurs, some ceratosaurs, some sauropods, a Torvosaurus... lots of different animals, this is a classic predator trap. But to find 7 individuals with no signs of canibalism.. no other animals... a trap that just caught one specific animal around the same time??? That's the best explination? Not that they were living together and were all killed at the same time via flood or volcanic gas or whatever? I'm even will to say we don't know for sure and will most likely never know, unless the bones were all jumbled together, that would mean they most likely died and decomposed together. But that's all we'll ever know for sure.
I keep being told that we can't use mammals for anything related to dinosaurs. But I just read a very interesting post over on Tetrapod Zoology about the neck posture of sauropods*. It turns out THEY used mammals for their comparison. Wait weren't we not supposed to use them?? And then in another post, Darren mentions another new paper about reptiles and birds playing... and how did they kow they were playing... why they were comapared to mammals of course! So what I'm being told is, it's only ok for SCIENTISTS to compare mammals to dinosaurs, just not some frindge artist who doesn't know any actual science.
I wouldn't have brought this up but the person I was arguing with has felt compelled to mention it on their blogs at least 3 times already, even after the papers comparing mammals to reptiles, birds and dinosaurs. I can't really comment there because it isn't in English and the translators are really bad. So I can't be 100 percent sure of what is being said, so I have to go off what I've gotten in English here.
I am of course, willing to change my mind when and if good evidence is ever found. But for now what's there is less than convincing, even to this frindge artist.
* Disclaimer: This paper used turtles, lizards, crocodilians and birds and mammals for neck postures. I focused on the mammals to prove a point.