Life of the past

6 06 2007

It’s a good time to be a paleontologist, and the papers just keep on coming in. First, a new study published in the last Journal of Theoretical Biology entitled “A 3D interactive method for estimating body segmental parameters in animals: Application to the turning and running performance of Tyrannosaurus rex” that seems to confirm that everyone’s favorite carnivorous dinosaur probably couldn’t repeat chase jeeps like its fictional representation in Jurassic Park. Using computer modeling, researchers were able to make a “virtual rex” to run tests on (after confirming the program worked by using measurements from an ostrich), and perhaps the most interesting part of the program (at least to me) is that different body segments could be programmed to have different mass. One of the many methods used to calculate a dinosaurs weight in the past was to create a scale model and immerse it in water, seeing how much water it displaced and then using calculations to figure out the weight; fine if your subject is a solid like your model, but we have to question how accurate this is when we’re dealing with live animals. The program seems like it makes some generalizations as well (which should be taken into account), but it seems far more flexible and able to more closely replicate the dimensions of a real animal than previous efforts. Still, the authors did recognize that it’s not easy to reconstruct an animal that no one has seen in life;

Fleshing out the skeleton was an eloquent reminder to us how much artistic license is inevitably involved. Importantly, we did not check the resulting mass set data as we fleshed out the skeleton, as that might introduce bias toward some mass set values. We merely attempted to reconstruct what we thought the entire body dimensions should look like for a relatively ‘skinny’ (minimal amount of flesh outside the skeleton, averaging just a few centimeters) adult Tyrannosaurus, using the skeleton and our experience as animal anatomists to guide us.

Still, the researchers have produced some interesting results; it appears that Tyrannosaurus could not run especially fast (the muscle structure necessary for fast running doesn’t seem to fit the skeleton), nor could it turn very fast (it takes a lot of energy to move such a massive head and torso), and while standing its leg was probably not as flat or flexed as is depicted by different artists. While the authors of the paper recognize that improvements could be made and their results may not represent the animal in life (what they essentially showed in the paper was that their models, given certain conditions and assumptions, behaved a certain way and we can make an inference about Tyrannosaurus), their results seem to make sense. Tyrannosaurus was a massive predator with a huge head; it might have moved fast in a relative sense (as in fast enough to catch prey) but it wasn’t fast in the “absolute” sense and could have easily been outrun by more fleet-footed prey or competitors. What I would like to see now, however, are analysis of 1) other tyrannosaurids, especially Albertosaurus, Gorgosaurus, and Daspletosaurus, and 2) analysis of contemporary potential prey like hadrosaurs and ceratopsians. Tyrannosaurus may have been slow, but could it be that some of its prey was even slower? We’ve still got a lot to learn when it comes to reconstruction predator/prey interactions we can no longer witness first hand.

Secondly, Bora directs our attention to a new article in ScienceDaily about the auditory ranges of dinosaurs (or, what they likely could and could not hear). The online “lay-article” seems to show what has been expected; the dinosaurs chosen for the study (Allosaurus fragilis and Brachiosaurus brancai) probably could hear low-frequency sounds, but not the high-frequency sounds of their bird descendants. This makes some sense given that large mammals today (i.e. elephants) can communicate over long distances by using low frequency sounds, and I would imagine that communicating in such far-ranging frequencies would be more effective for large animals that have large home ranges vs. high frequency squeaks and squawks that wouldn’t go very far.

The article seemed to focus on large dinosaurs, however, so we shouldn’t say that all dinosaurs could only hear low frequency sounds only. Birds are derived from dinosaurs, after all, and just like many other bird characteristics (i.e. feathers) I wouldn’t be surprised if high frequency communication arose in small, bird-like dinosaurs first. Just like the Tyrannosaurus study mentioned above, we can’t know what dinosaurs sounded like 65 million years ago, although certain inferences can be made from what they left behind and I’d like to see more work done on this subject, focusing on dinosaurs closely related to birds.


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16 03 2011
проститутки агенства

Девченки Киева очевидно наслаждаются сексом! Самые лучшие шлюхи Киева у нас!

15 09 2011
Phyllis

hiho, your website is realy nice.. I am pretty sure I will come back to find interesting blogposts!

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