Monday, November 29, 2010

This Week's Paper

This week's discussion will focus on the following paper.


Smith et al. 2010. The Evolution of Maximum Body Size of Terrestrial Mammals. Science 330: 1216-1219.
The discussion will be led by me. Can't help myself from plugging a paper on which my master's supervisor is an author!

Friday, November 26, 2010

Pterosaur Flight

The paper linked below describes the flight mechanics of pterosaurs based on bone strength, showing that large pterosaurs like Quetzalcoatlus could fly (despite some criticisms to the contrary).

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013982

Eocene Warmth and CO2

I haven't been keeping up with the hundreds of paper alerts and news articles I receive every week. However, I found one particular alert interesting primarily because I have read a lot about the interaction of atmospheric CO2 and Cenozoic climate change. The paper linked below identifies the importance of CO2 in during the Eocene climatic optimum.

http://www.sciencemag.org/content/330/6005/819.abstract?sa_campaign=Email/toc/5-November-2010/10.1126/science.1193654

Sunday, November 14, 2010

Next Week's Paper

Next week we will be reading:


Bebej, R. M. 2009. Swimming Mode Inferred from Skeletal Proportions in the Fossil Pinnipeds Enaliarctos and Allodesmus (Mammalia, Carnivora). Journal of Mammalian Evolution 16: 77-97.

Friday, November 12, 2010

Avian Origin of Flight

We had yet another successful discussion section this past week. We discussed a paper describing both the support for and limitations of the "ground up" and "trees down" hypotheses in the evolution of avian flight (paper cited below). The basics of the ground up hypothesis are that theropod dinosaurs utilized proto-wings as a means of lengthening a predatory strike, leaping into the air to catch insects, or to assist them in incline running. The trees down hypothesis suggests that bird ancestors were arboreal and used proto-wings for gliding from tree to tree before the evolution of flapping flight. The authors clearly support the latter hypothesis. They cite several reasons for the physical impossibility of the ground up method including the fact that theropods could not have run fast enough to gain lift from proto-wings and that there is no obvious intermediate form that would have been beneficial to these ancestral forms.

Besides the obvious fact that many discoveries have been made since this paper was published, there are several other questions that were brought up during the discussion. One concerned the usefulness of wings that have been adapted for gliding (and thus likely stiffened) in developing the dynamic flapping flight we see in birds today. In general, gliding structures are characterized by stability more than maneuverability (save flying squirrels whose "wings" are much different in form). We also had a difficult time imagining full flapping flight evolving from a completely terrestrial ancestor. We therefore imagined that a terrestrial ancestor that could use it's wings in incline running (say up the trunk of a tree) could then have used the same flapping mechanism from greater heights. In general, we feel that neither argument is mutually exclusive. However, the paper does clearly indicate that the authors do not recognize the relationship between birds and theropods. Given the mountain of evidence continuing to gather (feathered dinosaurs, morphology, frameshift mutations etc.) we feel that the relationship is well supported.

Wednesday, November 3, 2010

Next Week's Paper

The paper for next week will be:

Geist, N.R. and A. Feduccia. 2000. Gravity-defying behaviors: identifying models for protoaves. Amer. Zool. 40: 664-675.

Dinosaur Feeding

Yesterday's discussion was a successful one. The paper (cited below) described both the new and old means of determining dinosaur diet. These included morphological assessment (jaw mechanics, among others), finite element analysis, and tooth wear. The main thesis of the paper was that dinosaurs can be used to answer many macroevolutionary questions.

Our discussion focussed largely on the evolution of paleontological methods. The application of quantitative methods in paleontology is openning up new doors and generating new hypotheses. These methods are not limited to dietary analyses of dinosaurs. They have been applied in biomechanical studies of the post-crania, biogeographical studies, and in the illucidation of niche partitioning among co-existing taxa.

Another line of discussion concerned the importance of using the past to understand the present. In essence, the evolution of communities and ecosystems is shaped by their history and often constrained by it. An understanding of the evolution of the community/taxon you are studying can provide you with a deeper understanding and even determine some of the methods used to test hypotheses. It can also help in the prediction of future changes in the same group.

Monday, November 1, 2010

This Week's Paper

This week we will be discussing the following paper:

Barret, P.M. and E. J. Rayfield. 2006. Ecological and evolutionary implications of dinosaur feeding behavior. TREE 21:  217-224.