Tuesday, September 23, 2008

Head Butting Goats and FEM: Teaser

Finally! The first paper from my dissertation has made it into press:

Farke, A. A. 2008. Frontal sinuses and head butting in goats: a finite element analysis. Journal of Experimental Biology 211: 3085-3094. doi: 10.1242/jeb.019042

Abstract: Frontal sinuses in goats and other mammals have been hypothesized to function as shock absorbers, protecting the brain from blows during intraspecific combat. Furthermore, sinuses are thought to form through removal of `structurally unnecessary' bone. These hypotheses were tested using finite element modeling. Three-dimensional models of domesticated goat (Capra hircus) skulls were constructed, with variable frontal bone and frontal sinus morphology, and loaded to simulate various head-butting behaviors. In general, models with sinuses experienced higher strain energy values (a proxy for shock absorption) than did models with unvaulted frontal bones, and the latter often had higher magnitudes than models with solid vaulted frontal bones. Furthermore, vaulted frontal bones did not reduce magnitudes of principal strain on the surface of the endocranial cavity relative to models with unvaulted frontal bones under most loading conditions. Thus, these results were only partially consistent with sinuses, or the bone that walls the sinuses, acting as shock absorbers. It is hypothesized that the keratinous horn sheaths and cranial sutures are probably more important for absorbing blows to the head. Models with sinuses did exhibit a more `efficient' distribution of stresses, as visualized by histograms in which models with solid frontal bones had numerous unloaded elements. This is consistent with the hypothesis that sinuses result at least in part from the removal of mechanically unnecessary bone.


To get a PDF of this paper, try this link first. If you don't have institutional access via the link, email me at andyfarke [at] hotmail [dot] com, and I'll send you a (legal) link for a free download (more on this below).

Within the next few days, I'll have a post summarizing this research. For now, I'll just talk a little about. . .

JEB and Open Access
Journal of Experimental Biology is not an open access journal - although it does allow that option for a healthy (unaffordable, in my case) fee. But, they present an admirable compromise - all papers become freely available 6 months after initial publication. Although a full open access model would be ideal, I think the publishers have found a good middle ground. The publishers get their due priority, and folks who are willing to wait a few months will get full access to all papers (or can email the authors for a reprint). If only more upper tier journals were to follow this route!

Authors get a link that allows up to 50 free downloads of the PDF (for use before the PDF goes free in six months). As mentioned above, anyone who would like this link should email me at andyfarke [at] hotmail [dot] com. Out of respect for JEB (because I think they're one of the few commercial journals that might have researchers' interests at heart), I won't be posting the PDF outright at this time. But, don't be afraid to email me if you want a copy!

Thursday, September 11, 2008

Book Review: Microvertebrate Fossil Assemblages

Microvertebrate Fossil Assemblages: Their Role in Paleobiology and Paleobiogeography, edited by Julia T. Sankey and Sven Baszio (Indiana University Press, 2008)

Indiana University Press’s Life of the Past series has unleashed a wealth of scientific and popular books on various aspects of paleontology. The latest offering, Microvertebrate Fossil Assemblages: Their Role in Paleobiology and Paleobiogeography, continues this fine tradition. The editors, Julia Sankey and Sven Baszio, are no strangers to the world of microvertebrate fossils (those tiny teeth, vertebrae, scales and other bones from fish, reptiles, non-avian dinosaurs, birds, and amphibians), having published many papers of their own focusing on microvertebrate assemblages from the Late Cretaceous of North America. Here, the editors have brought together a fine collection of papers primarily addressing this very topic. The general nature of the volume’s title does not entirely accurately reflect the papers within, however – the vast majority of the 13 chapters focus on continental microvertebrates from the Cretaceous of western North America. It may disappoint workers of Cenozoic or Paleozoic strata, or those who study marine facies, to see such small notice given to non-Cretaceous, non-terrestrial deposits. Despite this debatable “shortcoming,” there is much to admire here.

The first chapter, by Sven Baszio, lays out potentials and pitfalls of microvertebrate assemblages for answering a variety of questions. Clearly, much progress has been made in this front since the first major screenwashing efforts of the 1960s. A second chapter, by Jamniczky et al., addresses a method for estimating the sufficiency of a sample for characterizing a microsite. Such statistical rigor is clearly needed. Schiebout et al.’s contribution represents the only section of the entire volume that does not dwell largely in the Mesozoic – here, the authors document associations of Cenozoic-aged mammalian fossils within pedogenic concretions.

The next three chapters address microvertebrate assemblages and their role in paleoecological reconstruction. Brinkman examines the role of microvertebrates in reconstructing guild structure within the Dinosaur Park Formation of Alberta, Canada. He pays particular attention to the role that taphonomy plays in how we reconstruct extinct ecosystems. Chapters by Sankey and DeMar and Breithaupt report on assemblages from the Aguja Formation of Texas and the Mesaverde Group of Wyoming, respectively.

A chapter by Fiorillo represents the only paper focused primarily on functional morphology. Here, Fiorillo uses microwear to examine potential variation in diet within sauropods from the Morrison Formation. Somewhat surprisingly, he reports that microwear patterns did not vary within taxa (regardless of where they lived), suggesting uniform diets. Unfortunately, no statistics are presented to validate this conclusion. This is a minor point, but a nagging one for my brain, which thrives on the “numbers game”!

The remaining chapters are largely systematic in nature. Sankey and Longrich each have their own chapter addressing theropod teeth from the Lance and Hell Creek Formations. Sankey provides a particularly useful table of measurements, and both chapters are well-illustrated. Apparently, the two authors come to somewhat different conclusions on systematics of isolated theropod teeth. In particular, Longrich floats the hypothesis that teeth referred to Richardoestesia (R. isosceles and R. gilmorei) all come from the same animal known as Paronychodon! This thus implies a heterodont dentition. Many of the small theropod taxa from the Lance and Hell Creek Formations are known only from teeth – it will take some well-preserved jaw material to sort out the true identity of most of these morphotaxa.

Currie and Coy report on a bird tooth from the Belly River Group; this tooth is particularly unusual for its serrated morphology. Welsh and Sankey then describe numerous types of eggshell from the Aguja Formation of Texas – clearly, a wide variety of dinosaur taxa were nesting in this area!

The final two chapters of the book, by Gardner and B√∂hme, and Gardner, focus on the less “glamorous” side of microvertebrate fauna: amphibians. Despite the fact that amphibians don’t have the cachet usually afforded dinosaurs, the chapters in question are important for clarifying the systematics and taxonomy of these groups. The numerous photographs in Gardner’s contribution on frogs will be very useful for those of us who have struggled with identifying frog material in the past.

Now, on to the “nuts and bolts” of the book itself. The hardcover volume is a convenient size and attractively jacketed, as is typical of the IUP series. The dust jacket art, by Russell Hawley with coloration by Nick Longrich, presents a dynamic reconstruction of many of the animals revealed in Cretaceous vertebrate microassemblages. In terms of the chapters themselves, the editors did a remarkably fine job of proofing the manuscripts, and typos are scarce (not always the case in some recent IUP volumes). One minor annoyance is the fact that none of the chapters have an abstract or summary at the beginning (and many don’t even have a summary at the end!). This makes it somewhat difficult for the casual reader to determine quickly the overall gist of an individual contribution. The illustrations are generally very well-reproduced, with good contrast and clarity. The book itself has a list price similar to comparable volumes ($59.95), but a quick search on Amazon (or a trip to the SVP meetings) will find some decent discounts.

My initial reaction to the papers in this book is that there is still a long way to go in understanding even the best-studied microfaunas of North America. Gardner’s chapter on frogs, and Sankey and Longrich’s chapters on theropods, particularly highlight this point. The taxonomy and systematics of these clades, even within the heavily-sampled Bug Creek fauna, or the Belly River Group fauna, is not yet settled in some cases. This should give heart to those of us early in our careers! And, the “guild analysis” presented by Brinkman also may point the way to other future studies. Finally, it never hurts to have more samples, focusing on different horizons and collecting methodologies.

So, who should buy this volume? I would say that anyone working in the Late Cretaceous of North America would do well to purchase a copy, as would those who work on some of the taxa detailed within (small theropods, frogs, etc.). Kudos to the editors and authors on this interesting contribution!

Tuesday, September 2, 2008

Paleo List Etiquette

I've been a member of the Dinosaur Mailing List (DML) and VRTPALEO internet mailing lists for over 10 years. They're fantastic resources, both for learning about the latest news in paleontology as well as a means to get connected with colleagues in far-off locales. In addition to being a fantastic resource, the lists are also a fantastic opportunity for people to make a big fool of themselves (however inadvertantly). Not that it will do any good, but this post is devoted to a discussion of recommended "do's and don't's" on these lists. Maybe I'm just old and crotchety, but here goes. . .

PDF Requests: Half of the traffic on the lists these days are requests for this or that PDF. It's easy to sympathize with the requests - after all, many of us work under library limitations of one sort or another. But. . .why not just write the author? It gives him or her a big ego boost, and it doesn't clutter up the list. As for requests for some obscure German monograph from 1903 on emu ovarian histology. . .if it's not findable on Google, there probably isn't a PDF available. How about trying a library?

Proofreading: it looks r3ally unprofesionil 2 send messages like this to a mailing list. You never know who is reading - or what they think of you based on your emails. Keep your correspondence professional - in content, grammar, and capitalization.

"Me too": If you agree with someone's post, let them know in a private email. Don't tell the rest of the world - it clutters the inbox!

Inane speculation: I know, I'm a fun-killer--This problem is particularly prevalent on the DML. But I really don't care to see a debate about whether or not Chuck Norris could beat Velociraptor in a cage match. In fact, discussion of theropods should pretty much be banned in general. Ornithischians (and sauropod vertebrae), please.

Not checking the reply address: I've done this more than once, to my embarrassment. VRTPALEO automatically replies to the list - not the sender. It happens to all of us!

What to do, then?
Exhaust other options first. Of course the lists are for finding information - but the members won't do the research for you. Make a good-faith effort to research your topic before making a request! People are really helpful, especially for those who have clearly done a little background reading.

Be part of the community. The neat thing about VRTPALEO and DML is that anyone can make a contribution. It's fun to know the answer to someone's question, and learn that your reply was really useful.

Check the reply address in your email program. Did I mention this already? Man, I'm embarrassed by that time I didn't. . .

And I'm off to the field tomorrow!