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!

4 comments:

220mya said...

I was a bit dissappointed that most of the papers did not use a strict apomorphy-based identification method. A lot of workers are afraid of this, because they know it will reduce the precision of their identifications. However, what you lose in precision you gain in accuracy. And, it prevents circular reasoning in determining the stratigraphic ranges and occurrences of taxa.

Nathan said...
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Andy said...

A lack of apomorphy-based identifications is pretty much standard for microvertebrate ID though, isn't it? (not that this makes it right, of course). Heck, are there even apomorphy-based definitions for most microvertebrate taxa? I would suspect that most researchers would be able to come up with some, given the appropriate push from reviewers and the paleontology community.

220mya said...

Andy;

I agree that it's not standard, but that doesn't make it right. I would say it isn't standard for macrovertebrates either. But hopefully with some prodding it will become more common, especially as more papers come out that show the problems with studies that don't use apomorphies to identify their fossils.