06 March 2011

José María Velasco

Serendipity can be a wonderful thing.  While doing research in Mexico City last September, I spent a day in the historic center of the city, and one of the places I visited was the Antiguo Colegio de San Ildefonso; tourists like me flock there because it was the birthplace of the Mexican muralist movement, but while I was there it was also hosting an exhibit celebrating the centennial of the Universidad Nacional Autónoma de México.  You can imagine how pleasantly surprised I was to round a corner in the geology section of the exhibit to see these:

The paintings above, as well as a third of cave bears that I couldn't find an imagine for online, are by the artist José María Velasco, who I have to admit I'd never heard of before my trip.  He lived and worked in the late 19th and early 20th Centuries and is best remembered for his landscapes of the Valley of Mexico, which have served as a touchstone of Mexican national identity.  He was also a scientist, with a particular interest in natural history (a running theme in his profession, it so transpires, as Mexico's greatest landscape artist, Dr. Atl, was also an amateur volcanologist and advocate for science); he even described a species of salamander, that has since been renamed in his honor.  This may explain why he was commissioned to decorate UNAM's Instituto de Geologia.  Velasco's paintings have adorned the palatial building (itself as glorious an example of early 20th Century museum architecture and design as you'll find anywhere in the world) near central Mexico City since the 1910s, and had been brought over to the UNAM exhibit during some renovations (you can get a sense of how they look in situ in this picture).  Information on the paintings is scarce, but it appears that Velasco painted two series: one tracing the history of marine life and one depicting terrestrial animals and landscapes through time.  These would have been painted at roughly the same time as some of the greatest works of Charles R. Knight and his European counterpart, Heinrich Harder, and I would argue that not only are Velasco's reconstructions in the same league as those of his more famous contemporaries (though it must be said that no one before or since can compete with the vibrancy of Knight's animals), but he in fact surpasses them in many ways; his paleo-landscapes are especially impressive (though sadly underrepresented online).  This should come as no surprise, as Velasco was, after all, a classically trained painter and one of his country's greatest artists of the pre-modern era.  It seems a shame that his contributions to scientific illustration and paleoart should have lapsed into obscurity, and I thought I'd do my humble best to try to share some of those contributions with the world.

02 March 2011

Brontomerus, Hell Creek, and Mesozoic Ecology

Two dinosaur-related stories have been getting a lot of press this month.  The first is the naming of the new sauropod Brontomerus mcintoshi (Taylor et al. 2011), which is remarkable for its name (literally 'McIntosh's Thunder Thighs'), its oddly large legs, and its implications for Early Cretaceous sauropod diversity.  The story that is more intriguing to me, though, is the publication of the results of the Hell Creek Project dinosaur census (Horner et al. 2011).  For those who aren't familiar with it, the Hell Creek Formation of eastern Montana and adjacent states has produced one of the richest assemblages of Late Cretaceous vertebrates in the world.  The fauna has been extensively sampled and studied, thanks in large part to the efforts of Jack Horner at MSU's Museum of the Rockies.  The completeness of the Hell Creek fossil record makes it an appealing subject for paleoecological analysis, which is the focus of Horner's new paper.  The authors draw two major conclusions: that the bulk of the large-bodied dinosaurs from Hell Creek represent individuals of intermediate age, while juveniles and old adults are rare, and that Tyrannosaurus was so common that it must have been more ecologically analogous to scavenging, opportunistic hyenas rather than predatory big cats (which require huge amounts of food and are therefore almost always much less common than their prey).  The first point should perhaps not be surprising; as is observed in the paper, there are compelling ecological and taphonomic reasons why very young individuals should not be found at Hell Creek, and it is likewise to be expected that most dinosaurs probably did not survive to extreme old age.  The argument that Tyrannosaurus could not have been an active hunter - the part of the research, incidentally, that has attracted the most media attention - is somewhat more problematic.  Certainly, a modern mammalian predator would not be as abundant as Tyrannosaurus was in the Hell Creek fauna, but using mammals as analogs for dinosaurs has its drawbacks.  Dinosaurs were biologically distinct from mammals (no mammal, for example, could grow to the sizes of sauropods without outstripping their food supply) and the Mesozoic world was fundamentally different from that of today, and as such dinosaurs played by a different set of rules than does anything currently living (including the dinosaurs' descendants, the birds).  Because of this, patterns such as predator/prey ratios that can be very informative when discussing community structure in Cenozoic ecosystems may mean something very different in the Mesozoic, and the preponderance of Tyrannosaurus may be due to biological factors such as metabolism or social structure or to taphonomic biases.  This post may sound like a criticism of Horner et al., but that is not its intent.  In fact, I think the finding that Tyrannosaurus was aberrantly common in the Hell Creek fauna is extremely interesting and certainly the authors' interpretation may be correct.  Further, Hell Creek is one of the only Mesozoic ecosystems that lends itself to fairly robust ecological analysis, and it's excellent that work along those lines is being conducted.  However, at the end of the day, there's a reason dinosaurs are so popular: they are utterly foreign to modern eyes.  This is something of a double-edged sword, because it does make dinosaurs fascinating animals, but it also means they have no good modern analog and that any reconstruction of their ecology will always be cursed with a lower degree of confidence than studies of animals such as reptiles, birds, and, of course, mammals.

01 March 2011

Fossil Vertebrate of the Month: Megaloceros giganteus

As my readers are no doubt aware, St. Patrick's Day is this month, and in honor of that March's fossil vertebrate is the extinct animal most strongly associated with Ireland: Megaloceros, the Irish elk.  It's common name, as famously observed by Stephen J. Gould, is a double misnomer, as Megaloceros was not exclusively Irish (it's remains have been found across Eurasia) and while it is a cervid (the largest ever known, in fact), it is not particularly closely related to elk.  However, the earliest specimens to be described were uncovered from Irish bogs, which still yield some of the most impressive Megaloceros fossils.  Because of this, the Irish elk remains something of a national symbol of Ireland, with its remains adorning museums, universities (such as the pair at left from Dublin's Trinity College), and castles alike.  The outsized antlers of Megaloceros males have, unsurprisingly, been the focus of a great deal of research.  Whether they were the product of sexual selection, allometric growth, or some combination of the two has been an area of debate, as has been their role in the animals' extinction.  A long-standing (but somewhat fanciful) hypothesis held that Irish elk went extinct when forests overtook the more open habitats to which they were adapted and that their large bodies and antlers made life in a closed environment impossible.  A more likely culprit is changing climate that ushered in flora that were nutritionally insufficient to support healthy populations of large, antlered animals such as Megaloceros.