Three Discoveries, Part I: The Skeleton

Last post, we  introduced Inkayacu, the newest fossil penguin species.  Over the next three posts, I’d like to write about the way the story took shape.  Inkayacu provides a great illustration of how science in paleontology proceeds, because in this discipline advances can come from two equally important events – discoveries of new fossils in the field and applications of new methods in the lab.   In this case, there were three big moments of discovery that contributed to the whole story.

Ali Altamirano, one of the authors of the formal  Science report, was responsible for the first big discovery.  Ali is a Peruvian student gifted with a talent for finding fossils in the desert.  Several years ago, while scanning the rocks of the coastal deserts of southern Peru, Ali caught the first glimpse of what may be the most significant bird fossil ever found in Peru.  When a team of paleontologists from the Museo de Historia Natural including curator Rodolfo Salas-Gismondi visited the site, they knew instantly this was no ordinary fossil.   Exposed near the surface was a scaley foot – 36 million year old bones wrapped in a remarkably well-preserved layer of skin.   This startling aspect of the find is what gave Inkayacu the nickname  Pedro.   The nickname comes from “scaley Pedro”, a scaley (slang for sleazy) character on a popular South American  TV show.

Ali Altamirano, discoverer of Inkayacu, records field notes at a fossil site.

Context of a fossil discovery is always important, and in this case it is quite remarkable.  Pedro’s skeleton was found in marine rocks, deposited when silts and sands from a coastal ocean environment compacted and lithified over time, and then were thrust up onto the land by plate tectonic action from the ongoing Andean uplift.  Indeed, the forces that heaved these oceanic slabs onto the continental crust are still operating today, as witnessed by the devastating earthquake that struck Peru in 2007.  Pedro lived in a very different environment than we typically think of when we envision ice-bound penguins at the South Pole.  The fossil site is near 14 degrees south latitude, close to the Equator, and so would have had a very warm climate. Furthermore, during the Eocene the Earth was warmer than today. Global sea temperature was several degrees higher on average, and there were no permanant polar ice caps.  So, Pedro was living in one of the hottest places on Earth during one of the hottest times in Earth history.

The skeleton of Inkayacu is beautifully well-preserved after such a stenuous 36 million year journal of burial, tectonic displacement, and ultimate exposure in the desert.  Below is a collage of most of the bones that were recovered (some are not shown because they were left in the rock so as not to disturb the feathers).  If you remember the post on Icadyptes salasi, you will note that the skull is similar to that species, especially in having a very long, pointed beak.  The flipper bones are a bit more slender, and also show evidence of key differences in the way the muscles and nerves were arranged that will no doubt lead to important new work on penguin flipper evolution.  Of course the attention right now is focused on the feathers, and rightfully so – we’ll delve into what they tell us in an upcoming post.

Skeletal elements from the Inkayacu holotype specimen, from the original paper by Clarke et al. (see references).

Reference:

Julia A. Clarke, Daniel T. Ksepka, Rodolfo Salas-Gismondi, Ali J. Altamirano, Matthew D. Shawkey,, & Liliana D’Alba, Jakob Vinther, Thomas J. DeVries, Patrice Baby (2010). Fossil Evidence for Evolution of the Shape and Color of Penguin Feathers Science : 10.1126/science.1193604 (Pre-print PDF at Science Express)