Paraptenodytes – Simpson’s Great Discovery

In 1933 the famous paleontologist George Gaylord Simpson led an expedition to collect fossils around the town of Trelew in Patagonia. At this time, Simpson was still a young man. Later he would become one of the “four horseman” of the New Synthesis of evolutionary theory, bringing the deep time perspective of paleontology into a new perspective on evolution unifying natural selection and genetics.  In 1933, though, he was focused just on the excitement of collecting fossils.  Near Trelew, the Chubut River meets the Atlantic today.  It seems that this area also comprised a rich estuarine ecosystem in the past and both terrestrial and aquatic animals gathered, lived, and died here, quite often making it into the fossil record. During the trip, the team collected many mammal fossils but also repeatedly came upon penguin bones.  These were not the focus of the trip, but no good paleontologist would leave well-preserved fossils in the field regardless of what type of animal they belong too.  More than a hundred scattered bones of average sized penguins were gathered up, but one find in particular changed the face of penguin paleontology.  This specimen was a roughly 20-25 million year old, nearly complete skeleton of a single bird – a rather large one by modern standards, approaching King Penguin size.  Most of the leg, part of the flipper, many vertebrae were intact. Most importantly, the skull was there too – the first time a skull had ever been found for a fossil penguin.

At the conclusion of the successful field season, the team returned to the US with a bounty of fossils to prepare and study.  Simpson was, as mentioned, a mammal paleontologist, more interested in marsupials and such than in birds.  Thus, he attempted to pass the fossil penguin skeleton to one of the American Museum of Natural History’s many ornithologists.  None, however, took him up on the offer.  At the time, ornithologist’s were absorbed in details of the feathers and beaks of birds and had little interest in the bones of a penguin. Collections of stuffed skins were emphasized over osteological collections at the time (and still are in many museums) and so most ornithologists probably had scant appreciation for skeletal remains of any kind of bird.

Around this time, World War II interrupted George Simpson’s pleasant work on fossils and he served several years in the Army as a staff officer to Patton.  By his own account, this was a low in his career and he longed to get back to scientific pursuits. With the conclusion of the war, he happily returned to the American Museum of Natural History.  Simpson found the penguin still unstudied, and tired of the poor bird languishing set about studying it himself.  This resulted in a monumental 1946 paper titled simply “Fossil Penguins”.  The skeleton was identified as belonging to the species Paraptenodytes antarcticus, previously known only from a few bones.  Besides describing the skeleton, Simpson’s monograph revised the dozens of fossil species that had been named by this time (discarding many ill-founded ones) and definitively traced the ancestry of penguins to a flighted bird, laying to rest some bizarre theories about flightless terrestrial birds or even reptiles as penguin ancestors.

George Gaylord Simpson's specimen of Paraptenodytes antarcticus, with reconstructed body outline. Some bones have been omitted for logistical reasons.

Simpson’s Paraptenodytes specimen was the key that opened the door to the modern study of penguin evolution.  Up to this time, almost all the penguin fossils that had been found were isolated bones.  This made it difficult to reconstruct what these extinct species might have looked like and how similar or different their lifestyles were from living penguins.  Paraptenodytes antarcticus gave us the first good look at an extinct penguin species.  The species certainly had a strong bite compared to living penguins, based on the insertions areas on the skull for the muscles that work the jaw.  The flipper is rather slender and intermediate between Eocene penguins and modern species in most aspects of the underwater flight muscle placements.  The leg is pretty standard, with the typical short stubby feet of today’s penguins.   Overall, compared to the older species known from Antarctica and New Zealand, Paraptenodytes was closer to having a modern skeletal plan. Morphologies of the skull were interpreted by Simpson as evidence of a close relationship between the Sphenisciformes (the penguin clade) and  the Procellariiformes (albatrosses and allies), a hypothesis that is well-supported by DNA evidence today.

This work was not to be Simpson’s only venture in to the world of fossils penguins.  Penguin are addicting, you see, and Simpson subsequently wrote around 20 additional scientific papers on penguins, named a dozen new species and visited every one of the living penguin species in the wild.  So by chance discovery (and the recalcitrance of the ornithologist’s at the museum), one of paleontology’s greatest minds was brought to bear on the evolution of this wonderful group.