Humble Beginnings: The First Fossil Penguin, Palaeeudyptes antarcticus
Scientific study of extinct penguins started exactly 150 years ago, when the first paper on a fossil specimen was published. The bone itself was actually collected a few years earlier, from a beach near Kakanui, a settlement on the east coast of the South Island of New Zealand. The Maori place name Kakanui means “noisy parrot”, preumably a reference to wide parrot populations that have sadly since been extirpated from the area. According to official accounts, the fossil was “found by a native in the limestone of Kakaunui [sic], and was brought to Mr. Mantell imbedded to some extent in a matrix which was readily recognizable as that particular limestone”. Unfortunately, this rather vague account leaves many important facts out. Some are of historic interest only – the name of the pioneering discoverer of the first penguin not even been recorded. Of more serious concern to paleontologists is the geological context. Without knowing what rocks the fossil came from, we lose information about the age of the fossil, the environment the penguin lived in, and the context of fossilization. These data are important – paleontologists often say that when the locality of a fossil is unknown, half of its information content is lost. Where was “that particular limestone”? This question is difficult to answer, but it may be a resolvable issue. I’ll write about this in a later post.
Moving back to the fossil itself, it quickly left Otago. Like many of the earliest fossils from New Zealand, it was spirited away to England for study. This was standard practice in colonial times – for example, the first described moa bones ended up in London in the possession of Sir Richard Owen, a renowned anatomist best known for coining the name “Dinosauria”. The fossil penguin bone we are interested in ended up in the possession of Thomas Henry Huxley, a formidable biologist who earned the nickname Darwin’s Bulldog for his vociferous defense of the theory of evolution during its earliest years.
It was instantly clear to Huxley that the bone represented an extinct species of penguin. First of all, it was larger than the same bone in even the biggest living penguin species, the Emperor Penguin (Aptenodytes forsteri). Second, many of the details of the bone differed. In living birds, the bones that form the base of the three toes fuse together into one. These bones are separated by deep grooves in living penguins, but not so in the fossil. One of the openings for blood vessels of the foot seen in living penguins was also missing, and the ridges of bone that guide the tendons used to flex the toes are arranged in a different manner. All these differences indicated a penguin that was distantly related to our modern species, so a new species name was proposed: Palaeeudyptes antarcticus. Palaeeudyptes translates roughly to “ancient true diver” and antarcticus refers to the southern latitude at which the fossil was recovered. He published the scientific paper making this name valid in 1859.
In reality, the fossil itself is not much to look at. Nonetheless, though much more complete penguin fossils have been found since, the Palaeeudyptes antarcticus holotype received pride of place as the starting point of comparison for subsequent discoveries. Since the original paper by Huxley, the fossil was visited by famous paleontologist George Gaylord Simpson, one of the architects of the “New Synthesis” of evolution, New Zealand’s Brian Marples, author of ground-breaking early studies of fossil penguins, and many other luminaries. Casts reside today in the American Museum of Natural History, Smithsonian Institution, Otago Museum, and many other museums.
Unresolved questions still surround this precious relic. Some are related to its legacy for taxonomy, the science of classification. Formal codes of taxonomic nomenclature dictate the way in which new species (living or fossil) are named. These help avoid a chaotic situation where the same species goes by different names in different regions or multiple species are inadvertently given the same name. Among the rules are the diagnosis of the species and the designation of a holotype. The holotype is a single specimen chosen to represent the species – the standard by which to compare all other exemplars. Obviously, the specimen selected to be the holotype is typically the “best” available – well-preserved, showing the distinctive characters of the species clearly, lacking any trace of injury, illness or damage. However, in paleontology complete skeletons are rare or completely unknown for many species, so often a less desirable specimen must be chosen for the holotype. In the case of Palaeeudyptes, only one foot bone was originally available, and so the taxonomic fate of the species became forever tied to this single bone.
At the time Palaeeudyptes antarcticus was named, no other fossil penguins were formally described in the scientific literature. Diagnosis was simple, because no living penguin tarsometatarsus closely resembled that of Palaeeudyptes antarcticus. But now, about 50 different fossil penguin species have been discovered and we know that many different species had a foot like that of Palaeeudyptes antarcticus. A lot of fossils from all around the world have been shoehorned into the species Palaeeudyptes antarcticus over the years because of these similarities, but this would mean a single species of penguin survived for tens of millions of years and spread throughout New Zealand, Australia and Antarctica. Essentially, a house of cards was built – rough guesses were made that other leg bones from new fossil sites belonged to Palaeeudyptes antarcticus because the foot bones were somewhat similar, then flipper bones were assigned to the species because they were from the same general area, then somewhat similar flipper bones from a new area were assigned to the species and so on. We now know this was just an artifact of misidentifying fossils and over-extrapolating, because analyses of the evolutionary relationships have shown that some of these fossils are only distantly related to the original Palaeeudyptes antarcticus and need to be given their own species names. These differences would probably have been recognized much earlier if there had been more than one bone to compare to.