Plenty of Penguins Once Roamed Africa
Evidence is mounting that Africa was once quite the penguin hotspot. Last year, Dr. Daniel Thomas and I published a paper looking at the biogeography of African penguins – that is, deciphering where they came from. We found evidence that penguins likely made it all the way across the Atlantic Ocean several times, crossing from South America to Africa by riding out the currents of the South Atlantic Gyre. The fossil species we looked at in that study were about 5 million years old. Today, our second article was released, detailing fossils from older deposits. These fossils come from the Miocene Saldanha Steel locality, which dates to nearly 12 million years in age. Penguin bones from Saldanha Steel have a sort of rugged appeal. They are stained a dark orangy-brown color and have been tumbled around with rocks and sand till they are quite worn. This created a bit of a puzzle, requiring some careful comparisons (and a little bit of adhesive) to figure out what each bone represented.
Although only isolated bones have been found so far, it is clear that there were at least four different species in the area around 12 million years ago. We can tell this based on the size differences of the elements that were found. Biggest of the Saldanha Steel penguins is a hefty bird that was about the same size as the living King Penguin (the second largest living species) based on the length of its flipper bones. In fact, the sternum of the animal suggests it may have been a relative of King and Emperor Penguins, but we will need more fossils to be sure. There are two average sized penguins, represented by an assortment of leg and flipper bones and one lower jaw bone. Smallest of the Saldanha Steel penguins was a tiny Little Blue Penguin sized species that would have been only a foot tall in life. We are lucky to have detected the presence of this tiny fellow, because small bird bones are rare at the site. Only a single vertebra (part of the spinal column) was uncovered. Despite being just a small bit of bone, it is an clear match for a penguin. Penguins have special ball and socket style joints in their lower vertebrae that almost no other birds possess. Beyond this, they have lost the pneumatic openings exhibited by the other birds which have this style of vertebrae (cormorants and gannets).
We were surprised to find so many different size classes living in the area. In the next post, we will explore what may have been going on back in the Miocene.
Reference: Thomas, D.B. and D.T. Ksepka. In Press. A history of shifting fortunes for African penguins. Zoological Journal of the Linnean Society.