Archive for December 2011
Today, the excursion comes to an end. After pursuing penguins in the quarry, in the museum, and in the oceans (we saw some Little Blues on one return drive), Dr. Brinkman and I will return to North Carolina. However, the work has only just begun. Over the next few months, Dr. Fordyce and I will continue studying the fossils and seeing just how much they can tell us about how ancient penguins lived. Eventually the results will be announced – and you can read about it right here. Thanks to everyone who followed along and posted comments. I’ll pick up the thread again after the holidays – some very exciting New Zealand penguin news is on the horizon.
One of our last stops on this research trip is the Otago Museum. This museum, located in Dunedin, has an important collection of penguin fossils, including many of the specimens that Dr. Brian Marples collected in the 1940s and 1950s. One of the exhibits features a line up of penguin silhouettes indicating the size of different species.
This motley line-up helps bring to life the idea of an ancient penguin fauna, where these birds made up a bigger part of the ecosystem than today. In late Paleogene and early Neogene marine communities in New Zealand, there were a great variety of penguin species spanning large size ranges. In these ancient times, the largest giant penguins may have played the role of sea lions, big penguins that of seals, and small penguins that of, well, penguins. Certainly there was room for different prey specialization between titans like Pachydyptes and small fellows like Korora.
Back in the lab, we have started preparing the penguin specimen collected from the Kokoamu Greensand. As each grain of matrix is removed, more of the animal springs to life. In the field, we noted that there were several wing bones exposed in the cliff face. Preparation proved two of these bones to be the humerus (the main bone of the flipper) and the coracoid (part of the shoulder girdle). But here was also a surprise. One of the small pieces of bone we exposed in the field turned out to be part of the beak (upper right). After preparing the area more extensively, we are now certain we have a spear-billed penguin.
It will take many more hours to reveal all the bones in the block. Let’s hope there are more surprises in the block!
Here are a few more images from our prospecting and collecting forays into the Oligocene and Miocene. It has been a busy week and we will be wrapping things up soon.
The latest stop on our search for penguins takes us to the Otekaike Limestone. This unit spans the Oligocene-Miocene boundary, with fossils dating to about 25 million years ago. Shells abound in the Otekaike Limestone – it is almost like walking along a never-ending high tide line after a storm.
Today’s trip yielded a few bits of penguin bone, including the base of a flipper and, more importantly from a scientific perspective, a whale skull bone. Each piece brings us closer to understanding what these extinct species were like. Even though the Otekaike Limestone is only a few million years younger than the Kokoamu Greensand, the penguins are much smaller and more modern looking. Comparing fossils from the two Formations is like viewing two frames of a film on penguin evolution, one taken a few moments after the other. Lots of other frames are missing, but the movie is still showing today in New Zealand, Antarctica, and everywhere else living penguins thrive.
Here is the end of the excavation. The cutting in the rock is much larger than the fossil, but we need to keep some leeway in the form of rock around the bone, so none are damaged by removal or transportation. The smaller opening is from another find, some fossil whale bones. Now, packed in burlap and cushioned by foam, the fossils will make the long journey back to the lab.
The Kokoamu Greensand is the final resting place of many archaic penguins and dolphins. Formed about 26 million years ago when much of present day New Zealand was covered by the Pacific Ocean, these deposits are exposed along modern day river valleys. Coarse grains of greenish to orange sand record the layering of sands and the burrowings of invertebrates over millions years. Some of the most common fossils are pectins (scallops) and brachiopods. The later are sometimes known as lampshells because of their vague resemblance to Roman oil lamps, and are very rare today.
Our main target on this trip is a fossil penguin that Dr. Fordyce found exposed along a cliff face. With the bones visible in cross-section a meter up, the only way to get the fossils back to the lab is to cut them out of the rock. Using a chainsaw, air scribes (aided by a gas powered compressor), picks and crowbars, we will slowly extract the fossil intact within the rock. In the montage below, you can see the start of the excavation.