Archive for September 2012
Spheniscus penguins are your basic model. Collectively, the four living species are sometimes known as “tuxedo penguins” for their striking color patterns, which resemble a tuxedo motif just a bit more than those of other types of penguins. These four species are among the most warm-weather adapted of modern penguins, and live in Africa, South America and the Galapagos Islands. Spheniscus penguins also have a really good fossil record, with lots of skeletons discovered in the past few years in places like Peru and Chile. Many of these specimens are very similar to the living Humboldt Penguin (Spheniscus humboldti), which plies the coasts of South America today. However, two species stand out for their remarkable appearance.
Spheniscus urbinai and Spheniscus megaramphus were discovered in the prolific fossil deposits of the Peruvian Atacama Desert (also referred to a the Sechura Desert). These penguins appear to be standard, although slightly larger, versions of the basic Spheniscus plan from the toes up the neck. Flippers, legs, vertebrae – all these bones are not easily distinguishable from the same elements in a Humboldt Penguin to the untrained eye. The head, though, is a different story. These two penguins have “bobble heads” – skulls that are proportionally too big for their body. Well, too big for a normal penguin’s body anyway – no one seems to have sent a memo to Spheniscus urbinai or Spheniscus megaramphus. Aside from the big heads, these penguins had killer beaks. The tips, instead of being straight like many fossil penguins or lightly down-turned like most modern species, were powerfully developed into a sharp menacing hook. This is a style of beak often seen in aeriel predators like eagles and fish-snatching birds like frigatebirds.
One of the basic facts about fossil bird beaks is that they tend to tell only half the story. That is because the bony part of the beak is covered by a layer of keratin in life. This sheath can greatly extend the tip of the bill in some species, and Spheniscus penguins are a perfect example. The bony beaks of these birds have a modest sharp hook at the tip. When the sheath is added though, the tips start looking pretty fierce. Adding the keratin layer to Spheniscus urbinai and Spheniscus megaramphus would rachet up the beak from menacing to downright scary. What were these fossil species doing with there intimidating beaks? Most likely catching tough prey. A powerful hook would be well suited to ripping into fish and squid, and is more useful for holding onto a larger victim than gathering up tiny things like sardines. Whatever their ecology, the bobble-headed Spheniscus species did not make it to the present day. After splitting off from the main Spheniscus lineage around 6 million years ago, Spheniscus urbinai and Spheniscus megaramphus enjoined a few million years of successful hunting before vanishing.
Here at March of the Fossil Penguins, the fossils we cover are usually skeletons. Sometimes, there are other types of fossil discoveries to discuss, including fossil eggs and fossil feathers. Today, for the first time ever we will feature a story about fossil penguin poop. Paleontologists refer to fossil droppings as coprolites, and they are no laughing matter. Coprolites can reveal a lot about an extinct animals diet and physiology. Recently, a link between long gone penguins and freshly growing plants was uncovered in Antarctica, and the link was seemingly forgotten penguin waste.
A team led by Sharon Robinson, from the University of Wollongong in Australia, recently reported new data on a remarkable type of moss that grows in Antarctica in incredibly harsh conditions. These plants can survive not only freezing temperatures and nearly total darkness during the winter, but also bombardment with UV rays that pierce through at the hole in the ozone layer which forms annually in over the South Pole. These hardships may seem like enough to make any plant give up, but the mosses face yet another difficulty – nearly barren rock with no nutrients. Yet onwards they grow. It turns out the secret source of nutrients is penguin poop.
How did the team figure out that the plants were using the penguin droppings for nutrients? Animal waste carries a chemical signal based on diet. One isotope that scientists can measure is nitrogen-15, which builds up to higher and higher levels as one moves up the food chain. A tiny larval critter that eats algae will have a low concentration, but the sardine that eats that critter will have higher concentration, and the penguin that eats the sardine will have the highest of all. This is because each “eater” absorbs the nitrogen-15 content of its prey and stores some of it. Analyzing a substance for chemical content can reveal its origin. In the case of the moss, nitrogen isotope data indicates they are gaining nutrients from a seabird source. Certainly the mosses are not eating the penguins, so droppings are the most likely substance
The kicker in the story is that there are no penguins living in the area where the moss grows today. The last penguin colony in the area appears to have failed at least 3000 years ago. Traces like nest pebbles show that Adelié penguins once bred in the area. Even though penguins have not returned, their latrines have provided a food source for remarkably hardly plants for millenniums. This study provides a great example of how animals can influence the environment over very long terms.
Coverage by the BBC is here: http://www.bbc.co.uk/nature/18704332