March of the Fossil Penguins

Fossil penguin discoveries and research

Dwarf Yellow Eyed Penguins

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On Tuesday, we met the recently extinct crested penguin Eudyptes warhami, discovered by a team studying subfossil penguin bones from the Chatham Islands. The study also turned up a “bonus” penguin. Some smaller bones collected at the sand dune sites were originally thought to belong to one of the smaller modern crested penguin species. However, mtDNA revealed something unexpected. The bones turned out to belong to a dwarf population of yellow-eyed penguin!

Flattened Megadyptes

Fossil bones of Megadyptes antipodes richdalei. Photos by Jean-Claude Stahl (Te Papa).

Yellow-eyed penguins are beautiful birds. They sport a yellow face mask, and as promised by their name have a bright yellow iris. It is easy to tell a yellow-eyed penguin skull from that of a crested penguin, due to the much more slender beak of the former. Yet, the rest of their bones are very similar and it is almost impossible to differentiate a large crested penguin from a yellow-eyed penguin based on the bones of the neck, flipper, or legs. Thus it is no wonder why the Chatham Island specimens were not identified immediately: the subfossil bones were so much smaller than the modern yellow-eyed penguins that the match seemed implausible.

ypen

A Yellow-Eyed Penguin, coming ashore in Dunedin, New Zealand. Photo by Daniel Ksepka.

Eudyptes warhami showed major DNA differences with living species, indicating it was a distinct species. Our team was also able to obtain intact mtDNA from the smaller bones. In this case they showed a very close relationship to modern yellow-eyed penguins. Indeed there were far fewer differences between the mtDNA sequences of the fossil and modern yellow-eyed penguins than between the fossil and modern crested penguins. Therefore, our team considered the smaller fossils to belong to a subspecies of the living Megadyptes antipodes, which we classified as Megadyptes antipodes richdalei, in honor of the late Dr. Lance Richdale, an expert on modern yellow-eyed penguins. While the concept of a subspecies is fairly messy, this recognizes that the Chatham Island dwarf penguins would have been easy to tell apart from their mainland relatives, but had not yet fully diverged genetically. Given a few hundred thousand more years, it seems likely that Megadyptes antipodes richdalei would have continued to evolve in isolation from its mainland relatives and eventually become a fully separate species.

 

Together, the crested penguin and yellow-eyed penguins of the Chatham Islands tell a complex tale of how species can be wiped out. Eudyptes warhami persisted for two million years only to be snuffed out in the blink of an eye. Megadyptes antipodes richdalei reveals a different kind of tragedy — it seems to have started on its way to becoming a distinct species, but had its evolutionary journey cut short before it had the chance.

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Written by Dan Ksepka

February 8, 2019 at 12:10 pm

Posted in Uncategorized

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