Plotopterids

 

Everyone knows about penguins, but most people have never heard of plotoperids.  Surely the main reason is that there are no plotopterids today.  These birds are completely extinct, but for millions of years they filled a role as the “penguins” of the Northern Hemisphere.  Plotopteridae is the scientific name for the small plotopterid family, which includes half a dozen species.  All of these species were flightless diving birds, with flippers, short feet, and dense bones like those of penguins.  We know precious little about their ecology, but they likely pursued fish, squid and shrimp through the water column.  Like penguins, they would have needed to come ashore for molting feathers and laying eggs.

Copepteryx hexeris, with a silhouette of an Emperor penguin for scale, from Olson and Hasegawa, 1979.

Penguins occur only in the Southern Hemisphere, while plotopterids lived only in the Northern Hemisphere.  Thus, even though ancient penguin species existed at the same time that plotopterids prospered, the two probably only met face to face in extremely rare occasions when cyclones or freak currents swept birds thousands of miles out of normal range.  All plotopterid fossils discovered so far come from the Pacific Northwest states of Oregon and Washington or from Japan.  It appears that although plotopterids were successful in the Pacific Ocean, they never made it into the Atlantic.  The oldest fossils found so far are from the Eocene and are a bit less than 40 million years old.  Some species reached very large sizes, and the largest species may have been bigger than even the giant penguin Pachydyptes.  However, complete fossils are rare and so we are only starting to work out the true proportions of these birds. According to the fossil record, the last plotopterids died out during the Miocene, about 20 million years ago.  There is no good evidence about what happened to them.

Plotopterids deserve more attention than they have been given over the past few decades.  There are many mysteries remaining, such as what living birds are their closest relatives, what their skulls looked like, where in the globe they originated, and why they vanished.  We will be sure to visit these fine creatures again in some future posts.

References:

Olson, S.L. and Y. Hasegawa. 1979. Fossil counterparts of giant penguins from the North Pacific. Science 206: 688-689.