Sequiwaimanu: a Middle Paleocene ‘penguin’ nests with loons and grebes in the LRT

Mayr et al. 2018 described,
“the best preserved Paleocene penguin”, they named, Sequiwaimanu rosieae (Figs. 1, 3).

By contrast, as everyone knows,
penguins swim with their wings, as did their ancestors, the murres (Uria, Fig. 2). This relationship is not traditionally recognized.

Having such a derived taxon in the Paleocene
indicates either an unknown Late Cretaceous slower radiation of crown birds or a more rapid radiation of crown birds following the K-Pg extinction event.

Given that Early Cretaceous Hongshanornis
is the proximal outgroup to crown birds (and therefore the current last common ancestor and therefore a crown bird itself, then the former hypothesis is supported. A long, slow Cretaceous radiation of birds is also supported by the presence of highly derived Sequiwaimanu in the Middle Paleocene. A slow radiation is also supported by the presence of a highly derived goose, Asteriornis, in the Latest Cretaceous (Fig. 5).

The Middle Paleocene appearance of highly derived birds,
like Sequiwaimanu is also intriguing evidence for rapid evolution in the post K-Pg extinction years, matched by Middle Paleocene mammal evolution that included uintatheres, arsinoitheres and other large, highly derived taxa relative to their Maastrichtian tree shrew ancestors. So Asteriornis and Hongshanornis are taxa that indicate a slow radiation during Cretaceous.

You might also remember
in the LRT African hornbills (Buceros) and South American toucans (Pteroglossus) are sister taxa, but separated today by the Atlantic Ocean. That means their last common ancestor must have existed on both continents before the appearance of the South Atlantic and the splitting of those two continents, 100 mya, a topic we looked at earlier here.

Taxon exclusion continues to be
the number one problem in paleontology. With every addition to the LRT, that problem is further minimized.

Adding Sequiwaimanu to the LRT
invited further study that re-nested several taxa (Fig. 5) after updating the trait scores. We will look at some of those changes in future posts. Apologies for the earlier mistakes. I am learning as I go and sometimes it takes several housekeeping sessions to figure out what exactly is going on with bird skeletons and skulls.

References
Mayr GVL, De Pietr L. Love L, Mannering AA and Scofield RP 2018. A well-preserved new mid-Paleocene penguin (Aves, Sphenisciformes) from the Waipara Greensand in New Zealand. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1398169.

wiki/Gavia
wiki/Anhinga
wiki/Sequiwaimanu
wiki/Plotopteridae