Mesetaornis polaris

By Scott Reid 

Etymology: Meseta Bird 

First Described By: Myrcha et al., 2002

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoromorpha, Maniraptoriformes, Maniraptora, Pennaraptora, Paraves, Eumaniraptora, Averaptora, Avialae, Euavialae, Avebrevicauda, Pygostaylia, Ornithothoraces, Euornithes, Ornithuromorpha, Ornithurae, Neornithes, Neognathae, Neoaves, Aequorlitornithes, Ardeae, Aequornithes, Austrodyptornithes, Sphenisciformes, Spheniscidae

Status: Extinct 

Time and Place: Between 40 and 38 million years ago, in the Bartonian age of the Eocene of the Paleogene 

Mesetaornis is known from the Telm 7 member of the La Meseta Formation on Seymour Island, Antarctica 

Physical Description: Mesetaornis is one of our early penguins – those long-billed weirdos of the first half of the Cenozoic, which paved the way for the adorable friends we known from the Southern Hemisphere today. It had extremely long toes compared to other penguins, and actually had the fourth toe (hallux), giving it very weird feet compared to its relatives. A small early penguin, it was much smaller than such species as Palaeeudyptes and Anthropornis, while probably around the same size as Delphinornis. This means it probably wouldn’t have reached taller than 70 or so centimeters in height (as a very rough estimate). Of course, this is just conjecture, as all we have of it are toe bones. Like other penguins, it would have stood upright, waddled about, and been more adept to life in the water than on land. 

Diet: As in other penguins, Mesetaornis would have primarily fed upon fish and other aquatic organisms. 

Behavior: Mesetaornis probably behaved like other penguins, spending most of its time near the water and diving about for food. Being closer to living penguins than earlier forms, it was probably not as good in the water as those today, but still better than those who came before. It could dive and fly through the water to some extent, using its flipper-wings to do so; it would have also been very awkward on land. As a penguin, Mesetaornis would have probably lived in large flocks, and taken care of its young with the help of others in the group. 

By Ripley Cook

Ecosystem: Mesetaornis lived in a subtropical coast, right off the edge of Antarctica, which was teeming with life unique to the area while the rest of the world was covered in a (slowly receding) jungle. Instead, this coast would have been rocky and cooler, surrounding a system of estuaries and bays with plants such as magnolias and ferns populating the shores. This would have been an extremely fertile environment for penguins, and it shows in the fossil record! There were plenty of bivalves, gastropods, cephalopods, sharks, and fish, as well as a variety of turtles. There were mammals there, too, including small rodent ones and larger, more bulky forms. As for other dinosaurs, there were Pseudotoothed Birds, early Petrels, flamingo-ducks, and a truly hopeless number of penguins – including Delphinornis, Palaeeudyptes, Marambiornis, Anthropornis, and Archaeospheniscus – making this the place to go to see the early evolution of penguins! 

Other: Mesetaornis is a very early derived penguin, grouped up with other early penguins like Delphinornis and Marambiornis. These were full penguins, not quite as weirdly loon-shaped as earlier forms like Waimanu, but they weren’t as big as later forms or had the same beak as living penguins. As such, it represents one of many early penguins that showcase the evolution of the group – and Mesetaornis was a weird one, since it had freakishly long toes! 

~ By Meig Dickson

Sources Under the Cut