Inkayacu paracasensis
By José Carlos Cortés
Etymology: King of the Water
First Described By: Clarke et al., 2010
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 37.2 and 33.9 million years ago, in the Priabonian age of the Eocene of the Paleogene
Inkayacu is known from Yumaque Point of the Otuma Formation in Ica, Peru
Physical Description: Inkayacu was an extinct penguin, and had a lot of similar traits to other extinct penguins - though resembling modern forms, extinct ones were unique in having extremely large bill size and just large body size in general. Inkayacu was about 1.5 meters long, which is a significant jump from the biggest living penguin (the Emperor Penguin at 1.2 meters long), and Inkayacu wasn���t even the biggest penguin at the time. It had a long, pointed bill, much longer than those seen on living members of the group. And - uniquely - we know the color of Inkayacu! Unlike living penguins, which are all varying shades of black and white with some splashes of other colors elsewhere, Inkayacu was grey and brown. We only known these colors form the flippers (wings), which show grey backs of the flipper and brown fronts, but it’s reasonable to suppose this pattern would follow the patterns of living penguins, where the color of the back of the flipper extends throughout the back of the animal, and the color of the front extends to the front. Thus, we depict Inkayacu with a grey back and a brown front, but this is still a conjecture. The melanosomes are similar to modern birds, long and narrow within the feathers - living penguins actually have wider ones. Other than that, the feathers of Inkayacu are similar to modern penguins in other ways, indicating that it had the same aquatic lifestyle. As such, it was flightless.
Diet: Inkayacu, like other penguins, would have fed on a wide variety of fish and aquatic invertebrates.
Icadyptes and Inkayacu by Apokryltaros, CC BY-SA 3.0
Behavior: Though shaped in a lot of ways like living penguins, Inkayacu was different in a number of ways. It had fewer melanosomes in its feathers than living penguins - and these melanosomes provide rigidity in modern penguin feathers that help with deep-sea diving. Without such melanosomes, Inkayacu might not have been as well adapted to deep diving. Still, it was clearly adapted for spending its life in the sea, diving and sea-flying all over its habitat. It would have used its long beak to stab and grab food, especially slippery food that might be hard to get a grip on. Using its flippers, it could propel itself through the water. Its feet were small and not good for moving, so on land it would probably waddle. This is not an uncommon bird to find, fossil-wise, and so it stands to reason that it would have been very social like living penguins. It would have probably laid its eggs on land, and took care of its young with mated partners. Given it lived in Peru, in the Eocene, it was more adapted for warm weather than cold, and wouldn’t have ventured very far south.
By Julio Lacerda, used with permission from Earth Archives
Ecosystem: Inkayacu lived along the Pervuian Priabonian coast, the Western coast of South America right as the global rainforest of the Eocene was collapsing and being replaced with more varying and arid climates. This was also a time of notable climate change and effects on the ocean, leading to a small mass extinction (especially in the oceans) at this time - killing off many iconic forms, including proto-whales. The conditions of this mass extinction actually allowed the penguins to flourish, and Inkayacu was a part of that flourishing. Inkayacu lived alongside proto-whales like Cynthiacetus and Mystacodon - a toothed baleen whale. Inkayacu wasn’t the only penguin in this area, but was joined by the larger and longer-beaked Icadyptes. As for proper fish, there were ray-finned fish like Engraulis and Sardinops, and unnamed sharks. There may have also been the marine snake Pterosphenus. There were many kinds of invertebrates as well. Inkayacu would probably have had to look out for the sharks and whales, though the fish would have had to look out for it! The coast that Inkayacu would have spent its time on would probably have been more rocky than sandy, though it’s uncertain either way.
By Ripley Cook
Other: Inkayacu is very closely related to living penguins and is just outside the group of modern penguins and their closest relatives, so it showcases the evolution of penguins towards what we’re familiar with today. It’s interesting to note that short beaks seem to be characteristic of the modern crown group of penguins, and that long beaks were found in penguins even as close to the crown group as Inkayacu.
~ By Meig Dickson
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