Yanornis is a songlingornithid bird from the Early Cretaceous of China. It was named in 2001 by Zhou Zhonghe and Zhang Fucheng. It was one of the first piscivorous birds to evolve, and its digestive system was much like those of modern birds.
Physiology[]
Similarly to many Cretaceous birds, Yanornis bore a resemblance to its modern brethren. It had a small, sleek body, moderately long legs, a short, feathery tail, long wings, and a small head with a long beak. However, unlike modern birds (and like its Cretaceous relatives), its beak was adorned with small teeth. Most of its body (excluding its beak and legs) would have been covered in long, vaned feathers.
Diet[]
Yanornis was a predator, preying on fish. Its teeth were small yet sharp, and were used to get a hold of struggling prey as the bird swallowed them whole.
Ecology[]
Previously, Yanornis was thought to have had a seasonally flexible diet, switching between fish and seeds every few months or so; this was based off by the discovery of what were presumed to be gastroliths in its gizzard (as gastroliths are associated with herbivorous animals). However, it turns out that the "gastroliths" were spread throughout its digestive system rather than clumping together in the gizzard, telling us that it may have accidentally swallowed sand while feeding, causing its digestive process to stop working and ultimately killing it; due to this, there is no evidence of an herbivorous diet in Yanornis, and it can be said with confidence that the bird was a piscivore. A close look at the exact specimen that died from indigestion showed that the species had a relatively modern digestive system, featuring a long esophagus that ran from the back of the mouth to the middle of the body, a crop for storing food, a gizzard for grinding food, and long, packed intestines for excreting waste. Finally, its shoulder structure was nearly identical to that of modern birds, allowing it to raise its wings above horizontal position and, by extension, fly more efficiently than other birds in its time.