Avisaurus is a type of bird that lived during the Late Cretaceous period, about 68 to 66 million years ago. It is known as a genus of enantiornithine, which means it is part of a group of ancient birds that are different from modern birds.
The name “Avisaurus” means “bird lizard.” Scientists first discovered Avisaurus archibaldi in a place called the Hell Creek Formation in Montana, USA. This area was once a swampy environment that is now dry land. The first fossil was found in 1975 and includes a part of its leg bone. The species name honors J. David Archibald, who found it.
Another species found later is called Avisaurus darwini, named after famous scientist Charles Darwin. This bird was also found in the Hell Creek Formation and was discovered in 2024.
In terms of size, Avisaurus was relatively large for its time. Avisaurus darwini weighed up to about 1.2 kilograms, while Avisaurus archibaldi was a bit heavier at 1.7 kilograms. The fossil of A. archibaldi is one of the largest of its kind known.
Avisaurus belongs to the family Avisauridae, which includes other similar birds found in South America. Scientists believe that birds like Avisaurus lived in both North and South America, suggesting there were land connections between the two continents during that time.
The birds lived in environments that were humid with lakes and rivers, and they probably hunted for other small animals, similar to how some modern birds of prey do today. The claws of Avisaurus suggest it could have been a predator, indicating it had a diet that included other vertebrates.
Overall, Avisaurus gives us a fascinating glimpse into the variety of life that existed on Earth before the mass extinction that wiped out many dinosaur species.