Alidens

Alidens are a group of extinct dinosaurs that belong to the family of theropod dinosaurs, specifically within the subfamily Alisaurinae. They lived during the Late Cretaceous period, approximately 75 to 70 million years ago, and are known from fossils found in what is now North America. Alidens are characterized by their relatively small size, with adults typically reaching lengths of around 3 to 4 meters. They had a slender, lightweight build, which is thought to have been an adaptation for quick movement and agility.

The most well-known species of Alidens is Alidens lacrima, which was named for the "tear drop" shape of its lacrimal bone, a small bone located near the eye. This species is known from a nearly complete skeleton found in the Hell Creek Formation of South Dakota. Another species, Alidens anceps, is known from a partial skeleton found in the Two Medicine Formation of Montana.

Alidens are thought to have been bipedal predators, with sharp teeth and claws adapted for catching and killing prey. Their small size and lightweight build suggest that they may have been active hunters, capable of pursuing and catching a variety of prey, including other dinosaurs and small mammals. However, their exact diet and hunting strategies remain topics of ongoing research.

Despite their small size, Alidens are an important part of the dinosaur fossil record, providing valuable insights into the diversity and evolution of theropod dinosaurs during the Late Cretaceous. Their discovery and study continue to contribute to our understanding of the ancient ecosystems and the complex web of life that existed on Earth millions of years ago.