👉 A branchiosaur is a type of dinosaur that lived during the late Cretaceous period, about 69 to 78 million years ago. They are often associated with the group of dinosaurs called theropods, which were a subfamily of birds that include the cheetahs and ostriches. Branchiosauers had a large, elongated head and a small tail that was used for walking and climbing. Their teeth were adapted for grinding hard bones and were highly specialized