Alexeyisaurus

Alexeyisaurus is one of the earliest known plesiosaurs, living during the Late Triassic period.3

Its body was about 7 meters (23 feet) long, which is as long as a small bus.2

The humerus (upper arm bone) was straight and very long, with flat ends that suggest the head of the bone was not fully hardened.2

Its femur (thigh bone) was slightly curved and had wider ends than the humerus, giving it a different shape.2

The vertebrae (back bones) were strictly amphicoelous, meaning they were hollow on both ends like a dumbbell.2

Scientists first thought Alexeyisaurus was an elasmosaur, but later studies say the skeleton is too poorly preserved to be sure.1