Xenolithosaurus was a small theropod dinosaur. It's pronounced "zeno-litho-sarus." Its name means "strange stone lizard" in Ancient Greek. It was the smallest Mesozoic dinosaur, at only 5 inches (12.5 centimeters) long. It was the ancestor of Archaeopteryx even though it was a predator of Archaeopteryx babies.
Xenolithosaurus probably evolved from Compsognathids such as Sinosauropteryx and Compsognathus. Actual evidence was that the pelvis of Xenolithosaurus was similar to those of Compsognathids. Other evidence shows that the dinosaur had a big cerebrum for its size.
Xenolithosaurus descendants include ancient birds like Archaeopteryx. However, Xenolithosaurus was a predator of Archaeopteryx offspring.
Xenolithosaurus was discovered in the Plaster Creek Watershed of Grand Rapids, Michigan, which, around the time of dinosaurs, was a swampland habitat. No evidence shows Xenolithosaurus fossils anywhere else.
Xenolithosaurus lived about 150,000,000 years ago. This is in the Middle Tithonian period. This is in the Late Jurassic period. The reason for this is because in Michigan only the Tithonian period fossils can be unearthed.