Here is an example of what you'll find in Thunder Lizards. Anatomically accurate skeletons and stunning illustrations with easy to follow steps. This is an Acrocanthosaurus (meaning "high-spine lizard" because of the spikes growing out of its spine.) It was a fierce predator that was roughly 30-40 feet (9-12 m) long and weighed about 5,000 pounds (2300 kg). It had a big head, with a 4.5 foot (1.4 m) long skull and 68 thin, sharp, serrated teeth. It had 17-inch (43 cm) spikes extending from its vertebrae, along the neck and tail, that may have formed a thick, fleshy sail on its back. It had powerful arms, and each hand had three fingers, equipped with long, sickle-like claws.