The biggest state in the continental U.S., Texas can boast about a correspondingly large number of dinosaurs and prehistoric animals, as listed below. (See an interactive map of dinosaurs and prehistoric animals in the United States.)
Although it was initially discovered in Oklahoma, Acrocanthosaurus only registered in the public imagination after two much more complete specimens were unearthed in Texas. This "tall-spined lizard" was one of the biggest theropods that ever lived: not quite as large as Tyrannosaurus Rex, but still a fearsome predator of the late Cretaceous period. More about Acrocanthosaurus
When the tiny, fossilized skull of Adelobasileus was unearthed in Texas in the early 1990's, paleontologists thought they had discovered a true missing link: one of the first true mammals of the middle Triassic period to have evolved from therapsid ancestors. Today, the exact position of Adelobasileus on the mammalian family tree is more uncertain, but it's still an impressive find.
A 50-foot-long titanosaur, Alamosaurus wasn't named after the famous Alamo of San Antonio, but the Ojo Alamo formation of New Mexico (where this dinosaur was first discovered). According to a recent analysis, there may have been as many as 350,000 of these 30-ton herbivores roaming Texas at any given time during the late Cretaceous period!
The most famous Texas dinosaur that wasn't actually a dinosaur, Dimetrodon was an earlier type of prehistoric reptile known as a pelycosaur, and died out well before the dinosaurs arrived on the scene. Dimetrodon's most distinctive feature was its prominent sail, which it probably used to warm up slowly during the day and cool off gradually at night. More about Dimetrodon
You'd expect a state as big as Texas to have an equally impressive state dinosaur, but the situation isn't quite as cut-and-dried as that. The middle Cretaceous titanosaur Paluxysaurus has been proposed as a replacement for the existing Texas state dinosaur, the very similar Pleurocoelus (below); the matter seems to be perpetually hung up in the Texas state legislature.
The oddly named Pawpawsaurus (after the Pawpaw Formation in Texas) was a typical nodosaur of the middle Cretaceous period (nodosaurs were a subfamily of ankylosaurs, the armored dinosaurs, lacking clubs on their tails). Unusually for an early nodosaur, Pawpawsaurus possessed protective, bony rings over its eyes, making it a tough nut for any meat-eating dinosaur to swallow.
The official state dinosaur of Texas--at least for the time being--Pleurocoelus may well have been the same dinosaur as Astrodon, a similarly proportioned titanosaur that's actually the state dinosaur of Maryland. Further confusing matters, Pleurocoelus may have been the same beast as Paluxysaurus, its proposed replacement as Texas dinosaur ambassador.
The biggest pterosaur that ever lived--with a wingspan of 30 to 35 feet--the "type specimen" of Quetzalcoatlus was discovered in Texas in 1971. Because Quetzalcoatlus was so huge, there has been some controversy as to whether or not this pterosaur was capable of flight, or simply stalked the late Cretaceous landscape like a comparably sized theropod. More about Quetzalcoatlus
Discovered in Texas in 2010, Texacephale was a pachycephalosaur, a breed of plant-eating dinosaurs characterized by their unusually thick skulls. What set Texacephale apart from the pack is that, in addition to its three-inch-thick noggin, it had characteristic creases along the sides of its skull, which probably evolved for the sole purpose of shock absorption.
10. Various Prehistoric Amphibians
They don't get the same attention as the state's dinosaurs and pterosaurs, but prehistoric amphibians of all stripes roamed Texas hundreds of millions of years ago. Among the genera calling Texas home were Eryops, Cardiocephalus and the bizarre Diplocaulus, which possessed an oversized, boomerang-shaped head. More about prehistoric amphibians