Science, Tech, Math › Animals & Nature 10 Facts About Acrocanthosaurus Share Flipboard Email Print Animals & Nature Dinosaurs Carnivores Basics Paleontologists Dinosaurs & Birds Herbivores Marine Reptiles Prehistoric Mammals Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated March 29, 2019 01 of 11 Meet Acrocanthosaurus, the "High-Spined Lizard" Dmitry Bogdanov Acrocanthosaurus was almost as big, and certainly as deadly, as more familiar dinosaurs like Spinosaurus and Tyrannosaurus Rex, yet it remains all but unknown to the general public. On the following slides, you'll discover 10 fascinating Acrocanthosaurus facts. 02 of 11 Acrocanthosaurus Was Almost the Size of T. Rex and Spinosaurus Sergey Krasovskiy When you're a dinosaur, there's no consolation coming in fourth place. The fact is that at 35 feet long and five or six tons, Acrocanthosaurus was the fourth-biggest meat-eating dinosaur of the Mesozoic Era, after Spinosaurus, Giganotosaurus and Tyrannosaurus Rex (to all of which it was distantly related). Unfortunately, given its clumsy name--Greek for "high-spined lizard"--Acrocanthosaurus lags far behind these more familiar dinosaurs in the public imagination. 03 of 11 Acrocanthosaurus Was Named After its "Neural Spines" Wikimedia Commons The vertebrae (backbones) of Acrocanthosaurus' neck and spine were punctuated with foot-long "neural spines," which clearly supported some kind of hump, ridge or short sail. As with most such structures in the dinosaur kingdom, the function of this accessory is unclear: it may have been a sexually selected characteristic (males with bigger humps got to mate with more females), or perhaps it was employed as an intra-pack signaling device, say, flushing bright pink to signal the approach of prey. 04 of 11 We Know a Lot About the Brain of Acrocanthosaurus Wikimedia Commons Acrocanthosaurus is one of the few dinosaurs for which we know the detailed structure of its brain--thanks to an "endocast" of its skull created by computed tomography. This predator's brain was roughly S-shaped, with prominent olfactory lobes that show a highly developed sense of smell. Intriguingly, the orientation of this theropod's semicircular canals (the organs in the inner ears responsible for balance) implies that it tilted its head a full 25 percent below the horizontal position. 05 of 11 Acrocanthosaurus Was a Close Relative of Carcharodontosaurus Carcharodontosaurus (Sameer Prehistorica). After much confusion (see slide #7), Acrocanthosaurus was classified in 2004 as a "carcharodontosaurid" theropod, closely related to Carcharodontosaurus, the "great white shark lizard" that lived in Africa around the same time. As far as paleontologists can tell, the earliest member of this breed was the English Neovenator, meaning that carcharodontosaurids originated in western Europe and worked their way west and east, to North America and Africa, over the next few million years. 06 of 11 The State of Texas Is Covered with Acrocanthosaurus Footprints Dinosaur Valley State Park The Glen Rose Formation, a rich source of dinosaur footprints, stretches from the southwest to the northeast of the state of Texas. For years, researchers struggled to identify the creature that left large, three-toed theropod trackmarks here, finally landing on Acrocanthosaurus as the the most likely culprit (since this was the only plus-sized theropod of early Cretaceous Texas and Oklahoma). Some experts insist these tracks record a pack of Acrocanthosaurus stalking a sauropod herd, but not everyone is convinced. 07 of 11 Acrocanthosaurus Was Once Thought to Be a Species of Megalosaurus Dmitry Bogdanov For decades after the discovery of its "type fossil," in the early 1940's, paleontologists were unsure where to place Acrocanthosaurus on the dinosaur family tree. This theropod was initially assigned as a species (or at least a close relative) of Allosaurus, then transferred to Megalosaurus, and even mooted as a close cousin of Spinosaurus, based on its similar-looking, but much shorter, neural spines. It was only in 2005 that its demonstrated kinship with Carcharodontosaurus (see slide #5) finally settled the matter. 08 of 11 Acrocanthosaurus Was the Apex Predator of Early Cretaceous North America North Carolina Museum of Natural Sciences Just how unfair is it that more people don't know about Acrocanthosaurus? Well, for about 20 million years of the early Cretaceous period, this dinosaur was the apex predator of North America, appearing on the scene 15 million years after the much smaller Allosaurus went extinct and 50 million years before the appearance of the slightly bigger T. Rex. (However, Acrocanthosaurus still couldn't claim to be the world's biggest meat-eating dinosaur, as its reign roughly coincided with that of Spinosaurus in northern Africa.) 09 of 11 Acrocanthosaurus Preyed on Hadrosaurs and Sauropods Wikimedia Commons Any dinosaur as big as Acrocanthosaurus needed to subsist on comparably big prey--and it's almost certainly the case that this theropod preyed on the hadrosaurs (duck-billed dinosaurs) and sauropods (huge, lumbering, four-footed plant-eaters) of south-central North America. Some possible candidates include Tenontosaurus (which was also a favorite prey animal of Deinonychus) and the enormous Sauroposeidon (not full-grown adults, of course, but more easily picked-off juveniles). 10 of 11 Acrocanthosaurus Shared its Territory with Deinonychus Deinonychus (Emily Willoughby). There's still a lot we don't know about the ecosystem of early Cretaceous Texas and North America, given the relative paucity of dinosaur remains. However, we do know that the five-ton Acrocanthosaurus coexisted with the much smaller (only 200 pound) raptor Deinonychus, the model for the "Velociraptors" in Jurassic World. Clearly, a hungry Acrocanthosaurus wouldn't have been averse to gobbling down a Deinonychus or two as a mid-afternoon snack, so these smaller theropods stayed well out of its shadow! 11 of 11 You Can See an Impressive Acrocanthosaurus Specimen in North Carolina North Carolina Museum of Natural Sciences The biggest, and most famous, Acrocanthosaurus skeleton is located in the North Carolina Museum of Natural Sciences, a 40-foot long specimen complete with an intact skull and more than half-reconstructed out of actual fossil bones. Ironically, there's no direct evidence that Acrocanthosaurus ranged as far afield as the American southeast, but given that a partial fossil has been discovered in Maryland (in addition to Texas and Oklahoma), the government of North Carolina may hold a valid claim.