Pentaceratops

pentaceratops
Pentaceratops (Wikimedia Commons).

Name:

Pentaceratops (Greek for "five-horned face"); pronounced PENT-ah-SER-ah-tops

Habitat:

Plains of western North America

Historical Period:

Late Cretaceous (75 million years ago)

Size and Weight:

About 20 feet long and 2-3 tons

Diet:

Plants

Distinguishing Characteristics:

Enormous bony frill on head; two large horns above eyes

 

About Pentaceratops

Despite its impressive name (which means "five-horned face"), Pentaceratops really only had three genuine horns, two big ones over its eyes and a smaller one perched on the end of its snout.

The two other protuberances were technically outgrowths of this dinosaur's cheekbones, rather than genuine horns, which probably didn't make much difference to any smaller dinosaurs that happened to get in Pentaceratops' way. A classic ceratopsian ("horned face") dinosaur, Pentaceratops was closely related to the more famous, and more accurately named, Triceratops, although its closest relative was the equally large Utahceratops. (Technically, all of these dinosaurs are "chasmosaurine," rather than "centrosaurine," ceratopsians, meaning they share more characteristics with Chasmosaurus than with Centrosaurus.)

From the tip of its beak to the top of its bony frill, Pentaceratops possessed one of the largest heads of any dinosaur that ever lived--about 10 feet long, give or take a few inches (it's impossible to say for sure, but this otherwise peaceful plant-eater may have been the inspiration for the huge-headed, human-munching queen in the 1986 movie Aliens.) Until the recent discovery of  the evocatively named Titanoceratops, which was diagnosed from an existing skull previously attributed to Pentaceratops, this "five-horned" dinosaur was the only ceratopsian known to have lived in the environs of New Mexico toward the end of the Cretaceous period, 75 million years ago.

(Other ceratopsians, such as Coahuilaceratops, have been discovered as far south as Mexico.)

Why did Pentaceratops have such a huge noggin? The most likely explanation is sexual selection: at some point in the evolution of this dinosaur, huge, ornate heads became attractive to females, giving big-headed males the edge during mating season.

Pentaceratops males probably butted each other with their horns and frills for mating supremacy; particularly well-endowed males may also have been recognized as herd alphas. It's possible that the unique horns and frill of Pentaceratops aided with intra-herd recognition, so, for example, a Pentaceratops juvenile wouldn't accidentally wander off with a passing group of Chasmosaurus!

Unlike some other horned, frilled dinosaurs, Pentaceratops has a fairly straightforward fossil history. The initial remains (a skull and a piece of hipbone) were discovered in 1921 by Charles H. Sternberg, who continued plying this same New Mexico location over the next couple of years, until he had collected enough specimens for his fellow paleontologist Henry Fairfield Osborn to erect the genus Pentaceratops. For nearly a century after its discovery, there was only one named genus of Pentaceratops. P. sternbergii, until a second, northern-dwelling species, P. aquilonius, was named by Nicholas Longrich of Yale University.