Dino do-overs: Fixes to paleontology

Three species of dinosaurs became one after a new study reanalyzed different specimens of each "species." (PLoS ONE)

Just when you thought dinosaurs couldn't get any more extinct, two species have been erased from existence.

Three for one
According to a new analysis of dinosaur fossils by University of Pennsylvania researchers, specimens once thought part of three distinct species of the genus Psittacosaurus all derive from a single species. The case of mistaken identity arose not from the anatomical variety among different animals, but rather the differences in how the fossil remains of each were buried and compressed.

Given that 65 million years separate modern humans from the last dinosaurs, it shouldn't be too surprising that paleontologists might get their facts wrong on some of these animals, only to be corrected by further study and fresh analysis.

Young and old
When science can't save a dinosaur species, you'd hope a little magic might be able to come to the rescue. Well, it can't.

In a story similar to the three species of Psittacosaurus consolidated into one, in 2009 two species of dome-headed dinosaur, one of which was named Dracorex hogwartsia after Hogwarts in the Harry Potter series, were wiped out of existence. What was once thought to be distinct animals were in fact juvenile and nearly sexually mature specimens from the same species.

One of the study's authors, renowned paleontologist John "Jack" Horner, suggested that as many as a third of named dinosaur species could be cleared from the record books as they might simply be juvenile versions of another identified dinosaur.

Hot or cold?
Given that dinosaurs have been gone for millions of years, no paleontologist has ever managed to take a dinosaur's temperature. As a result, researchers have had to surmise whether dinosaurs were warm- or cold-blooded based on fossil evidence.

Most dinosaurs were once believed to be slow-moving, cold-blooded creatures similar to today's reptiles. However, recently published research suggests that dinosaurs may have been warm-blooded.

A study in 2012 showed that growth lines on fossilized dinosaurs bones, once touted as evidence of dinos' cold-bloodedness, indicates the opposite. As LiveScience's Jennifer Welsh explained: "During slow-growing times like during the winter, they are darker and narrower, while in fast-growing times the bones have lighter, wider bands." Constant growth would indicate a warm-blooded animal, while varied growth, which appears in dinosaur bones, would suggest a cold-blooded creature.

The study's authors demonstrated, however, that even mammals can display interrupted bone growth depending on environmental conditions, such seasonal rainfall and temperature cycles, and physical considerations, such as animal's core body temperature and resting metabolic rate.

Bye bye, Brontosaurus
If this statue of a Brontosaurus looks as though the dinosaur has a bit of an attitude, it's because the Brontosaurus never in fact existed -- a fact that seems to give the Tyrannosaurus rex in the background the giggles.

The Brontosaurus is rather the result of an intense competition between bitter 19th-century rivalry between paleontologists Othniel Charles Marsh and Edward Drinker Cope that would become known as the Bone Wars, according to NPR. Marsh had discovered the partial skeleton of an giant, long-necked dinosaur he called the Apatosaurus, affixing the skull of another dinosaur, believed to be a Camarasaurus, to complete the find. Two years later, a second, more complete Apatosaurus skeleton was found, which Marsh called the Brontosaurus.

The mistake was detected in 1903, but the Brontosaurus endured in both museum collections and dinosaur books and film. Two Cargenie researchers in the 1970s put the final nail in the coffin of the Brontosaurus when they determined that a skull belonging to the original 1877 skeleton had been found in a quarry in Utah in 1910.

Guilty until proven innocent
If the Oviraptor had lived in a more litigious period than the late Cretaceous Era, it might have sued the scientist who discovered it for slander.

In 1923, the first Oviraptor skeleton was unearthed by Roy Chapman Andrews and later described by paleontologist Henry Osborn. Because the Oviraptor's remains were found near a clutch of what were believed to be Protoceratops eggs, it earned its monicker, which translates to "egg thief" in Latin.

What scientists later discovered with in the 1990s with new fossil evidence was that the original Oviraptor find was in fact guarding its own eggs.

The Case of the Stupid Stegosaurus
Long before researchers learned more about dinosaur social structure and behavior patterns, dinosaurs were thought to be pretty dumb animals, due to the size of the brains of some specimens relative to their bodies. No dinosaur's intelligence was quite so maligned as the humble but familiar stegosaurus.

When scientists first unearthed this dinosaur, stegosaurus was thought to have a second brain in its behind due to the small size of the one in its skull. In other words, paleontologists went on record stating they believed stegosaurus to be a prehistoric butthead -- the technical term for the condition anyway.

No, the stegosaurus didn't have a butt brain. No dinosaur has ever been found to have a second brain for that matter.

Dino descendents
Even before there was any evidence of feathers in dinosaurs, paleontologists and biologists had for 150 years suspected that birds were the descendants of dinosaurs.

The discovery of Archaeopteryx in 1861, just two years after Charles Darwin published On the Origin of Species, was the first species to create a link between modern birds and their prehistoric ancestors. The late evidence of feathers, anatomical similarities between some dinosaur fossils and modern birds and behavioral patterns bolster the hundreds of millions of years old connection between the two animal groups.

Dinosaurs of a feather
Classic depictions of dinosaurs typically feature scaly, often green but occasionally brown animals that looks almost like giant lizards. Fossilized feathers, however, are painting an entirely different picture of what these prehistoric creatures looked like.

Recent research has suggested that most if not all dinosaurs sported feathers. Originally found in the theropod Sinosauropteryx in 1996, more than 30 different feathered dinosaurs had been identified since.

Where'd they all go?
One of the most enduring mysteries among dinosaur enthusiasts was how this large, diverse group of animals that once dominated the planet went extinct. Theories ranged from volcano eruptions to death by catepillar to a giant asteroid impact that triggered a mass extinction. The last one is the most widely agreed upon cause of the dinos' disappearance.

Earlier this year, a group of 41 geologists, paleontologists and other researchers affirmed the theory, first posited in 1980, that an asteroid impact, later found at Chicxulub, Mexico, wiped out the dinosaurs 65 million years ago.