Tyrannosaurs didn't come into their own until the late Cretaceous period, when monsters like T. Rex, Albertosaurus and Tarbosaurus terrorized North America and Asia. Now, a new study of the sole fossil specimen of Proceratosaurus--a mysterious theropod dating from 170 million years ago--has shown it to be an extremely primitive member of the breed, a find that dials back the first tyrannosaurs to the mid-late Jurassic period. Interestingly, the tiny (75 pounds fully grown) Proceratosaurus was unearthed in England, where no later tyrannosaurs have been found.

Confusingly enough, similar T. Rex ancestors have been announced to the public with great fanfare--first the tiny, feathered Guanlong (dating back about 160 million years) from China, and more recently the pint-sized, central Asian Raptorex, a relative newcomer at a mere 125 million years old. What this means is that dinosaur evolution in general--and tyrannosaur evolution in particular--is a far more convoluted affair, far more dependent on the vagaries of fossil finds, than is presented in most popular accounts!

One of the problems with investigating pterosaurs is that these flying reptiles were so numerous, and so similar looking, that they can be hard to distinguish from one another on the genus (much less the species) level. A case in point is Germanodactylus, which for years was thought to be a species of Pterodactylus, until a more rigorous analysis showed that it deserved its own genus.

As pterosaurs go, Germanodactylus tended toward plain vanilla, except for its prominent (and probably prominently colored) head crest--which was composed of solid bone on the bottom and soft tissue on the top.

Read more about pterosaurs like Germanodactylus: Pterosaurs - The Flying Reptiles

Illustration: Wikimedia Commons

Every week, it seems, there's more evidence that dinosaurs of the same species regularly harassed, attacked, and even cannibalized one another. The latest is the discovery of tyrannosaur-sized bite marks on the skull of Tyrannosaurus Jane, a juvenile T. Rex that was probably about 12 years old when it died. The 1,500-pound Jane (who may or may not have been a female) almost certainly scuffled with a fellow T. Rex juvenile, based on the size and position of the numerous, non-fatal bite marks.

Why would Jane have tussled with a fellow tyrannosaur? Well, kids will be kids, and it's possible that two T. Rex siblings were simply engaging in a little horseplay. But it's also possible that the battle was more serious, and may have involved another genus of juvenile tyrannosaur attempting to horn in on T. Rex territory. (There's no evidence, by the way, that the puncture wounds were caused by trichomonosis, a parasitic infection implicated in the death of another T. Rex specimen, Tyrannosaurus Sue.)

Geosaurus is one of the less aptly named of all prehistoric reptiles: this so-called "earth lizard" is believed to have spent most, if not all, of its life in the sea. A direct ancestor of modern crocodiles, Geosaurus was a different animal entirely from contemporary aquatic reptiles like plesiosaurs and ichthyosaurs, though it made its living in the same way, by hunting down and eating smaller fish.

Read more about prehistoric reptiles like Geosaurus: Crocodiles - The Ancient Cousins of the Dinosaurs

Illustration: Wikimedia Commons

You'd think a brand-new genus of ankylosaur--the "armored lizards" characterized by their tough body plates and clubbed tails--would need to be named based on a near-complete skeleton. Well, you'd be wrong: witness Tatankacephalus, a 112-million-year-old herbivorous dinosaur (discovered in Montana in 1997) that has been "diagnosed" primarily on the basis of its almost 90-percent-complete skull.

Evolutionarily speaking, what makes Tatankacephalus important is that it's a kind of "missing link" between the primitive ankylosaurs of the late Jurassic and the fully armored monsters (such as Ankylosaurus and Euoplocephalus) of the late Cretaceous. And in case you were wondering, Tatankacephalus is Greek for "buffalo head," not so much for its resemblance to a modern buffalo as for the fact that the researchers who discovered it work for the Buffalo (NY) Museum of Science.

Ever since the first dinosaur fossils were discovered, experts have had a hard time distinguishing between adults and juveniles--with the result that many supposedly "new" dinosaurs (like the pint-sized Nanotyrannus) have turned out on further examination to be juveniles of existing species (e.g., Tyrannosaurus Rex). Now, a new analysis of pachycephalosaur fossils by a joint team from The University of California, Berkeley and The Museum of the Rockies has cast doubt on two named genuses of pachycephalosaur, Dracorex and Stygimoloch.

According to the team (which includes the famous paleontologist Jack Horner), specimens of Dracorex and Stygimoloch probably represent earlier growth stages of Pachycephalosaurus. As this article on the UC Berkeley website says, "The confusion is traced to their bizarre head ornaments, ranging from shields and domes to horns and spikes, which changed dramatically with age and sexual maturity, making the heads of youngsters look very different from those of adults."

Based on these findings, Horner has issued a shocking statement, speculating that as many as one-third of all the dinosaur species named so far are spurious, and represent different growth stages of previously named dinosaur genuses. If he's right, a lot of the current dinosaur literature is going to have to be completely rewritten!

One of the earliest of all the ankylosaurs (armored dinosaurs), Gastonia's claim to fame is that its remains were found in the same quarry as those of Utahraptor--the largest, and fiercest, of all the North American raptors. We can't know for sure, but it seems likely that Gastonia was on Utahraptor's lunch menu, which would explain its elaborate back armor and shoulder spikes. (The only way Utahraptor could have made a meal of Gastonia would have been to flip it onto its back and bite its soft belly, which must not have been an easy task!)

Read more about dinosaurs like Gastonia: Ankylosaurs - The Armored Dinosaurs

Illustration: Wikimedia Commons

Real dinosaurs went extinct 65 million years ago, and they're never coming back--but you can't say the same about dinosaur toys. Witness the recent resurrection of Pleo, a robotic dinosaur (modeled after a baby Camarasaurus) that earlier this year succumbed to the dire economy when its manufacturer, Ugobe, went bankrupt. In a desperate stab at survival, Ugobe had cut Pleo's list price from $350 to $250, but no luck--which is why it's surprising that new owner Innvo Labs has reverted back to the budget-busting former price tag ($400, if you opt for the rechargeable battery pack). Another hopeful sign for the dinosaur economy!

About the size and weight of a typical second-grader, Gasparinisaura is important because it's one of the few ornithopods known to have lived in South America during the Cretaceous period. Based on the discovery of numerous fossil remains in the same area, it's believed that this small plant-eater lived in herds, which probably helped protect it from the larger predators in its ecosystem (as did it ability to run away very quickly when threatened!).

Read more about dinosaurs like Gasparinisaura: Ornithopods - The Small, Herbivorous Dinosaurs

Illustration: Wikimedia Commons

One usually pictures woolly mammoths (and other prehistoric elephants) as flourishing in cold, northern climates like Siberia and Canada. That's why it's such a surprise that researchers have discovered woolly mammoth remains in southern Spain, well below the 40 degree latitude line once thought to demarcate the expansion of these shaggy beasts.

Interestingly, according to this article on Science Daily, woolly mammoths grazed on Granadan grasslands at the same time as their proboscid relatives spread to eastern China and even parts of Japan. This indicates that, for a few thousand years at least, the Ice Age wasn't quite as icy as usual, freeing these giant herbivores to amble their way to more southerly climates.