Dinosaur for dinner

Earlier this week, scientists announced the discovery of an extraordinary fossil. It contained the body of snake caught in the act of devouring newly-hatched sauropods! Dominant terrestrial predator they may have been, but the dinosaurs didn’t have it all their own way. Here, I take a look at a few of the beasts that could terrify even those terrible lizards!

Slithering hunter

Caught in the act - Sanajah devours a titanosaur. Image: Wilson et al/PLOS Biology

The early snake Sanajeh indicus could never have tackled an adult titanosaur: sauropods such as the titanosaurs were some of the largest animals ever to walk the earth. Fully grown titanosaurs could reach 25 metres long and weigh more than 38 tonnes and were almost completely immune to predators: but when young they were just as vulnerable as any other small animal.

Sanajeh took full advantage of this, hunting amongst the titanosaur nest fields littering the landscape of India 67.5 million years ago. Sanajeh wasn’t huge – around 3.5 metres long – and couldn’t expand its mouth to swallow large prey, unlike modern snakes. It did manage to devour 0.5 metre long baby sauropods, however, and one unlucky snake was frozen in time as both it and its prey were engulfed by a landslide. The fossil not only tells us about the hazards facing newly-hatched dinosaurs, it also gives us an insight into the evolution of snakes, with their amazing expandable skulls.

Amphibian Ambush

You may want to show a bit more respect to the frogs in your garden pond. Small and slimy they may be, but their ancestors were willing to go up against the toughest of them. Lurking in the late Cretaceous undergrowth of Madagascar, Beelzebufo ampinga was waiting for small dinosaurs to put a foot wrong…

Beelzebufo was a 40-centimetre-long ambush predator. It sat, perfectly camouflaged, waiting for its prey to come along before striking with its immensely powerful jaws. Sadly, there’s no direct evidence that it dined on small dinosaurs, but its size, and the location it inhabited, do suggest dinosaur was part of this primitive frogs’ diet.

Feisty Furball

Psittacosaurus - a tasty snack for a rodent? Image: bumblesweet/Flickr

The Cretaceous period wasn’t just the age of the reptiles. One small furry group – the mammals – was making its presence felt in smaller ways, even managing occasionally to drag down one of the mighty reptiles that ruled the land. A few years ago, Chinese and American scientists unearthed Repenomamus giganticus, a giant fossil rodent from 139 million years ago. Incredibly they found the remains of a young ceratopsian dinosaur in the rodent’s stomach.

Repenomamus had sharp, pointed teeth, which hint at its carnivorous habits, and weighed around 13kg. This may be small compared to today’s mammals but it was a giant amongst the mammals alive at the same time. This obviously gave it the muscle, and courage, required to hunt juvenile Psittacosaurus, a distant relative of the more-famous Triceratops armed with a fearsome hooked beak.

Paper References:

Wilson J., Mohabey D., Peters S., Head J., (2010) Predation upon Hatchling Dinosaurs by a New Snake from the Late Cretaceous of India. PLoS Biology 8(3): e1000322. doi:10.1371/journal.pbio.1000322

Hu Y, Meng J, Wang Y, Li C (2005) Large Mesozoic mammals fed on young dinosaurs. Nature 433: 149–152.

Evans, S., Jones, M., and Krause, D., (2005) A giant frog with South American affinities from the Late Cretaceous of Madagascar. PNAS 105:2951-2956; doi:10.1073/pnas.0707599105

Dinosaur extinction continues in lab

Evolution results in the formation of many species from a single ancestor, but what could possibly result in the formation of one species from several others? The answer is simple mis-labelling, according to a recently-published study of dinosaur skulls.

Dracorex hogwartsia: such an odd-looking child... Image: Flickr/Roger Lynn

According to the study, researchers may have wrongly identified juvenile dinosaurs of one species as two completely different species. The results mean we could see the extinction (again!) of many other supposed species of dinosaur, as they are also found to be the young of other dinosaurs.

The confusion arose because the skulls of the dinosaurs, which are often used to tell species apart, change dramatically as they age. The dinosaurs being studied were pachycephalosaurids, famous for their heads covered in horns and lumps and crowned by spectacular bony domes – which were used, as birds use their feathers today, to advertise sexual maturity and to allow the dinosaurs to identify members of their own species. Young Pachycephalosaurus had no domes, and their horns were arranged differently to the adults, leading researchers to name the young dinosaurs as entirely different species.

The new study looked at sections of bony skull from three pachycephalosaurid ‘species’ under a microscope and found they were made of bone which changed shape dramatically over the dinosaur’s life time. Similar shape-shifting bone has been found before in dinosaurs like the famous Triceratops, whose three curving horns grow from the same substance. As Triceratops aged, its horns twisted and turned until they reached their adult form. A similar re-shaping of skull bones as the animals matured is thought to have led to the pachycephalosaur confusion.

So what does this mean for palaeontology? As well as the loss of the two pachycephalosaur species, the researchers think it could result in even more species being recognised as the young of others, particularly amongst other dinosaur species in the group known as marginocephalians, which includes animals such as Pachycephalosaurus and Triceratops.

The species lost in this case include Dracorex hogwartsia, named for Hogwarts School in the Harry Potter children’s books, and Stygimoloch spinifer. Both are thought to be juvenile Pachycephalosaurus wyomingensis, from the Upper Cretaceous period of North America.

Paper reference: doi:10.1371/journal.pone.0007626

What makes a bird?

New findings could knock Archaeopteryx off its perch as the oldest-known bird. According to an international team of scientists, Archaeopteryx “…was simply a feathered and presumably volant [flying] dinosaur.”!

Is it a bird, is it a ... dinosaur?! Image: Wikimedia/Luidger

The scientists, from the USA, Germany and China, looked at the fossilised bones of Archaeopteryx under a microscope. The bones contained very few spaces for blood vessels, resembling instead the slow-growing bones of a reptile. In contrast, modern bird bones contain lots of spaces for blood vessels, as their rapid growth means their bones need a substantial supply of nutrients.

Young birds grow up very quickly; reaching their adult size in just a few weeks before they leave the nest (this is why you never see a ‘young’ pigeon in the flocks that crowd our cities). Scientists had thought the earliest birds, which evolved from dinosaurs 150 million years ago, grew up just as fast, but the new evidence suggests they grew up  slowly, just like the dinosaurs from which they evolved. Only later did they acquire the speedy metabolism needed to support the rapid growth we see in modern birds.

The dinosaur-like growth rates cast doubt over the theory that Archaeopteryx is the oldest known bird. It’s teeth, clawed hands and long bony tail show Archaeopteryx is closely related to dinosaurs, but the presence of well-developed feathers (which can be clearly seen as impressions in the rock surrounding fossil Archaeopteryx found at Solnhofen in Germany) has marked it out as a true bird. The new findings could overturn this, as the slow metabolism and un-bird-like growth rates suggest Archaeopteryx may be essentially just another feathered dinosaur.

Paper Reference: doi:10.1371/journal.pone.0007390

Section through an Archaeopteryx femur. Image: PLOS one

Diseased dinosaurs starved to death

The mighty Tyrannosaurus rex suffered from a common infection found in modern birds, according to new research. The tiny parasite called Trichomonas gallinae might even have killed some T. Rex: painful sores in the mouth and throat would have made eating impossible, starving the mighty beasts.

A sore throat is the least of his problems... Image: Flickr/Jeff Kubina

The team of American and Australian researchers found tell-tale holes in the jaw bones of ten of the 61 fossil tyrannosaurids – the group of dinosaurs including T. rex and its close relatives – they examined. When compared with modern bird skeletons, the scientists realised the holes look just like those caused by the Trichomonas gallinae parasite, which infects most pigeons, turkeys and chickens, and many birds of prey. The parasite is endemic – always present – in many bird populations, but did it plague dinosaurs in the same way?

As ten of the 61 dinosaurs showed some sign of infection, the researchers think it did. Trichomonas parasites were probably passed between tyrannosaurs, either from parent to offspring in contaminated meat, via cannibalism of dead tyrannosaurs, or during fights between two tyrannosaurs. There’s plenty of evidence such fights occurred, as tyrannosaur fossils have been found with head injuries that look just like tyrannosaur teeth marks. Head-biting would transmit the parasite between animals quite effectively, just as happens with the infectious facial tumour currently spreading through Tasmanian Devil populations.

The endemic parasite didn’t kill every dinosaur it infected, but it did cause the demise of some of them. In particular, a famous fossil T. Rex called “Sue” has a lot of the holes in her jaw, suggesting she had a major infection. Birds with no immunity to the parasite develop painful sores in their mouths, throat and crop, and if Sue had the same symptoms she would have been unable to eat, eventually starving to death.

Paper reference: doi:10.1371/journal.pone.0007288

Dinosaurs actually quite small?

As a child, did you ever peer up in wonder at the enormous fossilised remains of a dinosaur and just think “Wow, that’s really big!”? Well, according to a recently published paper, it wasn’t nearly as big as you thought!

New research has suggested that one of the mathematical formulae scientists use to estimate how heavy a dinosaur would have been, based on the size of its skeleton and comparisons to living animals, is wrong. The standard way of working was compared to a new technique using information from large living animals such as elephants to check their accuracy. The results suggested some of the largest dinosaurs (such as Apatosaurus) were only half as heavy as previously thought. If they’re right, scientists will have to re-examine how they think dinosaurs grew and lived.

Body mass is important for several things, not least of which is the on-going debate about whether dinosaurs were warm- or cold-blooded.  It’s also important when we look at how quickly dinosaurs reached maturity, and how they moved around.

All in the bones

With few exceptions, the only information we have about dinosaurs comes from their fossilised bones. These are excellent if we want to know how tall they stood, or roughly what they looked like, but tell us little about the really interesting behavioural questions – how did they hunt? Did they live in family groups? Which would win in a fight, a Tyrannosaurus or a Triceratops?

To answer such questions about these enigmatic monsters scientists employ all manner of trickery: Computer models can tell us about how dinosaurs moved; patterns of tiny grooves on their teeth can show what they ate; and formulae can be used to calculate how much they would have weighed.

None of these are infallible, and occasionally we’re lucky enough to find fossils that tell us more. Fossils have been found showing gut contents, skin and feathers, even two animals locked in combat and a mother protecting her eggs. These give us an incredibly rare and precious insight into dinosaur behaviour, but to answer the most exciting questions we need to rely on our ingenuity and guesswork. Sadly, sometimes we need to accept that even our best guesses are wrong.

Happily, every step we take is a step closer to these most famous of extinct beasts!

Dinosaurs tiny enough to rampage across your desktop? No.