Fantastic Fish Fossils Found

Researchers have found several new species of gigantic extinct fish that fed solely on the tiniest of food-sources – plankton. The fossil fish fill a gaping hole in the fossil record: before now, large plankton-eating fish were missing from a 100million year chunk of prehistory.

A modern Basking Shark - such a big mouth for such tiny prey. Image: Wikimedia

Long before the evolution of filter-feeding whales and sharks the seas were home to nine-metre long fish, such as the newly-discovered Bonnerichthys, which took advantage of the same food source. Until recently, researchers believed the group to which these fish belonged, the pachycormids, went extinct around 172million years ago, in the Jurassic period.

The new discoveries, which included fossils from the USA, UK and Japan, show that the pachycormids actually went extinct at the same time as the dinosaurs, 65 million years ago. Only once they were gone was there an opportunity for modern ‘planktivorous’ groups, like baleen whales and basking sharks (Cetorhinus maximus), to evolve.

Plankton – the collection of microscopic marine creatures found in every sea and ocean around the world – today supports gigantic marine animals such as the blue whale (Balaenoptera musculus). These animals use comb-like structures called baleen plates to filter the tiny plants, animals and bacteria out of seawater.

The hole in the fossil record was a complete mystery. Plankton is so abundant, and supports such large animals today that researchers expected something to eat it. Bonnerichthys and friends are, it seems, just the massive fish required to plug such a massive hole.

Paper Reference: Friedman et al. 100-Million-Year Dynasty of Giant Planktivorous Bony Fishes in the Mesozoic Seas. (2010). Science, 327 (5968), p990-993 DOI: 10.1126/science.1184743

‘In a hole in the ground there lived…’

‘…a hobbit.’*

Fossil ‘hobbits’ found on an Indonesian island and reported in Nature in 2004 are a new species after all, according to a new study by American researchers. Statistical analysis of the fossil skulls and limb bones show it did not belong to a diseased modern human, or a pygmy, but a unique species. But haven’t we heard such claims about the ‘hobbits’ before?

H. floresiensis: small, yet distinctive. Image: Wikimedia/Ryan Somma

Yes, we certainly have. The diminutive fossil hominid, found on the island of Flores in 2003 and nicknamed ‘hobbits’ by their discoverers, were at the centre of an international argument. Initially hailed as a new species known as Homo floresiensis, several researchers dismissed the fossils as the remains of diseased humans. Since then, claims and counter-claims have appeared in the scientific literature and the press. This latest study agrees with the well-supported ‘unique species’ hypothesis.

The researchers carried out a statistical analysis of important physical features of the best-preserved H. floresiensis fossil. They found that its skull retained some very primitive features, such as thick bones and primitive teeth. These features do not fit the pattern seen amongst modern humans, pygmies, or people with a rare condition known as microcephaly.

The researchers also examined the shape of other hominid skulls and established the pattern of changes seen as the skulls get smaller. By carrying this pattern downwards to very small skulls, the researchers ended up with something very similar to H. floresiensis, suggesting H. floresiensis was a perfectly healthy member of the great hominid family to which we ourselves belong.

In case that wasn’t enough, the researchers also demonstrated that the body proportions of H. floresiensis were completely dissimilar to modern pygmies. Short (they stood around one metre tall) and stocky, the hobbits resembled no-one alive today.

*From ‘The Hobbit’ by JRR Tolkien, but you knew that, didn’t you?

Paper Reference: Jungers, W., and Baab, K. (2009). The geometry of hobbits: Homo floresiensis and human evolution. Significance, 6(3), 159- 164. DOI: 10.1111/j.1740-9713.2009.00389.x

Liang Bua cave, Flores. A long way from Bag End! Image: Wikimedia/Rosino

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

Incoming! Giant flying reptiles left touchdown tracks

Quetzalcoatlus - the largest pterosaur ever to live. Image: John Conway (http://jconway.co.uk)

A study by French researchers has revealed new aspects of the behaviour of extinct winged reptiles known as pterosaurs, including details of how they managed to land, by examining the fossil trackways they left behind.

The trackway – an unusual pattern of footprints left in soft mud – suggests the pterosaur landed in much the same way as birds do today, by ‘stalling’ just above the ground. Importantly, this requires very precise flight controls, which means pterosaurs must have had well-developed brains to handle the complex manoeuvres.

The researchers looked at a set of fossil footprints left by a small pterosaur in soft mud in a region of what is now south-west France. From other tracks we know pterosaurs walk on all fours but the landing track appears to show a pterosaur touching down on its rear legs first and making a small hop. Only then did it put its front legs, which also supported its wing membranes, down on the ground.

The pterosaurs were incredible beasts: the smallest was the size of a sparrow, whilst the largest ( Quetzalcoatlus – named after an Aztec god) had a 15-metre wingspan. They were one of only three groups of animals with backbones to achieve true flapping flight (with birds and bats being the other two).

Whilst we know that pterosaurs could fly, we’re still not sure how they managed to take off and land safely: with a 15-metre wingspan, just getting airborne is extremely difficult. Scientists have long debated how creatures like pterosaurs behaved as there are no similar species around today to compare the fossils to, and old bones can only tell us so much. Evidence of behaviour like this is rare in the fossil record, and the trackway described by the researchers is a very fortunate find.

(Incidentally, the image above came from the website of an artist called John Conway, which I stumbled across while researching this post. He’s produced some fantastic paintings of dinosaurs, so I suggest any dinosaur fans check it out!)

Diamonds may shed light on ancient murder mystery

12,900 years ago, our ancestors may have witnessed one of the most terrifying events imaginable – a direct strike by a massive meteorite.

At this point in our history many large mammal species went extinct, including pygmy mammoths and the sabre-toothed cat (with the excellent scientific name Smilodon fatalis!). Researchers have long argued over what was to blame: climate change, human hunting, or disease. New research by a team from the University of California in the USA now lends support to a fourth compelling possibility – a meteorite strike.

The meteorite hypothesis is supported by the presence of “nanodiamonds” in geological layers of the right age. These microscopic gems require immense temperatures and pressures to form. On Earth they are only ever found near meteorite impact craters.

The nanodiamonds aren’t the only thing in favour of the meteorite claim. Like any good murder investigation, there are multiple lines of evidence pointing to the suspect. The geological period in question, the Pleistocene, also shows evidence of wildfires across North America and dramatic cooling of the climate. The heat released by a meteorite impact would ignite many square miles of forest and grassland, generating large quantities of soot. The force of the impact would also throw dust high into the atmosphere. Combined with smoke from the fires, this would reflect a lot of sunlight back into space, cooling the climate.

Unfortunately, there’s no evidence for a crater of the right age, which would provide much more conclusive evidence.

It is almost impossible to identify the killer in such ancient mysteries. Even the well-studied end of the dinosaurs, sixty five million years ago, remains unclear; with volcanoes in India, meteorites in Mexico, or a combination of the two to blame. The new research into the events of 12,900 year ago presents an interesting argument, but I suspect we’re still a long way from knowing for certain what happened in these dark days before the blossoming of human civilisation.

Diamond hunt, anyone? Image credit Cburnett. Used under GFDL