An Ancient Hitch-Hiker

The fantastic computer model of the 50 million year old,
amber preserved spider with a mite hitch-hiking on its back

In recent times, samples of amber have revealed many fantastic specimens. They have given us  fantastic new knowledge about the evolution of everything from arthropod groups to feathers. Sometimes the fossils which they give up are not exciting new species or revolutionary insights into evolutionary history, but are instead curious specimens which are simple snapshot of a single moment in time, perfectly preserved for millions of years.

Such a piece was recently unearthed at the world famous, 50 million year old Baltic Sea deposits. A team from the University of Manchester analysed the amber fossil, using the most advanced computer scans and modelling available. In recent years, advances in computing power and innovative new analysis techniques have allowed palaeontologists to study fossils and extract a greater wealth of detail than ever before. A couple of decades ago, fossils required a physical study utilising arduous and inaccurate processes which risked damaging the specimens.

Now CT scans, MRI imaging and synchotron x-ray analysis can collect vast amounts of data to create 3D digital models, which are accurate to scales of hundredths of micrometres, with no damage to the specimens themselves. Inside this particular piece of amber, they found a spider, barely 156 micrometres in length, just visible to the naked eye. What made it special was that there was an even smaller mite, a type of arachnid, hitching a lift upon its back.

The specimen was described as 'one in a hundred thousand.' The hitch-hiking, better known as phoretic behaviour, is used by small creatures as a means of getting a free ride to a new and potentially food-rich environment. Fossil mites themselves are incredibly rare, making the discovery of this specimen a fantastic find. The scientists also believe that it is the oldest known member of the modern day mite family, Histiostomatidae.

They were able to draw this conclusion by using the computer to dissect the models, removing the mite from the spider's back, allowing them to view its underbelly. Professor Phil Withers, co-author of the paper published in the Royal Society journal Biology Letters, from Manchester's School of Materials, said: 'We believe this to be the smallest amber inclusion scanned anywhere to date. With our sub-micron phase contrast system we can obtain fantastic 3D images and compete with synchrotron x-ray systems and are revealing fossils previously inaccessible to imaging. With our nano-CT-lab systems, we are now looking to push the boundaries of this technique yet further.'

The Common Ancestor Of All Alligators and Crocodiles

Today the largest reptiles on Earth are the crocodiles and alligators. They are not the most diverse of groups with only around 20 different species overall, but hundreds of millions of years ago they were numerous and varied. Creatures such as Postosuchus or Dinosuchus were top predators in their ecosystems, giant, scale-covered, cold-blooded reptiles that were reduced to the twenty or so forms today just a few million years ago.

An artist's impression of Stomatosuchus inermis

Now palaeontologists believe that they have found a crocodilian which is the common ancestor to both groups of giant reptiles. Stomatosuchus inermis was first discovered in the early 2000s in continental freshwater deposits in Morocco and stored in the vaults at the Museum of Ontario, Canada. It is known from just one 99 million year old skull. However calculations suggest that it would have had a body length of ten metres and a skull of two metres. The fossil was incomplete.

Stomatosuchus inermis had a very unusual feature. Its skull was very flat, very wide and covered in a dome of dense tissue, packed with blood vessels. It is likely that this was used partially to control its body temperature, partially in mating displays. After it was named and analysed, it was simply consigned to the ranks of the giant prehistoric crocodiles....until now. Recent analysis suggests that it is the ancestor of both crocodiles and alligators, both extinct and modern. Gharials did not evolve until later.

99 to 65 million years ago, the lush marshlands of Morocco were home to hundreds of different crocodile species. Stomatosuchus was one of the older beasts. Genetic and fossil analysis shows that the common ancestors to crocodiles and alligators probably lived in the part of Laurasia that would become modern day Morocco. Careful taxonomic work supports the theory that this creature, commonly called the 'shield croc,' was the common ancestor.

While it was a pescivore, feeding upon large coelacanths, its anatomy, based upon the skull, point towards such a conclusion. 'Like most of today's crocs, it was likely opportunistic, feeding on whatever it could. However, it was likely not capable of wrestling large vertebrate prey given the slenderness of its jaws,' says Assistant Professor Casey Holliday from the program of Integrative Anatomy at the University of Missouri. Future analysis and, hopefully new fossils, will either confirm or disprove this theory.

Cave Paintings May Have Been Made By Prehistoric 'Realists'

The Dappled Horses of Peche Merle

Cave paintings are some of the most beautiful forms of art on Earth. Vast underground galleries have been found all across the world. Some of the depictions are massive, metres in size.

Alongside the familiar shapes of horses and lions are beasts outside of human experience such as the mammoth. Alongside these are even stranger creatures and abstract shapes and symbols. For many years archaeologists and palaeoanthropologists were unsure what many of the images were or why they were created.

One such mystery is the 25,000 year old 'Dappled Horses of Peche Merle' which adorns the rocky walls of the cave system in France. No such creature exists today. We have no physical evidence of it in the fossil record, as pelts rarely preserve and even then, colours do not remain. Now a team led by Dr Melanie Pruvost of the Department of Evolutionary Genetics at the Leibniz Institute for Zoo and Wildlife Research, and the Department of Natural Sciences at the German Archaeological Institute in Berlin, have solved this problem.

They took samples from the teeth and bones of more than 30 different ancient horses with a geographical range from western Europe to Siberia with a maximum date of 35,000 years old. From these samples they extracted and decoded the fragments of DNA, setting up a rough genomic sketch. They specifically looked at the genes which encoded the colouration of the coat. They found that 25 had the single colour 'patterning' with five possessing black fur and 18 with bay fur.

However 6 possessed the genetic variation that encoded a spotted, leopard-like, coat. Ultimately, they found that all of the different coat variations, depicted at the Peche Merle cave, could be found in the prehistoric horse populations across Europe and Siberia. The team suggest that many early artists were realists, as opposed to surrealists or dreamers. Genetic analysis is fast becoming a part of earth sciences like anthropology and palaeontology. When fossil evidence fails to provide, only genetic evidence can fill the gap.