Amazing Cretaceous Bony Fish Preserved in Flint

For a local Kent resident the habit of picking up unusual objects to place in his rockery at home has enabled scientists to get to grips with a rare example of a fossilised Cretaceous fish.

The stone shaped fish head was spotted by Peter Parvin and his wife whilst they beach-combed on a caravan holiday to Pevensey in East Sussex in 1993.  Found amongst the pebbles as the tide was going out, Mr Parvin thought nothing of his find, simply placing it amongst the other curiosities he had collected in this rockery.  However, a chance conversation with a volunteer from Maidstone museum in a pub, led to him bringing this rare, ancient relic to the museum for closer examination.

Fossil Fish

The fish head fossil measures approximately 15 cm across, it is shown in the photograph facing to the right of the screen.  The eye, mouth and shape of the gills can clearly be seen.

“I have never seen one of these before”, commented Dr Ed Jarzembowski, the Keeper of Natural History at Maidstone Museum.  “Quite simply it’s priceless”.

In contrast with most fossils found from this period (which are associated with chalk), the fish head has been preserved in flint, this makes it particularly rare and valuable.  The hard flint would have helped maintain the quality of preservation, even as this stone was bumped and bashed on the shoreline of Pevensey beach.

Found on Pevensey Beach

The fish has been dated to around 80 million years ago (Late Cretaceous) and is a representative of the modern bony fish group the Teleosts.  This type of fish, with its streamlined fins, highly manoeuvrable body and ability to open its jaws wider than other more primitive fish forms evolved from the Acanthodian fishes.  Bony fish dominate the world’s freshwater and oceans with a greater diversity of animals at the taxonomic level of Family than any other group of vertebrates.

During the Late Cretaceous, most of the UK was covered with a warm, shallow tropical sea.  These seas swarmed with life and there are a number of common fossils associated with flint nodules.  Sponges are often found in association with flint nodules.  Flint occurs as extremely hard nodes in chalk deposits.  It is formed by chemical reactions within the chalk sediments and it is composed of silica in the form of microscopic quartz crystals.

The silica came mainly from the exoskeletons of dead sea sponges (these are made of silica), and they were subject to dissolving into solution under the alkaline environment of the chalk deposits.  The silica tended to re-solidify if it encountered local acidic conditions such as the acidic conditions surrounding decaying organic material such as this fish head.  This may help to explain how this fish head fossil was formed.

There are plans to put the fish head on display at the local museum, although it may be ultimately sold in order to help raise funds for the museum’s development.

Everything Dinosaur stocks a range of prehistoric fish figures including prehistoric sharks and Dunkleosteus.

To view the models in stock: Dinosaur and Prehistoric Animal Models.

Scientists Discover Remains of Juvenile Tarbosaurus

A joint Japanese and Mongolian expedition have successfully recovered a nearly complete skeleton of a young dinosaur, a relative of the monstrous Tyrannosaurus rex.  This rare and important find will enable palaeontologists to better understand how Theropod dinosaurs grew and developed.

Juvenile Tarbosaurus

The dinosaur, a Tarbosaurus (Tarbosaurus bataar) is a juvenile and the skeleton is nearly complete, all that is missing are some neck vertebrae and a few bones from the tip of the tail.  Tarbosaurus was a member of the Tyrannosauridae and this creature is the largest known predator from Asia.  Associated with the very end of the Cretaceous, just like its North American cousin T. rex (Maastrichtian faunal stage), this fierce carnivore grew up to 12 metres in length.  Although known for at least sixty years, scientists still debate whether Tarbosaurus is sufficiently different from Tyrannosaurus rex to be regarded as a distinctive genus.  The fossils found to date (there are more Tarbosaurus remains to study than its more famous relative T. rex), indicate that these two animals were very similar.  There are minor differences in skull morphology, with Tarbosaurus having a proportionately larger head but a shallower snout and less powerfully built lower jaw.  Some scientists claim that Tarbosaurus was more lightly built than Tyrannosaurus rex, perhaps the result of the slightly different ecosystem in Mongolia and China compared to Late Cretaceous western North America.  A more agile, gracile predator Tarbosaurus may have specialised in tackling lighter prey animals.

PNSO Prehistoric Dinosaur Models: 51 Chuanzi the Tarbosaurus.

The picture (above) shows a replica of a Tarbosaurus in the PNSO Age of Dinosaurs range.

To view this range of figures: PNSO Age of Dinosaurs Models and Figures.

The joint Mongolian/Japanese expedition, made up of scientists from the Mongolian Academy of Scientists and the Hayashibara Museum of Natural Sciences in Japan first found the fossilised remains of this dinosaur in August 2006.  The skeleton was encased in a block of sandstone and it has taken nearly two years of careful, patience preparation to extract this young dinosaur from its rock tomb.

Commenting on the completeness of the fossil, Takuji Yokoyama, a spokesperson for the Hayashibara Museum stated:

“We were so lucky to have found remains that turned out to be a complete set of all the important parts”.

Fossilised Skeletons

Fossilised skeletons of young dinosaurs are extremely rare and the discovery of such a well-preserved and complete specimen is an exceptional find.  The bones of juveniles, being lighter than adults are often scattered and broken up or destroyed by weathering on the surface.  The corpse of a young dinosaur would have been attractive to any passing scavenger and many remains would have been devoured leaving little chance of fossilisation for the fragments that are left over.  This fossil was probably covered very soon after death and this has led to the preservation of over 95% of the bones.

The latest discovery from the Gobi desert will help provide more information on the ontogeny of dinosaurs (growth rates and development).  The animal was over 2 metres long when it died and it is believed to have been around the age of 5.  It has not been possible to determine the gender, but had this dinosaur lived to reach adulthood it would have been the top predator of the area and may have exceeded 12 metres in length.

New Study Indicates Dinosaur Divergence well before Late Cretaceous Demise

There is a popularist view that the dinosaurs were at their most diverse and at the peak of their evolution in terms of the number of new species evolving; at the very end of the Cretaceous.  The Chicxulub impact then wiped out the great dinosaur dynasty leaving the world for the mammals to exploit.  Fossil evidence does not support this idea, studies in the Hell Creek Formation (Maastrichtian faunal stage), of the western United States indicate that the number of species of dinosaur was declining in this part of the world towards the end of the Cretaceous.

Approximately ten different genera are known from the youngest Cretaceous sediments, whilst older strata from this area show evidence of many more different dinosaur types.

Certainly some of the best known dinosaurs date from the very end of the Mesozoic.  Animals wandering the Hell Creek area at the end of the Cretaceous include Triceratops, Ankylosaurus and of course Tyrannosaurus rex.  In the past, these gigantic representatives of their dinosaur families, (Triceratops, Ankylosaurus and T. rex are just about the largest type of dinosaur from these three families), were thought to indicate that dinosaurs just got too big and lumbering to survive and this is why they went extinct.

Scientists now know that the reasons for the end Cretaceous mass extinction event, the extinction not only of the dinosaurs but also the ammonites, plesiosaurs, mosasaurs, pterosaurs and a whole host of other plants and animals, were complex and probably involved a number of factors.

Everything Dinosaur has received a big delivery of CollectA prehistoric animal models and figures. This substantial shipment includes 35 different prehistoric animal figures.  This image shows the diversity of prehistoric animals.  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

To view the extensive CollectA range of not to scale figures that demonstrates the diversity of prehistoric animals in the fossil record: CollectA Prehistoric Life Replicas and Figures.

Given the limitations of the existing dinosaur fossil record it is difficult to piece together a “dinosaur family tree” but a project to map dinosaur evolution and to highlight the main evolutionary shifts in Dinosauria has just been completed.  The results of this study, led by a team of researchers from the University of Bristol has just been published in the British Journal Proceedings of the Royal Society B.

This study indicates that the dinosaurs as a group diversified rapidly in the Late Triassic (225 – 200 million years ago) and then underwent a second evolutionary surge in the Middle Jurassic (170 -160 million years ago).  The scientists studied a large portion of the described dinosaur species and pieced together an evolutionary “family tree of dinosaurs”.  The team estimate that their study covered something like 70 percent of all the known and described dinosaur species.

This new study contradicts earlier research that shows the dinosaurs diversifying during the Cretaceous.  The established view is that although dinosaurs as a group diversified during their entire existence, in certain periods, the evolution of new forms was speeded up.  One such period was the Early Cretaceous which saw the emergence of a greater variety of ornithischian dinosaurs – the rise of the hadrosaurs, ceratopsians and the pachycephalosaurs, for example.  These types of new dinosaur were evolving during a time when many life forms on Earth were diversifying.

Dating from about 125 to 80 million years ago, there seems to have been a huge surge of increased terrestrial biodiversity.  This time period is referred to as the Cretaceous Terrestrial Revolution, life on Earth over this period changed dramatically.  The angiosperms (flowering plants), social insects, modern lizards, mosasaurs and many types of mammals all evolved.  It had been thought that the rapidly diversifying dinosaurs were part of this move towards greater biodiversity, the paper published by the Bristol team demotes dinosaur evolution during this period to a more peripheral role.  This new study indicates that by the time of the Cretaceous Terrestrial Revolution, all the main dinosaur types that were to survive until the end of the Cretaceous were already established.

This new work certainly contrasts with much of the accepted thinking regarding dinosaur diversity.  Most palaeontologists believe that during the early to middle Jurassic there were only four main groups of dinosaurs, whilst during the Cretaceous this expanded to nine, namely:

megalosaurs/allosaurs, tyrannosaurs, sauropods, hysilophodontids, hadrosaurs, pachycephalosaurs, ceratopsians, ankylosaurs and stegosaurs.

The fossil record for all the terrestrial vertebrate life of the Mesozoic is very incomplete so it is difficult to trace evolutionary links between different types of animals.  The work of the Bristol University team is certainly helping to open up the debate, but not having reviewed the actual paper we cannot really comment any further.  It would be interesting to find out how the evolution of non-avian dinosaurs, the birds has been assessed in this study.

Very little is known about the evolution of birds, but they do seem to have diversified and developed new species very quickly during the mid to late Cretaceous, a growth in speciation that was largely unchecked by the Cretaceous mass extinction event.

Certainly, it is not surprising that the dinosaurs diversified during the Late Triassic, the world was just recovering from the Permian mass extinction (an event that saw an estimated 57% of all marine families and 70% of all terrestrial vertebrate genera becoming extinct).  Life on Earth slowly began to recover and those types of organisms left began to diversify to fill those environmental niches that were empty and those soon to be left empty by the “dead clades walking” such as the last of the Lystrosaurs.