The Tree of “Lice” – Parasites “Bugging” the Dinosaurs

Feathered dinosaurs and their non-feathered relatives were probably plagued by parasitic lice.  For the short-armed tyrannosaurs and the even shorter-armed abelisaurids not being able to scratch themselves would have made life quite unpleasant for these animals during the Mesozoic.  Perhaps extinction was a kindness after all, or maybe if the Dinosauria were weakened by parasites, this could help explain their demise sixty-six million years ago.

A new study carried out by an international team of researchers suggests that lice that plague those extant relatives of the Dinosauria (birds) and lice that associate themselves with mammalian hosts were diversifying quite merrily whilst dinosaurs still reigned supreme.  This suggests that the Aves and Mammalia were also diversifying in the Age of Reptiles, a concept alien to many members of the public but the fossil record shows that for both mammals and birds many new genera were evolving long before the dinosaurs, Pterosauria and the marine reptiles became extinct.

Dinosaurs, just like other reptiles had their fair share of biting insects and parasitic bugs and tics, fossils found in Cretaceous amber indicate this.  Indeed, some scientists have even cited the rise of parasites as a contributory factor leading to the demise of the dinosaurs.

To read an article on this: Did Bugs and Biting Insects Cause the Dinosaur Demise?

The lack of avian and mammalian fossils from the Mesozoic makes determining their speed of speciation (new species evolving), difficult.  However, by studying lice, scientists can draw conclusions on the hosts that the lice associated with.  Many lice only affect a single species.  For instance, lice of many bird species have evolved special hooks that permit them to lodge themselves between the filaments in a feather, thus making them almost impossible to remove by preening.

If the host evolves, then the parasites evolve to in a process called co-speciation.  Scientists used the fossil record for mammals and lice enabled scientists to build up a picture of the radiation of mammal species.  As if lice can be seen diversifying into different types, then it can be assumed that they are evolving and adapting to exploit a new host that has also evolved.

The researchers built up a map of related lice fossils and noted that these creatures began to radiate much earlier than previously thought, around 115 million years ago (Early Cretaceous – Aptian faunal stage).   The research work has been published in the scientific journal “Biology Letters”.

Lice Plagued the Dinosaurs

However, not wanting to put a fly into the ointment, sticking to the Arthropoda as it were,  but there is an additional factor that needs to be considered.  The Dinosauria were also diversifying at this time.  New types of dinosaur – hadrosaurids, pachycephalosaurids and ceratopsians were evolving and indeed many dinosaurs were feathered (fossil evidence suggests this).  Is it appropriate to assume that the lice were living on mammals and birds, the radiation of lice species could reflect increased diversity amongst the Dinosauria, after all, feathered dinosaurs would have been prone to parasites just as much as their avian cousins.

Either way, this work shows how relationships between a parasite and a host can help scientists to “plug” the gaps in the vertebrate fossil record.  For us, it still does not explain how the short-armed theropods were able to scratch themselves, perhaps they scratched up against a tree (Baloo in the Jungle Book style), or maybe there were smaller birds and dinosaurs that provided a tic removing service just as we see today on tropical reefs with cleaner fish.

Visit Everything Dinosaur’s award-winning website for fantastic dinosaur and prehistoric animal toys and models: Everything Dinosaur.

Zhuchengtyrannus magnus – A fearsome Chinese Tyrannosaurus

It may have been a little awkward, after all, with the press releases about the discovery of a new member of the tyrannosaur clade (Zhuchengtyrannus magnus), one that may rival the likes of Tarbosaurus bataar and Tyrannosaurus rex in terms of size on the eve of April Fool’s Day, but the good news is the ever growing family of Tyrannosauridae has definitely got a new member, and who knows, perhaps a second one is on the way.

The trouble is, if there is a press release sent out about dinosaurs at the end of March, some parts of the media automatically query it as they regard such information as a potential April Fool story.  There are a number of bogus articles doing the rounds, we know, we have been asked to comment on a few and indeed, aid in the preparation of one (sauropod femurs turning up on the coast of Cumbria).

However, amongst an extensive hadrosaur bone-bed an international team of dedicated palaeontologists have literally pieced together the evidence to indicate that there was at least one giant tyrannosaur theropod roaming the Shandong province of China in the Late Cretaceous and what a fearsome beast Zhuchengtyrannus may turn out to be.

An Illustration of Zhuchengtyrannus magnus

Picture credit: Robert Nicholls

Zhuchengtyrannus magnus

With the information being published in the scientific journal “Cretaceous Research” we can reveal that based on measurements made of the fragmentary elements of the skull material found, it seems that this particular tyrannosaur may have measured as much as 11 metres long with a body weight tipping the scales at around six tonnes.

Dr David Hone from University College (Dublin), the palaeontologist given the job of naming this ferocious predator and the scientist who led the research team that has worked on the fossilised bones stated:

“There is no doubt that Zhuchengtyrannus was a huge Tyrannosaurine.”

More information on this remarkable discovery, we think only the second really big tyrannosaur to be discovered in this region of China, can be found on David’s excellent and highly informative web log – Archosaur Musings.

Doctor Hone went on to comment:

“With only some skull and jaw bones to work with, it is difficult to precisely gauge the overall size of this animal.  But the bones we have are just a few centimetres smaller than the equivalent ones in the largest T. rex specimen.”

The binomial name for this new member of what is a rapidly expanding clade of the dinosaur family tree is Zhuchengtyrannus magnus. The name means “Tyrant from Zhucheng city”, as the fossils were found in the city of Zhucheng – a part of the world gaining a reputation as a “hot spot” for dinosaur fossils.

This is the first dinosaur that Dr Hone has named (as a first author) and although the lack of fossil material prevents the scientist from making more definite calculations as to the size of this tyrannosaur; from the dentary (lower jaw bone) and the maxilla (upper jaw bone), it is clear that this dinosaur was very, very big.  The species element of the binomial name reflects the large size of this dinosaur.

Zhucheng is a relatively small town and has already been recognised in recent years for the great vertebrate fossil potential the area has.  A number of new dinosaurs have been discovered in this area, this new tyrannosaur is just the latest of a whole range of important discoveries that have been made by palaeontologists.  It seems that much of the strata in the area may represent flood deposits where a large number of corpses have been washed up together forming extensive bone-beds.  The material ascribed to Zhuchengtyrannus (pronounced “zoo-cheng-tie-ran-us”) was found in a hadrosaur bone-bed deposit.

A Scale Drawing of the Newly Described Tyrannosaur Zhuchengtyrannus magnus

Everything Dinosaur’s scale drawing of the giant, Late Cretaceous Asian tyrannosaur Zhuchengtyrannus magnus. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Tyrannosaur maxillae are important bones as they help distinguish different genera, the different taxonomic characters can be determined by careful study of certain parts of the fossil skeleton and the maxilla and other parts of the skull are key bones in helping researchers to determine whether or not they have discovered a new genus.

To view models and replicas of Chinese dinosaurs including Zhuchengtyrannus (whilst stocks last): PNSO Age of Dinosaurs Models.

Importantly, what fossil material that has been found is in excellent condition and measurements taken of the dentary show that this new tyrannosaur would probably only have been slightly smaller than its Chinese cousin Tarbosaurus (Tarbosaurus bataar) and also not quite the size of the largest specimen of Tyrannosaurus rex known to science.  But this new discovery suggests that there are other super-sized, apex predators in the tyrannosaur family.

Dr Hone comments:

“Zhuchengtyrannus is basically just another giant Tyrannosaurine in the mould of these two more famous giants [T. rex and Tarbosaurus].“

Remarkably, the site where the fossils of Zhuchengtyrannus were found may yield many other discoveries, including another giant tyrannosaur.  The research team excavated a number of teeth and postcranial elements including vertebrae, femora and various metatarsals (backbones, thigh bones and toe bones).  Importantly they found another maxilla and another dentary, neither of which match the material ascribed to Zhuchengtyrannus magnus or other known tyrannosaurs. This suggests that there may be at least one other tyrannosaur at the dig site awaiting further analysis.

However, if there is another taxon present, then this will complicate matters for the palaeontologists.  Imagine trying to put together a jigsaw puzzle, without knowing for sure how many pieces you have or indeed the precise identity of what you are trying to create.  Then imagine the added complication of having to try to put together two similar but definitely different jigsaws, with all the known pieces you have jumbled up together, each one having no illustration to guide you, and you still do not know how many pieces of each you have to work with – tricky.

The potential to find another taxon is covered in the scientific paper, but for the time being just one new taxon has been named and described.  Expect to hear a lot more about the bone-beds of Shandong Province and the amazing dinosaur fossils that await discovery.

Our congratulations to Doctor David Hone and his colleagues for their work.