Birds and Pterosaurs

Pterosaurs and birds were both competing for space in the Mesozoic skies.  However, the pterosaurs diverged as an order before the birds, and this was a clear advantage.  If the number of currently defines species are plotted on a graph by geological age, an interesting trend is observed.

Pterosaurs emerged in the Late Triassic, becoming the dominant flying creatures of the Era.  The birds are first seen in the Middle Jurassic, and start off as localised communities, as did the pterosaurs many millions of years earlier.  As bird species increase throughout the Cretaceous, the pterosaur species are seen to peak in numbers and then fall into decline.  By the end of the Cretaceous, pterosaurs were specialised as very large and wide ranging flying animals - most of the smaller pterosaur species having disappeared towards the end of the Cretaceous.

Birds clearly had an ecological advantage in most niche environments, eventually forcing pterosaurs into decline.  By the time of the Mass Extinction Event at the end of the the Mesozoic, There were only a handful of pterosaur species left, and these were too highly specialised to survive as an order of animals. The changes in ambient temperature and atmospheric oxygen content that resulted from the meteor impact and ensuing lava flows would have been biologically catastrophic, making life impossible for the large pterosaurs.

Kindle

 I have recently discovered that .pdf documents can be uploaded or imported to Kindle.  They do not display a front page image, but they are as readable as standard kindle documents.  This is a convenient way of carrying lots of scientific papers around without the need to Internet access or a laptop.  The system works well on kindle handheld or kindle for PC, which is how I processed these images.  Of course, the conversion to kindle hand held reader looses all colour, but that is seldom an issue.

Technology is always moving on and I would expect with the new generation of readers, the colour loss will be corrected.

Jehol Biota

 Eastern Chinese Provinces

The Jehol Biota contains probably the most prolific fossil producing strata in China.  It is found within the Eastern Provinces, forming a complex and heavily folded sediment which shows poor conformity across the regions.  For this reason, the dating and comparison of fossils is difficult at different geographical points in the sediments.

The associated rock formations are shown in the table, with the Jehol Biota marked with a blue background.  There are 5 distinct stages across 6 rock formations, extending from 110Ma to about 138Ma ago.
These deposits, along with the Daohugou Beds, which sit stratigraphically below the Jehol levels have produced significant pterosaur specimens that have enhanced the understanding of this fossil group considerably.

Toys

There are lots of pterosaur toys on the market.  Many of them are quite good, but there are a vast number of toys that are badly designed with respect to accuracy.

This model, from China, is of a mythical bat winged pterosaur with a strange head.  As a toy it works well and it is fun to slot the bits together to assemble the final model.

A much more realistic model comes from Germany.  Here a plastic Anhanguera has an appropriate stance and a good head reconstruction, based on prehistoric art work.

There are lots of slot together gliders made from polystyrene foam or similar soft plastics.  This mini pteranodon was produced for the Natural History Museum, London.  There are many more types available and thay all seem to fly quite well, being softand light enough to be relatively safe to use in confined spaces

Occasionally there is a different toy, like this jigsaw for younger children.  With 20 pieces and a simple picture it is quite easy to assemble in its own wooden base frame.

There are also a multitude of snap together models of skeletons like this pteranodon in a jar kit.  I have also seen glow in the dark skeleton models and Woodcraft do a self assembly fret saw wooden kit which is like a 3D jigsaw.
Add to this the rings, pendants, tee shirts and colouring books and the pterosaurs are well covered by the toy market.  Here are a few links:

http://www.everythingdinosaur.com/

http://www.dinosaurtime.co.uk/

http://www.amax-toys.com/

http://www.prehistoricstore.com/

http://ovirc.free.fr/

The pterosaur head crest investigated

There have been many discussions and proposals about the function of the pterosaur head crest.  They have ranged from display and sexual dimorphism to stability when dipping to feed in water and so on...  Brian Roberts and Rick Lind of the University of Florida and Sankar Chatterjee of Texas Tech University have recently published work that suggests another option for the crest.


They have designed an aircraft with a variable position tail fin on the nose.  This has been found to improve the efficiency of turning in flight.  Such an aerodynamic option would be advantageous to pterosaurs in positioning themselves to feed whilst in flight.  This option seems a sensible and practical explanation for the nature of the head crest as an aerodynamic feature associated with feeding.  Biologically and in an evolutionary context, this is the best explanation I have heard to date.


Brian Roberts, et al., 2011, Flight dynamics of a pterosaur-inspired aircraft utilizing a variable-placement vertical tail. Bioinspiration & Biomimetics 6. 026010. 11pp.


PhysOrg.com - "By morphing and repositioning a small aircraft's vertical tail to resemble the cranial crest of a pterosaur, researchers have shown that the aircraft's turn radius can be reduced by 14%. The ability to make sharper turns is especially important for small aircraft that operate in urban environments and in the presence of obstacles."

Survivorship

Were pterosaurs in decline before the Extinction event at the end of the Cretaceous Era?

The answer to this question depends upon what is meant by decline.  At the end of the Cretaceous there were a few species of large pterosaurs and no apparent small pterosaurs.  Birds were more numerous and it is likely that small pterosaurs could not compete with the birds.  The large pterosaurs seem to be very successful and show a wide ranging distribution.

If you apply the techniques used by Roup and Sepkosky to look at pterosaur survivorship, then this may give a clue.  Below is a graph of pterosaur families for each of the main geological ages during the mesozoic.

Survivorship of pterosaurs at the family level

This graph shows that the pterosaur families increased to a peak in the Upper Jurassic and then reduced in number into the Cretaceous.  The graph only includes pterosaurs where a family can be assigned with confidence.

If these data are applied to individual species, then a different shaped graph is seen.

Survivorship of pterosaurs at the species level

At the species level, the graph shows a peak in species numbers in the Lower Cretaceous and a fall in species numbers in the Upper Cretaceous.

It appears that pterosaurs, as an order of animals, were in decline before the great cretaceous extinction event.  The success of the large pterosaurs is most likely a result of them being able to occupy niches that the birds are unable to exploit.

Raup D. and Sepkoski J., 1986, Periodic extinction of families and genera. Science 231 (4740): 833–836

Pterosaur Tee Shirts

Today I chanced upon a young man and his mother.  The lad was sporting a rather fine Tee Shirt with a pterosaur design.  This immediately raised my awareness of the option to look at which pterosaur Tee shirts are available.

This particular example was produced by Mini Boden and after some investigation, it was found to be a limited production which is no longer available.

There are lots of pterosaur Tee Shirts on the market and a quick search on Google found hundreds of examples, mostly with cartoon representations or interesting mottos.  These 3 caught my eye as being more to my own taste in Tee Shirts;

zazzle.co.uk - rhamphorhynchus tee shirt

Redbubble.com - I love pterodactyls Tee Shirt

Cafepress - pterodactyl tee shirts