Friday, 29 May 2009

Pterosaur Classification

The concept of classifying pterosaurs into a family hierarchy is a complex business. The current test for species does not apply to extinct animals unless DNA comparisons can be made. This is not possible for pterosaurs.

A species can be defined as occurring “when interbreeding can produce viable offspring”. To get around this problem, fossil species are arranged in Clades. These are groups of animals with similar characteristics. For this reason, scientists cannot be certain that their comparisons produce a valid result, so there is a level of disagreement amongst the scientific community as to the true lineage and relationships of many pterosaurs.

To complicate this further, pterosaurs exhibit a trend called convergent evolution. Because the success of different groups depends upon the physical limitations of flight, there is a limit to the variation in wing and body mass change that will be tolerated in natural systems. This can make unrelated pterosaurs look very similar.

The big classification difference is seen between the long tailed pterosaurs (Rhamphorhynchoidea) and the short tailed pterosaurs (Pterodactyloidea). The two main groups can be divided into family clades which exhibit a common range of major characteristics with relative ease in most cases – then the job gets extremely difficult.

The people who, in my world of logic, have made the most perceptive attempts to classify the pterosaurs, based on current knowledge, are Harry Seeley, Peter Wellnhofer and David Unwin. There have been many other brave attempts which have produced quite credible lineages, but have been less accepted within the scientific community. The main argument now that the fossil record is better known is where the family divisions should be placed and what the families should be called. I am happy to follow the current lead of David Unwin at present, until a better model is devised.

ORDER PTEROSAURIA (After Unwin 2006)
Suborder Rhamphorhynchoidea
Family Dimorphodontidae
Family Anurognathidae
Family Campylognathoididae
Family Rhamphorhynchidae
Suborder Pterodactyloidea
Superfamily Ornithocheiroidea
Family Istiodactylidae
Family Ornithocheiridae
Family Pteranodontidae
Family Nyctosauridae
Superfamily Ctenochasmatoidea
Family Gallodactylidae
Family Pterodactylidae
Family Ctenochasmatidae
Superfamily Dsungaripteroidea
Family Germanodactylidae
Family Dsungaripteridae
Superfamily Azhdarchoidea
Family Lonchodectidae
Family Tapejaridae
Family Azhdarchidae

The current consensus (which is probably changing as you read) will develop constantly as new ideas are incorporated and new research is completed. There are many possibilities for naming the groups, but the general relationship of family groups will be similar in any scheme as can be seen in the diagram below;

Sunday, 24 May 2009

The First Pterosaur

The Handbuch der Palaohepetologie, Teil 19, Pterosauria, starts;

"Der erste Pterosaurier wurde im Jahre 1784 von Cosmus Collini beschrieben und abgebildet (Abb. 1). Es handelte sich um das vollständige Skelett eines Pterodactylus aus den Solnhofener Schichten von Eichstätt und lag seinerzeit in Naturalinkabinett der kurpfälzischen Akademi zu Mannheim. Es ist der spätere Holotypus zu Pterodactylus antiquus (Soemmering) und befindet sich heute in der Bayerischen Stattsammlung für Paläontologie und historisch Geologie in München."

"The first Pterosaur was described in 1784 by Cosmus Collini and was illustrated (Fig 1). It was a complete skeleton of a Pterodactylus from the Solnhofen Shales of Eichstätt and it was kept at this time in the Naturalinkabinett kurpfälzischen Akademi at Mannheim. It is the current Holotype to Pterodactylus antiquus (Soemmering) and today is in the Bavarian State Museum for Palaeontology and Historical Geology in Munich."

The fossil was originally held in the Palace at Manheim where it was part of a collection of natural artefacts. Such objects as fossils had usually been considered as evidence of the biblical flood at that time, though scientific attitudes were changing. The fossil, which was owned by Karl Theodore was examined by Collini in 1757. Cosmo Collini was a Florentine academic from Italy, who had a keen interest in the natural world.

Collini recognized this fossil as an amphibious sea creature, which was a fair consideration as he had nothing to compare it with. Johann Frederick Blumenbach had also examined the fossil and in 1807 he pronounced that it was an unusual water bird. The thinking about this fossil was moving in the right direction.

George Cuvier was probably the most respected mind working in this field and in 1809 he recognised the fossil skull as reptilian in structure and identified the pectoral extremities as wings. He considered the fossil to have a membrane of skin stretched out along the wing fingers which would have formed a wing structure. This idea was quite perceptive and captured the agreement of many of his peers at that time. It was Cuvier who named the fossil Pterodactylus (Winged Finger). There were some disagreements and in 1812 Samuel Thomas von Soemmerring considered the fossil to be mammalian and bat like, being in disagreement about a reptile being able to produce enough energy for flight.

With the discovery of more fossils in the following years, it became clear that these creatures were flying animals with associations to the Reptilia. By 1840 it was generally accepted that Pterodactyles were flying creatures with an unusual wing structure supported on a long flight finger. The hollow bones were becoming more easily recognised and many partial specimens that were thought to be of bird bones could be re-classified as pterosaur.

Holotype: No. AS-I-1739 Bayerischen Stattsammlung für Paläontologie und historisch Geologie

Collini, C A. 1784 Sur quelques Zoolithes du Cabinet d’Histoire naturelle de S. A. S. E. Palatine & de Bavière, à Mannheim. Acta Theodoro-Palatinae Mannheim 5 Pars Physica, pp. 58–103 (1 plate).

Wellnhofer, P. & Khun, O. 1978 Handbuch der Paläoherpetologie. Teil 19. Pterosauria. Stuttgart: Verlag Gustav Fischer.

von Soemmerring, S. T. 1812 Über einen Ornithocephalus oder über das unbekannten Thier der Vorwelt, dessen Fossiles Gerippe Collini im 5. Bande der Actorum Academiae Theodoro-Palatinae nebst einer Abbildung in natürlicher Grösse im Jahre 1784 beschrieb, und welches Gerippe sich gegenwärtig in der Naturalien-Sammlung der königlichen Akademie der Wissenschaften zu München befindet. Denkschr. k. bayer. Akad. Wiss. math.-phys. Kl. 3, 89–158, plates.

Wednesday, 20 May 2009

Dendritic pyrolucite

Sometimes, when finding fossils in flaggy limestones, the bedding is subject to different forms of mineralization. This pterosaur fossil in the Natural History Museum, London, has a formation of black Manganese dioxide - MnO2 (Dendritic pyrolucite) forming crystal structures around the fossil bones. This is quite common in these Bavarian specimens, though they are not very frequently seen beyond the storage rooms of museums.

Pyrolucite - MnO2 is used in Zinc Oxide dry cell batteries as an oxidising agent. This is a stable compound formed in nature from unstable ions. It can be reduced to Manganese oxide MnO with the addition of Hydrogen.

In the Fossils, the dendrites of Pyrolucite grow away from the fossil bones, along the bedding plane of the sediment, forming a fern like pattern on the rock. The crystals are orthorhombic in form and have a hardness of 2. Excessive contact will result in staining to the fingers and the mineral has a streak colour like graphite. This crystal formation is a result of ions carried in water which is forced through the sedimentary beds during the later stages of rock formation. The fluid is forced through the rock bedding planes where it will deposit materials in cavities and structures within the rock. When the hardening sediments are under pressure stress, the areas around impurities, like fossils and hard mineral grains will form micro cavities within the nearby sediment which allows deposition of crystals. The dendritic solidification of MnO2 around the fossil is a reflection of the sedimentary stress patterns and this is seen as a series of frond like patterns emanating from the bones. Quite often, the deposition is greater on one side of the fossil, or in some cases near a small area or part of a fossil. The example shown in the photograph is an extreme case.

Monday, 11 May 2009

Dragons of the Air

Harry Govier Seeley was assistant to the famous palaeontologist, Adam Sedgwick, at the Woodwardian Museum, Cambridge. He was a very astute palaeontologist and stratigrapher in his own right and remained in post for many years despite offers of prestigious jobs elsewhere in the academic world.

Throughout his career, he was often in dispute with the considered expert on fossil life, Richard Owen. Some of Seeleys papers are quite scathing about Owens ideas and theories. Seeley believed the fossil pterosaurs (and many dinosaurs) must have been warm blooded in order to function effectively in their environment. Owen considered them to be very reptile like and cold blooded. With the hindsight of modern science, Seeley was right on many points. He also considered both birds and pterosaurs to be separate groups with common affinities,
placing them between the reptiles and mammals in his classification. This is also now accepted as good classification.

Towards the end of his career in 1901, Seeley wrote and published a book on fossil pterosaurs, both in the UK and USA. This book was a very popular text, selling out very quickly and requiring a second prin
t run to satisfy demands. It was the first popular book on pterosaurs, and as such, quite an historic text.

The book "Dragons of the Air, an account of extinct flying reptiles" was produced as a hard back text and printed in the UK by Methuen and Company of London. The US edition was printed by D. Appleton and Company, New York. The reprint was produced in the UK and distributed worldwide. Many Universities and Museums had pre-ordered copies. Dover Paperbacks also re-printed the book in 1966

The text contained what I consider to be the first sensible reconstructed diagrams of fossil pterosaurs. The illustrations, whilst economical for their day, were good quality and relevant to the text.


The classification is interesting - for instance - the illustration above shows a reconstruction of Cycnorhamphus, a Pterosaur from Solenhofen in Germany. The holotype is now in the University Museum at Tubingen. This was re-classified as Gallodactylus suevicus for many years, but convention has now dictated that the original classification is used.

I have now transcribed this text, which is well out of copyright, and added it to the archive texts of The Pterosaur Database. This is something that I had intended to do many years ago. The transcript can be downloaded from; Bibliography menu -Archive Papers. This is a 12MB file in .pdf format and will take a little time to download.

Seeley H G; 1901, Dragons of the Air: an account of extinct flying reptiles, London, New York (reprint - Dover Paperback, 1967) 240 pp.

Friday, 1 May 2009

A New Blog

There are many good web logs and websites that include fossil pterosaurs, but not many blogs dedicated to them. It is for this reason that I have created this web log. As webmaster of The Pterosaur Database, I thought it was about time that there was a source of information to provide snippets and contextual notes on all sorts of aspects of fossil pterosaurs that are not necessarily covered by the wider web resources.

My intention is to add a post each week, lets see how it goes.