Tuesday, 30 June 2009

A very Peculiar Pterosaur

Pterodaustro is represented by a number of specimens from Argentina. There is a complete skeleton, a partial juvenile and an egg, just to mention a few. This unusual pterosaur is quite well represented in the fossil record, certainly enough is known to make a convincing reconstruction.
Most unusually, this was a filter feeder with a fine sieve of unusually adapted teeth that would have been ideal for filter feeding on small aquatic living organisms. This was the Flamingo of the ancient world!
The diagram of the skull shows the peculiar nature of this animals jaw. This pterosaur has more teeth than any other pterosaur. It is likely that it has more teeth than any other Dinosauromorph. It is also the first pterosaur where gizzard stones have been observed to be present.

The holotype, which was originally described by Bonaparte, is PLV 2571 and is a right humerus in the Institute Miguel Lillo, Universitat Nacional Tucuman, Argentina. Most of the specimens come from South America which is probably where the species evolved within a specific shallow water habitat, where zooplankton and phytoplankton were abundant.

In 2004 un-hatched egg containing a juvenile Pterodaustro, from the Lagarcito Formation in Central Argentina was described. The lacustrine deposits in which it was found are called the Loma del Pterodaustro and they are dated to about 100 million years ago. The specimen MHIN-UNSL-GEO-V 246 has been studied using electron micrographs of the egg shell suggesting a leathery shell. Ghosting of proteins can be interpreted within the shell structure which has yealded a significant amount of information about this pterosaurs eggs.

Bonaparte J F, 1970 Pterodaustro guinazui gen.et sp.nov.. Pterosaurio de la formacion Lagarcito, Provincia de San Luis, Argentina, Acta Geologica Lilloana, 10(10):207-226

Bonaparte J F, 1971 Descripcion del craneo y mandibulas de Pterodaustro guinazi (Pterodactyloidea - Pterodaustriidae), de la Formacion Lagarcito, San Luis, Argentina, Publ. Mus. Mun. Cienc. Nat. Mar del Plata, Pp. 63-272

Bonaparte J F & Sanches T M, 1975 Restos de um Pterosaurio,Puntanipterus globosus de foracion la Cruz, provincia de San Luis, Argentina, Actas Primeiro Cong. A

L. M. ChiappeA. Chinsamy, 1996, Pterodaustro's true teeth, Nature 379, 211 - 212 (18 January 1996)rgentino Paleont. Biostretigr., 2:105-113

Frey E., Martill D. M., Chong-Diaz G. and Bell M., 1997, New pterosaurs from the Lower Cretaceous of Chile. J. Vert. Paleont. 17 (3)

Codorniú L, Chiappe L.M. Early juvenile pterosaurs (Pterodactyloidea: Pterodaustro guinazui) from the Lower Cretaceous of central Argentina. Can. J. Earth Sci. 2004;41:9–18

Chiappe L.M., Codorniú L., Grellet-Tinner G. and Rivarola D., 2004, Palaeobiology: Argentinian unhatched pterosaur fossil, Nature. 432, pp. 571-572 (2 Dec 2004)

A Chinsamy, L Codorniú, and L Chiappe, 2008, Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guiñazui, The Royal Society, Biol Lett. 2008 June 23; 4(3): 282–285

Saturday, 20 June 2009

Mary Annings Pterodactyle

On 21st May 1799, Mary Anning was born, daughter of Richard and Mary Anning of Lyme Regis, Dorset, England. During her life she collected curiosities from the beach at Lyme Regis and nearby coastal areas. She became a very proficient and knowledgeable collector of fossils and made a number of remarkable discoveries. She often referred to experts for advice and support and her main sources were William Buckland, Henry de la Beche and William Conybeare, who were able to develop their reputations on many of Mary's discoveries.
In 1828, Mary discovered a fossil pterodactyle (later named Dimorphodon macronyx) which she discussed with William Buckland. Buckland wrote a paper on this fossil and it was known to be the finest of the English pterodactyles. The remains are now in the Natural History Museum, London.
Shortly after the discovery, her brother Joseph made a sketch of the fossil skull. He used reconstituted belemnite ink from the finds on Lyme Regis Undercliff. This drawing is now held by the Philpot Museum, Lyme Regis - though neither the fossils or the sketch are on display as they are considered too valuable to be exposed to the public.
The remaining bones of the fossil find were almost a complete skeleton and an additional find revealed the whole of the animals tail. This was one of the few pterosaurs that enabled a complete reconstruction to be attempted. A second skeleton and skull (minus tail) gave a better insight into the association of the bones and over the years, several small bone finds have been made. Many of these are in private collections.

Thackray J. C. A., 1995, A catalogue of portraits, paintings and sculpture at the Natural History Museum London. Mansell: London. xii, 70pp.

Torrens H. S., 1995, Mary Anning (1799-1847) of Lyme : ‘the greatest fossilist the world ever knew’. British Journal for the History of Science, Vol. 28, pp.257-284.

Buckland W. 1829, On the discovery of a new species of pterodactyle in the Lias at Lyme Regis. Trans. geol. Soc. Lond. ser. 2, 3, 217–222, pl. 27.

Padian K, 1983, Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea). Based on new material in the Yale Peabody Museum. Postilla 189.
Pierce P., 2006, Jurassic Mary, Mary Anning and the Primeval Monsters. Sutton Pp238.

Monday, 15 June 2009

Discovering Pterosaur flight - Part 2

The design of Flying model pterosaurs was taken a stage further in 1957 when Erich von Holst made a flying model of Rhamphorhynchus. This model was powered by a coiled elastic band which was connected to a rocker device which flapped the wings of the model. The tail sail had to be horizontal to stabilise the model in flight. From this experiment it was clear that the Rhamphorhynchus form had the potential to be a very good flying animal.

In the 1970's a bat expert (Cherrie Bramwell) and an engineer (R G Whitfield) teamed up to examine and analyse the joints of large pterosaurs. They defined the range of movement in the wing joints and proposed a postural model for Pteranodon. G R Whitfield had flown a fully controlled life size model in 1973, but that model was eventually destroyed in a crash landing. This work was an extension of the Hankin and Watson work and was to provide a basis for future flying models.
Stephen Winkworth was a model aeroplane builder who had an interest in anything that flies. In 1984 he designed a pterosaur flying model, based on the Bramwell and Whitfield work which was flown in January 1985 on the cliffs along the Dorset coast. The model was filmed for the BBC television production "Pteodactylus Flies". This 15 foot wingspan model was an excellent radio controlled glider, though to overcome some stability problems, additional stability fins had to be incorporated in the design.  

The Quetzalcoatus Project was started in 1984 and in December1985 Paul MacCready flew a half size flying model of Quetzalcoatlus. This flying model was much more sophisticated than the balsa and fabric model of Stephen Winkworth and used aviation technology for its construction. It had an autopilot device and a recovery parachute which could be controlled from the ground. The project was used to produce an IMAX movie in 1986 for the Smithsonian Air and Space Museum in Washington D. C.

Up to this point, the flying models of Pterosaurs had all been gliders or simple flapping models, using aeroplane aerodynamic theory in their production. The Stanford Project, which was supported by National Geographic was intended to build a flying model that worked like a real animal. This was an ambitious project and had an extensive team headed by Margot Gerritsen. The model flew in many forms, first taking to the air in 2006 with a stabiliser tail boom to allow the electronic movements to be tested. The model was air lifted and launched at altitude by a carrier plane. The Stanford model was nicknamed Herki and featured in the TV program "Sky Monsters", which is now available on video.

What next?......

Holst E. von.,
1957, Der Saurierflug, Paleontologische Zeitschrift, 33, pp. 15-22. 7 figures.

Bramwell C. D. & Whitfield G. R., 1974, Biomechanics of Pteranodon. Philosophical Transactions of the Royal Society, London, B.267, pp.503-581

Winkworth S., 1985, Pteranodon flies again. New Scientist, 3 January 1985:32-33

MacCready P,, 1985, The Great Pterodactyl Project. Engineering and Science, November 1985: 18-24

Wednesday, 10 June 2009

Discovering Pterosaur flight - Part 1

In the early days of research, Samuel Thomas von Soemmering made the first sensible reconstruction of a pterosaur skeleton in 1812. The reconstruction was missing several skeletal elements, but was a sound model based on the available evidence. He also proposed a wing membrane form which, although too generous in area was a good attempt at theoretical reconstruction.
It was not until 1882 that the wing structure was known from the fossil record. A specimen originally named Rhamphorhynchus phyllurus was discovered in the Lithographic Shale of Bavaria. At about the same time an isolated wing known as the Zittel wing (above) was published. Both fossils showed the outline and structure of the wing membrane of Rhamphorhynchus. This enabled much better reconstructions to be made.

In 1910 C. F. Eaton produced a paper on the osteology of Pteranodon with a skeleton reconstruction This was an inspired paper showing the skeletal form of a large pterosaur. Pteranodon was only known from crushed and distorted remains and this paper showed the skeletal form in a realistic way.

Ernst Stromer was inspired by the Rhamphorhynchus wing membranes and he produces a flying glider in 1913 which demonstrated that Rhamphorhynchus could fly with the known wing form.

By1914 the Hankin and Watson paper on the flight of Pteranodon gave us an insight into the structure of large pterosaurs that was related to the way they could fly. The framework was set for some real flying models.

Watch this space.......

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.

von Zittel, K. A., 1882, Über Flugsaurier aus dem lithographischen Schiefer Bayerns. Paläontographica 29, 47–80 & pls 10–13.

Eaton, G. F., 1910, Osteology of Pteranodon. Mem. Conn. Acad. Art. Sci. 2.pp.1-38.

Marsh, O. C., 1882, The wings of Pterodactyles. Am. J. Sci. (3)23, 251–256 & pl. 3

Stromer E., 1913, Rekonstruktionen des Flugsauriers Rhamphorhynchus gemmingi, H. v. M., Neues Jahrb. Min. Geol. Pal., II, pp. 49-68.

Hankin E. H., & Watson D. M. S., 1914, On the flight of pterodactyls. Aeronautical Journal 18, 324–335.

Tuesday, 2 June 2009

The Origin of Pterosaurs

Where did pterosaurs come from? This has been a question that scientists have considered for a long time.
It is clear from the skull of pterosaurs that they belong to a group of reptiles called the Diapsids. This just happens to be the biggest group of reptiles that there is. This group is classified on the basis of individuals having a pair of openings in the back of the skull. It can be seen in the sketch of Eudimorphodon, a very early pterosaur, that there are two openings behind the orbit. There is also a sclerotic ring within the orbit.

Another feature of early pterosaurs is their tricuspate teeth. Later pterosaur teeth are single cusped. These features link the pterosaurs to basal dinosaur groups, making them Dinosauromorphs. This is still a very big group to pin them down within.

The problem with trying to examine pterosaur origins is a complex one. Firstly, the earliest pterosaurs that are recorded in the fossil record are very well adapted for flight. Their bone shape and structure have significantly changed with adaptations for flight, being thinner, lighter and structurally strengthened. These changes cannot easily be reconciled with an ancestral form. Secondly, pterosaurs are limited in their adaptation by the physical requirements for flight, so any evolutionary changes tend to have a convergent element. Similar wing shapes, structures and balance are needed to be able to compete and survive.

Pterosaurs had air sacs and flow through lungs, similar to those found in birds and in some dinosaurs. It seems likely that these structures developed only once in these animals and they had common ancestors. The most likely candidate for this ancestry would be within the Ornithodirs. This is a view supported by several researchers.

It is likely that the pterosaur ancestors evolved as a small isolated community in a localised area of the world. It may be that the habitat did not produce fossils easily (erosional environment) or that any sediments holding such fossils have not yet been found. It may also be the case that the sediments containing such fossils have been eroded away in the recent past. Whatever the reason, the elusive missing link has not been found.

Of course, the other factor in the equation is the choice of characteristics to compare when looking for an ancestral species. Depending upon which characters are given dominance, different conclusions can be made. For instance, if you classify based on neck structure, the pterosaurs are more likely to seem like Archosauromorphs. If the dominant characteristic is the foot, then they come out ar Dinosauromorphs. At present, there is not enough evidence to identify an ancestral species and make the link back to any specific group. Ornithodire ancestry is just a best guess based on sound, but incomplete, evidence.

Padian K., 1984, The Origin of Pterosaurs, Third Symposium on Mesozoic Terrestrial Ecology, Pp.163-168 Tubingen, Attempto Verlag

Bennett S. C., 1996, The origin of pterosaurs and their systematic position within the Diapsida. Journal of Vertebrate Paleontology, 16; Sup.3

Hone D. W. E. and Benton M.J., 2007, An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles, Journal of Systematic Palaeontology, 5: 465-469.

Claessens L. P. A. M., O'Connor P. M. and Unwin D. M., 2009, Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism. PLoS ONE 4(2): e4497. doi:10.1371/journal.pone.0004497