Tooth Quiz

Following on from my last post, I thought it would be interesting to give readers a chance to look at some teeth pictures. This should test even the most experienced eye as it is always difficult to examine teeth from photographs. The photo below is of some of the teeth in my own collection of fossils. Tooth 1 is 3.5 cm long for scale.
Question:- which teeth are pterosaur and which teeth are non-pterosaur?

You may even like to suggest a family or species for each tooth. Answers will follow in a future post.

Pterosaur Teeth

I am frequently asked to identify pterosaur teeth. Sadly, in most cases, the teeth turn out to be non-pterosaur. Many are of fish like Enchodus sp., the sabre toothed herring. These teeth are common and can easily be passed off by dealers as pterosaur teeth to increase profit. Many dealers will also obtain pterosaur teeth from suppliers without knowing that they have been duped.

This is my identification check list - most pterosaur teeth will exhibit these features.

1. Evenly curved and consistently tapering tooth.
2. Wear bevel at the top smooth with no abrasions.
3. Enamel cap at the crown.
4. Fine striations may be present towards the base of the tooth.
5. Open root.

Some larger pterosaur teeth may also show an oval shaped wear patch half way down the tooth where it has rubbed on the side of the opposing tooth when the jaw was closed.
If the tooth does not conform to this type, then the only sure way to know that it is a pterosaur tooth is for it to be fixed within a fragment of fossil jaw bone where the bone structure can be determined.
Most pterosaur teeth are evenly oval in cross section and generally of smooth appearance. There are some exceptions, like the tricuspate teeth of the very early pterosaur species. Specialist feeders like Dsungeripterus and Pterosdaustro, but the shapes of these exceptional teeth are well documented.
The moral of this post is - if you are buying an isolated pterosaur tooth, expect it to be non-pterosaur unless it has provenance and an expert opinion attached. It is also unwise to buy a fossil unless you know the locality, sediment and age of the site that it came from.

Rhamphorhynchus Wings

In 1882 Carl Zittel described a fossil pterosaur wing with the membrane preserved. This remarkable find was the highlight of that year and the Zittel wing became a very famous fossil. Casts were distributed to all of the main national museums and by 1883 most researchers and interested students of fossils had seen the wing.
In 1880, a fine fossil of Rhamphorhynchus was found in the Solenhofen Shales. The work was published in 1882 and clearly showed the wing membranes and tail fin. This specimen was originally named Rhamphorhynchus phyllurus (now Rh. muensteri) and it was sold to the Yale Peabody Museum in New Haven, USA. As with the Zittel specimen, casts were taken and distributed to National Museums.
Since the original finds of pterosaurs with wing membranes preserved, There have been many examples from the Lithographic Shales in Bavaria. The specimen above is in the Humboldt University Museum in Berlin.
Perhaps the best specimen of a Rhamphorhynchus with wing membrane preserved is the 'Dark Wing' specimen which is sometimes called the 'Tischlinger' specimen. This is a reflection of the work of Helmut Tischlinger who produced an amazing set of ultra-violet photographic images of this fossil to enable more detail of the wing to be observed.

These and other fossils enabled the wing structure to be studied in detail, from the fibres that run across the cord of the wing to the different layers of tissue within the wing membrane. As a result, there is a high level of understanding about the wing membrane structure of these and other pterosaurs.

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

Padian K & Rayner J M V; 1993, Structural fibres of the pterosaur wing: anatomy and aerodynamics. Naturwissenschaften 80: 361-364.

Martill D M and Unwin D M; 1989, Exceptionally well preserved pterosaur wing membrane from the Cretaceous of Brazil, Nature, 340:138-140

Tischlinger, H. and Frey, E. 2002. Ein Rhamphorhynchus (Pterosauria, Reptilia) mit ungewöhnlicher Flughauterhaltung aus dem Solnhofener Plattenkalk. Archaeopteryx, 20, 1-20.

Highlights of 2009

There have been some remarkable finds published in 2009. Something of a stepping stone in the understanding of pterosaur evolution.

1. Changchengopterus pani was found in Upper Jurassic rocks in China. It is a basal, non-pterodactyloid pterosaur. Basal simply means a more primitive form of pterosaur with characteristics of much earlier species.

2. Darwinopterus modularis is a Middle Jurassic pterosaur with an interesting combination of Rhamphorhynchoid and Pterodactyloid features. A whole new branch of classification had to be devised to accommodate this fossil between the Rhamphorhynchoids and Pterodactyloids. This is a good example of what Darwin meant when he developed the idea of modular evolution. Different characteristics developing at different times within a family of animals.

3. Wukangopterus lii is another Upper Jurassic Rhamphorhynchoid from China. It has a long toothed skull and shows more primitive features than Rhamphorhynchus.

4. Another Pterosaur track way has also been published. Pteraichnus nipponensis is a distinct and new type of pterosaur track way from the Lower Cretaceous. It was originally discovered in 1990 at Kiladani Dinosaur Quarry in Japan and it has just been published. This paper makes the point that most Cretaceous pterosaurs are very large species, but this and other track ways were made by smaller pterosaur species. There must be many fossils out there still to find.

There are a number of other pterosaur finds which are being worked upon at present and some of them are remarkable fossils. Hopefully they will be published soon, so that they can enter the scientific discussions and shed new light on the development of this interesting group of ancient fossil animals.

Happy New Year.

1. Lü, J. 2009. A new non-pterodactyloid pterosaur from Qinglong County, Hebei Province of China. Acta Geologica Sinica (English Edition), 83(2): 189-199.
   
   
2. Lü J. Unwin D. M., Jin X., Liu Y. and Ji Q., 2009, Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society B. Published on line 14 Oct 2009.
   
   
3. Wang X., Kellner A. W. A., Jiang S. and Meng X., 2009, An unusual long-tailed pterosaur with elongated neck from western Liaoning of China. Anais da Academia Brasileira de Ciências 81 (4):793–812.
   
   
4. Lee, Y.-N., Azuma, Y., Lee, H.-J., Shibata, M., and Lü, J., 2009., The first pterosaurtrackways from japan. Cretaceous Research

Comparative Studies

By looking at specific features of the fossil skeletons of pterosaurs it is possible to compare them to see how closely individuals are related. The science of comparative anatomy is limited in its application, but it is a very useful tool when dealing with fossil species. For instance - does Pterodaurstro fit more closely with the Pterodactyloids of the Rhamphorhynchoids.By looking at a comparison of wing bone lengths in relation to the wing metacarpal bone, it can be seen that the shape formed on the above graph places Pterodaustro clearly alongside that of a Pterodactyle. In many cases, the relationship of the wing bones to the wing metacarpal can be used to distinguish families of pterosaurs. However, this type of analysis should be used with caution as there are a few exceptions to the rule. Other features like skull anatomy, vertebra structure and pelvic anatomy are also needed to confirm any comparative relationships.

This graph shows the wing profile relationships between two individuals of the same species of pterosaur, found within the same sediment. The slight difference is likely due to natural variation.
Here is a wing profile graph that is generated from two unrelated pterosaurs from different sites at about the same geological age. The pterosaurs look similar in most features, but the analysis suggests significant differences in wing bone development.
When using comparators, patterns will emerge to indicate differences. Scatter graphs will often be a useful way of determining differences. The above plot shows the relationship between wing metacarpal length and first wing phalanx length in a random selection of pterosaurs. The differences between the Rhamphorhynchoid pterosaurs and the Pterodactyloid pterosaurs can be indicated by circling each group.
The final graph shows a calculated plot based on the relationship of measurements for the humerus, ulna and wing metacarpal. In this plot, there is no overlap between the two major pterosaur groups within this sample. The scales displayed are arbitrary units in the plot calculations.

Comparative anatomy is all that we can use for direct comparison of extinct fossil species. It gives a very good indication of relationships and enables structure to be developed in an evolutionary hierarchy. However, whilst this is a useful tool, it is only a guide and must be treated as such. It is often down to individual opinion as to how accurately the selected comparator work. This is why scientists develop slightly different evolutionary trees of the pterosaurs. Each may be valid within the scheme of analysis and each should be respected in that light.

Good science is all about debate and discussion but in the case of fossil analysis the picture is often quite disjointed. differences of opinion are what makes this subject interesting.

Pterosaur Eggs

Speculation about how pterosaurs reproduced has been enhanced over the years by lack of evidence. Many scientists believed that pterosaurs must have laid eggs, but were they hard shelled as in birds, or leathery as in reptiles. To some, the thought of how a long bony wing would work in an egg was a problem to imagine. Bats give birth to live young without the need for eggs, so perhaps pterosaurs could also give birth to, live young.

Speculation became analysis when, in 2004, a pterosaur egg fossil was found in China.


Avodectes pseudembryon (Wang and Zhou 2004), IVPP-v13758, was discovered in the Jehol Biota, being about 121 million years old. It was a complete embryo in a shell. The wings were coiled as they developed (sketch above) and the preservation indicates clearly that the bones were well ossified before hatching. This would enable the newly hatched pterosaurs to use the wings very quickly after emerging from the egg.

Observations of the porosity of the egg shell suggested possible burial during development and the form of the shell was soft and leathery like a reptilian egg, having a shell that was non-laminar and 0.25mm thick. The embryo wingspan was estimated to be 27cm. The bone proportions are unlike any known pterosaur, but show similarities with Anhanguera and Istiodactylus specimens. This should not be taken as an indication of species, since the bone development and proportions may have been subject to changes during juvenile life.

A second egg, JZMP-03-03-2, was somewhat similar, but the skeletal bones were not articulated in the same clear way, so interpretation is a little more complex.
In the same year, a pterosaur egg, MHIN-UNSL-GEO-v246, was discovered in the Lagarcito Formation in Argentina. This formation is well known for the Pterodaustro fossils and this egg was clearly a Pterodaustro egg. The embryo was intact and articulated.
The egg was also from the Lower Cretaceous deposits about 100 million years ago, and the proportions of the embryo closely matched those of known juvenile specimens. Measurements of the shell indicated a very thin (30μm) leathery shell which was long and oval in shape measuring 22mm by 66mm. The estimated embryo wingspan was 27cm. This egg has many differences from the Chinese finds, but it does support the idea that all pterosaurs probably laid eggs.
The questions that are difficult to resolve are;

1. How many eggs did pterosaurs lay?
2. Did pterosaurs care for their young?
3. Where did pterosaurs nest and what nesting structures did they create?

I suspect that the answers to these types of questions will be different for each type of pterosaur. These creatures would have been subject to the same variations and constraints in their habitats as modern animals are subject to today.

Wang, X., and Zhou, Z., 2004, Pterosaur embryo from the Early Cretaceous: Nature, vol.429, p.621.

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

Pterosaur Database Topics - eggs
 

The Pterosaur Brain

In 1888, Newton published the first account of a pterosaur brain exposed in a skull from the Lias at Whitby, North Yorkshire. The skull fossil had to be excavated to reveal the exposed brain more fully. Before the work, a number of casts of the original were made and one such cast is shown below.

Perhapsicephalus purdoni, National Geographic Survey, Nottingham.

The brain fossil showed the main lobes clearly and the auditory and semicircular canal structures were identified during excavation of the skull. The analysis applied to the brain by Newton suggested that the brain of the pterosaur was in many ways similar to the brain of a lizard, but in some respects it was charactaristically similar to the brain of birds. His conclusion was that pterosaurs, birds and lizards evolved from common ancestors.

In 1941, Tilly Edinger, a German physiologist, examined two distinct pterodactyl fossils where the brain was exposed. Her findings were similar to those of Newton, but with the advantage of the intervening progress of science since the earlier investigation, Edinger was able to make a more defined conclusion about structure.

Pterodactylus elegans, MCZ, No. 1505

The pterosaur fossils that Edinger worked with had been described by several earlier and well respected German scientists, though the work that they did was descriptive and comparative. This later work looked more closely at the structures and extrapolated the knowledge to a general description of the pterosaur brain for the first time.

Developments in the brains of pterosaurs show similarities with the development of the brain in birds. These changes are attributed to the requirements of flight, with a more developed optic lobe and a fissure (Vallecula Silvii) like that found in the fore brain of birds. At this point there is no evidence for the structure of the base of the pterosaur brain.

These are the two defining works on the nature of the pterosaur brain. With the advance in medical scanning techniques, the destructive analysis of pterosaur brains is a thing of the past. It is now possible in some cases, to examine the cranial cavity of a fossil by electronic means to develop an understanding of its brain anatomy.

Newton E. T., 1888, On the skull, brain and auditory organ of a new species of Pterosaurian (Scaphognathus purdoni) from the Upper Lias near Whitby, Yorkshire. Proceedings of the Royal Society, London. 43, pages 436–440.

Edinger T., 1941, The brain of Pterodactylus. American Journal of Science. 239, 665–682.