Courtesy of the Bayerische Staatsammlung für Paläontologie und historische Geologie

         
Pterosaurs

Introduction

This general account has no intention to be exhaustive but is rather meant as a very short introduction on pterosaurs in general. Some topics are therefore simplified. No references are made, but a good and beautifully detailed introductory book on pterosaurs, although not completely up to date anymore because new research changed insights, is Wellnhofer, 1991a. Besides this, there is a fast amount of scientific publications. 

 History of the study of pterosaurs

The first fossil of a flying reptile is discovered at the end of the 18th century in Solnhofen, Bavaria, Germany. Initially, people thought this to be the victims of the Deluge. The Italian scientist Collini however came to the conclusion that the animal was a marine animal. Obviously, some scientists did not agree and identified the strange animal as an extinct bat (see also Veldmeijer, 2000). Yet others thought the creature being a bird. Finally, the French scientist Cuvier, regarded as the ‘father of vertebrate palaeontology’ recognized the creature as a reptile and proposed the name ‘Pterodactylus’ which means ‘wing finger’, referring to the elongated finger to support the wing (see below). As late as 1819 the correct name, as according the rules of the International Code of Zoological Nomenclature, was established: Pterodactylus antiquus. A subdivision between the long tailed and short tailed pterosaurs was made in 1901 by Plieninger.

 Origin and evolution

Pterosaurs belong to the subclass of diapsids. This division is based on the number of skull openings behind (posterior to) the eye socket. Pterosaurs have two openings posterior to the eye socket and are therefore called diapsid. But archosaurs and pterosaurs have another opening in the skull, besides the two posterior to the eye socket, namely one between the nose and eye opening. And this common opening is the reason why they are placed in one group, the archosaurs. Their closest living relatives are crocodiles and alligators.

It is still not clear what the ancestor of pterosaurs is (for a review see Wellnhofer, 1991a). The first pterosaurs, the long tailed Rhamphorhynchoidae, appear in the geological era called ‘Trias’ (213-248 million years ago). Though is was thought for long time that hese pterosaurs disappeared in the second half of the Jurassic era (144-213 million years ago), recent discoveries proves that they still occurred in the Cretaceous period (Wang, Zhou and Zhang, 2002). At that point, short tailed Pterodactyloidae already existed and reached their hey-day in the Cretaceous period (65-144 million years ago). Pterosaurs were extinct together with the dinosaurs and many other animal groups at the end of the Cretaceous period. 

In general it is thought that the younger pterodactyloids evolved from the older rhamphorhynchoids because the structure of the skeletons have a lot in common. On the other hand, it is clear from the fossil record that the Jurassic pterodactyloids already had a long evolutionary history because there were already various different forms for inhabiting different niches when they appeared in Solnhofen.

 Skeletal features 

Far left: The small Pterodactylus micronyx. The skull measures 33 mm (photograph by A.J. Veldmeijer). 

Photo courtesy of Teylers Museum, Haarlem, the Netherlands. 

Left: Dorygnathus banthensis with a skull length of approximately 100 mm 

From Ziegler, B. Guide to the Löwentor Museum. - Stut.Bei.Nat. C, 27: 45 (Allgemeinverständliche Aufsätze).

The elongated fourth finger, which supports the wings and is therefore called ‘wing finger’ are most characteristic for pterosaurs and differ markedly with the wing construction of bats and birds. The bones of pterosaurs are hollow with transverse bony struts. The walls of the bones are incredibly thin, often even less than 1 mm. The combination of hollow bones with transverse struts results in a light but very strong skeleton, suitable to withstand the forces exerted on it by flying. Pterosaurs have a remarkable birdlike brain and large eyes.

Longitudinal section of the upper arm of a Brazilian pterosaur. Note the thin outer wall and bony transverse struts (photograph by A.J. Veldmeijer).

Photo courtesy of the Bayerische Staatsammlung für Paläontologie und historische Geologie, Munich, Germany.

Rhamhorhynchoids have a long, often sturdy tail. The caudal vertebrae are sometimes reinforced ventrally and dorsally by long stiffening extensions (chevrons). The pterodactyloids have a very short tail. The jaws of the 'old' pterosaurs are always completely filled with teeth, whereas the jaws of pterodactyloids are completely or partly filled with teeth. Edentulous pterodactyloids do exist as well, but edentulous rhamphorhynchoids not. The feet of rhamphorhynchoids have a long fifth toe and a short palm of the hand, whereas the fifth toe of pterodactyloids is small and the palm of the hand is long. The nasal and preorbital opening in the oldest pterosaurs are always separated but are evolved into one opening (nasopreorbital opening) in the younger pterosaurs. Finally (there are more differences but these will not be discussed here), the last cervical and first few dorsals (this depends on the taxon) might be grown into one rigid block the so-called notarium (the same notarium as seen in birds) in pterodactyloids. A notarium does not exist in rhamphorhynchoids.

 Non-skeletal features

The wings consist of skin, supported by stiff fibres and differ completely from the wing membranes of bats, which are supported by all fingers and no fibres. The exact shape of the wings as well as the attachment of the wings to the body probably differed with different species. The same is probably true for the flight membrane between the legs, the uropatagium. There is however, ongoing research and debate on this.

Various wing shapes, as argued in literature. The wing span of this Coloborhynchus spielbergi is approximately 6 m; the length from the tip of the snout to tip of the tail is approximately 160 cm.

From Veldmeijer A.J. 2003. Coloborhynchus spielbergi sp.nov. (Pterodactyloidea) from the Albian (Lower Cretaceous) of Brazil. – Scripta Geologica, 125: 37–156.

Some fossils reveal a hairy body covering, which is one of the features of warm-bloodedness, and a hair-like covering is universally accepted. On the other hand, the amount of covering and which parts of the body exactly, is still unclear. Warm-bloodedness was already suggested by Seeley back in 1870. Active flying, as most pterosaurs were capable of, requires high energy levels generated by high metabolic rates. This could only be achieved by being warm-blooded. Also the hollow bones, possibly filled with air pockets as are the hollow bones of birds nowadays, is used as argument for warm-bloodedness as well as the fast growing rate.

Terrestrial locomotion is still a point of controversy. Some scholars argue in favour of bipedal stance whereas other for a quadrupedal stance. The discussion involves plantigrade and digitigrade as well. A debate is continuing whether they were capable of walking on all fours, because of the small hind legs.

Though it seems obvious that pterosaurs laid eggs, no eggs are encountered (yet?). 

 Food

Most of the pterosaurs are thought to have been fish eaters, because the fossils originate predominantly from deposits in watery environment. On the other hand, the chance of fossilisation of these extremely fragile skeletons in watery environments is far larger relative to inland living pterosaurs. Furthermore, one should not forget that also non fish-eaters, more inland living species, might have been fossilized in these watery environments, for instance because they died during migration. Examples of non fish eaters are Quetzalcoatlus, who is thought to have been a meat-eater, feeding on carrion (although opinions differ). Tapejara wellnhoferi might have been frugivory, Pterodaustro was a filter feeder, with teeth not unlike the baleens of whales and Anurognathus and Batrachognathus are thought to have been feeding on insects.

Pterodaustro, sieved the water for food such as algae and shrimps.

Courtesy of P. Wellnhofer.

Skull of Tapejara wellhoferi, a supposedly frugivory pterosaurs. The length of the skull is approximately 185 mm long (photograph by A.J. Veldmeijer).

Courtesy of the American Museum of Natural History, New York, USA. 

A small pterodactylus species (the head is less than 100 mm long) with throat pouch for
storing predigested fish (photograph by A.J. Veldmeijer).

Courtesy of the Bayerische Staatsammlung für Paläontologie und historische Geologie,
Munich, Germany. 

Skull of "Criorhynchus" mesembrinus, a fish eating pterosaur (photograph by E. Endenburg).

Courtesy of the Bayerische Staatsammlung für Paläontologie und historische Geologie, Munich, Germany. 

 

Publications (selected, see CV)

Veldmeijer, A.J. 2000. Over waarom men pterosauriërs voor uitgestorven vleermuizen aanziet en of dit begrijpelijk is of niet. – Cranium 17: 17-29 [Why pterosaurs are interpreted as extinct bats and whether this is understandable or not].

Abstract:
Flying reptiles (pterosaurs) are often regarded as extinct bats. In the article of which the following is a summary  it is tried to discover the reasons why by comparing the two animal groups, after being introduced, and discuss the conformities and differences. Attention is given to the history of reconstruction as well.

In the paper, it is argued that one of the reasons why layman look upon them as bats is because they are able to fly but don’t look like birds at all. On the other hand, the only other familiar flying animal nowadays are bats and at first glance they have the same kind of wings. And as so often, for people the familiar is the departing point for the unfamiliar. However, the construction of the wings is completely different but the public do not know this. And the many obvious differences in skeletal features are not known as well. Furthermore, bats are mammals and pterosaurs ‘reptiles’. Conformities can be found in the morphological variety of the flight membranes (wing as well as tail), the morphological variety of the head but also in food diversity. With the latter, caution is necessary because of gaps in the fossil record.

What about the influence of artists’ work (of artists and scientists alike)? Soemmerring, who was the first person that interpreted the remains of a pterosaur as such, made the first reference to bats as far back as 1812. The first scientific essay on these extinct animals was written only 28 years before (Collini, 1784). Buckland published in 1836 also a paper in which he referred to bats. These are only instances of scientists and artists that reconstructed pterosaurs as bats or reconstructed them strongly batlike, even until far in the 20th century (for instance Abel, 1925; Augusta & Burian, 1961). These reconstructions must have influenced the public tremendously.

The discussion argues why it is important to compare pterosaurs with bats (one of the few airborne animals, wing membrane, pterosaurs’ ‘reptile-bird-mammal’ discussion) and gives an answer to the title. To the public, the general appearance of pterosaurs is more batlike than birdlike. This appearance is more important to a non-expert than differences that can only be seen after a detailed study of remains. For a picture is worth a thousand words.

Literature used:
Augusta & Burian, 1961; Abel, 1925; Altringham, 1996; Bakker, 1988; Collini, 1784; Cuvier, 1809; Desmond, 1978; Edinger, 1927; Gardiner, et al, 1989; Norman, 1985; Padian, 1984; Padian & Warheit, 1989; Seeley, 1864; Sharov, 1971; Shipman, 1998; Soemmerring, 1812; Unwin & Bakhurina, 1994; Urlichs, et al, 1994; Wellnhofer, 1991; Wellnhofer & Kellner, 1991.

Postscript (2002):
1) Padian (1987) discusses the same problem but investigates the influence of pictorial representation on scientific perception, rather than its influence on the public. He showed that this influence is large, which supports the theories presented in the here discussed paper.
2) The reconstruction of pterosaurs in books and movies, available and popular to the public is often inaccurate. For instance: Pteranodon with teeth in Jurassic Park III and Quetzalcoatlus with teeth in BBC’s Walking with dinosaurs (the website). Bye the way, the t/v serial and book of Walking with dinosaur is stuffed with errors and misconceptions (Veldmeijer, 2003).

Veldmeijer, A.J. 2003. Pterosauriërs in de media. – Grondboor & Hamer, februari 2003: 1-9.

Abstract:
The numerous Hollywood productions, t/v productions, documentaries and semi-scientific literature resulted in a dinosaur hype. And interest in pterosaurs increased as well. But are the images of the animals put forward by these productions correct? In the paper, this topic is discussed by a critical analysis of the BBC t/v production, the accompanying book and the website 'Walking with dinosaurs' and Stephen Spielbergs' production 'Jurassic Park III'. Comments are made on scientific books as well.  

Veldmeijer, A.J. 2002. Pterosaurs from the Lower Cretaceous of Brazil in the Stuttgart Collection. – Stut.Bei.Nat. B 327: 1-27.

Abstract:
Bones of pterosaurs from the Cretaceous (Albian) of Brazil kept in the collection of the State Museum of Natural History in Stuttgart, Germany, are described and classified. One complete mandible is assigned to Criorhynchus, three humeri and two ulnae are assigned to Santanadactylus and one ulna is assigned to Coloborhynchus. It proved not possible to determine various other bones more precisely than suborder or family. Few notes on the diagnostic status of post-cranial material in general and humeri in particular are presented.

Left: anteriormost part of mandible (scale bar = 50 mm, photograph by A.J. Veldmeijer). 

Courtesy of the Staatliches Museum für Naturkunde, Stuttgart, Germany.

 

 

Veldmeijer, A.J. 2003. Coloborhynchus spielbergi sp.nov. (Pterodactyloidea) from the Albian (Lower Cretaceous) of Brazil. – Scripta Geologica, 125: 35–139.

 Abstract:
A new species of pterosaur, Coloborhynchus spielbergi sp. nov. (Pterodactyloidea), from the Romualdo Member (Albian) of the Santana Formation is described. The specimen (RGM 401 880) in the collection of the National Museum of Natural History (Naturalis) of The Netherlands, consists of the skull, mandible and several post-cranial bones. The specimen displays a high degree of co-ossification indicating that the animal was an adult and likely quit old when it died. The wingspan is reconstructed at nearly 6 m. Among the characteristic features are a large anteriorly positioned premaxillary sagittal crest and a smaller, also anteriorly positioned dentary sagittal crest, a flat anterior aspect of the skull from which two teeth project and a ventrally fused pelvis. Comments on Brazilian pterosaurs are made in connection with the classificiation of the Leiden specimen. 

Download the description

Left: skull of Coloborhynchus spielbergi sp.nov. (photograph by A. 't Hooft).

Courtesy of the the National Museum of Natural History (Naturalis), Leiden, The Netherlands.

  

Veldmeijer, A.J. 2003. CT-scanning a pterosaur skull; supplement to the  description of Coloborhynchus spielbergi in Scripta Geologica, 2003, 125: 35-139. - webbased publication http://members.lycos.nl/palarch/palaeontology/pal.htm.

Abstract:
The complete ct-scanning of the skull of the Brazilian pterosaur Coloborhynchus spielbergi in the collection of the National Museum of Natural history, Leiden, the Netherlands is presented and shortly discussed. The scans give an insight in the completeness of the skull of this Cretaceous pterosaur. Furthermore, the shape of the brains can be established. The present work is a supplement to the description and classification.

 Download the supplement

Go to appendix 1 Go to appendix 2 Go to appendix 3 Go to appendix 4

Go to film 1+2  Go to film 3+4

Photographs by Dr. S. Boor & Prof.Dr. P. Stoeter of the Department of Neuroradiology, University of Mainz, Germany.

Courtesy of the the National Museum of Natural History (Naturalis), Leiden, The Netherlands.  

Veldmeijer, A.J. 2003. Preliminary description of a skull and wing of a Brazilian Lower Cretaceous (Santana Formation; Aptian-Albian) pterosaur (Pterodactyloidea) in the collection of the AMNH. – PalArch, series vertebrate palaeontology 0, 0: 1-13.

Abstract:
The skull and wing of a pterodactyloid pterosaur from the Brazilian Lower Cretaceous (Albian) in the collection of the American Museum of Natural History, New York, USA displays the general anatomical features characteristic for these pterosaurs and is shortly described. The largely embedded skeletal remains are tentatively assigned to Brasileodactylus. More precise classification, other than genus, proved not possible.

Left: the partially embedded skull and mandible of Brasileodactylus sp. (drawing by A.J. Veldmeijer).

Courtesy of the American Museum of Natural History, New York, USA.

Veldmeijer, A.J. In review. Pterosaurs from the Lower Cretaceous of Brazil in St. Gallen, Switzerland.– Ec.Geol.Hel.

Abstract:
Two mandibles (one crested/teethed and one crestless/edentulous) of pterodactyloid pterosaurs from the Lower Cretaceous Santana Formation (Romualdo, Albian) of Brazil kept in the collection of Urs Oberli, St. Gallen, Switzerland are described and classified. The crested/teethed mandible is assigned to Anhanguera (being one of the most complete ones of this genus). The edentulous mandible is classed as new species of Thalassodromeus. T

Left: skull of Coloborhynchus araripensis (photograph by E. Endenburg).

From left to right: anteriormost part of the mandible of Anhanguera sp. and anteriormost part of the mandible of Thalassodromeus sethi (photographs by E. Endenburg).

Photo's courtesy of Urs Oberli, St. Gallen, Switzerland.