Could Pterosaurs really use Water Skimming Techniques to catch Fish?

Almost since the first pterosaur fossils were studied closely scientists have speculated about how good they were at flying and how these flying reptiles might have fed.  Since many pterosaur fossils have been found in coastal or marine deposits it is believed that many were piscivores (fish-eaters).  The teeth in many primitive pterodactyloids such as Criorhynchus and rhamphorhynchoids like Eudimorphodon seem well suited for grabbing and holding slippery fish.  The dentition supports the theory that these animals fed on fish, but how these animals actually captured fish remains a bit of a mystery.  The question is, how did pterosaurs feed?

Pterosaur

It had been thought that some pterosaurs used fishing techniques similar to the black skimmer (Rhynchops niger), a tern-like sea bird from the Americas.  This bird skims the surface water of lakes and lagoons with its lower mandible ploughing through the water.  When a small fish is detected the bill snaps shut.

The lower mandible is larger than the top part of the bill and the skull and jaws are quite robust, able to withstand the stresses of this type of feeding behaviour.

Clumsy in the Air?

In the past, pterosaurs were thought to be clumsy fliers, little able to do more than glide, but more recent studies have shown that these animals were accomplished fliers. For example, on the front of a pterosaur’s long wrist bones (carpus), there was a small bone that curved back towards the shoulder.  This is called the pteroid bone and is unique to pterosaurs.  At first, palaeontologists thought this to be the atrophied remains of a digit but this extension of bone is now thought to have supported a smaller flight membrane in front of the arm.   This smaller wing-like structure in front of the main wing would have helped control the flow of air over the wing, thus controlling speed and altitude.  This supports the view that these animals were sophisticated fliers.

A Replica of a Pterosaur (Guidraco)

A replica of a pterosaur (CollectA Guidraco figure).  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Recently scientists at the University of Reading (UK), led by Stuart Humphries have studied the proposed feeding habits of pterosaurs.  Using models of the jaws of pterosaurs and a black skimmer, Stuart and his colleagues set up a series of experiments to test whether pterosaurs could use their lower jaws to plough through water hunting for fish.

Results from Experiments

Results from the experiments show that up to 20% more power is required for the animal to keep flying straight when the jaw is immersed in water.  As the models skimmed the water in this way, they produced drag which compromised their ability to fly and demanded more muscle activity to keep them airborne.  This need for increased power for this type of flight may have prevented flying reptiles from hunting in this way.  This evidence, coupled with close studies of pterosaur skulls and jaws which do not show the expected modifications required such as thicker bones to cope with the stresses of this type of foraging makes this team doubt whether pterosaurs fed by skimming.

Keen Eyesight

Perhaps pterosaurs used their relatively keen eyesight to spot prey in the surface water and then swooped down on it plucking the fish out of the water.  Jerking the head downwards to permit the jaws to enter the water may provide one of the reasons why many pterosaurs developed complicated crests.  These crests could have acted as aerial stabilisers as well as display items for courtship and to intimidate rivals.  The rhamphorhynchoids had their heyday in the Jurassic but were replaced with the long-necked pterodactyloids by the Cretaceous.  Perhaps the longer necked pterodactyloids had an advantage when feeding by plucking fish from the sea.

Click here to see pterosaur and flying reptile models: Pterosaur and Dinosaur Models.

More study is required, but as more and more remains of pterosaurs are discovered so we may one day be able to solve this mystery.

One of the anomalies with Black Skimmers is that it is easy to get the wrong idea about how these bird feed.  When they are featured in nature programmes they are often shown skimming the water.  This is certainly a spectacular sight, but documentaries can be misleading.  Black Skimmers are just as likely to be seen feeding by wading and stabbing their bills into the water to catch fish, but as this is not as “photogenic” as their aerial acrobatics, it is rarely seen in photographs or TV programmes

Huge Elephant Tusks from Greece – Can they provide a glimpse of Ancient Climates?

Two enormous prehistoric elephant tusks have been unearthed by a joint Dutch and Greek research team from a dig site in northern Greece.  One of the tusks, believed to belong to a type of Mastodon (primitive elephant) is 5 metres long.  As a comparison, the tusks of a large Imperial Mammoth (Mammuthus imperator) were up to 4.4 metres long, although they were much more curved compared to tusks uncovered in Greece.

Prehistoric Elephant Tusks

The mastodon remains, which include limb bones, teeth and jaw bones have been excavated from a sand quarry near the village of Milia about 250 miles north of Athens.  The larger of the tusks probably belonged to a male and that stood over 3.5 metres at the shoulder and could have weighed in excess of 5 tonnes.  A number of other prehistoric mammal remains have been excavated and these latest finds have been dated to the end of the Pliocene epoch, making them approximately 2.5 million years ago (mya).

The excellent state of preservation has permitted the research team to speculate that they may be able to study the annual growth rings laid down in the tusk enamel.  This would provide a valuable insight into the seasonality of the climate in Greece around this time.

Mastodons roamed extensively across Europe, Asia and North America but began to decline at the end of the Pliocene epoch with the last of the Mastodons surviving in North America into the end of the Pleistocene (10,000 years ago).  Such well preserved tusks are an important find, given their excellent condition the growth rings from the tusks plus micro fossils such as plant remains and pollen may provide a detailed picture of the climate at the time when these huge elephants roamed the Mediterranean.

There have been many prehistoric elephant remains found in Greece and on the Greek islands.  It is thought that the legend of the one-eyed monster called the Cyclops came from the misinterpretation of extinct elephant remains by the ancient Greeks.  The large nasal space in the centre of an elephant’s skull (the part where the fleshy trunk would be attached) may have given rise to the myth of the one-eyed monster.

Certainly, many elephant skulls have been found in this region, with many scientists speculating that it was the discovery of a relatively dwarf species of extinct elephant on Crete that marks the starting point of the Cyclops legend.

When you view an proboscidean skull from the front (anterior view), you can see how this misinterpretation may have come about.

When viewed from the front the idea of a one-eyed man (cyclops) can be postulated. Picture credit: Everything Dinosaur.

Eofauna Scientific Research have specialised in producing replicas of prehistoric elephants.

To view the Eofauna range: Eofauna Scientific Research Models.

Mass Dinosaur Grave Discovered in Switzerland

Palaeontologists from the University of Bonn have been busy making preliminary surveys of what may turn out to be Europe’s biggest mass deposit of dinosaur bones.  About 300 dinosaur bones have been recovered so far but there may be thousands more buried under the Swiss village of Frick in the canton of Aargau.

An amateur palaeontologist exploring a small building site found the remains of a Plateosaurus and then shortly afterwards discovered a second one just a few metres away.  Early indications are that this could be a mass grave of many hundreds of these large herbivores, with the bone bearing deposit stretching for at least 1.5 kilometres.

Plateosaurus was a large herbivorous dinosaur from the Late Triassic (222 million years ago to 210 million years ago).  Adults could grow to over 8 metres long and weigh up to 4 Tonnes.  Other mass graves of plateosaurs have already been discovered most notably at Trossingen in southern Germany.  Plateosaurus means “flat lizard”, it is the best known of the prosauropod group of dinosaurs with fossils having been found in over 50 separate European locations.

Dinosaur fossils are relatively plentiful in this part of the Swiss/German border, although the picturesque village of Frick has a population of less than 5,000 it has its own village dinosaur museum.  It looks like they are going to have to extend it somewhat if they want to display all the fossils from the Plateosaurus bone bed, as scientists have speculated that they could be as much as one compete skeleton every 100 square metres.

A Model of Plateosaurus

A rearing Plateosaurus. The CollectA rearing Plateosaurus dinosaur model.

As yet scientists say it is to early to state how all the fossils ended up together, they are remarkably well preserved and are likely to yield more information.  The jumble of disarticulated and disassociated bones could represent members of a large herd of plateosaurs that got stuck in marshland in a river delta and drowned in a sudden catastrophe.  Perhaps this mass grave could have accumulated over many hundreds of years with seasonal floods in the river delta washing animal carcasses into an area where they accumulated, settled and were buried.

Plateosaurus is a very important dinosaur, it was named and described 170 years ago and the vast number of fossils of this animal has given scientists a tremendous insight into the anatomy and physiology of this large herbivore.  Plateosaurs were extremely successful and a number of species have been identified, the large number of fossils from adults, sub-adults and juveniles has helped provide more information on the growth habits of dinosaurs.

To view a range of European manufactured prehistoric animal models: Dinosaur and Prehistoric Animal Models.

Canadian Pterosaurs Eaten by Velociraptorine Dromaeosaurids

We have been reviewing the paper written Phil Currie (Royal Tyrrell museum – Canada) and Aase Roland Jacobsen (Aarhus University – Denmark) published in 1995 about the evidence of predation on pterosaurs.

The paper, entitled “An Azhdarchid Pterosaur eaten by a Velociraptorine Theropod”; was first published in the Canadian Journal of Earth Sciences (32: 922-925), it reviews the evidence of small theropod dinosaurs of the Late Campanian (74 mya) feeding on a tibia from a pterosaur.

Azhdarchid Pterosaur

The tibia (TMP 92.83.2) is the most complete tibia known from the Dinosaur Provincial Park area of Alberta.  The bone measures 58.5 cm in length, but the exact genus cannot be identified from this one fossil alone.  However, it most probably came from a pterosaur from the Azhdarchidae family as most other pterosaur remains from this area seem to belong to the long-necked azhdarchids, the large, soaring forms of pterosaur – such as Quetzalcoatlus.  The lack of co-ossification (ossification the term for bone growth); with the other lower limb bone related to the tibia, the fibula, may indicate that this is a tibia from a immature animal that when fully grown would have had a huge wingspan perhaps exceeding 10 metres in length.

Marks on the Bone

The distal end of this bone (the end of the bone which attached to the tarsals or ankle bones) has unusual scratch marks on it.  At first Currie and Jacobsen were unsure as to the cause of these strange scratches, but closer examination showed that they were small tooth marks.  This was confirmed when a single fractured tooth was discovered embedded in the bone.  The tooth has been identified as belong to a velociraptorine dromaeosaurid called Saurornitholestes (sore-or-nith-oh-less-tees).  Saurornitholestes was one of the commonest small theropods in the area during the mid to Late Campanian.  It was a lightly, built animal perhaps weighing less than 15 kgs but with its long slender tail it could have been up to 2 metres long.

Saurornitholestes

Saurornitholestes means “lizard bird thief”, it is known from some partial skeletons, isolated bones and a number of teeth.  This was certainly a fleet footed meat-eater but whether it was able to overcome a sub-adult azhdarchid pterosaur is open to speculation.  Currie and Jacobsen concluded that the Saurornitholestes was scavenging on the carcase of the large flying reptile, but the lack of other bones and evidence prevents a more definite conclusion being drawn.  If these light-weight carnivores hunted in packs then they may have been able to mob a large, grounded pterosaur and over power it.  Had the azhdarchid been caught on the ground it would have been particularly vulnerable to attack, particularly against a relatively intelligent little dinosaur with perhaps the ability to learn from experience of stalking similar animals.

Saurornitholestes langstoni Scale Drawing

Saurornitholestes langstoni illustration (scale drawing).  Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

The Beasts of the Mesozoic articulated model range includes a variety of dromaeosaurids including Saurornitholestes: Beasts of the Mesozoic Articulated Dinosaur Models.

Canadian Pterosaur

The azhdarchids with their huge wings, long necks and relatively large heads were perhaps particularly clumsy on the ground.  As with other pterosaurs, Currie comments on the metatarsal-phalangeal joints (foot bones), their arrangement would not make these azhdarchids well adapted to cursorial activity.

It is interesting to note that the tibia stood up remarkably well to the ravages of this little carnivore.  pterosaur bones tend to be thin and highly pneumatised (lots of air cavities).  The feeding scratches and the fractured tooth may pay more testament to the robust nature of pterosaur skeletons rather than to the voracious feeding of a small theropod.

Unfortunately, the lack of a complete skeleton prevents scientists from making further conclusions, but it is interesting to speculate how tooth marks in bones give us an insight into the interrelationships between extinct species.

We have reviewed a number of articles written about the pterosaurs in the Dinosaur Provincial Park formation of Alberta, to read another article on the pterosaur finds from this part of Canada click below:

Did birds wipe out the Pterosaurs?