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.
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.
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.
Saurnitholestes 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 Saurnitholestes 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.
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: