Robust Necks Indicate Apex Predator Niche

Amongst all the amazing genera that are now grouped into the Order Pterosauria, it is perhaps, the azhdarchids that are the most spectacular.  When other types of flying reptile were in decline and heading towards extinction in the Late Cretaceous, the Azhdarchidae were still going strong.  Some of these Late Cretaceous azhdarchids, animals such as Quetzalcoatlus, Arambourgiania and Hatzegopteryx stood as tall as a giraffe and had wingspans the size of small aircraft.  These large wings, combined with their light bodies (even the very largest are estimated to have weighed no more than 225 kilogrammes), permitted these creatures to fly extremely long distances.  Studies of wing function and biomechanics indicate that some of the largest forms could have traversed continents and crossed the recently formed Atlantic Ocean with ease.

A Model of the Giant Late Cretaceous Azhdarchid Pterosaur Quetzalcoatlus (Q. northropi)

Quetzalcoatlus model.

A model of the giant Pterosaur Quetzalcoatlus.

Picture Credit: Safari Ltd

To read an article about the flight dynamics of giant Cretaceous Pterosaurs: Cretaceous Runways – Flight Dynamics of Pterosaurs

Which Niches within Ecosystems?

Our understanding of the Pterosauria has been much revised over the last three decades or so.  Recent fossil finds and new research on previously collected and catalogued material has provided a wealth of scientific information and a new paper written by the eminent British pterosaurologists Darren Naish (University of Southampton) and Mark Witton (University of Portsmouth), further supports the hypothesis that some super-sized Pterosaurs occupied apex predator niches within Late Cretaceous ecosystems.  A study of two Pterosaur neck bones (cervicals), including one giant, twenty-four-centimetre-long cervical suggests that the body proportions of azhdarchids may not have been as uniform as previously thought.  The researchers postulate that the enormous Hatzegopteryx had a proportionately shorter, more stocky neck that was very strong.

Line Drawings Showing Various Views of the Giant Azhdarchid Pterosaur Fossil (EME 315)

Giant Neck Bone of a Pterosaur (Hatzegopteryx).

Giant azhdarchid cervical vertebra referred to Hatzegopteryx sp. (A–D) line drawings of EME 315 in anterior (A) right lateral (B) ventral (C) and dorsal (D) views.

Picture Credit: PeerJ

In the picture above, four views of the Pterosaur neck bone are shown (A) viewed from the front, (B) viewed from the right, (C) viewed from underneath and (D) viewed from the top.  The lighter areas in the drawings indicate where damage to the bone has occurred, the darker shading indicates the presence of filler.  Scale bar equals ten centimetres.

A strong, powerful neck would have been resistant to the forces and stresses imposed upon it by a prey struggling in the Pterosaur’s large beak.  The specimen (EME 315) is almost as wide as it is long and as it was excavated from the Maastrichtian Sebeş Formation of the Transylvanian Basin, (Romania), it has been assigned to the Hatzegopteryx genus, as Hatzegopteryx thambema fossil material is known from the adjacent and contemporaneous Densuş-Ciula Formation, of the northern Haţeg basin.

Thick, Robust Neck Bones Support the Idea of Pterosaurs Feeding on Dinosaurs

The scientists compared the dimensions of EME 315 (believed to be cervical VII, which is from the base of the neck, articulating with the first of the thoracic or dorsal vertebrae), to the neck bones from other azhdarchids and they argue that in the absence of large, terrestrial predators on the ancient island, known as Hateg, azhdarchids such as Hatzegopteryx occupied the role of top predators in the ecosystem.

The Robust and Relatively Short Neck of Hatzegopteryx Helps this Pterosaur Overcome a Struggling Dinosaur

Powerful necked Hatzegopteryx feeds on a dinosaur.

Transylvanian giant azhdarchid pterosaur Hatzegopteryx sp. preys on the rhabdodontid iguanodontian Zalmoxes.

Picture Credit: Mark Witton

Azhdarchids had proportionately bigger skulls than any other known terrestrial vertebrate.  Their size and these huge skulls, if related to a relatively, short but powerful neck would lend support to the idea that these creatures stalked smaller animals in the same way that extant Marabou storks (Leptoptilos crumenifer) do in Africa.  However, unlike the modern Marabou, which catches frogs, lizards, small mammals and fish, Hatzegopteryx would have been capable of swallowing whole a dinosaur the size of a Cocker Spaniel!  Hatchling dinosaurs would have been especially vulnerable to attack and with a number of dwarf dinosaur forms known from the Hateg Formation (Magyarosaurus), juveniles could have been predated upon also.

Giant Azhdarchid Neck Bone (EME 315) Compared to Arambourgiania Giant Cervical

Pterosaur cervical bone comparison.

The giant neck bone compared to the only other giant Pterosaur cervical Arambourgiania.

Picture Credit: PeerJ 

Writing in the journal “PeerJ” the researchers compare the Hatzegopteryx cervical (cervical VII), with the only other giant azhdarchid neck bone known, a single cervical representing Arambourgiania philadelphia, from the Late Cretaceous of Jordan (see picture above).  The paucity of the fossil record restricts accurate size estimates for entire animals, but the cervical assigned to A. philadelphia, believed to represent cervical V is approximately seventy centimetres long.  Its morphology and proportions are very different from the Hatzegopteryx material (EME 315).  This suggests that there may be greater variation in the body proportions of the Azhdarchidae then previously thought.  Some members of the Azhdarchidae may have had shorter and stronger necks than other genera.  This leads to the tantalising idea that, giant Pterosaurs did indeed occupy apex predatory roles in isolated island ecosystems such as Hateg, which was largely devoid of large, carnivorous Theropods and that proportional differences between super-sized taxa may even hint at distinct feeding specialisms.

Late Cretaceous Jordan Two Arambourgiania Fight Over a Luckless Dinosaur

Azhdarchid pterosaurs feeding on dinosaurs.

Arambourgiania philadelphia (giant Pterosaurs) squabble over a small Theropod dinosaur.

Picture Credit: Mark Witton

Giant Pterosaur Scavengers?

If we reflect on the feeding habits of the Marabou stork, it is known to feast on carrion.  Few carnivores will turn up the offer of a free meal if they find a corpse to feed on.  It could be speculated that some of the more robust-necked azhdarchids may have specialised in scavenging the carcases of dinosaurs.  The absence of teeth in the jaws, may have inhibited these reptiles from being able to eviscerate a dead dinosaur, but this could have been compensated to some degree by having a strong, pointed beak and a powerful neck.  As well as being apex predators, some Late Cretaceous Pterosaurs may have occupied an ecological role similar to today’s vultures.  Ironically, when Quetzalcoatlus northropi was first named and described back in 1975, several palaeontologists argued that this giant flying reptile filled a scavenger niche.

For an article which examines the role of Azhdarchid Pterosaurs in ecosystems (based on research published in 2015): Understanding Azhdarchid Pterosaurs

The article: “Naish D, Witton MP. (2017) Neck biomechanics indicate that giant Transylvanian azhdarchid pterosaurs were short-necked arch predators”.  PeerJ 5:e2908, (published in the online journal PeerJ).

To read the PeerJ article: Peer J Article

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