Why I'm Ptero-fied of Pterosaurs: Giant Pterosaurs and Killer Storks

AHHH!!! RUN AWAY!!! HIDE ME!!!
Image by Mark Witton

Putting aside the horribly awful, facepalm-inducing title as well as the girly screams from your host here at the moment, Pterosaurs are a group of archosaurs related to (but not considered) dinosaurs that lived during the Mesozoic. They were the first vertebrates to develop powered flight, which they developed by evolving an elongated 4th finger and a layer of skin called the patagia from this finger to the hind limbs, and they just took off from there (no pun intended). In recent years especially, fossils of this family have shown really amazing things about their lifestyles and behavior. We now have fossil eggs showing that unlike many modern-day birds and bats, some pterosaurs may have been able to fly right after birth (Unwin 2005); specimens preserving soft tissue have shown that many pterosaurs had crests made up of soft tissue on their heads for displaying their age, health, and even gender (Lü et al. 2011), as well as being covered in some kind of fuzz termed pycnofiber (Alexander et al. 2009). In my opinion though, the most ground-breaking of all is that despite being often portrayed as giant seagulls and pelicans, the majority of species didn't practice this diet. Indeed, we now know of vulture, hawk, bat, stork, and even toucan analogs among the pterosaurs.

Terrifying Terror that is an Azhdarchid

Seeing as I've given a lot of love to crocs (speaking of which, I'll continue that crocodylomorph series in a bit) and other ambiguous animals from the Mesozoic here, it only seemed like a matter of time before pterosaurs popped up. However, seeing as I am a big fan of these animals, it seems ironic that I'm writing a post on how I'm downright scared of them. Given it's not the whole group that I'm afraid of, it's a specific family of them called the azhdarchids.

My God, it's eyeing him hungrily.....
Pic by Mark Witton, and showing him.

The azhdarchidae is a family of pterosaurs which only appeared near the end of the Cretaceous (although I have heard of some possible early Cretaceous remains) and include the largest of all pterosaurs, such as Hatzegopteryx and the famous Quetzalcoatlus, which could have wings up to 33 ft long, and stand as tall as a giraffe (earlier claims that these animals reached sizes in excess of 40 ft aren't considered valid). These animals, like most pterosaurs were, for a long time, portrayed as skim feeders — skimming along the surface of the water picking up fish as they went. However, most recent work on these animals have shown that they were in fact stork-like in ecology, and were better adapted to ground-feeding than aerial skimming (for a review, see Naish 2010 or follow this link), and this is the key reason why I personally find these animals rather threatening. Storks and birds with a similar ecological niche today eat just about any small animal they can fit in their mouth, and seeing as Hatzegopteryx and Quetzalcoatlus both reached titanic sizes, would that mean we would be on the menu?  Most people would probably think that time travelers going back to the Mesozoic would meet dangers mostly from carnivorous theropods, but could these azhdarchids be an equal, if not greater threat? It's an interesting idea, and indeed, it's been talked at length before by other scientists. But just to see how dangerous they would be, I'm going to look over them a bit and see for myself.

To determine how much of a threat an animal might be to humans, normally there are three factors involved. The first is behavior: is the animal naturally agressive? This is the major determining factor to tell how dangerous many animals are, but since azhdarchids are extinct we can't know this. The other two are easier: numbers and threat. Is the animal common enough that it will come into contact with people often? And what features does it have that can cause damage to us? Knowing this, let's see what azhdarchids bring to the fray:

As for numbers, we know of numerous giant azhdarchids as of now, and it doesn't seem like Hatzegopteryx and Quetzalcoatlus are alone: two more undescribed giants have been found in the Dinosaur Park and Two Medicine Formation, both of which may reach the same sizes. Thus, there are a lot of species which could hypothetically be a threat, and since the fossil record tends to be rather fragmentary, it is quite possible that there were even more giant pterosaurs out there that are waiting to be found, and indeed, may never be found. Thus, seeing as they are a common animal in their ecosystem, they fill at least the quota for frequent interactions for hypothetical time travelers. But could they actually pose a threat? 

Hatzegopteryx's reconstructed head compared to, believe it or not,
Giganotosaurus', the theropod with the largest head. Who's scarier again?
Pic from Deviantart's Dean Hester (Fragillimus335)

The answer is, somewhat surprisingly, a most definite yes. They could indeed pose a great threat to us humans. And no, not in that cliche "Pteranodon with teeth flying off with people in its talons" imagery shown in so many old movies; but in a dynamic, cursorial running-down fashion. (Seriously, Pteranodon means "toothless wing," so why do movie makers constantly show it with teeth? It's more comical than scary!) Studies of azhdarchid proportions have shown that their limbs are actually similar to those of living hooved animals, and that while they might not be able to actually run, they could still move at fairly high speeds over land (Unwin 1997) (Unwin 2005) (Mazin 2003). But what could they do when they actually caught up to us? Again, they're equipped for handling prey our size: the adjacent image shows the reconstructed heads of Hatzegopteryx and Giganotosaurus, currently the theropod with the largest skull. As you can see Hatzegopteryx dwarf's Giganoto's 1.8 meter skull, reaching an astonishing 3 meters long (I'll admit the proportions may be a bit off though; Giganoto's head looks too big). You might think that this is only the case with the skull's length, but that's also not the case; Hatzegopteryx's jaw was an astonishing minimum width of 50cm at the rear (Buffetaut et al. 2003). I, for example, have a shoulder width of about 46cm, Hatzegopteryx could easily swallow me whole.

Now, you put all those traits together, and then realize that along with being fast runners, having huge skulls, and being downright gigantic, they could also fly. Despite some scientists saying that some of these huge pterosaurs were in fact too large to fly, most of these conclusions are based off bad assumptions of flight mechanics and scaling (Witton 2010). Thus, what would stop them from just flying into something like a Terra Nova-style compound and eating everyone in sight? The only way time-travelers would be safe would be if they either built large domes (which would cost an immense amount of money) or by residing in caves or underground bunkers, which might produce other problems. Of course, the most cost effective way to avoid all this would just be to shoot them, but I would like to keep such amazing animals away from such a sad fate.

So as you can see, I would personally find these animals to be a far greater threat in any time travel or Jurassic Park-style film than the majority of the dinosaurs that show their faces on-screen. In fact, based on living animals, I would imagine that predatory dinosaurs would spend most of their time sleeping, like living predatory animals, and would've probably only fed once every one or two weeks. Azhdarchids on the other hand, would've probably been feeding far more frequently on us smaller animals, like living storks and herons, and would be a much more common and frequent threat. Of course, azhdarchids are long extinct, and us humans have never had to worry about giant, long- necked animals with beaks coming down to snatch us up. Or have we?

The Dwarf Man vs The Giant Stork

 

In 2010, fossils from the Liang Bua cave on the Island of Flores in Indonesia had identified such an example of a relationship. The cave is best known for its assemblages of fossil stegodonts, giant rats, and the dwarf human species Homo floresiensis, who is arguably the most important human species ever found. Discovered in 2003, Homo floresiensis, or the Hobbit Man, was discovered and announced to be the only example of a species of dwarf human, which evolved by the means of island dwarfism. These hobbits were only about a meter at their tallest, and are really interesting in the size of their brain and apparent ability to use tools and produce fire. I won't go into it, as this is not my specialty, but I recommend people check them out even if you're not very interested in human evolution.

 

It's not fantasy: man-eating storks in recent times!
Image by Inge van Noortwijk

Anyway, what do tiny humans have to do with giant killer azhdarchids? As I was saying, in 2010 fossils of a giant bird were uncovered in the same cave. Dubbed Leptoptilos robustus, it was a giant flightless stork and stood a staggering 2 meters tall, or twice as tall as these hobbits. It's a member of the same genus as living marabou storks, but had reduced flight abilities, such as robust bones. It's unknown if they actually were flightless though, since a complete skeleton has yet to be found, but they were definitely losing their flight capabilities. This has been attributed to the fact that Flores 20,000 years ago was devoid of mammalian predators, and thus the stork may have been taking up the same role as they did on mainland continents (Meijer & Due 2010). True, it had to share that role with Komodo Dragons, which lived on the island at the same time. But what does this mean for our little hobbit?

Seeing as adult Homo floresiensis were still a good 3ft tall, it's safe to say that they were likely off this bird's menu, as its beak was simply too small to manage them. This doesn't exclude children though, and indeed, these storks would've posed a great threat to any baby or even young hobbits on the island, but would the hobbits have fed on these birds? Fossils have shown cut marks on other animals from the island, notably the stegodonts, but according to an interview, cut marks have yet to be found on any of this bird's remains. Still it would be great to actually see a fossil showing predation on one or the other now, wouldn't it?

Anyway, as for what you've gotten out of this today? The lesson is, if you're ever stuck between a T-rex and a Quetzalcoatlus, take your chances with the Rex. Stay sharp and see you soon.

References:

Alexander W. A. Kellner, Xiaolin Wang, Helmut Tischlinger, Diogenes de Almeida Campos,, David W. E. Hone, & Xi Meng (2009). The soft tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane Proc. R. Soc. B : 10.1098/rspb.2009.0846

Buffetaut, E., Grigorescu, D. and Csiki, Z. 2003. Giant azhdarchid pterosaurs from the terminal Cretaceous of Transylvania (western Romania). In: Buffetaut, E. and Mazin, J. M. (eds.) Evolution and Palaeobiology of Pterosaurs, Geological Society Special Publication, 217, 91-104.

Mazin JM, Billon-Bruyat J, Hantzepergue P, Larauire G (2003) Ichnological evidence for quadrupedal locomotion in pterodactyloid pterosaurs: trackways from the late Jurassic of Crayssac. In: Buffetaut E, Mazin JM, editors. Evolution and Palaeobiology of Pterosaurs, Geological Society Special Publication,. 217. : 283–296.

Meijer, H. J.M. and Due, R. A. (2010), A new species of giant marabou stork (Aves: Ciconiiformes) from the Pleistocene of Liang Bua, Flores (Indonesia). Zoological Journal of the Linnean Society, 160: 707–724. doi: 10.1111/j.1096-3642.2010.00616.x

Lü J, Unwin DM, Deeming DC, Jin X, Liu Y, & Ji Q (2011). An egg-adult association, gender, and reproduction in pterosaurs. Science (New York, N.Y.), 331 (6015), 321-4 PMID: 21252343

Naish, Darren. Tetrapod Zoology Book One. Great Britain: CFZ Press. (2010)

Witton MP, Habib MB (2010) On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness. PLoS ONE 5(11): e13982. doi:10.1371/journal.pone.0013982

Unwin DM (1997) Pterosaur tracks and the terrestrial ability of pterosaurs. Lethaia 29: 373–386.

Unwin, D. M. 2005. The Pterosaurs from Deep Time. New York, Pi Press.

Websites:

Pterosaur.net, It’s dumb, it’s awesome, it’s… Our lives with pterosaurs, part 2, accessed March 3, 2013. http://pterosaur-net.blogspot.com/2012/04/its-dumb-its-awesome-its-our-lives-with.html