January 30, 2013 | 87
Another day, another new paper out in PLOS ONE. Today sees the publication of the new azhdarchid pterosaur Eurazhdarcho langendorfensis Vremir et al., 2013, a new species from the Upper Cretaceous Sebeş Formation of the Transylvanian Basin in Romania (Vremir et al. 2013). ‘Vremir’ is my good friend Mátyás Vremir; he worked together with Alex Kellner of the Museu Nacional in Rio de Janeiro, and with myself and Gareth Dyke (both of the University of Southampton) in the description of this new species.
Azhdarchids will already be familiar to a great many Tet Zoo readers; indeed, in recent years they’ve become more familiar to interested people in general thanks to appearances in books, TV documentaries and films. These are the often gigantic, long-necked, long-skulled pterosaurs of the Cretaceous (and especially of the Late Cretaceous), best known for Quetzalcoatlus from Texas, a giant form in which the wingspan was about 10 metres and the total weight was somewhere round about 200-250 kg (Witton 2008, Witton & Habib 2010).
Eurazhdarcho is not a giant: it had a wingspan somewhere round about 3 m (Vremir et al. 2013), making it one of the smallest known azhdarchids. But it’s significant for several reasons, one of them being that it’s known from a comparatively large amount of material. Most azhdarchid fossils consist of isolated vertebrae and other fragmentary remains, with associated or articulated skeletons being very rare. Our description of Eurazhdarcho is based on 15 bones, all discovered together at Sebeş-Glod in Transylvania, and most of which were collected by Mátyás in 2009. We know that other bones from the same specimen were collected later on, but they’re currently inaccessible to our research group.
This all makes Eurazhdarcho Europe’s most complete azhdarchid yet reported… as you can see from the reconstruction shown at the top, however, that doesn’t exactly make the specimen all that outstanding. Eurazhdarcho is known from part of the neck skeleton as well as part of the right wing (Vremir et al. 2013). That’s enough for us to gauge the approximate size of the animal and to work out what its proportions were like. The silhouette shown here – showing Eurazhdarcho reconstructed in quadrupedal launch pose – was kindly produced by Mark Witton.
Azhdarchid cervical vertebrae are highly distinctive and there’s nothing else quite like them. Because they’re often found in isolation, and because they’re so distinctive, we probably understand them better than we do the rest of the azhdarchid skeleton. Indeed, it’s been possible to show that azhdarchid species can frequently be distinguished on the basis of differences and key features present on these bones. Eurazhdarcho has unique cervical vertebrae where the third one is especially long compared to the fourth one (these pterosaurs have nine cervical vertebrae in total) and where the prezygapophyses (the forward-pointing articular ‘prongs’ on the front surfaces of the vertebrae) are longer, and directly dorsally more strongly, than is normally the case in azhdarchids (Vremir et al. 2013). Other unique features are present in its cervical vertebrae as well.
Based on these assorted anatomical features, we are confident that Eurazhdarcho langendorfensis represents a new taxon. Azhdarchids as a whole are named for Azhdarcho, a Central Asian form named by Lev Nesov in 1984 for the Uzbek word azhdarkho, meaning dragon* (Nesov 1984). Eurazhdarcho essentially means, therefore, just ‘azhdarchid from Europe’, or ‘dragon from Europe’. The species name refers to the old Transylvanian-German name for Lancrăm, the village in the Sebeş-Glod area closest to the discovery site (Vremir et al. 2013). We abandoned early plans to name the species after our favourite local alcoholic beverage, the fruit brandy known as Pálinka.
* I have never known whether azhdarkho refers to dragons in the generic sense, or a specific dragon from a specific story or mythology. Do say if you know.
Our description of Eurazhdarcho is just the latest of several projects that involves both my own research group (led by Gareth) at the University of Southampton, and Mátyás (associated with the Transylvanian Museum Society at Cluj-Napoca) and our other colleagues in Romania. Mátyás has been discovering, preparing and describing Romanian pterosaur bones (and other tetrapod fossils) for years now. Gareth and I previously worked with him on the Romanian enantiornithine eggshell assemblage we published last year (Dyke et al. 2012).
More results of our collaborative efforts will be appearing in future – the Upper Cretaceous rocks of Romania are a fertile area for the discovery of dinosaurs, pterosaurs and other Mesozoic animals and numerous exciting discoveries have been made. Anyway, as always for a PLOS paper, the Eurazhdarcho research is fully open-access and available free to all.
Romania: where the gigantic azhdarchids are
Pterosaurs have been known from the Upper Cretaceous rocks of Romania for a while, with most of the fossils concerned being isolated teeth and collections of vertebrae and limb bones. None of these fossils are that impressive, but things changed in 2002 when Eric Buffetaut and colleagues named Hatzegopteryx thambema. This new species was named for a partial skull, an incomplete humerus and assorted bone fragments (all from the Maastrichtian Ciula-Densuş Formation of the Haţeg Basin). The bones are enormous: in fact the deep, robust section of the skull known for Hatzegopteryx had earlier been identified as that of a large theropod (Weishampel et al. 1991). Buffetaut et al. (2002) estimated the wingspan of the live animal to be more than 12 m. A lower estimate of 10-11 m has been published more recently (Witton & Habib 2010), putting this animal on the same footing as Quetzalcoatlus northropi.
Some additional Romanian azhdarchid bones that also come from large to gigantic animals (and are probably referable to H. thambema) have been found since the Hatzegopteryx holotype was described, including a femur, an enormous cervical vertebra and a section of lower jaw tip (Buffetaut et al. 2003, Vremir et al. 2013). Some of these are from the Sebeş Formation, the same unit that produced Eurazhdarcho, and from localities in the Sebeş-Glod region close to the one that yielded Eurazhdarcho.
We don’t know as much as we might like to about Hatzegopteryx, but there’s no doubt that it was enormous, and overall much like Quetzalcoatlus. These azhdarchids were so large that some workers have seriously proposed that they might have been flightless (Henderson 2010: see Witton & Habib 2010). We desperately want to test this hypothesis but it’s difficult to know what to do when their forelimb bones remain so poorly known. We’re working on it though.
Things to do in Romania when you’re an azhdarchid
Eurazhdarcho doesn’t just provide new anatomical information on azhdarchids. It also augments the debate we’ve been having on azhdarchid lifestyle and ecology. As Tet Zoo regulars will know, there was a time when azhdarchids were consistently portrayed as ‘vulture pterosaurs’, specialised for a life of picking at dinosaur carcasses. It was later argued by some authors that some, most or all azhdarchids were aquatic ‘skim-feeders’, strongly tied to aquatic or even marine environments and specialised for hunting while on the wing. Other authors have interpreted azhdarchids as animals that frequented mudflats and either probed into the sediment or pulled invertebrates from burrows; others have suggested that azhdarchids were stork- or heron-like in ecology and, again, tied to watercourses.
Back in 2008, Mark Witton and I put forward the case that azhdarchids were well suited for terrestrial locomotion, and that there was a strong continental, terrestrial signal in the azhdarchid fossil record (Witton & Naish 2008). Data from azhdarchid posture, limb proportions, body shape and trackways all shows, we think, that these animals were swift, competent terrestrial striders, able to walk rapidly (and perhaps even to trot or run) with their wings folded up and their limbs held directly beneath their bodies (Witton & Naish 2008).
Incidentally, claims that azhdarchids were not as tall as we said they were (Paul 2011) are based on the incorrect assumption that azhdarchids walked with sprawling forelimbs. Trackways and the degree of motion present in pterosaur shoulder joints show that they didn’t (ironic that Greg Paul – of all people – should use this line of argumentation!).
Ideas that azhdarchids were habitual denizens of wet places where the sediment was soft and waterlogged are contradicted by the proportionally small, compact feet of these animals (Witton & Naish 2008). Meanwhile, the notion that any large, long-headed, ultra-long-necked flying animal might be able to make a living by grabbing things while in flight – especially from the water – is, in my opinion at least, an absurd concept best left to the world of sci-fi. Remember that animals that feed habitually on the wing possess numerous specialisations for this way of life. Azhdarchids emphatically lack such specialisations, and look absurdly ill-suited for it. This has all been covered on Tet Zoo before: visit the links below for more.
Eurazhdarcho is yet another azhdarchid from a terrestrial, continental environment. Like most fossil animals, its remains were preserved within sediments laid down by a giant, braided river system, but the sediments and other fossils found in the same geological unit show that forested swamps, dry floodplains and riverside habitats all occurred in the region at one time or another. The layers of the Sebeş Formation that preserved Eurazhdarcho reveal evidence of topsoil. It seems that this was an inland, forested environment when Eurazhdarcho was alive. Turtles and small crocodyliforms are known from here, but so are hadrosaurs, rhabdodontids, the dromaeosaurid Balaur, and birds (Vremir et al. 2013).
Carving out niches in the Cretaceous
What makes Eurazhdarcho further interesting, I think, is the fact that its remains are about contemporaneous with, and discovered in close geographical proximity to, gigantic azhdarchid remains that probably belong to Hatzegopteryx. We assume that both were inhabitants of the same fauna and that their living spaces quite probably overlapped (Vremir et al. 2013).
So far as we can tell at the moment, the two are distinct in many details of their anatomy, meaning that we can’t seriously consider the idea that they might be growth phases of the same species. During Maastrichtian times, the Transylvanian Basin was therefore home to both a gigantic azhdarchid – one of the largest known – and a far smaller one; one of the smallest known, in fact. I think we can logically assume that these animals were doing different things ecologically, and living very different sorts of lives. In other words, we’re seeing clear evidence for niche partitioning in azhdarchids here.
This is one of those discoveries that doesn’t really represent any sort of surprise. We know from the modern world that ecosystems are often packed with closely related but differently sized members of a group: there is often or sometimes a bit of overlap in ecology and behaviour, but big-bodied species typically do ‘big animal things’ that small-bodied species typically don’t. We certainly assume that things were like this in the Mesozoic, but we can’t always know that they were. And, in some cases, they weren’t like this: you can have a fauna where a member of a group is a singleton, there on its own and without close relatives.
This new information on the sympatry of small and large azhdarchid species led us to look anew at other geological horizons that yield azhdarchid fossils. Azhdarchids were widely distributed, their fossils being known from numerous Upper Cretaceous sites in North and South America, Europe, Asia, Africa and probably Australia (Barrett et al. 2008, Novas et al. 2012). Of these sites, several show the same pattern: small-bodied azhdarchid species co-existing with giant ones. Quetzalcoatlus northropi – the most famous member of the group – is from the Maastrichtian Javelina Formation of Texas. It’s well known that a smaller azhdarchid is known from the Javelina as well: known only as Quetzalcoatlus sp. (and still unnamed despite being known since the 1970s), it has frequently been discussed and illustrated, typically whenever Q. northropi is mentioned. Even better, there’s a third species in the Javelina. Pterosaur workers mostly know it thanks to the photo of its snout and lower jaw included in Peter Wellnhofer’s Illustrated Encyclopedia of Pterosaurs (Wellnhofer 1991) where it’s labelled as the partial skull of Quetzalcoatlus sp. (p. 144).
This specimen (technically, TMM 42489-2) is superficially thalassodromid-like in some respects (Thalassodromidae is the azhdarchoid clade that includes the Brazilian taxa Tupuxuara and Thalassodromeus. Thalassodromids were somewhat azhdarchid-like, but their neck vertebrae weren’t as long and they possessed giant, sail-like bony head crests). In view of this, Dave Martill and I wrote in 2006 that TMM 42489-2 should be regarded as a species of Tupuxuara (Martill & Naish 2006); Alex Kellner had done likewise somewhat earlier (Kellner 2004). I now think that we were wrong on this: in TMM 42489-2, the dorsal and ventral margins to that part of the rostrum dorsal to the nasoantorbital fenestra aren’t sub-parallel as they are in Tupuxuara and Thalassodromeus. Rather, the specimen seems to represent a relatively short-snouted azhdarchid, as Mark Witton explained in this 2010 Pterosaur.net Blog article.
Both Quetzalcoatlus sp. and TMM 42489-2 were in the 5-m-wingspan size range. That’s big, but it’s substantially less big than Q. northropi. The point here is that three sympatric azhdarchids were sharing the same point in time and space (well, near enough. You know what I mean). And we know that two of those animals at least (Quetzalcoatlus sp. and TMM 42489-2) differed in jaw shape.
The Campanian Upper Two Medicine Formation (famous for such dinosaurs as the duckbill Maiasaura and the horned dinosaurs Einiosaurus and Achelousaurus) also yields a very large azhdarchid (an unnamed form with an 8 m wingspan) as well as the small (2.5 m wingspan) Montanazhdarcho minor. And the Dinosaur Park Formation in Alberta (famous for its many, many dinosaurs) preserves evidence of, again, a giant with a 10 m wingspan as well as a far smaller azhdarchid half this size. The assumption is that one of these Canadian animals is a species of Quetzalcoatlus, but we need more information before we can commit to that possibility.
So there’s something like a pattern here. Several – certainly not all –azhdarchid-bearing localities preserve evidence of two or even three sympatric species. Based on differences in body size and jaw shape, it’s reasonable to assume that these animals were doing different things. In other words, they were almost certainly practising niche partitioning, with the smaller species using different resources from the bigger ones.
Imagine yourself as a time-tourist, walking about any one of these Late Cretaceous environments. If azhdarchids were the terrestrial stalkers that Witton & Naish (2008) envisioned, you might turn a corner and encounter a gigantic, striding azhdarchid, as tall as an adult giraffe and reaching down to grab little dinosaurs, mammals and lizards from the undergrowth. Some short distance away, foraging together in a small family group, are members of a second species, less than half as big and ‘only’ 2.5 m tall. There are dinosaurs here – big ones, in the distance, as well as chicken-sized theropods lurking in the undergrowth – but here’s another reminder that the Mesozoic wasn’t a ‘Dinosaurs Only Theme Park’: there was room for big, terrestrial, ground-striding pterosaurs as well, and also room for lepidosaurs, crocodyliforms and so on.
Island Romania, land of azhdarchids… and nary a big theropod?
Actually, one interesting thing to remember when discussing the Maastrichtian animals of Romania is that they were living on a large island, known as Haţeg Island. The exact size of this island has been debated, with projected sizes ranging from about 7500 sq km (similar to the combined land area of the Galapagos Islands) to over 200,000 sq km (similar to Ellesmere Island) (Benton et al. 2010).
It seems that some of the animals here were island-dwelling pecularities: the titanosaurian sauropods are dwarfs, the theropod Balaur and the ornithopod Zalmoxes are both highly peculiar members of their groups, and the hadrosaur Telmatosaurus is both a dwarf and an evolutionary relict that looks decidedly anachronistic for its time, for example. Intriguingly, big theropods are (so far) absent from the fossil record of the region. It might be tempting to suggest that the presence on Haţeg Island of these different azhdarchid species is linked in some way to this absence of large theropods. However, as is obvious from the discussion above, we already know that azhdarchids large and small were quite capable of inhabiting ecosystems where diverse theropods (including even giant tyrannosaurids) were present, so this idea may be moot. But, here’s an idea – could Haţeg Island be the perfect place for a flightless azhdarchid to evolve? Watch this space…
Azhdarchids (and their relatives within Pterosauria) have been covered on Tet Zoo a few times before. See…
Refs – -
Barrett, P. M., Butler, R. J., Edwards, N. P. & Milner, A. R. 2008. Pterosaur distribution in time and space: an atlas. Zitteliana B28, 61-107.
Benton, M. J., Csiki, Z., Grigorescu, D., Redelstorff, R., Sander, P. M., Stein, K. & Weishampel, D. B. 2010. Dinosaurs and the island rule: the dwarfed dinosaurs from Haţeg Island. Palaeogeography, Palaeoclimatology, Palaeoecology 293, 438-454.
Buffetaut, E., Grigorescu, D. & Csiki, Z. 2002. A new giant pterosaur with a robust skull from the latest Cretaceous of Romania. Naturwissenschaften 89, 180-184.
- ., Grigorescu, D. & Csiki, Z. 2003. Giant azhdarchid pterosaurs from the terminal Cretaceous of Translyvania (western Romania). In Buffetaut, E. & Mazin, J.-M. (eds) Evolution and Palaeobiology of Pterosaurs. Geological Society Special Publication 217. The Geological Society of London, pp. 91-104.
Dyke, G. Vremir, M. Kaiser, G. & Naish, D. 2012. A drowned Mesozoic bird breeding colony from the Late Cretaceous of Transylvania. Naturwissenschaften 99, 435-442.
Henderson, D. M. 2010. Pterosaur body mass estimates from three-dimensional mathematical slicing. Journal of Vertebrate Paleontology 30, 768-785.
Kellner, A. W. A. 2004. New information on the Tapejaridae (Pterosauria, Pterodactyloidea) and discussion of the relationships of this clade. Ameghiniana 41, 521-534.
Martill, D. M. & Naish, D. 2006. Cranial crest development in the azhdarchoid pterosaur Tupuxuara, with a review of the genus and tapejarid monophyly. Palaeontology 49, 925-941.
McGowen, M. R., Padian, K., de Sosa, M. A. & Harmon, R. J. 2002. Description of Montanazhdarcho minor, an azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana. PaleoBios 22, 1-9.
Nesov, L. A. 1984. Upper Cretaceous pterosaurs and birds from central Asia. Paleontology Journal 1984 (1), 38-49.
Novas, F. E., Kundrat, M., Agnolín, F. L., Ezcurra, M. N. D., Ahlberg, P. E., Isasi, M. P., Arriagada, A. & Chafrat, P. 2012. A new large pterosaur from the Late Cretaceous of Patagonia. Journal of Vertebrate Paleontology 32, 1447-1452.
Paul, G. S. 2011. Azhdarchids were NOT as big as giraffes! Prehistoric Times 97, 22.
Vremir, M., Kellner, A. W. A., Naish. D. & Dyke, G. J. 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS ONE 8(1): e54268. doi:10.1371/journal.pone.0054268
Weishampel, D. B., Grigorescu, D. & Norman, D. B. 1991. The dinosaurs of Transylvania. National Geographic Research & Exploration 7 (2), 196-215.
Wellnhofer, P. 1991. The Illustrated Encyclopedia of Pterosaurs. Salamander Books Ltd., London.
Witton, M. P. 2008. A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana B28, 143-158.
- . & Habib, M. B. 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