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| The newly-discovered azhdarchid, Eurazhdarcho. Reconstruction by yours truly. |
This week, news of a new species of azdarchid from
Romania was published. Eurazhdarcho
langendorfensis had a wingspan of 3m (~10ft), and while it wasn’t the
largest species (in fact, it is ranked among the smallest), it still would have
been a sight to behold in the flesh. The discovery of any new species from this
bizarre family of reptiles is significant, as most fossilized azhdarchids are
known from very fragmentary remains. E.
langendorensis, in fact, is one of the most complete specimens, yet it is
only known from 15 individual bones.
Even more interesting than the (relative) completeness of
E. langendorfensis is the environment
in which it lived. At the time when Eurazhdarcho
lived, Romania was an island in the Tethys Sea. As part of a great archipelago,
it was one of numerous scattered islands which would one day form Europe. On this island, which was then covered
in dry forests and seasonally swamped with monsoonal rain, Eurazhdarcho lived alongside a variety of dinosaurs. This was a
continental, terrestrial environment rather than a coastal or oceanic one, further
enforcing the hypothesis that azhdarchids were the “terrestrial stalkers” that
Witton and Naish had proposed.(Vremir et.
al, 2013) However, Eurazhdarcho
wasn’t the only stalker on the island. There was something far, far bigger.
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| The monstrous Hatzegopteryx. Reconstruction by Mark Witton. |
Hatzegopteryx
thambema was a tremendous animal: as tall as a bull giraffe, it weighed up
to 250kg (~550lb) and sported a 12m (~40ft) wingspan. Four times as large as Eurazhdarcho, H. thambema was likely the dominant predator of the island; with a
massive, toothless beak, it likely ate just about everything it could swallow,
from amphibians to small dinosaurs to foliage. Yet, while H. thambema grew to epic proportions which far dwarfed Eurazhdarcho, the two species were able
to coexist.
Sympatry is when closely-related species, which differ in
size, overlap in range but not in niche. This is a common occurrence in the
modern world, and it comes as no surprise that it happened in the Mesozoic Era,
but fossil evidence of this is uncommon. The fact that H. thambema and Eurazhdarcho
overlap in range indicates an instance of prehistoric sympatry. The two avoided
competition by simply feeding on different diets; the larger of the two species
was adapted for a larger menu, while the smaller could exploit resources which
the larger may overlook. This eliminates competition and allows the two
species, no matter how different in size or similar in genetics, to both
survive in the same habitat.
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| Evidence for sympatry in azhdarchids has been found in both North America and Europe. Image from Vremir et. al, 2013. |
The remains of small azhdarchids are commonly found in the
same formations as giants are. Perhaps, like herons or egrets, several species
of azhdarchid inhabited the same environment and used the same generalist
feeding strategy, separated only by size. Fossils not only have the ability of
individual animals and species, they give us a clear picture of how these
species interacted with one another. Each discovery we make, the Mesozoic world
becomes a much more complex and beautiful one.
References
Coverage by Darren Naish: http://blogs.scientificamerican.com/tetrapod-zoology/2013/01/30/new-azhdarchid-pterosaur-eurazhdarcho/
Vremir M, Kellner AWA, Naish D, Dyke GJ (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
Witton MP, Naish D (2008) A Reappraisal of Azhdarchid
Pterosaur Functional Morphology and Paleoecology. PLoS ONE 3(5): e2271.
doi:10.1371/journal.pone.0002271
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