Most of us know of Transylvania, an historical region in Romania, from Bram Stoker's novel, Dracula. But even this fictional thriller almost pales in comparison to what really took place in Transylvania around 70 million years ago.
The linked cast of characters from then until now includes dwarfs, an eccentric Austro-Hungarian motorcycle-riding baron, and now a kickboxing dinosaur with off-the-chart claws.
(Dwarf Dinosaurs; Credit: Vlad Codrea)
(Baron von Nopsca; Wikimedia Image)
(The Kickboxing Dinosaur: Balaur bondoc; Credit: Mick Ellison, Zoltan Csiki, Matyas Vremir, Stephan Brusatte, Mark Norell)
The motorcycle rider, Baron von Nopsca, comes into the real life story circa 1900. During that year, his sister found a tiny bone on the family estate in Transylvania. The baron, who was a dinosaur buff, identified the bone as belonging to a dwarf dinosaur that likely once lived on an island in the region.
His theory was immediately ridiculed and largely dismissed. But over a century later, paleontologists have proven that most of Baron von Nopsca's discoveries and theories were legit.
Earlier this year, I wrote about new evidence further supporting the dwarf dinosaur claims. Today comes the news that a predatory dinosaur, the "kickboxer," likely feasted on the dwarfs and goodness knows what else.
Below is a transcript of my interview with University of Bucharest paleontologist Zoltan Csiki, who led the research project concerning Balaur bondoc:
Jennifer Viegas: Is it true that this dinosaur had two enormous claws on each of its feet? And isn't that unprecedented for a dromaeosaur?
Zoltan Csiki: Yes, indeed, it had two large sickle claws on both feet. This is not only unlike any other dromaeosaurid known to date, with only one enlarged claw on each foot, but unlike almost all other theropods (the group of mainly predatory dinosaurs to which Balaur belongs), in which the reduction of the digits is the norm, having only three functional digits. Balaur is outstanding because it had both FOUR functional digits on its hind limb, including TWO enlarged and hyperextensive claws.
(Balaur bondoc's double sickle-clawed foot: Credit: Mick Ellison)
JV: Your PNAS paper mentions that Balaur bondoc had large muscles around its pelvis area, as well as fused bones. How then would this dinosaur have moved?
Large pelvic muscles mean large forces exerted along the hind limbs – it looks that Balaur had more powerful hind limbs than its relatives. However, strong and powerful legs do not necessarily mean speed; and indeed, while other dromaeosaurids such as Velociraptor and Deinonychus (both close relatives of Balaur) are usually depicted as fast runners, Balaur almost certainly was not one like that. Not a sprinter, Balaur was probably using his powerful hind limbs for a different function – but we are as yet unsure what that might have been. The foot, equipped with the double set of sickle claws, suggests it used these to attack prey; functional morphology studies and lucky discoveries such as the famous “fighting dinosaurs” from Mongolia allow us to infer that dromaeosaurids did use their enlarged claws to attack prey, and can hypothesize that Balaur used them the same way. But either it delivered its blows in a more powerful way, or else it might have used his powerful hip and tight musculature for other reasons, not necessarily directly related to its hunting strategy. Detailed functional anatomy studies are needed to clarify this issue, and this is planned for the future.
As for the fused hand and foot bones, we have no clear ideas as to their exact use. Fusion in the hind-limb is used sometimes to stabilize limb posture, especially along the most unstable ankle joint, if the animal lives and moves in mechanically stressful environments. On the other hand, we see similar modifications (even if not to the extent seen in Balaur) in relatively closely related taxa such as birds or Velociraptor. So whether these are phylogenetically or ecologically driven modifications, is unclear for the moment, and should be explained only after detailed functional morphology analyses of Balaur.
JV: Please describe a possible scenario in which this predatory dinosaur attacks, kills and consumes one of its prey species.
ZC: As we do not have as yet a good
understanding of the lifestyle and hunting habits of this animal, imaging such
a scenario would be a little far-fetched.
For the moment what is sure is that, if functional morphology reasoning
is reliable to any reasonable degree, Balaur did what it did in a markedly
different manner than its close relatives.
JV: Why do you think this dinosaur evolved such unusual features? And why didn't
it shrink to become a dwarf, as so many of the other dinosaurs on islands
did?
ZC: Our most parsimonious explanation for the highly unusual (autapomorphic ) nature of Balaur is that it represents a by-product of its insular habitat. Animals tend to do strange things on islands, simply because they are allowed to – selective forces and restrains are more relaxed in island environments than within the more competitive continental environments. But even these “strange things” must have had biological explanations, being the results of different constrains related to its lifestyle, feeding strategies, social structure, sexual behavior and so on. Because Balaur is so unlike any other dinosaur for which a reasonable connection between morphology and function was suggested, for the moment we (or at least I) do not have a sound understanding of the nature of the evolutionary forces that drove its peculiar anatomical adaptations. But hopefully we’ll be able to better answer these questions in the future.
What is important for the moment is that the discovery of Balaur brought us in front of the recognition that we are still far from fully comprehending the complexity and diversity of Mesozoic life, not even within groups so thoroughly studied and considered relatively “conservative” as the dromaeosaurids. It's something like the discovery of a lion with elephantine hind limbs and a grasping ape-like hand – it would do such unexpected and unsuspected things that these would be difficult (near to impossible) to be deduced by simply watching the daily activities of its closest relatives, the lions, which will feed, hunt, mate, and behave completely differently. Most probably so did Balaur as well, and this is the main challenge coming out of its discovery – understanding how it actually lived.
Size reduction, as an evolutionary
consequence of island habitation, is not universal, it's not a “law” of nature;
it is only a case made based on a statistical tendency for such a size change,
observed in a wide range of animals, a “rule." And this rule states that, once
entering an island, large animals tend to become smaller, generally because of
space and resource limitations, while small ones might become larger. However, some
modern predators (such as mammalian carnivores) were suggested to be excepted
from this “rule”, as they do not regularly dwarf in island habitats. It is thus possible that the
same was applicable to Mesozoic predators as well. On the other hand, the
relatives of Balaur (the
velociraptorines) were already relatively small in absolute size, so that
possibly they were below a threshold size that would have triggered dwarfing,
even on an island, possibly because it had sufficient food resources, or
because its main prey species, although dwarfed, were still large enough to not
be taken down by a severely downsized predator.
(Balaur bondoc; Credit: Mick Ellison)
JV: Is it thought that land bridges connected this
island (now Romania) to the mainland, helping to explain how dinosaurs came to the island in the first place?
ZC: That Balaur is so closely related to animals living in the same time in other parts of the world (such as Saurornitholestes in North America or Velociraptor in Asia) clearly demonstrates that it is not the descendant of a long line of animals that would have lived in isolation in the Late Cretaceous archipelago – while this is indeed the case of other dinosaurs, turtles or mammals from the same assemblage. This means, in turn, that the line leading to Balaur separated relatively recently from the larger stock of velociraptorines (the likes of Velociraptor or Deinonychus, its closest relatives), more recently that the barriers (seaways) separating its homeland from other continental areas were put in place before its divergence, and that the immediate ancestors of Balaur must have moved somehow across these barriers. We do not yet have a definitive idea as to the ways this migration happened. Intermittent faunal connections do not necessarily require land bridges to connect isolated areas only to be afterwards destroyed; they can occur as results of “island hopping” (certainly a good candidate hypothesis in the case of the Late Cretaceous South European archipelago), as chance dispersal over marine barriers (we know that recent terrestrial animals can spread actively or be rafted passively across stretches of marine waters) or during sea-level drops that would have united previously isolated areas. Nor do we have an idea as to the timing of these faunal connections. Actually, it looks that they took place several times during the Late Cretaceous, allowing the dispersal of different groups of animals from and to Asia, North America or the southern Gondwanan landmasses (Africa, South America, India). A more sound phylogeny of Balaur, together with a better understanding of the geological evolution of southern Europe, is required to pinpoint the mode, timing and even the direction of these faunal connections.
But, the bottomline is – Balaur being so closely related to animals from Asia
and North America suggests interchanges with that area. Besides understanding
the lifestyle and functional morphology of this peculiar animal, this is a
second important challenge for us – to decipher its origin and ways of
evolving.
JV: How many millions of years ago did this predatory dinosaur
live, and when did it die out?
ZC: Dating of continental deposits, such as those yielding the remains of Balaur, are often difficult, as these usually lack good age indicators. Nevertheless, we can reliably restrain the age of these deposits (and thus that of Balaur) to the Maastrichtian, that is, the last stage of the Cretaceous, spanning the 72 to 65 Mya time period, because these continental deposits rest on top of marine ones which can be dated using different fossils as ending with the uppermost Campanian (the stage of the Upper Cretaceous preceeding the Maastrichtian). That means that our record of Balaur is restricted to the very end of the Cretaceous. But it is not impossible that it (or its ancestor species) might have lived during earlier time periods in the European archipelago.
On the other hand, there is no data about
where it went extinct. Usually dinosaurs are considered to be one of the flagship casualties of
the Cretaceous-Tertiary boundary events, and thus the most obvious answer would
be – at the end of the Cretaceous. But, as we have only two specimens of Balaur known as yet, whose relative ages
are unknown, we cannot say for sure whether it (or any of its contemporary
dinosaur species) lived up to the very end of the Cretaceous or if eventually went extinct earlier. There is just not enough data to decide.
JV: In a nutshell, please explain why this dinosaur was so "aberrant"
and "strange?"
ZC: Balaur was aberrant and strange first of all because it is morphologically so divergent and shows so many unique features that it actually revealed to us a completely new body plan that existed during the Mesozoic. But it's also strange because it is a member of a group considered for a long time well-known and over-studied – the dromaeosaurids— although the recent discovery of “aberrant," unusual South American dromaeosaurids (the unenlangiines) already hinted at the fact that there is still much to discover and learn about these. Yet it is so different from any other known dromaeosaurid that it suggests we're still far from fully understanding the real diversity of the group.
Unlike other contemporaries from the
Romanian paleo-islands, that were strange because they were like their relatives
from much earlier times, but unlike those living in the same time (kind of
“living fossils” of their times, such as the duckbill Telmatosaurus or the armored Struthiosaurus),
Balaur is unlike BOTH its predecessors and its contemporaries. It is simply
unique...for now, at least.
Tags: Dinosaurs, Extinct Animals, Late Cretaceous Dinosaurs, Paleontology, Prehistoric Animals
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