The shark-toothed dinosaur with a ‘fin’ on its back (Pocket Science)

By Ed Yong | September 8, 2010 1:00 pm

Dinosaur bodies are covered in all sorts of spikes, horns, plates that were used for defence, combat and identification. But sometimes, these body parts are so bizarre that their purpose is a mystery.  The latest in these strange projections belongs to Concavenator, a new giant predator with two spikes sticking up from the vertebrae just in front of its hips. They would probably have given the dinosaur a strange hump on its back.

Concavenator’s  skeleton – virtually complete and beautifully preserved – was discovered by Francisco Ortega in Spain’s Las Hoyas formation. At six metres long, it dwarfed most of the other bones recovered from the area but it was still a runt within its own family tree. Concavenator was a primitive member of the carcharodontosaurids, a group of “shark-toothed” predators, many of which were larger than Tyrannosaurus. And while it shared the basic body shape of its relatives, two of its features stand out.

The most obvious ones are the bizarre spikes on its hips. Back when the animal was flesh as well as bone, these spikes would have formed a kind of hump. “The most plausible role for this structure is that of a deposit of fat,” says Ortega. It might be like the hump of modern animals like zebu cattle, but these humps have no internal bony supports. Alternatively, a structure that striking could allow individuals to communicate with one another. The spikes could also have supported a fold of skin that helped Concavenator to keep cool. “For the moment, we can consider that all these options are reasonable interpretations, but they still remain in the realm of speculation,” says Ortega, who has no favourites among the three hypotheses.

Concavenator’s arms are potentially even more interesting. Its forearms have a row of small bumps and Ortega thinks that these are quill knobs, bony lumps that act as attachment points for feathers. The primary feathers of modern birds connect to their forearms via quill knobs. Similar bumps were discovered on Velociraptor a few years back, providing hard evidence that this small dinosaur has feathers. Whether Concavenator had feathers is a different matter. The things that sprouted from the knobs were probably short, rigid filaments, only distantly related to the full-blown feathers of birds and other smaller dinosaurs.

Reference: Nature http://dx.doi.org/10.1038/nature09181

More on predatory dinosaurs:

Balaur the stocky dragon – Velociraptor’s double-clawed Romanian cousin

Terminatorsaurus

Groovy teeth, but was Sinornithosaurus a venomous dinosaur?

The plague of tyrants – a common bird parasite that infected Tyrannosaurus

Raptorex shows that T.rex body plan evolved at 100th the size

MORE ABOUT: concavenator

Comments (5)

  1. Zach Miller

    Very strange beastie indeed! If the quill knobs turn out to be genuine quill knobs, a more interesting question may become “why did so many other large theropods LOSE them?”

    The fin is odd, too, but I wouldn’t be surprised if it turned out to be a display structure. Is the fin supported by neural spines or separate ossifications?

  2. Zach Miller

    Gotcha. Might this have implications for the strange dorsal vertebrae of Becklespinax?

  3. jdmimic

    It seems the reconstruction of the hump on its back is extremely conservative. They took virtually the minimum possible covering that would fit on the spines. Considering the pes showed soft tissue preservation, the sediment around those spines should really be examined in detail as I would not be at all surprised to find a much more elaborate structure than what has been drawn.

    The spines almost assuredly had some display function, but that would not rule out other uses, such as moose antlers, clear display structures that are also very good at keeping wolves at bay. I find a lot of these sorts of discussions quickly become far too dichotomous.

    As far as why did so many other large theropods lose them, one answer is likely the same as why large mammals are not generally covered in thick fur. It was hot, especially so back then.

    And is it fair to say that what sprouted from the knobs were probably short, rigid filaments when nothing is known other than the knobs were present? On what basis do you make that claim? I can see stating that whatever was there was most likely more akin to the simple fibers found on the earlier coelurosaurs than the feathers seen on the more derived maniraptorans. The difference in meaning is subtle to be sure, but at least to me, present.

  4. Has anyone seen actual footage from the skeleton itself instead of just a rendered image? I’m asking because I’m wondering whether the vertebral column has two or more shackles attached to each other without cartilage like some flying dinosaurs had.

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