Size and Weight:
Discovering a new genus of dinosaur is rare enough, but discovering a new genus of dinosaur possessing a never-before-seen anatomical feature is a once-in-a-lifetime event. So imagine the wonderment of the Spanish team of researchers that recently dug up Concavenator, a large theropod of early Cretaceous Europe that sported not one, but two, extremely odd adaptations: first, a triangular structure on its lower back, just above the hips, that may have supported a sail or fatty hump; and second, what appear to be "quill knobs" on its forearms, that is, bony structures that probably supported small arrays of feathers.
So what accounts for these strange features? Well, the 20-foot-long Concavenator was a close relative of Carcharodontosaurus, which was itself related to the huge, sail-backed Spinosaurus--so the hump/sail on this new dinosaur shouldn't come as a surprise, even though it was situated much further down the spinal column than on other dinosaurs (another surprise: until recently, these types of theropods were thought to be restricted to South America and Africa). As for the quill knobs, those are more of a mystery: to date, only much smaller theropods than Concavenator, mostly "dino-birds" and raptors, have shown evidence of arm feathers. Clearly, the feathers on Concavenator's forearms (and probably only on its forearms) were meant for display rather than insulation, which may provide clues about the subsequent evolution of feathered flight.