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closeRunning is not the only high speed bipedal gait
Posted by Hoyasaur on 15 Jun 2012 at 01:30 GMT
Your very interesting article makes the explicit assumption that bipedal dinosaurs employed a symmetrical running gait -- alternating footfalls, etc., which is of course metabolically expensive However, some or many bipedal dinosaurs may have employed an alternate high speed gait -- hopping -- that did not incur the metabolic cost of running.
Most, if not all, dinosaurs descended from bipedal ancestors. However, the origin of dinosaur bipedality remains a big mystery. To quote Gregory Paul from his 1988 book, Predatory Dinosaurs of the World, "The reason predatory dinosaurs became bipedal is not at all clear. […] The only thing that can be said in the end is that bipedalism was a serendipitously crucial adaptation...."
I believe that bipedal hopping behavior in the very first dinosaurs in the Mid-to-Late Triassic (roughly Carnian time) led directly to obligatory bipedality, which characterized most primitive and many advanced dinosaurs, as I argued here.
http://frontier-knowledge...
Bipedal hopping would have enabled dinosaurs to move very quickly without being warm-blooded because hopping relies on elastic storage-and-release rather than metabolism, and it may help explain how the cold-blooded dinosaurs suppressed the increasingly warm-blooded mammal-like reptiles and mammals.
Incidentally, footprints of hopping dinosaurs have been found - http://www.paleoglot.org/...
Also, check this out -- http://www.youtube.com/wa...
RE: Running is not the only high speed bipedal gait
JohnRHutchinson replied to Hoyasaur on 31 Jan 2013 at 09:35 GMT
Apologies for the delay in replying; I just noticed this comment.
We are very aware of hopping gaits, but there is no convincing evidence that dinosaurs routinely, or even ever, used them. The Bernier et al. study's footprints are ambiguous.
More importantly, the thousands of trackways of bipedal dinosaurs spread across all of dinosaur history and geography document walking and fast running gaits as the standard mode of locomotion.
Furthermore, the absence of adaptations clearly related only to hopping and not to walking/running in bipedal dinosaurs does not favour the speculation that dinosaurs hopped.
Additionally, the highly derived evolutionary polarity for hopping within extant birds does not lend any support for hopping being ancestral for birds; rather, all evidence supports bipedal walking and running as the ancestral mode of locomotion at the crown group node.
Finally, biomechanical evidence, discussed by Hutchinson 2004 (J Morph biped mechanics papers), strongly disfavours hopping as a gait for dinosaurs. The peak ground reaction forces are ~2x those of running at the same speed, which makes hopping dangerous at moderate body sizes and impossible at large or giant sizes in dinosaurs.
We consider this evidence to thoroughly debunk the speculation that dinosaurs normally hopped. We invite those with more compelling evidence in favour of this hypothesis to submit their ideas to the peer-reviewed literature in paleontology and see if they can convince a scientific audience.