tag:blogger.com,1999:blog-3459964428093088507.post5675397164505136607..comments2019-11-15T22:18:37.207+01:00Comments on Tuesdays are for Tyrannosaurs: The paradoxical arms of T. rexHypnotosovhttp://www.blogger.com/profile/11469293434683944221noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-3459964428093088507.post-18311903611522250042012-04-27T00:13:24.812+02:002012-04-27T00:13:24.812+02:00"Keep in mind that one of the reasons that th..."Keep in mind that one of the reasons that the forelimbs are strong in bending is simply that they are quite short - this reduces the moment arm for cantilever bending, but may be a side-effect of reduction"<br /><br />I hadn't thought of that. My first thought is that this could have been a serendipitous advantage, which would explain why forelimb length is constant in Tyrannosauridae (relative to hindlimb length). Unlike in Abelisaurids where the known forelimbs are truly vestigial.<br />But that is of course ad hoc speculation on my part, I'm going to mull this over.Hypnotosovhttps://www.blogger.com/profile/11469293434683944221noreply@blogger.comtag:blogger.com,1999:blog-3459964428093088507.post-22023967843051911122012-04-26T23:47:24.940+02:002012-04-26T23:47:24.940+02:00There is definitely evidence for damage to the arm...There is definitely evidence for damage to the arms because they were as you say "in the line of fire". Rothschild mentions (among the many, many pathologies in Tyrannosaurs) infections caused by bite wounds to the manus. But the stress fractures mentioned concern small fractures caused by repeatedly overstressing the bone, rather than breaks caused by trauma.<br />The resulting pathologies are generally not crippling either, Google Books has the relevant part of the article, including the image of a bump caused by a stress fracture: http://goo.gl/cC1NO. That seems especially minor considering how common pathologies are in T. rex, Rothschild and Molnar quote Larson as stating that injury and disease is invariably found in Tyrannosaurus specimens if more than 10% of the skeleton is known. Tyrannosaurs certainly lived interesting lives!<br /><br />I have to admit that I don't know anything about stress fractures in extant predators (and a quick search didn't turn up anything either), but stress fractures on the manus and pes are apparently common in Theropods. They are especially common in Allosaurus, dromaeosaurids and Tyrannosaurids* which suggests they all used their arms and legs** in predation.<br />I personally think this is a strong case for functional use of the arms in Tyrannosaurus, even if their role would be clearly secondary to that of the mouth. <br /><br /><br />* Article by Tanke and Rothschild on Darren Tanke's site: http://goo.gl/Xrp88<br />** Rothschild demonstrates that the pattern of the pathologies is unlikely to have been caused by strain from running, suggesting that kicking was involved.Hypnotosovhttps://www.blogger.com/profile/11469293434683944221noreply@blogger.comtag:blogger.com,1999:blog-3459964428093088507.post-76272189687161549662012-04-24T12:19:00.498+02:002012-04-24T12:19:00.498+02:00Keep in mind that one of the reasons that the fore...Keep in mind that one of the reasons that the forelimbs are strong in bending is simply that they are quite short - this reduces the moment arm for cantilever bending, but may be a side-effect of reduction. It also seems plausible (at least to me) that the arms may have accumulated heavy damage and pathologies because they were "in the line of fire" but *not* important functionally - sustaining consistent damage and fracture to a critical bony feature would typically be lethal for a large carnivore.<br /><br />I see little reason to presume that tyrannosaurs did anything interesting with their forelimbs at all.Michael Habibhttps://www.blogger.com/profile/03641371798541261487noreply@blogger.com