Naturalis Historia

Everyone has encountered a T. rex in books, movies or museums.   Besides its size and menacing jaws one of the most striking features of a T. rex is its diminutive arms.   So why were the arms of T. rex so short?   There have been many hypotheses including: 1) they had no use and were like a vestigial organ, 2) they were used to hold on to potential mates, 3) they were used to hold onto small prey while they ate, 4) they were used to help them get up when they fell down or 5) some combination of these explanations.  Can these hypotheses be tested?  Well, yes and no.  Behavior traits are notoriously difficult, by not impossible, to assess with the fossil record. For example, see my post on extinct elephant behaviors deduced from fossil footprints (Preservation of Behavior: Fossilized Elephant Tracks from the Arabian Peninsula)…

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2 thoughts on “

  1. Interesting post. My guess is that the arms first became useless for locomotion, atrophied, and later took on a different function (which would explain the strong muscles you mentioned). Similar to how penguin flippers previously served a flight function which now serve a swimming function. Just a guess 🙂

    1. It’s a nice logical guess, I would not go very far from what you are saying either. Infact many scientists think that the same happened to the homo species which started walking on two legs, rather than four.

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