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Cranial Anatomy = Age Classification?

(3 posts)
  • Started 10 months ago by Jason Testin
  • Latest reply from Jeff Martin

  1. Jason Testin
    Member

    Some of you may seen the special on the Nat Geo channel a few weeks ago where Jack Horner, among others, discussed cutting down the number of dinosaur species by considering them to be developmental stages of the same species.

    Here is a link to a paper Horner and Mark Goodwin wrote on triceratops. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1635501/pdf/rspb20063643.pdf

    Now I consider myself a "lumper" and feel that is some cases new species are named erroneously, and based on little to no evidence. But some of the bone re-modeling that are suggesting sounds extreme, but I'm no biologist so if someone has evidence of this in modern animals please share.

    With the exception of the "baby" form, which is clearly a young animal, I would be more willing to except Sexual Dimorphism at this point; keeping in mind I am researching sexual dimorphism in theropods for another of my many projects, so I am bias.

    So what do you all think? Can bone remodeling cause the horn to rotate 90 degrees from pointing up and back to forward? Is there modern evidence for this kind of change? Are we looking at evidence of differences between the sexes? Or are we looking at different species?

    Posted 10 months ago #

  2. Jeff Martin
    Moderator

    I could see this being legit. I would however, like to see more examples, larger data base to do statistics.

    With bison, the calves have just buttons for horns, and for one year and two old's, the horns point lateral and just slightly dorsal. As the horn grows, the angle changes to more of a dorsal direction by age of 3-7. As they get even older, from wear and tear, the horn begins to point dorsally of course, but now more towards each other. This is prevalent in males.

    The females as calves are the same as the bull calves as well as the one to two year old's. However, by the age of 3-7 or so, the horns make a large change in direction, the will usually begin to point at each other, or just straight up immediately. As the females get even older, their horns begin to wear and tear as well, and begin to wear down.

    Now I do realize that this a mammal, and I'm talking about a hair composed horn sheath that you see on the outside, but the bone (horn core) on the inside is altering.

    The wear and tear is due to rolling on the ground, and rubbing against trees, rocks and etc.

    Posted 9 months ago #

  3. Jeff Martin
    Moderator

    I would like to ask if these animals are close to the same geologic age? Within a certain time frame?

    And Josh Ratliff brought up a good point, was there a horn sheath on Triceratops? Like bison do, or more like a beak on a bird? Keratinized?

    Just a food for thought...

    Posted 9 months ago #

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