Re: I think I have something on extinction

[Phillip Bigelow <n8010095@henson.cc.wwu.edu>]

Josh Williams wrote:
>Yes, but how could you tell teeth marks from some other kind of mark?  Is 
>there some kind of unique pattern if they are teeth marks or is it just a 
>bunch of scratches on the bone that you guess are teeth marks?

  There is a passel of processes that can mark-up a bone before it gets
fossilized; all of which leave distinctive patterns on the bone. Fossilized
marks often (not always!) are nearly the same color as the surrounding bone.
Marks produced after fossilization (such as scratches imposed on the bone by
a sloppy preparator, or by fractures caused by lithostatic
loading/unloading) sometimes have a different color than the surrounding
bone.
So far, the following types of marks can be identified on fossil bone (with
a lot of effort and attention!)  (if you want, skip to number 6):

  1) trampling marks (from other dinos. walking on the bones; they usually
     look like superficial scratches).

  2) Tooth marks:
      a) puncture marks.
      b) scrape marks (serrated or non-serrated). 
      c) laceration marks.
      d) indentation marks (incomplete puncture marks).
      e) gnaw-marks (which of course suggests a mammalian carnivore, or a
         rodent, rather than a dinosaur!). 

 3) Holes produced in the bone by insect borers (or pholadid bivalves, if 
    the bones were deposited in the sea). There are also micro-organisms
    that can produce some funny looking bore-holes in fossil bone.

4) Polished bones (usually implies that the bones were exposed for a time in
   rapidly flowing water).

5) Crush marks (caused by a biting force or by stepping on the bone by a heavy
   animal). 

**6) What YOU would want to look for are called "ballistic-marks".  These
   are produced by a rapidly-moving object penetrating bone.  The marks can
   easily be confused with tooth puncture marks, but there are some ways to
   distinguish between the two (unfortunately, I don't know what the
   criteria are).  Various marine organisms are also known to produce
   ballistic marks on sea shells (again, I don't know how this is
   accomplished).

Note that most of these marks can't be easily duplicated on already-fossilized 
bone. They are produced on fresh bone. If you try to make them on fossilized  
bone, all you get is a crude facsimile. 
This list of identifiable marks on bone is probably very incomplete.  To
learn more about how dino bones get marked-up before they get buried, there
is a good paper on the subject (provided you have access to a nearby university 
library):
            Rogers, R.R., 1990. Taphonomy of three dinosaur bone beds
              in the Upper Cretaceous Two Medicine Formation of Northwest
              Montana: Evidence for drought-related mortality.
             _Palaios_ v. 5, pp. 394-413.