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Back to climbing coelurosaurs (was RE: Species & Giraffe necks)



At 03:16 PM 4/12/99 -0500, Tim Williams wrote:

>I've seen leopards featured up in a tree, often with a carcass (or 
>part of a carcass) dragged up with them.   Can tigers or lions climb 
>trees the way a leopard does?  I was wondering - does a leopard have 
>any special adaptations in its skeleton for climbing trees, not 
>present in a lion or a tiger?  

Lions & tigers can both certainly climb: I don't know if either of them
bring prey items up in trees, though (and my subjective impression, not
based on hard numerical data, is that the bigger two species spend less time
in trees).  The postcranial anatomy of leopards is not greatly different
from lions or tigers (and very similar to younger lions or tigers), other
than size and robusticity.

>Extrapolating this to dinosaurs, some little (or not-so-little) 
>theropods could have spent some of their time in trees, without their 
>skeletons necessarily showing any obvious adaptations for climbing.

Well, the cat skeleton in general shows a LOT of climbing adaptations: if
lions and tigers are less good at climbing (and again I don't know that that
is necessarily true), it is almost certainly a size-related function.
Remember also that the cat skeleton evolved among small forms generally
regarded as scansorial mammals (and indeed, the majority of living felids
are great climbers).
  
>I'm thinking dromaeosaurids, troodontids (but not tyrannosaurids).

Actually, most coelurosaurs show plenty of adaptations for getting up into
trees: inwards-facing grasping limbs being one of the most obvious.
Grasping is pretty much grasping: it doesn't matter as much if it is an
animal or a tree trunk, the morphometrics are often the same (as shown by
the morphometrics analysis of Hopson at the Ostrom Symposium).  Basically,
to make a grasping foot or hand, elongate the penultimate distal phalanges;
to make a better running foot or hand, elongate the proximalmost phalanx and
shorten the distal phalanges.  Pattern works well for the feet of
ornithothoracine birds, and the hands and feet of non-ornithothoracine
theropods.

Ornithomimosaurs and tyrannosaurs have very non-climbing like feet (not a
big surprise, although Chattejee placed ornithomimosaurs in the trees in his
recent book!).  Oviraptorosaurs, troodontids, dromaeosaurids, and the like
have somewhat more grasping foot ability (not much more, though), while more
basal forms have less specialized feet.  _Archaeopteryx_ falls in the same
cloud as primitive theropods like _Coelophysis_, and _Confuciusornis_ and
other early climbers are in the climbing-bird part of the plot.

In terms of hands, the classic Maniraptora (oviraptorosaurs, troodontids,
dromaeosaurids, and basal birds like Archie and _Confuciusornis_) have among
the more "grasping" hands (not terribly surprising...).

So, nothing wrong with getting small-to-midsized coelurosaurs up in the
trees per se.  However, graspability has other (not mutually exclusive)
functions, and the feet of these forms do not show marked climbing
adaptations.  So, you could argue pretty well for scansoriality, but it
would be more difficult to defend full-fledged arboreality.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661