Arboreal Deinonychus

["Richard L. Dieterle" <Richard.L.Dieterle-1@tc.umn.edu>]

Assuming that Deinonychus could climb trees, just how adept would he be in an 
arboreal environment?  To get the best model of Deinonychus in this context, we 
should turn to arboreal animals that are at least quasi-bipedal such as bears 
and apes.  When such an animal evolves beyond the size of a monkey, certain 
adaptive changes are triggered: the neck shortens, the arms come to be of such a
length that they can be raised above the head, the feet become (or remain) more 
like the hands, and the tail radically shortens or disappears.  These animals 
also seem to acquire the ability to locomote upright with greater facility.  
None of this happens to large cats because they are committed quadrupeds: they 
do not have the postural and locomotor flexibility to take advantage of more 
upright postures when in the trees. 

The length of the neck and shortness of the arms of Deinonychus would make it 
difficult (impossible?) for it to grasp overhead branches.  The head mounted as 
high as it is would get in the way of arboreal locomotion, although this would 
be diminished if the animals prove to have had greater adeptness at a 
quadrupedal gait than cursory examination would suggest.  However, the main 
impediment to arboreal locomotion for an animal that size would be its tail, 
most especially if it contained any kind of straightening rod (which would make 
it radically different from the tail of a leopard).  Such a tail would make 
Deinonychus more accident prone than a 10 year old hominid, and cause him to be 
Disastrously Ejected from his Arboreal Domain (DEAD) with such frequency that 
Mother Nature would soon impress the solution upon his anatomy, as She did with 
ourselves (hominoids) and bears.  

Also, how common were Cretaceous trees with wide, low crowns (like broad leaf 
trees)?  

Richard Dieterle

"stupid, clumsy and insensitive"