Great hopping theropods!

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>Incidentally,  has anyone given thought to the notion that
>many therapods might have hopped rather than run with a bipedal motion?  It's
>interesting to me that kangaroos also have foreshortened arms and elongated
>legs,  much like many of the larger therapods,  including T-rex.

Actually, kangaroo arms are much longer proportionately than those of
almost any large theropod (except for Deinocheirus), and of course,
kangaroos use their forelimbs on the ground when moving slowly.

>This
>doesn't mean T-rex did the bunny-hop;  however,  many birds hop rather than
>run,  and some do both,  depending on the situation.  I'd guess t-rex
>himself,  because of his size,  probably couldn't have hopped,  but I expect
>some of his smaller ancestors probably hopped more than they ran.  --Merritt
>Clifton,  editor,  ANIMAL PEOPLE.

The main evidence for striding (rather than hopping) in theropods is the
trackway evidence.  Theropod trackways of all sizes show one foot before
the other, not both feet next to each other.  There has been a report
(which I have misplaced) about a hopping (?French) theropod track site, but
the vast majority of these clearly show walking as the mode of locomotion.

Additional evidence of the pelvic musculature attachments suggest a
standard walking habit.  Bird hips, and the associated muscle connections,
are very transformed, and only really approached by dromaeosaurids among
the nonavian theropods.  In fact, I suspect that the only nonavian
dinosaurs that could concievably have been hoppers would be the
dromaeosaurids, but I have my doubts about that.  Hopefully, someday,
someone will find legitimate dromaeosaurid tracks, and that question can be
answered.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.