Here's a comment from Steve Brusatte, a paleontologist at the University of Edinburgh, and author of numerous books including The Rise and Fall of the Dinosaurs: A New History of a Lost World (2018):
"Nice article Richard ... it is a neat study. And jibes well with a lot of
what I've read recently while working on my next book, which is all
about bird origins and evolution. That crouched posture developed in a
transitional sequence as maniraptorans got bigger wings and flight
muscles, so it does seem to be a tradeoff with center of mass issues.
There were some scientists (John Hutchinson, Matt Carrano, and others)
who looked at the issue of limb posture in T. rex awhile back, and
concluded that it was a fully upright walker, not a croucher. So its
femur is a more traditional theropod dinosaur femur, its muscles more
traditional theropod dinosaur muscles, which make sense as it still
has the very long tail to which the main limb controller muscles
attached (that tail and its muscles are lost in birds). But...if this
new study is proposing that T. rex and other big theropods may have
employed something of a crouched posture or ground-based running, even
if it is just in some incipient stage, that would be really
intriguing. I'll have to take a closer look. Hope all is well. Cheers,
I've changed this article to reflect a correction from A.M. van Biljert, lead author of the Science Advances study. Small birds ALWAYS run with one foot firmly attached to the ground, and so do larger birds like ostriches when traveling at intermediate speeds. But at top speeds, ostriches and their ratite cousins switch to aerial running. "We show," van Biljert writes, "that this is partly attributable to how crouched the small birds are--if you’re very crouched, you spread out the range of speeds over which grounded running is optimal."
Here's a comment from Steve Brusatte, a paleontologist at the University of Edinburgh, and author of numerous books including The Rise and Fall of the Dinosaurs: A New History of a Lost World (2018):
"Nice article Richard ... it is a neat study. And jibes well with a lot of
what I've read recently while working on my next book, which is all
about bird origins and evolution. That crouched posture developed in a
transitional sequence as maniraptorans got bigger wings and flight
muscles, so it does seem to be a tradeoff with center of mass issues.
There were some scientists (John Hutchinson, Matt Carrano, and others)
who looked at the issue of limb posture in T. rex awhile back, and
concluded that it was a fully upright walker, not a croucher. So its
femur is a more traditional theropod dinosaur femur, its muscles more
traditional theropod dinosaur muscles, which make sense as it still
has the very long tail to which the main limb controller muscles
attached (that tail and its muscles are lost in birds). But...if this
new study is proposing that T. rex and other big theropods may have
employed something of a crouched posture or ground-based running, even
if it is just in some incipient stage, that would be really
intriguing. I'll have to take a closer look. Hope all is well. Cheers,
Steve
I've changed this article to reflect a correction from A.M. van Biljert, lead author of the Science Advances study. Small birds ALWAYS run with one foot firmly attached to the ground, and so do larger birds like ostriches when traveling at intermediate speeds. But at top speeds, ostriches and their ratite cousins switch to aerial running. "We show," van Biljert writes, "that this is partly attributable to how crouched the small birds are--if you’re very crouched, you spread out the range of speeds over which grounded running is optimal."