Does anything run like a theropod?

[Sight Reader]

I’m a dinosaur newbie, so I apologize if this is a silly question, but is there anything still around that runs and maneuvers like the non-avian theropods did? I looked at guys like ostriches but their power stroke seems to come more from push from the knee joint rather than from the hip. I don’t know if we humans are very good models of them either since we don’t have tails?

Anyway, I’ve seen beautiful, convincing animations of theropods running in straight lines, but I was having trouble picturing how a small, agile theropod might do a series of hard, abrupt turns as would be necessary to evade a pursuer. Could they plant their legs off to the side like we do when trying to surprise with a lateral cut - or did they have to keep their legs directly under their hips? If so, would that mean that they’d have to lean hard in a direction first before making a sudden change in course?

Thanks for clearing me up on this; the question is purely out of curiosity… thanks!

[John Harshman]

Clearly, birds are as close as you can get. They have shorter femurs and
longer tarsometatarsi, proportionately, than non-avian theropods. But
that still seems your best bet. Try looking at how roadrunners pursue
prey for clues. Or maybe secretary birds or seriemas. Evading predators
is probably the wrong behavior to examine, because most birds can just
fly away, and the ratites don't really have predators (of adults, at least).

[Pandora]

Not entirely true, but it takes three to tango:
https://youtu.be/pkhE14Rou-E?t=137

[Sight Reader]

Dang. I was hoping there would be something out there that could help me visualize how the little ones could zip and dodge about. The ostrich footage was interesting: I notice that it did not attempt to zigzag to evade the cheetah: it’s only hope seemed to be to accelerate, to make itself look big, and to kick. The turns it did attempt seemed relatively gradual and it seemed unable to do the sort of radical and sudden course changes that you might expect from dogs, rabbits or even humans.

Were the small, cursorial theropods - especially the little knee-high guys - also similarly limited? From just from looking at their bones, would you be able to tell if their hips allowed their legs to swing out, plant, and push the body laterally or did were the hips limited to forward and back leg motion? Is swinging legs really the only way to suddenly push a body sideways or are there other ways of doing it?

[Peter Nyikos]

Sight Reader hasn't posted to the active threads in three days, so it's time to revive an inactive one.

On Thursday, January 27, 2022 at 7:16:01 PM UTC-5, thesigh...@gmail.com wrote:
> On Wednesday, January 26, 2022 at 4:17:05 AM UTC-7, Pandora wrote:
> > On Tue, 25 Jan 2022 17:09:01 -0800, John Harshman

> > <jhar...@pacbell.net> answered the subject question as follows:

> >
> > >Clearly, birds are as close as you can get. They have shorter femurs and
> > >longer tarsometatarsi, proportionately, than non-avian theropods. But
> > >that still seems your best bet. Try looking at how roadrunners pursue
> > >prey for clues. Or maybe secretary birds or seriemas. Evading predators
> > >is probably the wrong behavior to examine, because most birds can just
> > >fly away, and the ratites don't really have predators (of adults, at least).
> > Not entirely true, but it takes three to tango:
> > https://youtu.be/pkhE14Rou-E?t=137

Above, John mentioned three birds that frequent open country.
But one needs also to look at birds that inhabit forests.

> Dang. I was hoping there would be something out there that could help me visualize how the little ones could zip and dodge about. The ostrich footage was interesting: I notice that it did not attempt to zigzag to evade the cheetah: it’s only hope seemed to be to accelerate, to make itself look big, and to kick. The turns it did attempt seemed relatively gradual and it seemed unable to do the sort of radical and sudden course changes that you might expect from dogs, rabbits or even humans.

That is because ostriches are built for straight-line speed, like horses. Forest animals need maneuverability, and the
ratite to study closely is the cassowary:

"Cassowaries can run at up to 50 km/h (30 mph) through the dense forest and can jump up to 1.5 m (5 ft). They are good swimmers, crossing wide rivers and swimming in the sea."
--https://en.wikipedia.org/wiki/Cassowary

> Were the small, cursorial theropods - especially the little knee-high guys - also similarly limited? From just from looking at their bones, would you be able to tell if their hips allowed their legs to swing out, plant, and push the body laterally or did were the hips limited to forward and back leg motion? Is swinging legs really the only way to suddenly push a body sideways or are there other ways of doing it?

I once read a fascinating book on what is known as Equine (horse) conformation. Alas, I don't remember the title, nor what it said about
details like this. It would be nice to be able to compare all the voluminous details about the bones and ligaments, etc. in the following
article with that of an animal built for maneuverability:
https://en.wikipedia.org/wiki/Equine_conformation

The reason I mention this book is that, much to my delight, it compared two Oligocene ungulates,
the early horse *Mesohippus* (ca. 40-30 mya) and camelid, *Poebrotherium,* (ca. 46—13 mya) for their running abilities.
The two were roughly the same size, but they occupied different habitats.

It said that on a straight-line racecourse, the camelid could beat the early horse hands down;
but in an obstacle course, the conformation of *Mesohippus* would make it the winner.
Unlike the modern horse *Equus,* it was a lithe, flexible animal who could run through
dense forest, but perhaps not as fast as a cassowary.

As forests gave way to grasslands over more and more of North America, the descendants
of Mesohippus split at least two ways; one lineage went on being forest animals but grew in height.
The second lineage is what lives on in *Equus*. It adapted to life in open country where straight line speed is at a premium,
as it is for the ostrich, whose range overlaps it to a considerable extent.


As for theropods, they might have been as varied as the ostrich and the cassowary.
If there are films of cassowaries running, they might give a good idea of what
some theropods might have run like.


Peter Nyikos
Professor, Department of Mathematics
University of South Carolina -- standard disclaimer --
https://people.math.sc.edu/nyikos/