

speed and ratios

Per made some comments worth discussing. 

Per argues that high cited speed estimates for ungulates in the wild may be 
accurate. But speeds from films can be way off if the frame speed is 
incorrect (this has happened in the literature). Speeds measured from chasing 
vehicles can be inaccurate is the speedometer is errant, which used to be 
fairly common especially in banged up field vehicles. The decades old claim 
that a wild horse ran nearly 20 miles at about 30 mph is itself suspicious. 
Was the speedometer properly calibrated? Did they REALLY chase a poor horse 
for 20 miles? It is most odd that the one effort to rigorously measure speeds 
in wild ungulates (Alexander et al. 77) could not get them to go faster than 
~30 mph. They made the point that thoroughbred horses are engineered for 
speed at the exclusion of other factors to the point that they are 
dysfunctional in other regards. Maybe wild ungulates don't get much over 30 
mph, it's a plausible point until it's rigorously demonstrated otherwise. 
That's how science is supposed to work from what I hear tell. Is a shame 
these basic questions are not better settled with sound data.
Cheetahs may use their extremely high but short burst speed to make up for 
the prey's head start. Antelope seem to try and dodge rather than flat outrun 
cheetah. Since force increases to velocity squared I wonder if animals could 
really turn as hard as they do if they were running nearly as fast as cars on 
highways. As cheetah (which are basically all legs and little gut) catch up 
with the turning prey (which are vegetation fermenting vats trying to run) 
the cat may have to slow down to avoid overshooting and being outmaneuvered. 
Rather like air-to-air dogflights, which occur at relatively slow speeds 
where hard turns are possible (which is why in Vietnam all dogfights occurred 
between subsonic Mig-17s [with big high lift wings] and US supersonic jets 
[with rather small low drag wings] that slowed way down to try to turn with 
the nearly Korean War Soviet machines  -- the supersonic Mig-21s [small 
wings] only made high speed climbing passes at US aircraft, popped off an 
Atoll missle or two, and then immediately left the area; likewise in WW II 
turing dogfights occurred in the 200-300 mph zone even though the craft could 
do 330-470). I don't know if anyone has done the work necessary to see how 
cheetah/ungulate combat really works. 

Concerning limb flexion, Per has shown that it was less in large theropods in 
general than in small theropods in general. However, as I explain in Dinos of 
the Air, small theropods were probably good climbers and leapers etc and this 
may bias the sample. In my Gaia paper I observed no consistent difference in 
knee flexion in two groups of theropods least suited for climbing and most 
adapted for running, ornithomimids from a few kilograms to the biggest 
tyrannosaurs. I have repeatedly shown in the literature with diagrams and 
everything that theropods of all sizes had bird type knees that were 
configured to be permanently flexed and would have been extremely vulnerable 
to total dislocation if straightened due to the structure of the lateral 
femoral condyle. People go on about the structural dangers of Tyrannosaurus 
running and then restore the 6 tonne beast with knees so straight that they 
would have been unbraced along the longitudinal axis and subject to 
dislocation on the next step. Ouch! No one has published a detailed 
refutation with diagrams and everything. I notice that in a lot of the 
computer generated diagrams of giant theropods with straight knees the 
resolution of the knee structure is so poor that the failure of the joint to 
be fully articulated is obscured. In more detailed drawings showing straight 
theropod knees the lateral condyle is clearly unarticulated with the 
tibia-fibula as though it had nothing to do and no purpose to serve, which 
leaves one wondering why big theropods had the lateral condyle at all. Since 
the knee of Tyrannosaurus had pretty much the same structure and orientation 
of a chicken, and was markedly different from that of sauropods and 
elephants, it should be concluded that it had a flexed rather than a straight 
knees. To argue that despite its knee anatomy big Tyrannosaurus had to have 
unflexed knees because big animals must have straight knees is going in 
circles and only serves to verify the latter hypothesis without verification 
by anatomy. Makes me dizzy just thinking about it. Instead the knee anatomy 
is clearly telling us that the big T had flexed knees like running rhinos 
rather than straight knees like walking elephants, and that theories that 
demand straight knees in giants may not be in accord with reality as many 
think. Human constructed hypotheses do not always explain reality.