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Speed in giants and cursors



In his recent comments John H. made some statements that warrent a brief 
reply and comments, some of which are also in reply to other assorted 
comments on the lists and in the media. 

The ability to achieve a suspended phase run is primitive and normal for 
amniotes that live on flat land and have well developed legs. Among living 
animals it is a rare and derived condition to not be able to run, terrestrial 
turtles and elephants being the chief examples. Among extinct amniotes 
unambiguous nonrunners include sauropods, stegosaurs, unitatheres, and giant 
slothes. 

Contrary to common claims (incl a Harvard researcher on NPR), elephants do 
not establish that large animals cannot run for two reasons: they cannot run 
at any size, and they cannot run because they are not designed to. If 
elephants could run when they are the size of horses and lost the ability as 
they grew up that would be one thing. But they are as unable to run when 
young as when grown up. (The best source to see this? Why the John Wayne 
African classic Hatari! You see, the female lead thinks her budding 
relationship with the Duke is over, poor thing, so she flees to the not so 
big city only to be chased by assorted vehicles and two baby orphan elephants 
that think she's their mum. Long stretches of film of the elephants going 
full tilt trying to catch up. Frame by frame analysis shows that they never 
achieve a suspended phase with all four feet off the ground. The little dears 
are fast walking their hearts out. [Aside from all the neat animals include 
galloping rhinos and giraffes and the really cool use of the rocket net to 
catch the monkies what's the main feature of the Kennedy era Hatari!? That 
everyone man and girl smokes like factories and swills alcohol by the gallon 
- ah the good old prepolitically correct days.]) As I've explained in the 
literature many a time, elephants of all sizes cannot run because they lack 
the anatomical adaptations to do so, most especially the long feet with 
flexible ankles needed to push off into a suspended phase. If all elephant 
sized animals with flexible ankles could not run then the hypothesis that 
giants cannot run would be supported. But all are extinct (your giant 
theropods, ceratopsids, iguanodonts/hadrosaurs, titanotheres, indricotheres, 
recently extinct horned rhinos that reached 5 tonnes), so it is not possible 
to so directly test the question and resolve it in either direction. I 
believe John said on NPR that elephants don't leap because they are too big. 
Again, they lack the limb adaptations needed to do leap so his statement is 
not proven by the example. 

For the above reasons, the burden of proof is not upon those who argue that 
giants can run, it is at least as upon those who argue they cannot. 

John suggests that "cursorial" adaptations are useful to any erect limbed 
animal regardless of speed, and that "the burden of proof is on people to 
demonstrate that these (cursorial) features are useless or unimportant for 
fast walking or slow running." No way and not even close. All living animals 
that have such limbs can run fast, so John's opinion is at best speculative 
as well as doubtful, and the burden is absolutely upon those who wish to show 
that cursorial features will evolve among, or be retained by, nonrunners. 
Bears and elephants roam long distances without cursorial limbs, and 
sauropods once did, and it seems to do them no harm, even the elephant 
locomotary energy efficiency is typical for animals of their size contrary to 
predictions that such heavy limbed beasts should be inherently energy 
inefficient. Interesting how real life often contradicts mere theory and 
calculations. 

It is notable that no wild ungulate has been shown to be able to exceed 30 
mph (carefully documented in Alexander et al 1977), claims of higher speeds 
are not verified. Nor has it been documented that speed in wild ungulates 
declines with size, data suggesting so is likewise not rigorously measured, 
while there are accounts in Muybridge of rhinos outsprinting horses and 
riders during hunts. When big tyrannosaurs and other extinct giants with 
flexible ankles ran it was probably in this speed range. Genetically 
engineered race horses can reach 43 mph (actually faster since the speeds are 
timed from a standing start) and cheetahs have been timed on a course at 65 
mph. Olympic sprinters can manage just 23 mph. 

As Tom H noted the limb ratios of tyrannosaurs are, contrary to propoganda to 
the contrary, in the high range usually associated with running. The 
tibia/femur ratio of tyrannosaurs including T rex were similar to those of 
horses - all the are more remarkable since the theropods were so much bigger 
- much higher than those of similar sized rhinos, and far exceed those of 
elephants. A strange pattern for animals that did not run. 

Greg Paul