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EQ (was RE: Tyrannosaur age-population distributions)

> -----Original Message-----
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu]On Behalf Of
> K and T Dykes
> <<If you look at the E.Q. (encephalization quotient) for tyrannosaurids and
> the E.Q. for chickens (and the E.Q.s for *all* living birds, in fact), you
> will find that _T. rex_ adults lag behind all extant birds in the Brainiac
> Department.>>
> I think I'll dare to suggest that bodysize may explain part of that, Phil,
> and I stress part.  Going by E.Q. alone (with no bodysize weighting), a tree
> shrew should be regarded as the brainiest mammal on Earth as its E.Q. is
> higher than mine.  (My wife actually confirms this is a reasonable
> conclusion.)  My E.Q. is about the same as that of a mouse.  (I'm not going
> to mention what my wife said about that comparison, as I was too stupid to
> understand it.)  E.Q. alone leaves various small birdies as prime candidates
> in quiz shows on television, and this might explain why Sylvester never got
> his paws upon Tweety Pie.

EQ DOES normalize for body size. It isn't the ratio of brain to body size: it's 
a **residual from the curve** of brain vs. body
mass. Specifically, it is:
EQ = (E<sub>i)/(E<sub>e)
were E<sub>i is the measured brain size, and E<sub>e is the expected brain size.

Traditionally (e.g., much of Hopson's work), the EQ curve used for dinosaurs 
compared them to the curve found in modern non-avian
E<sub>e = 0.005 P^0.6667
where P = body mass.

So the classic "Troodon is the brainest dinosaur" statement comes from Hopson's 
calculation that "Stenonychosaurus" had an EQ of 5.8
(in other words, about 5.8 times larger than expected of a 45 kg 'reptile').

E<sub>e for mammals, by the way, falls on a curve 0.12 P^0.6667.

                Thomas R. Holtz, Jr.
        Senior Lecturer, Vertebrate Paleontology
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796