Re: Fw: late night thoughts: misunderstand what?

[David Marjanovic <david.marjanovic@gmx.at>]

> ......... I understood you earlier as saying that _average_ bodysize had 
> not
> changed through time.

Rather, there is no trend in sauropod body size.

> The above statement means that the maximal sauropods are equal through 
> time,
> a much more radical statement. In other words, at any timeslice in the 
> total
> time of their existence, the largest sauropods known from that
> timeslice are equal to those found in any other timeslice.

Not necessarily -- I'm just saying that there's no trend in sauropod body 
size.

> I learned years ago that the largest sauropods known from the L. Jurassic
> are larger than the largest known from the L. Triassic, whether measured
> by height at the shoulder, or weight,

Correct, but you must take phylogeny into account. (I said science is a lot 
of work!) The Early Jurassic *Gongxianosaurus* already reached 15 m in 
length, more than all other Early Jurassic and many Middle Jurassic 
sauropods, but it is very basal, more so than the Late Triassic 
*Antetonitrus* and *Isanosaurus* for example. Likewise, there's a 1 m long 
humerus from the end-Triassic of Thailand attributed to an adult 
*Isanosaurus*; that hints at a 15 m long animal, too.

> and that the very largest known are actually from the Cretaceous. Has this 
> changed?

Well... *Amphicoelias fragillimus*, from the Late Jurassic, is a size class 
of its own. Then comes the trackmaker of *Breviparopus*, estimated to be 48 
m long last time I checked, and Middle Jurassic in age. Next are 
*Argentinosaurus* and *Paralititan* from the "middle" Cretaceous together 
with *Turiasaurus* from the Late Jurassic and *Puertasaurus*. The 
distribution of giants and supergiants among the sauropods looks rather 
chaotic from the Middle Jurassic onwards.

> How big is the earliest known sauropod?

No matter which one that is (it's not easy to correlate between continents), 
it's a lot bigger than *Anchisaurus*, the smallest known sauropod, which is 
a lot younger. :-) Importantly, the reconstructed size of the _really_ first 
sauropod is also above that of *Anchisaurus*. Some sauropods got smaller, 
not larger.