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Re: "Largest" dinosaurs...



Pluto77189@aol.com wrote-

I assume you checked out this-
http://www.cmnh.org/dinoarch/2003Jul/msg00355.html

> I am a bit frustrated about these claims.  It seems that they are based on
WAY to fragmentary remains for
> such claims.  Even Spinosaurus, which remains SEEMED to be suggestive of a
huge animal, were not really, > ahhh...complete.

Not complete, but still unambiguously huge.  Its holotype has a dorsal
centrum 210 mm long.  That's >190% the size of the largest dorsal centrum in
the related Baryonyx holotype.  Baryonyx's length is fairly well known,
except for the tail.  And since vertebral length is what total length is
based on, our estimate should be quite accurate.  Baryonyx is ~9 meters
long, so Spinosaurus was ~17 meters.  You'd have to be off by a good fourth
of this length to make Spinosaurus smaller than the largest fairly complete
theropod skeleton (Giganotosaurus holotype).  Not likely in my opinion.

> I just find it difficult to put any credibility in these claims.  With
T-rex, we have sufficient remains to know--> definitavly--how big any of the
individuals was, at least in length, height, etc.  Recent therapods claiming
> the BIGGER THAN T-REX!!!! status are doing so with only one or two
fragmentary remains.

Well, there are only a few theropods that seem larger than Tyrannosaurus.
Giganotosaurus is known from a rather complete specimen, and Spinosaurus is
effing huge no matter how you look at it.  Even Deltadromeus is complete
enough to know its general proportions, except the head and neck.

> I cannot see how any such claim can be taken seriously given the inability
to accuratly extrapolate lengths > from the complete remains of OTHER
species using the FRAGMENTARY remains of "new" ones and
> scaling the up.--pardon the run-on.

Scientists do this for the same reason we feel justified in referring single
bones to a certain group.  Parsimony.  A huge spinosaurid is most likely to
be proportioned like a large spinosaurid, given no other data.  Well,
ideally we'd scale it allometrically, but spinosaurid growth series are
sorely lacking.  Anything has the potential to be strange in areas that
aren't preserved, but it's not scientific to assume such without evidence.
If we didn't make assumptions in paleontology, virtually nothing would be
known.  Phil Hore explained this in more detail.

> I saw the skeletal reconstructions of argintiniosaurus( I think it was
argintiniosaurs...) and Giganotosaurs
> mounted in a museam.  I Assumed that to do such an extensive
reconstruction, much of the fossils were
> known.  I was wrong.

Giganotosaurus carolinii
Holotype- (MUCPv-Ch1) (12.5 m, 5 tons) (skull- ~1.8 m) premaxilla, maxilla,
nasal, lacrimal, postorbital, quadrate, braincase, anterior dentary, teeth,
most cervical vertebrae (including axis and eighth cervical), most dorsal
vertebrae, dorsal ribs, first caudal vertebra, caudal vertebrae 7-21, two
distal caudal vertebrae, eight chevrons, scapula (727 mm), coracoid, ilium
(1.54 m), pubes (1.11 m), ischia (1.2 m), femora (1.43 m), tibia (1.12 m),
fibula, metatarsi, pedal elements

Argentinosaurus huiniculensis
Holotype- (PVPH-1) (22-26 m) partial neural arch of first(?) dorsal,
incomplete second(?) and third(?) dorsal vertebrae (490 mm), 3 incomplete
posterior dorsal vertebrae (500 mm, ~450 mm, ~450 mm), partial dorsal rib,
incomplete sacrum, sacral ribs, incomplete tibia (1.55 m)

> The fact that anyone could give an estimation in mass(for
argintiniosaurus) with a degree of error greater in > size than any living
animal EXCEPT for the sauropods, is in my book, enough evidence that they
had no
> buisness making such an estimation in the first place.

You must realize a few things.  Mass actually varies by quite a bit even in
the same individual, due to the availability of food and other factors.  So
even a modest 10% difference is going to be a LOT in a huge animal.  Also
realize that mass increases with the cube of length, so a 26 m long sauropod
will weigh 64% more than a 22 meter long one.  Thus, if you try to give a
realistic range of lengths (+/- 10%), you're going to get a much larger
realistic range of weights (+/- 33%).

Mickey Mortimer