Re: Amazing Tendaguru and the most prolific localities in the world

[Mike Taylor <mike@miketaylor.org.uk>]

> Date: Wed, 18 May 2005 16:47:03 -0500
> From: Tim Williams <twilliams_alpha@hotmail.com>
> 
>> From Christian and Heinrich (1998)...
>> 
>>      In addition, a left femur and a left zygopodium (tibia,
>>      fibula) have been included in the skeletal reconstruction.
>>      They have been obtained from the Middle Saurian Bed exposed at
>>      Tendaguru localities "Ni" and "Bo".  The left tibia and fibula
>>      from site "Bo" are of the same size as the installed right
>>      tibia and fibula of specimen S II (Janensch 1950b).  In
>>      contrast to that, the involved left femur from locality "Ni"
>>      is slightly shorter than the installed right thigh bone of
>>      specimen S II.
> 
> The femur from SII is incomplete.

Yes.  I've seen it described as such many times, but never read any
detailed statement of what the damage is and how it affects the
measurable length.  (This is surprisingly common: I think people like
the simplicity of describing a bone just as "damaged", or "partial" or
"fragmentary" and leaving it at that, as though that closes the
issue.)  However [disclaimer] I don't have Janensch 1961, which would
be the obvious place to look for such information.  However^2
[dedisclaimer] I am reliably informed that this paper's figuring is
inadequate ... plus of course there is that terribly inconsiderate
writing-in-German barrier to overcome.

Unfortunately my own photos do not much elucidate matters.  When I
went to Berlin it was mostly to study the vertebrae, so I didn't
carefully shoot any of the appendicular elements.  I do however have
two fairly good photos of the mount that show the right femur in situ:
        http://www.miketaylor.org.uk/tmp/sii/right-femur/lateral.jpeg
        http://www.miketaylor.org.uk/tmp/sii/right-femur/posterior.jpeg
Neither of these shows any part of the femur to be obviously
reconstructed.  The lateral view is particularly informative, as the
femur is shown next to the plaster replicas of the ilium and the first
caudal, which are very obviously replicas.  The surface of the femur
looks nothing like them.

At this stage, I would welcome a contribution from someone who knows
what they're talking about :-)

> Heinrich (1999) estimates a total length of 1960 mm for the femur,
> which makes it shorter than the SII humerus (2130 mm, which is
> complete).  Thus the humerus would appear to be longer than the
> femur, as in _B. altithorax_ (in which the humerus is only slightly
> longer than the femur).

In the _B. altithorax_ type, these two elements are so close in length
(203cm vs. 204cm) that they are essentially equal.  If the SII
measurements are to be trusted, then the humerus is 8-9% longer than
the femur, which _may_ be significant.

> However, because the SII femur is incomplete, we cannot ascertain
> the exact humerofemoral ratio for SII.  Do you have lengths for (a)
> the *restored* femur of the mounted specimen SII and (b) the femur
> from locality "Ni"?

Neither, I am afraid.  It is becoming increasingly clear that I am
going to have to learn some German.  Fortunately,
"centroparapophysealleiste" is easy to translate :-)

> In any case, it appears that the mounted skeleton is not only a
> composite of several comparably-sized individuals, but made up of
> individuals from <different horizons>.

Yes, but only just.

> Brachiosaur elements from both the Middle and Upper Saurian Beds
> went into making the mounted skeleton.

The Middle and Upper Saurian Beds are separated by only about one
million years (Russell et al. 1980), so it is perfectly within the
bounds of reason that the animals above and below the marine incursion
are very similar.

> Can we be 100% certain that the brachiosaur specimens from both
> horizons (Middle and Upper Saurian Beds) come from the SAME species?

Can we be 100% certain that the brachiosaur specimens from either
_one_ of these beds come from the same species?  Not really.  It's all
a judgement call.  However, while there are noticable
("species-level") differences between the _Dicraeosaurus_ material
from the Middle and Upper beds, I have never heard it suggested that
the same is true of the _Brachiosaurus_ material.  (BTW., I seem to
recall reading somewhere that the more recent _Dicraeosaurus_, may be
more closely related to _Amargasaurus_ than to its apparent ancestor
_D. hansemanni_.  I don't recall the details, though.)

> (To complicate matters further, alleged _B. brancai_ material is
> also reported from a THIRD Tendaguru horizon: the "Transitional
> Sands between _Trigonia smeei_-Bed and the upper Saurian Bed"
> (Heinrich, 1999)).

Well, sort of.  The Trigonia smeei bed is the result of the incursion
between the Middle and Upper Saurian Beds, so your third horizon is
between the first two.

However, now that I check my Russell et al. 1980, I see that their
Table II (page 171) shows (from oldest to youngest) one
_Brachiosaurus_ individual known from the "Base, Middle Saurian Bed",
26 from the Middle Saurian Bed, three from the Lower Transitional
Sands, four from the the Upper Transitional Sands and ... [drum-roll]
NONE from the Upper Saurian Bed.  That is of course in conflict with,
for example, Christian and Heinrich's (1998) assertion that:

        A fairly complete caudal series of 50 vertebrae
        recovered from the Upper Saurian Bed at Tendaguru site
        "no" has been installed as the tail of the skeleton
        (Janensch 1950a, b).

I have no idea what's going on here.  Anyone?

>> * Paul claims that the first three neck vertebrae are missing (but
>>    this I know to be a mistake, as C3 is both figured in Janensch 1950
>>    and on display in a non-public gallery).
> 
> Hmm... both SI and SII have many cervicals preserved (six and
> eleven, respectively) (Heinrich, 1999).

Yes indeed.  Cervicals 2-6 of SI are nicely mounted in a row (though
sadly down in the basement, where no-one can see them):
        http://www.miketaylor.org.uk/tmp/si/c2-6.jpeg
C7 is just below them; you can see its neural spine in the photo.  The
"eleven preserved cervicals" of SII are of course C3-13; the problem
is that the spine is preserved only in C3-5 and C8; the rest are just
centra.  So AFAIK _nothing_ is known of how the brachiosaurid neural
spine develops through C9-D3.  A sobering thought.

>> * Paul claims that the tail is too small for the rest of the mount,
>>    but Christian and Heinrich say that "its size seems to correspond
>>    well to main skeleton S II".
> 
> This may be a judgement call, considering that the tail of SII is
> not actually preserved.

Yes indeed.

REFERENCES

Christian, Andreas, and Wolf-Dieter Heinrich.  1998.  The neck posture
of _Brachiosaurus brancai_.  _Mitteilungen aus dem Museum fur
Naturkunde, Berlin, Geowissenschaften, Reihe, 1, p73-80 (German sum.)

Janensch, Werner, 1961, Die Gliedmaszen unde Gliedmaszengurtel der
Sauropoden der Tendaguru-Schichten: Palaeontographica, 7 (1), teil 3,
lief. 4, pp. 177-235.

Russell, D., P. Beland and J. S. McIntosh.  1980.  Paleoecology of the
dinosaurs of Tendaguru (Tanzania).  Memoirs Societe Geologie Francais
59 (139): 169-175.

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