Re: Sloping terrain Re: Woman against Abelisaur

[Tim Williams <tijawi@gmail.com>]

Don Ohmes <d_ohmes@yahoo.com> wrote:

> That camels have died of thirst in the desert does not imply that camels are
> out of their element in the desert.
>
> Given an animal that spends a lot of time hip-deep in mud, one would
> certainly expect to occasionally find one preserved "in mired position" --
> perhaps even having died as a result of miring. E.g. -- drought can change
> mud to virtual concrete, and the change can occur rapidly. Elephants
> sometimes become trapped in muddy pits that have steep slippery sides --
> certainly their remains could be preserved in "mired position" -- and
> certainly they love mud, and are notably NOT hampered by their large size.


The hypotheses that _Giraffatitan_ individuals were trapped in mud at
the time of drought, and that large individuals were more susceptible
to miring, is based on an interpretation the taphonomic record at
Tendaguru:


Heinrich, WD (1999) The taphonomy of dinosaurs from the Upper Jurassic
of Tendaguru (Tanzania) based on field sketches of the German
Tendaguru expedition (1909-1913).  Mitt. Mus. Nat.kd Berl., Geowiss.
Reihe 2: 25-61


Henrich, WD, Bussert, R, and Aberhan M. (2011) A blast from the past:
the lost world of dinosaurs at Tendaguru, East Africa.  Geology Today
27: 101-106


Although both papers (especially the 2011 review) include some
speculation concerning how certain sauropod specimens came to be
preserved at Tendaguru, said speculation is based on taphonomy rather
than an intuitive interpretation of sauropod biology.


>> Larger individuals got stuck in the mud, but
>> smaller/lighter individuals could pull themselves out.
>
> I think this interpretation is not the best fit.


You may well be right.  But I'll counter with the relevant paragraph
from Heinrich et al. (2011):

       "Several fully articulated feet of Brachiosaurus, Janenschia
        and Tornieria, buried in an upright natural
        position, indicate that huge sauropods also visited the
        lagoon and, at least occasionally, got stuck in the
        mud. Such articulated parts of skeletons are rare and
        accumulations of disarticulated bones of sauropods
        prevail. Interestingly, all these assemblages are dominated
        by bones of adult individuals. Therefore, some
        palaeontologists believe that body weight was an important
        selective factor for the survival of sauropods.
        Because of their lower weight, juvenile sauropods less
        frequently mired than adults who often passed the
        point-of-no-return due to their heavier body weight."




Cheers

Tim