[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Flying giraffes



[Rescuing my own message from truncation]

Hi all,

Just to confirm my agreement with Jaime and Mike, basically: a lot of
what's said in Greg's comment has been mentioned elsewhere.

I've never hidden the fact that my giant azhdarchids are fairly
generalised creatures based on lots of different species. I make them
taxon specific where I can, depending on what I'm meant to be showing,
but these differences are often largely undectable in the finished
work (i.e. palatal structure). There's no other way to reconstruct
them presently, but they remain popular species for use in books and
exhibitions and, because they've always been based on fossil material
and their proportions are, to greater and lesser extents, OK, I've not
had a problem with this. They are certainly not 'misleading to the
public' (unlike the unsubstantiated claims about azhdarchid taxonomy
and diversity made elsewhere in this thread). My 2007 reconstruction
is full of errors (including the gigantic torso mentioned by Mike),
but people keep using it all the same. I've not used it for a long
time myself, but some folks seem to prefer it to more recent versions.
I do have another in the works which has corrected torso sizes and
slightly different proportions all round, but the basic total height
(4 - 5 m) is accurate. I think it's pretty universally agreed that the
combined length of the humerus, ulna and metacarpal in a 10 m span
azhdarchid equate to 2 - 2.5 m standing heights. Greg's (2012) article
in Prehistoric Times questioned this a while ago because it assumed
azhdarchid humeri were held horizontally when standing, but this
contradicts trackway data for azhdarchids and pterosaurs generally. If
anything, azhdarchid humeri were held more vertically than other
pterosaurs. Given that the giant Arambourgiania had a neck up to 3 m
in length (my own estimates suggest 2.3-2.9 m when taking into account
azhdarchid neck allometry) and that long necks are a shared feature
across Azhdarchidae, it's perfectly logical to present restorations of
giant azhdarchids with long necks. Put these neck and arm lengths
together and a giraffe-sized azhdarchid is hard to miss (taken as
'average' giraffe size here, 4-5 m). Greg's own 2011 restoration, when
the forelimb stance is corrected, is giraffe sized. It's not far off
giraffe-proportions even in it's squating pose.

As for the skull reconstructions: the situation is not as
straightforward as Greg indicates. We have at least two azhdarchid
skull types in the Javelina: the gracile Q. sp. anatomy and TMM
42489-2, the 'robust' rostrum and mandible mentioned by Greg above
(discussed here:
http://pterosaur-net.blogspot.co.uk/2010/02/tmm-42489-2-hypersonic-uberbass-slide.html).
We can be confident that the latter is an azhdarchid not because it's
from the Maastrichtian, but because it bears characteristic azhdarchid
anatomy in its rostrum and mandible. Several authors have now
mentioned this. TMM 42489-2 is about 800 mm long and, based on the
shape of the mandible and decreasing dimensions of the posterodorsal
extension of the premaxilla, it's clearly a fairly complete rostrum
belonging to a skull about 1 m or so in length. This is the same size
skull as we see in Q. sp.. Thus, TMM 42489-2 is not a giant at all,
and thus has no greater likelihood of representing Q. northropi than
the gracile skull type of Q. sp.. Other giants don't help deciding on
a likely skull type here either. Arambourgiania almost certainly has a
gracile skull, what with it's neck being so long and slender, while
the skull fragments known for Hatzegopertyx indicate a much chunkier
cranium. Which one fits Q. northropi? Do any? We don't know.

Furthermore, why is it a stretch to have three azhdarchid species in
one formation? We know virtually nothing about diversity of these
animals and cannot come close to evaluating 'typical' numbers of
pterosaur species for any given unit. Indeed, even when pterosaur
material is well preserved and abundant, there is virtually no
consensus among experts on taxon counts. So what is this assumption
based on? Until a full appraisal of the Q. northropi and Q. sp.
material evaluates their relationships to one another and other
azhdarchids generally, we really can't make any confident claims about
the affinities of the specimens in question here.

Right, that's a lot more than I mean to write: best sign off there.

Mark

On 21 June 2013 10:28, Ruben Safir <ruben@mrbrklyn.com> wrote:
>
>
> http://www.youtube.com/watch?v=5wmds4zq5Eg



-- 
Dr. Mark Witton
www.markwitton.com
Palaeobiology Research Group
School of Earth and Environmental Sciences
University of Portsmouth
Burnaby Building
Burnaby Road
Portsmouth
PO1 3QL
Tel: (44)2392 842418
If pterosaurs are your thing, be sure to check out:

- Pterosaur.Net: www.pterosaur.net
- The Pterosaur.Net blog: http://pterosaur-net.blogspot.com/
- My palaeontological artwork: http://markwitton-com.blogspot.co.uk/