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

Re: Deinocheirus

I did it again, didn't I? Pointed out a few characters without 
describing them too far (or not at all). Damn. Gotta stop doing that. 
Well, here goes:

Jonathan R. Wagner wrote:

>Jaime Headden wrote (on _Deinocheirus_):
>>The scapula and coracoid point at the [oviraptorosaurs], [...]

>In what way?

In that the scapula is anteriorly flanged, both dorsally and ventrally. 
This is true, also, of ornithomimosaurs. The scapulocora- coid is 
pentagonal in general shape, with a sharp dorsal sutural prominence; the 
glenoid joint is also processed post- and pre- in both groups. The 
coracoid deeply juts down like a finger on all three forms, giving an 
interesting synapomorphy that no other theropod enjoys.

>>[ornithimimosaurs and oviraptorsaurs]
>>when considering that the two groups are pretty close to each 
>>other anyway, in a sister-clade relationship-like way,

>Interesting... is your source on this Sereno 1997?

My source is myself. Sorry, but I can name as references all photographs 
and drawings (published in the '93 National and _Dinosaur Encylopedia_ 
British version---I don't know the publisher, and don't have the book on 
hand---and in Glut's book, either first edition or second of the 
_Dinosaur Dictionary_ or whatever book it was in [getting very vague 

Now, sister-taxa characters are the scapulocoracoid (above) forelimb 
structure, femur, and pelvis (degrees from *Gallimimus*).

>>not unlike allosaurs and metriacanthosaurs [sinraptorids].

>Considering that _Metriacanthosaurus_ is not well known at this time 
>(although it appears to share one synapomorphy with Allosauridae 
>proper), I would encourage you to use the officially named taxon 

I use both, and here's why:

Metriacanthosauridae ~
*Metriacanthosaurus* + *Yangchuanosaurus*, their common ancestor, and 
all descendants thereof, minus sister group Allosauridae.

*Sinraptor* + *Yangchuanosaurus*, their common ancestor, and all 
descendants thereof, minus sister group Allosauridae.

The pelvis of Yang and Metria are very similar, and Sin is more 
divergent, except for characters of the vertebrae, skull, and ischium; 
pretty good characters, but we might have a subfamily for this one 
genus. The supposed metriacanthosaur from China is considered very 
similar to Metria, and being Chinese, could be metriacanthosaurid 
[sinraptorid], thus quantifying the two---but slim evidence, and 
therefore _nomen dubium_.

I based my assumption of Paul's taxon because PDW is considered a 
"paper" and viable reference for such work, is an officially recognized 
work, and therefore valid. Metriacanthosauridae holds priority, but as 
you said, is based on slim-pickin's. Until quality data is found, I will 
consider both doubtful, but based on the rules of priority, 
Metriacanthosauridae is valid.

>>but the forearm still looks a lot like oviraptorosaurs to be too 
>>close for comfort. Ah well, nothing's easy.

>I am afraid I simply do not know enough about the subject to tell
>this myself. Are these similarities derived?

Curve of the humerus compared between *Deinocheirus* and *Harpy- mimus* 
(in the strongest curve I've seen in the Ornithomimosauria) and 
*Oviraptor* are all similar, and even close to *Anserimimus*; shortened 
ulna compared to humerus, and metacarpals very strong, the claws 
similarly curved and "knobbed."

Derived? Convergent would be a good guess, but I go with derived, more 
on the line of giganto-paleo-arctometatarsalian, or the first of such.

o_(unnamed node)
    |  \
    |   \_Ornithomimosauroidea

The clade above proposes this relationship, and is quite similar to what 
has been defined before---*Deinocheirus* lies between ornithomi- mosaurs 
and oviraptorosaurs. More detail, like I said, needs to be found of this 
giant, and the known vertebrae and ribs need to be examined, not just 
the arms.

>>So, we get convergence in this dinosaur, [...]

>I'll try to contain my shock. :)

Convergence on the part of the ornithomimosaurs.
>>On a project with some theropods (allosaurians to be exact) that 
>>I'll be posting soon, I've run into the chance of making 
>>proportionate ratios, and one of these is a humerus-to-neck ratio.

>As many workers have commented on, ratios really aren't always all
>that useful. They may help to quantify a general observation ("arms 
>greater than 75% of dorsal vertebral column length" works better than 
>"long arms"). However, allometry, changes in proportions during 
>ontogeny due to differential growth, can really mess with ratios. 
>There are statistical methods designed to "filter" allometry, if you 
>will. Unfortunately, they are not as accessable as ratios. 

When *Deinocheirus* came to light, he was called a 30ft. giant 
ornithomimid derived from the ornithomimid _ancestry_. Oviraptorosaurs 
are also derived from the same ancestry, though it is unclear who that 
long-ago-ancestor is, or will we still have to dig? My ratios agree 
that, on the larger side of the 25-27 foot span, I'm pretty close. 
Sizing up the arms to either oviraptorid or ornithomimid dimensions 
brings us to the same variability. Even comparing the arms to 
therizinosaurs, we come to the same conclusion in length, so one can 
safely assume that, if my ratios are not exact, they are pretty close to 
the truth and very useful as estimates.

>Just thought I'd point this out, in case somebody doesn't seem all
>that impressed with whatever ratios you come up with.

I understand. I should not get ahead of myself as I did previous- 
post--wise, but I had a reason to do so. I had a "strong feeling" and it 
verified by good ol' scientific double-checking. My allosaur ratios were 
compared, too. The formula for the ratio is, by the way

                               t = fx

where t is the total length
      f is the femur length
  and x is the ratio between the two

or, the total length equals the femur length (in meters of feet) 
multiplied by the total length. The ratio I got from *Allosaurus atrox* 
in both juvenile and adult specimens was a 9.0 average, and the ratio 
proved itself backwards; I tried the adult ratio on the juvenile and 
vice versa, and my end figure varied only to the margin of 1/4 to 1/3 of 
a meter, very small room for error. Not exact, but neither is 
dinosaurology. The exact same method on *Oviraptor* and *Gallimimus* was 
also workable.

After the first post, by the way, I saw *Garudamimus'* metatarsals, and 
they resemble *Oviraptor's*, in proportion and general physiology.

Jaime A. Headden

Get Your Private, Free Email at http://www.hotmail.com