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

Massive macronarians with missing measurements (long)



(How do you like that for some alliteration? ;) )

I was/am trying to work on a research paper dealing with the size of sauropod 
dinosaurs, and for that my plan was to restore the skeletons of multiple large 
titanosaurs in multiple-views for each genus (most of which have not been given 
a rigorous skeletal treatment, to my knowledge).  However, upon getting the 
research papers that describe them, there is an apparent lack of measurements 
for many of our massive macronarian friends. Most frustrating is when a taxon 
is 
known from fairly complete remains, and yet measurements of the material are 
almost completely lacking or are contradictory.

A case in point is _Futalognkosaurus_, for which an apparently complete 
skeleton 
is known, but for which measurements are lacking. The first paper in which it 
was described had an almost complete lack of measurements, with the exception 
of 
a 137 cm length for the pubis. The second paper on _Futalognkosaurus_  had a 
few 
more measurements, but still not enough to give a complete picture. For 
instance, in regards to dorsal vertebrae length, the latter paper says, and I 
quote:

"The ten articulated dorsal vertebrae are partially prepared, all being 
opisthocoelous (Fig.14). The most anterior dorsal has an elongated centrum and
the second is 2/3 the length of the first. The centrum length gradually reduces 
in the more posterior elements of the sequence, with the first one being 43cm 
long and the last one 28cm (without considering the anterior ball)." 


Now, from the wording here it isn't clear if the first *posterior* dorsal  is 
43 
cm long or if the first dorsal vertebrae in the dorsal column is 43 cm long 
(which makes a big difference in regards to total torso length and because 
there 
is sometimes a clear distinction between anterior and  posterior dorsals, 
evidently). The wording is not clear. Assuming it is the first dorsal, for the 
length of the second dorsal, why not just list the length, instead of saying it 
is 2/3 the length? What does that mean? Is it 2/3 of the total length of the 
centrum of the first dorsal (including the anterior "ball"), or is it 2/3 of 
the 
*functional* length of the first dorsal? Is this 2/3 in as exactly 
66.66666......% of the length of the first dorsal or 2/3 as in 67% or 66%, or 
as 
in "2/3 of the Senate majority" which is actually 60%? Assuming the former, 
then 
the functional length of the 2nd dorsal is ~28.7 cm long, which means if 
centrum 
length gradually reduces to 28 cm functional length for the 10th dorsal than 
the 
total dorsal column length is just shy of being 300 cm long (my exact estimate 
is 298.4 cm, but I digress). To compare, the dorsal column of the HMN SII 
_Giraffatitan brancai_  is estimated by Greg Paul to be about 378 cm for its 
*12* dorsals, which means, that on average, the dorsal column of 
_Futalognkosaurus_ is about 79% of the length of _Giraffatitan_ and roughly 95% 
of the length per individual vertebrae. So it is not immediately clear that 
_Futalognkosaurus_ was the 32-34 m in length as originally claimed, especially 
since HMN SII was only about 22.3 m long (if one goes off of Paul's estimates).

Further problematic, is that in the original paper, the scale bar was off in 
the 
skeletal as noted by Matt Wedel and Mike Taylor on SV-POW! Now, one would hope 
this scale bar issue would be correct in the follow-up paper. But, no, in fact, 
for the cervical vertebrae for which multiple views are given, one gets 
consistently inconsistent lengths! Going off the scalebars in Fig. 3, the atlas 
is ~27 cm tall, but in Fig. 4, the scalebar indicates a height of ~20 cm tall. 
In Fig. 5, the scalebar indicates a total preserved length for the axis of ~35 
cm, but in Fig. 6 it appears to be ~32 cm long. In Fig. 7, the scalebar 
indicates a height of 26 cm, but in Fig. 8, ~32 cm tall. In Fig. 11, the 
photographed portion of the posterior cervical from base of the posterior 
portion of the centrum up is indicated to be ~101 cm tall, but in Fig. 12 it is 
80 cm tall (also odd is that the parapophysis visible in Fig. 11 disappears in 
Fig. 12). So what are the dimensions of these cervicals? I do not know. I made 
an attempt to contact Jorge Calvo as well as Bernardo Gonzalez Riga about this, 
but neither have replied to my emails. My hope is that someone on the list has 
personal knowledge and is willing to contact me about this issue, but I'm not 
holding my breath. At any rate, _F. dukei_ is apparently far shorter in length 
than originally reported (maybe only 25 meters in length compared to 32-34 
meters as originally reported). 


However, Calvo et al. (2007) and Calvo et al. (2008) are not the only papers in 
which this is a problem. Take the description of _Argentinosaurus_ for instance 
and the figures therein. In the paper, the maximum width between the 
diapophyses 
for the dorsal described as potentially the first dorsal vertebrae is 129 cm 
and 
77 cm from between the parapophyses. However, depending on which measurement 
you 
"believe" the apparent width from the figures between the diapophyses is ~122 
cm 
or the width between the parapophyses is ~80 cm. Similarly problematic, is that 
measurements for the centrum lengths are only given for 2 of the 5 vertebrae 
for 
which measurements could be given. In light of the apparent impreciseness of 
the 
drawings, scaling from known measurements might be problematic. However the 
measurements I get are as follows:

2nd? dorsal (preserved portion)...~43 cm
3rd? dorsal...49 cm (given in paper)
Fused posterior dorsals: anterior...46 cm
                                    posterior (preserved proportion)...44 cm
Posterior dorsal...50 cm (given in paper)

(Note, however that Novas revised the sequence positions of these vertebrae 
(but 
I forget the reference), so that the 2nd? is actually the 10th dorsal, the 1st? 
is actually the 5th, the single posterior dorsal is the 4th, and the fused 
posterior dorsals are actually the 6th and 7th. The 3rd was still considered 
the 
3rd.)

And again, vertebral measurements are missing for _Andesaurus_  in the original 
description (although measurements are given for the appendicular elements...), 
and only 3 of the preserved 31 vertebrae are figured, and only 2 of these have 
scalebars with a listed measurement for the scalebar. In view of the previous 
problems mentioned with scalebars, I am hesitant to take these scalebars at 
face 
value. Although, if one did take them at face value, _Andesaurus_ was 
apparently 
not as large as some have estimated. The posterior dorsal then is only about 23 
cm long in functional length, which is about 82 % the length of the posterior 
dorsals of _Futalognkosaurus_ which suggests a length of 20-22 m for 
_Andesaurus_ or even less.

Another case is Daxiatitan. Known from 22 vertebrae, measurements are only 
given 
for 5 of the cervicals and none of the dorsals or caudals, also only 2 of the 
cervicals and 4 of the dorsals are figured. Quite similar to _Euhelopus_ in 
anatomy, and some of the elements of _Daxiatitan_  overlap with _Euhelopus_,  
in 
particular, the overlapping posterior cervicals and anterior dorsals of 
_Daxiatitan_ are 6.1 m compared to 2.06 m in _Euhelopus which may mean 
_Daxiatitan_ was ~3.03 times the length of Euhelopus. The tail of _Euhelopus_ 
is 
unknown, but comparing from other sauropods the tail may have been about 3 
meters long, with the precaudal series about 6 meters long for a total length 
(excluding the skull) of 9 meters, meaning _Daxititan_ may have been over 27 
meters long. Unfortunately, the total width and height of the vertebrae are not 
given so it is difficult to compare in the other dimensions. However, if it was 
basically a _Euhelopus_ scaled up by 3.03 in each dimension, it may have massed 
over 27 times that of _Euhelopus_, meaning if _Euhelopus_ massed 2800 kg, 
_Daxiatitan_ *might* mass over 75,600 kg! That is, it might be one of the 
largest sauropods. However, we can't be sure because the other dimensions of 
the 
vertebrae are not given! 


Similarly, _Puertasaurus_ has a anterior dorsal vertebrae (considered to likely 
be the 2nd dorsal) 106 cm tall and 168 cm wide. However, the centrum length is 
not given! Scaling off the illustrations, the centrum is ~41.6 cm long in 
total, 
with a functional length excluding the anterior convexity of ~30.3 cm long. 
_Puertasaurus_ has some similarities with _Futalognkosaurus_ , and in Calvo et 
al. (2008) paper on _Futalognkosaurus_ anatomy, the anterior dorsals are 
described as being 100 cm wide between the transverse processes. This would 
seem 
to indicate that _Puertasaurus_ is 68% wider than _Futalognkosaurus_. However, 
as I estimated above, the D2 in _Futalognkosaurus_ is around 28.7 cm long, 
meaning _Puertasaurus_ is only about 5.5% longer than _Futalognkosaurus_. So 
instead of being 1.68^3=4.74 times the mass of _Futalognkosaurus_, 
_Puertasaurus_ *might* only be 1.68*1.055*1.055=1.87 times the mass of 
_Futalognkosaurus_.

This illustrates why, in the case of _Daxiatitan_, for instance, one needs 
multiple measurements of each vertebrae (total height, length and width). So 
while _Daxiatitan_ might be 3.03 times the length of _Euhelopus_,  maybe it is 
a 
much gracile animal and only mass maybe 5 times the mass of _Euhelopus_ for a 
mass of maybe 14,000 kg versus 75,600 kg.

In conclusion, all sauropod workers should have to recite to themselves when 
working on "their" specimen: "Measure my massive macronarian!" (from hereon, 
M^4. More alliteration--it's a mnemonic device, so use it). So please, if you 
are working on a large sauropod (or a small one, or any dinosaur or extinct or 
extant vertebrate), remember to measure your massive macronarian! It's science, 
it ain't that hard people, and people such as myself will be able to do useful 
work and cite you for it! 


Hopefully I haven't hurt any one's feelings for criticizing their work, which 
was not my intention, but something has to be said! And if anyone has, or knows 
where I can get, more reliable information on measurements, by all means send 
it 
my way! And if you feel I have unfairly criticized your or someone else's work, 
email me and we'll talk.

Best regards,

Zach