Re: AMNH Apatosaurus mount

["Alessandro Marisa" <iguanodontia@yahoo.it>]

----- Original Message -----
From: "Mike Limonite" <taradosgon@yahoo.com>
To: <Dinosaur@usc.edu>
Sent: Wednesday, May 14, 2003 2:40 AM
Subject: AMNH Apatosaurus mount

> For example, the postspinal laminae is not curved in
> the AMNH specimen on the cervicals (at least the
> anterior ones) I cannot tell (I'm looking at an old
> photograph of the individual being mounted) if the
> more posterior cervicals (last 3-4) have curved or
> straight post spinal laminae. CM 3018 has flat post
> spinal laminae, CM 563 and YPM 1980 do not.

Dear Mike, in regard to the postspinal lamina I don't know which
laminal-terminology you're based on for your comparison, but if you follow
Wilson's terminology (1998/1999) you can see that in both CM 3018 and CM 563
(I don't know about YPM 1980, because I've only a drawing of the eighth
cervical, that lack the neural spine) the postspinal lamina are absent from
the cervical series, and in both the specimens the postspinal lamina begin
from the fourth/fifth dorsal, the first presacral in which the neural spine
is not bifid.
Wilson (1999) describe the postspinal lamina as follows: the postspinal is
the complement to the prespinal on the posterior aspect of the neural spine
and probably served as the other attachment for the interspinous ligament.
The postspinal is usually ABSENT from the cervical region of most Sauropods,
althought it is present in posterior cervical of Titanosaurus colberti (and
Brazilian Titanosaur Series B). In posterior dorsal, the postspinal and
medial spinopostzygapophyseal coalesce to form a composite lamina. Like the
prespinal, the distribution of the postspinal within the vertebral column of
bifid-spined form is restricted to the posterior dorsal region. I think that
if we take a look at plate.XXV for CM 3018 and plate.XXXII for CM 563 of
Gilmore 1936 monograph on Apatosaurus we can see that the postspinal begin
at the level of the fourth or fifth dorsal, I think that in Apatosaurus the
postspinal lamina is restricted to the middle and posterior dorsal.

>Also the neural spines are  relatively tall, though not as tall
> as those of CM 563 or CM 3018 or as short as those of
> YPM 1980 (which are noticeably shorter than the other
> two).

I don't know about the cervical in the AMNH specimen, but in CM 3018 and CM
563 there're some difference, first of all in view of the fragmentary nature
of the CM 563's cervical there're only two cervicals, the eighth and ninth
(based on plate-number of Gilmore 1936) for which the comparison are
available. In CM 3018 the neural spine is directed slightly forward, while
in CM 563 it is nearly vertical, in CM 3018 in anterior and posterior view
the neural spine has a U-shaped bifurcation, while in CM 563 the bifurcation
is more Y-shaped, and in CM 563 this type of bifurcation is present also in
the most anterior dorsal, in CM 3018 the neural spine has a deep to shallow
cavity, absent in the neural spine of CM 563.

By
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Alessandro Marisa
Via Achille Grandi n°18
38068 Rovereto (TN) ITALY
Email: iguanodontia@yahoo.it
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