Re: achillobator

["Mickey Mortimer" <Mickey_Mortimer111@msn.com>]

ville sinkkonen wrote-

> this was write in old dinosauricon page.
>
> "A large deinonychosaur with unusual pelvic features."
>
> Why the pelvic features are unusual?

>From http://www.cmnh.org/dinoarch/2000Oct/msg00476.html -
The ilium is very unique in structure.  It is very tall with a short
preacetabular process and longer postacetabular process.  The preacetabular
process is like a dorsoventrally expanded version of Deinonychus', with a
posteroventrally slanted concave anterior edge.  The dorsal margin is
slightly convex and slopes ventrally over the postacetabular process.  The
postacetabular process is quite tall, extends ventrally past the ischial
peduncle and has a vertical posterior margin, with a posterodorsal and a
posteroventral tubercle.  The pubic peduncle is nearly vertical and has a
concave ventral edge facing slightly posteriorly.  The ischial peduncle is
reduced, perhaps with a prominent antitrochantor, and the acetabulum is
partially closed off medially.  Several sinuous ridges are present on the
lateral surface above the peduncles and acetabulum.  In addition, there are
many other ridges and striations for various muscles on different areas of
the medial and lateral surfaces.
The pubes are well-preserved and distict from other dromaeosaurids.  I
estimate they were projected ventrally or slightly posteriorly.  They are
straight with the proximal end expanded a bit anteriorly and a small
obturator notch.    There is no pectineal process and the shafts are
circular in cross section.  The distal foot is slightly longer anteriorly
than posteriorly with a pointed anterior foot and a convex ventral edge.
The two pubes are joined for 69% of their length and have straight lateral
margins the whole way down, unlike the narrow foot of Deinonychus.
The ischium has a more proximally placed obturator process than Deinonychus
(18% down shaft) and is longer compared to the pubis (69%).  The pubic
peduncle is narrower, the obturator process longer and the distal end is
blunt.  There is a small proximodorsal process.  The two ischia were not
fused, but may have had a mobile articulation.

Mickey Mortimer