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Unquillosaurus and Lameta abelisauroids
I just received the reprint, and will scan it soon so that pdf's may be
Novas and Agnolin, 2004. Unquillosaurus ceibali Powell, a giant maniraptoran
from the Late Cretaceous of Argentina. Rev. Mus. Argentino Cienc. Nat., n.s.
The proximal sulcus doesn't exist, and is actually the pubic peduncle of the
ilium broken and displaced. This is where the "ventrally concave pubic
peduncle" comes from, and the angle between the anterior and ventral edges
supports opisthopuby. What's normally seen as the acetabular surface of the
pubis is the posterior part of a very long ilial peduncle, leaving a very
tiny space for the acetabulum, which is said to resemble maniraptoriformes.
Jaime and I previously hypothesized Powell had the pubis reversed, and the
supposed lateral side was really the medial side. Novas keeps Powell's
orientation, remarking on the "prominent external longitudinal ridge" (=
pubic apron?), odd medially convex pelvic canal margins (concave if
reversed) and lack of an apron or medial symphysis. In addition, the medial
end is described as "flattened and lacks marks for the articulation with the
opposite bone". I see no reason to doubt Jaime's and my hypothesis, though
the outline in anterior view does resemble Deinonychus, with a sharply
narrowed distal portion.
As for phylogenetic identification, in addition to characters listed in the
abstract ( http://dml.cmnh.org/2004Aug/msg00011.html ), Novas notes the
reduced pubic acetabular surface, dorsoventrally low ischial peduncle and
reduced pubic symphysis as characters supporting a maniraptoriform
assinment, close to alvarezsaurids or basal avialans. He says it may not be
carnosaurian (one of my preferred hypotheses) because "carnosaurs retained a
pubic symphysis and developed very large pubic boots". If Jaime and I are
correct, the first character is moot. Many carnosaurs had smaller pubic
boots too- Monolophosaurus 16% of shaft length, Sinraptor dongi 24%,
Gasosaurus 26%, Sinraptor hepingensis 29% (23% in Unquillosaurus). Still,
the opisthopuby and ventrally concave pubic peduncle are rather convincing.
Lameta theropod paper discussion coming soon...
Undergraduate, Earth and Space Sciences
University of Washington
The Theropod Database - http://students.washington.edu/eoraptor/Home.html