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RE: Ceratonykus braincase described
Tim Williams wrote-
> On another alvarezsaur-related issue, Alifanov and Saveliev poo-poo
> the proposed alvarezsaur affinities of _Haplocheirus_. I initially
> didn't understand their reasoning: "because the manus of this species
> displays typical theropod features." But it's apparent later on in
> the paper that the authors have some pretty heterodox views on the
> evolutionary history of alvarezsaurs.
Yup, this dates to the original Ceratonykus paper. As I wrote then...
Alifanov and Barsbold question the placement of alvarezsaurids within
but their reasoning is not cladistic, based largely on autapomorphies (dorsal
jugal process absent; dorsal quadratojugal process absent; postorbital
quadrate; ventral flexure of endocranium absent; posteroventral dentary
absent; fused sternal plates; highly flattened metacarpal I; pubic symphysis
absent), characters absent in basal members (fused metacarpals; proximally
pubic tubercle; metatarsal III does not reach tarsus), characters present in
related theropods (enlarged prefrontal; dentary teeth in common groove;
caudal centra; obturator fenestra absent in pubis), and characters unknown in
alvarezsaurids (gastralia absent; pentadactyl manus). Other theropods are
to have lost dorsal jugal and quadratojugal processes, to have fused their
and lost their pubic symphyses as well, of course. The remaining
are unique among archosaurs as far as I know. The authors state "it is
interesting that many of the characters listed are recorded in
but while Lesothosaurus has enlarged prefrontals (primitive for archosaurs),
a flattened metacarpal I and a proximally placed pubic tuber, the other
listed and present in alvarezsaurids are absent. The synapomorphies shared by
Theropoda and its subgroups are far more numerous, and any suggestion for
alvarezsaurids outside that clade can be ignored.
It's one of those many times that make you wonder where the reviewers were (or
how much input Barsbold had). Russia seems to be stuck in the 70's where
phylogenetics is concerned, resulting in heterodox hypotheses, since there's no
constraint like parsimony to hold them in check. A similar example is
Ivakhnenko's (2009) "Eotherapsid hypothesis for the origin of Monotremata." It
has monotremes evolving from anomodonts and supports groups no cladist believes
in, like "Eotherapsida" containing sphenacodonts and some therapsids, but not
cynodonts and mammals. And there's Kurochkin's "enantiornithines are theropods
but ornithuromorphs aren't" ideas. Do they just lack access to new articles?
Are the professors all 'old school' and pass on outdated thinking to their
Ivakhnenko, 2009. Eotherapsid hypothesis for the origin of Monotremata.
Paleontological Journal. 43(3), 237–250.
Alifanov and Barsbold, 2009. Ceratonykus oculatus gen. et sp. nov., a
new dinosaur (?Theropoda, Alvarezsauria) from the Late Cretaceous of
Paleontological Journal (English edition). 43(1), 94-106.