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Re: Falcarius, new therizinosaur from Utah
Whew! It's even mentioned on the title page of Nature -- even though the
genome sequence of *Dictyostelium* is published in the same issue!
Comments and quotes (refs and mentions of figures removed):
Incredibly long tail. 40 vertebrae or something. At least in the
reconstruction -- the text (Methods) says "vertebral numbers estimated on
changing proportions of the vertebrae and comparisons with other
The alveoli for the first dentary teeth have twice the cross-sectional area
of the others. Gnawing teeth? In any case the condition is compared to the
premaxillary gnawing teeth of *Incisivosaurus*/*Protarchaeopteryx*.
Pneumatic fossae in the middle 3 (of 5) sacral vertebrae.
"Medial to distal caudals are more than four times as long as high. All
caudal vertebrae seem to be apneumatic with loss of caudal ribs and neural
spines distal to caudals 11â13, in contrast to the condition in derived
oviraptorosaurs and derived therizinosauroids."
Functionally tridactyl foot.
"A phylogenetic analysis provides strong support for the hypothesis that
*Falcarius* is the basalmost therizinosauroid known. *Falcarius* possesses
several maniraptoran synapomorphies not previously documented in basal
therizinosaurs, including hypapophyses on the presacral vertebral column,
bowed ulna, presence of a semilunate comprised of fused distal carpals one
and two, ischium less than two-thirds pubis length, and distally positioned
obturator process of the ischium."
Simplified cladogram (57 taxa, 231 characters):
| `--see below
| `--rest of Troodontidae
"See below", the clade that should be called Therizinosauroidea, is an
unresolved polytomy of *Segnosaurus*, *Erlikosaurus*, *Alxasaurus*,
*Nothronychus* and *Beipiaosaurus*.
"The Early Jurassic Chinese jaw from the Lufeng Series in southern China
described tentatively as the basal therizinosauroid *Eshanosaurus* is more
derived in having a lateral shelf and down-turned symphysis, which are
absent in Falcarius. Its therizinosauroid identification have been
considered problematic by some authors. *Falcarius* casts further doubt on
the affinities of [*]Eshanosaurus[*] by increasing its stratigraphic and
phylogenetic inconsistency. Given the discovery of North American members of
the therizinosauroid clade, together with the poor record of Middle
Cretaceous dinosaurs, it seems that the generally accepted hypothesis of an
Asian origin and radiation for Therizinosauroidea requires additional
"Collections from the Crystal Geyser Quarry made so far preserve a minimum
of ten individuals based on prepared femora, but the quarry size indicates
that perhaps hundreds of disarticulated individuals remain interred,
representing multiple growth stages as well as robust and gracile
morphotypes. The locality spans about 8,000 mÂ and the bone-bearing stratum
is, on average, 1 m thick, with bone densities in some areas exceeding 100
elements per cubic metre. There is no evidence of another small theropod
taxon, so all of the therizinosauroid materials are here referred to
*Falcarius*. In addition to the therizinosauroid elements, the quarry
contains rare remains of an unidentified ankylosaur. About 99% of all
identified bones from the type locality (about 2,000 identifiable bones)
Some bones are "associated", so perhaps articulated. Most aren't, however.
"Five unambiguous synapomorphies support Therizinosauroidea: teeth serrated
(reversal); ventral surface of dentary descends strongly posteriorly;
ventral edge of anterior ala of ilium hooked anteriorly; distal humerus with
large medial condyle, centred on distal end; and preacetabular portion of
ilium laterally flaring. The basal position of *Falcarius* is supported by
the absence of the following characters: labial face of dentary with lateral
ridge and inset tooth row; interdental plates on dentary; obturator process
of ischium does not contact pubis; metatarsal I without proximal
articulating surface. Therizinosauroidea + Oviraptorosauria characterized by
basipterygoid processes abbreviated or absent; suborbital fenestra reduced
in size or absent; basipterygoid processes hollow; symphyseal region of
dentary strongly recurved; maxillary and dentary teeth lanceolate and
Many typos, especially in the cladogram.