Re: Falcarius, new therizinosaur from Utah

[David Marjanovic <david.marjanovic@gmx.at>]

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 
maniraptoran theropods".

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):

+--*Allosaurus*
|--*Sinraptor*
`--+--Tyrannosauridae
  `--+--Ornithomimosauria
     `--+--*Ornitholestes*
        `--+--Compsognathidae
           `--+--+--Oviraptorosauria
              |  `--+--*Falcarius*
              |     `--see below
              `--+--Alvarezsauridae
                 |--Dromaeosauridae
                 |--+--*Sinovenator*
                 |  `--rest of Troodontidae
                 |--*Sinornithosaurus*
                 |--*Microraptor*
                 `--+--*Rahonavis*
                    `--+--*Archaeopteryx*
                       `--*Confuciusornis*

"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 
testing."

"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 m 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) 
represent *Falcarius*."

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 
subsymmetrical."

Many typos, especially in the cladogram.