Re: Planet of the New Papers

[Michael Mortimer <mickey_mortimer111@msn.com>]

Tim Williams wrote-

> Mickey Mortimer wrote:
>
> >  um... Hulsanpes is a troodontid. :)
>
> OK, I'm curious.  Why is _Hulsanpes_ a troodontid?  (I had it pegged as a 
> basal bird.)

As did I, back in 2000.  However...

The proximoventral heel on phalanx II-2 and hyperextendable second digit 
show Hulsanpes is non-ornithurine (sensu Gauthier) eumaniraptoran. When 
entered into Senter's (2007) matrix, Hulsanpes emerges as a troodontid based 
on the distally narrowing metatarsus. Hulsanpes resembles Sinovenator more 
than other troodontids in having a ginglymoid metatarsal II, but resembles 
most eumaniraptorans besides Sinovenator and some avialans in having a 
ginglymod metatarsal III. It shares anteroposteriorly deep metatarsals with 
troodontids more derived than Sinovenator. It is more basal than 
Sinovenator, Mei and other troodontids in having a broader metatarsus, and 
it is more basal than Mei and other troodontids except Sinovenator in having 
metatarsals II and IV subequal in thickness. The basic morphology of the 
metatarsus is extremely similar to Sinovenator, including the short 
metatarsal II with reduced distal condyle and large somewhat divergent 
condyle of metatarsal IV.

Osmolska allied this species with dromaeosaurids based on the ginglymoid 
second and third metatarsals and subequally developed metatarsals II and IV, 
but noted it resembled troodontids in the narrow metatarsus and weakly 
developed second pedal digit. She dismissed avian origins based on the lack 
of fusion. Senter et al. (2004) is the only published analysis to include 
Hulsanpes, which emerged as a dromaeosaurid because they miscoded the 
ginglymoid metatarsal II as absent in Sinovenator. Chiappe and Norell 
(Norell pers. comm. to Currie, 2001) think Hulsanpes is not a dromaeosaurid, 
but from "another more speciose branch of the Maniraptora". Holtz (DML, 
1995) wrote that the metatarsals and distal tarsals are fused at least 
distally in this species, like birds. He also cryptically said "future work 
may show why this is no surprise....". Then in May of 1997 (DML), Holtz said 
that Hulsanpes is almost certainly not a dromaeosaurid. The description 
specifically states that the metatarsus is unfused however, contradicting 
Holtz's statement (but not his conclusion). However, the only obviously 
birdlike character is the proximally expanded metatarsal III also seen in 
Yandangornis and basal avebrevicaudans. Though not included in Senter's 
character list, placing Hulsanpes in Avialae results in trees at least three 
steps longer. Thus the expanded third metatarsal would not be enough to 
remove Hulsanpes from Troodontidae. An additional test was carried out by 
adding Hulsanpes to a matrix of published Mesozoic birds (using the 
characters of Clarke and Chiappe, along with many more taxa). Though the 
excavated plantar metatarsus surface is similar to some pygostylians, 
Hulsanpes still falls out by deinonychosaurs at the base of the tree.

Of course after adding other paravians to Senter's analysis (Pedopenna, 
Neuquenraptor, Graciliraptor, Shanag, Pyroraptor, Variraptor, Ornithodesmus, 
Yixianosaurus, Archaeornithoides, Urbacodon, Jinfengopteryx), Neuquenraptor 
ended up as a basal troodontid and shoved Hulsanpes into derived 
Dromaeosauridae.  But there are still a few taxa to add (IGM 100/1005, 
Sinusonasus, Yandangornis, Dalianraptor, Jixiangornis for example) before I 
report the results to the DML.

Mickey Mortimer
The Theropod Database
http://home.myuw.net/eoraptor/Home.html