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Re: Planet of the New Papers

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