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Details on Hulsanpes



This post on Hulsanpes exists for two resons.  One, Mike Keesey requested
newer dromaeosaurs be featured.  Two, rumors of avian relations for this
taxon have been circulating around the list for a while.  Let's see what we
find.

Hulsanpes Osmolska 1982
H. perlei Osmolska 1982
etymology- "Perle's Khulsan foot", Altangerel Perle being a paleontologist
and Khulsan being the Mongolian locality where it was discovered.
mid Campanian, Late Cretaceous
Baron Goyot Formation, Mongolia
holotype- (ZPAL MgD-I/173) (juvenile) (30-40 cm) otico-occipital fragment,
metatarsal II (~34 mm), phalanx II-1 (~6.5 mm), proximal phalanx II-2,
metatarsal III (~39 mm), proximal phalanx III-1, metatarsal IV (~36 mm)
Diagnosis- metatarsal III flattens and widens to overlap metatarsal II in
anterior view.
Description-
This specimen was discovered in 1970 and described twelve years later.
Using Confuciusornis and Yandangornis as guides, we can estimate Hulsanpes
was about 30-40 cm long, but it was juvenile based on the rough bone texture
and the badly abraded articular joints.
The metatarsus "lacks even incipient fusion" (contra Holtz), and is
non-arctometatarsalian to the point that metatarsal III expands proximally.
It is fairly slender and metatarsal III is slightly more robust than the
others.  Distally, metatarsal III flattens and widens to partially overlap
metatarsal II.  The metatarsus is concave posteriorly, with metatarsal III
inset compared to the others.  The distal end of metatarsal III is shallowly
grooved with a symmetrical ginglymus.  The distal end of metatarsal IV is
transversely flattened and diverges from metatarsal III.  The articular
surface is narrow and undivided, with a groove posterior to it.
Pedal phalanx I-1 is rather similar to Deinonychus.  The proximal end has an
elongate articular surface divided asymmetrically by a ridge, showing that
the articulation of metatarsal II was ginglymoid.  The distal end is divided
asymmetrically by a long groove that extends more dorsally than ventrally.
The medial condyle is a bit wider and lower.  The ligamental fossae are deep
and the lateral one is more centrally placed.
Although the second digit could apparently hyperextend, the proximoventral
heel of phalanx II-2 was not well-developed.
Relationships-
First of all, let's try to figure out why Hulsanpes has been connected to
birds lately.  Tom Holtz wrote in September of 1995 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, Tom said that Hulsanpes is almost certainly not a
dromaeosaurid.  So Tom seems to be the start of all this.  If this is based
off a published work, I have not heard of it.  The description specifically
states that the metatarsus is unfused however, contradicting Holtz's
statement (but not his conclusion).  So, let's compare this species to basal
avians as well as dromaeosaurs to see if there is any additional support for
avian relations.
Osmolska allied this species with dromaeosaurids, but noted it resembled
troodontids in the narrow metatarsus and weakly developed second pedal
digit.  He dismissed avian origins based on the lack of fusion.
The non-arctometatarsalian pes agrees with both dromaeosaurs and basal
avians, but it is less constricted proximally than either Deinonychus,
Velociraptor, Rahonavis or Archaeopteryx, instead expanding slightly as in
Yandangornis, confuciusornithids, enantiornithines and Patagopteryx.  The
posteriorly concave metatarsus is absent in Velociraptor and Mononykus,
present in some enantiornithines, Patagopteryx and Vorona, but in Elmisaurus
as well, so this isn't neccessarily an avian character.  The second digit
was clearly hyperextendable, based on the dorsally extended articulation on
phalanx II-1.  This is of course present in dromaeosaurids and Rahonavis,
has been advocated for Archaeopteryx and Patagopteryx, but is absent in
Confuciusornis.  Hulsanpes certainly lacks the ornithurine character of
"proximal end of metatarsal III displaced plantarily compared to other
metatarsals".  Hulsanpes also lacks the enantiornithine character of
"strongly reduced metatarsal IV", though this is only verified to my
knowledge in American specimens and Concornis.  So Hulsanpes is a member of
the Yandangornis + Pygostylia clade based on the proximally expanded third
metatarsal, but not an enantiornithine or ornithurine (although comparisons
with Asian enantiornithines would be useful).  This leaves Yandangornis,
confuciusornithids, Vorona and Patagopteryx as possible close relatives.
Perhaps Hulsanpes is just basal to the Yandangornis + Pygostylia clade,
based on the lack of fusion, or it may be due to the juvenile age of the
specimen.  Hulsanpes appears to resemble Vorona and Patagopteryx more than
confuciusornithids based on the presence of a ginglymoideal articulation on
metatarsal II.  Data for Yandangornis is lacking.  So I recommend referring
Hulsanpes to the Yandangornis + Pygostylia group, but excluding it from the
Ornithurae and provisionally the Enantiornithines.
reference-
Osmolska, 1982. Hulsanpes perlei n. g. n. sp. (Deinonychosauria, Saurischia,
Dinosauria) from the Upper Cretaceous Barun Goyot Formation of Mongolia.
Neues Jahrbuch fur Geologie und Palaeontologie, Monatshefte 1982(7), pp
440-448

Figures of the metatarsus and phalanx II-1 are available to those who
contact me offline.

I hope I've cleared some things up regarding this oft-mentioned, little
understood taxon.  Next is another taxon that's been occasionally excluded
from the Dromaeosauridae- Adasaurus mongoliensis.  Then we'll get to some
recently discovered dromaeosaurids.

Mickey Mortimer