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Hi all!
After doing some extra reading on Troodontids
and mainly the paper describing Sinornithoides, there is a short mentioning of
an unnamed Troodontid specimen named GIN 100/44 that was described by Barsbold
in 1987 which is the indeterminate Troodontid in The Dinosauria pictured on page
263.
The reference is: Barsbold, R.,
Osmólska, H., and Kurzanov, S.M. 1987. On a new troodontid (Dinosauria,
Theropoda) from the Early Cretaceous of Mongolia. Acta Paleontologica Polonica,
32: 121-132
For those interested, but there is no further
mentioning of this animal anywhere, except for the few pictures available in The
Dinosauria. These comprimise a right manus and metacarpus and the left pes and
left metatarsus. The material, at least as far as the text mentions it,
comprimises: a quadrate, partial dentary and poorly preserved postdentary
section, a partial basioccipital, a poorly preserved series of 5 cervicals, a
semilunate carpal, the complete metacarpus, several phalanges and unguals,
fragments from the pelvis and a partial left foot. Maybe more elements were
discovered, but these are the elements mentioned.
At a first glance at the age, I thought the
material could be assigned to a specimen of Sinornithoides (Currie, P.J.,
Zhiming, D. 2001), but as a I started to look at details, some differences
appeared. The most eye-catching one is the major difference in metatarsal
morphology: in GIN 100/44 the overall appearance is clearly more robust than is
in Sinornithoides, as is in the distal elements of the metatarsals. Another
thing regarding the metatarsus, in the unnamed Troodontid shows a distinctly
less compressed distal metatarsal III than this is the case in Sinornithoides.
Metatarsal I is placed more to the end in Sinornithoides compared to GIN 100/44.
Unfortunately the paper describing
Sinornithoides doesn't show the metatarsus in extensor view, so no further
comments can be made regarding this elements. Pedal digit II 2 is also
relatively longer in Sinornithoides, which is a primitive character in the
Troodontid family according to the Dinosauria. The manus is uncomparable between
the two, because the distal metacarpals are not illustrated in the
Sinornithoides paper.
The relationships that are discussed in the
Sinornithoides-paper available for GIN 100/44 state that this unnamed genus
seems to be the sister taxon to Sinornithoides which is again a sister taxon to
genera such as Byronosaurus, Troodon and Saurornithoides, which results
in:
|GIN 100/44
`- +Sinornithoides youngi
`- |Byronosaurus
|Troodon
|Saurornithoides
According to the text the preserved
basioccipital portion of the braincase in specimen GIN 100/44 had not developed
the lateral depression, or at least it still lacked the basioccipital portion of
that depression.
But my question is: what is it? Has it been more
thourougly described recently and does someone have any additional pictures of
this specimen that I could have? And what other info is available for the
specimen?
Thanks in advance!
Rutger Jansma
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