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Much ado about a bird
Has anybody out there in etherland had a look at either the specimen itself
or a cast of the early Cretaceous Chinese bird foot Gansus yumenensis
(Hou L. and Liu Z., 1984, A new fossil bird from Lower Cretaceous of Gansu
and early evolution of birds, Scientia Sinica 27: 1296 ff)? I would like to
add measurements of the phalanges of this specimen to my data base of
bipedal dinosaur and bird feet, and I need to know how much confidence I
can place on the measurements reported by Hou and Liu.
So here's what's confusing me: For openers, there
is a gap in the specimen, as preserved, between the tarsometatarsus and
the proximal ends of phalanges I-1, II-1, and what is either III-1 or
IV-1 (see below). Are the proximal ends of these phalanges as preserved
the actual proximal ends of the toebones, or are the proximal ends of
the phalanges missing?
I am also confused about the identification of digits III and IV on
this foot. There is a phalanx preserved adjacent to the end of the
tarsometatarsus corresponding to digit III, and so one might think this
bone to be III-1. What I take to be the remainder of the same digit is offset
from this bone, however ; if this IS digit III, though, it looks like there
would be 5 phalanges in the toe, which seems unlikely. Furthermore, Hou
and Liu give measurements of only 4 phalanges (including the ungual) of this
So maybe this bone adjacent to the trochlea III of the metatarsus is
in fact IV-1. This would give the normal phalangeal count for both
digits III and IV, which would make me much happier. Unfortunately, Hou and
Liu report measurements for only FOUR phalanges on digit IV. I could
rationalize this by thinking that they were only giving data for non-ungual
phalanges, except that they report measurements for 2 digit I phalanges,
3 for digit II, and 4 for digit III. Gack! Furthermore, the way the
length of phalanx IV-4 is reported on p. 1299 of the paper is odd, being
offset from the rest of the numbers, and with no number in the tenths place
behind the decimal point---making me wonder if this entry is a typo.
Looking at fig. 1 of the paper, I would guess that the length of ungual
IV-5 (assuming that's what it is) would be about 4 mm.
For those of you uninterested in bird tootsies, my apologies for
sending this out, but if any of you has seen the specimen, and can clarify
my understanding thereof, I'd be beholden to you.