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SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
J Presbyornis
FIGURE 2.—Right coracoid in ventral view, with inset showing the head in medial view. Juncitarsus gracillimus:
USNM 468466. Presbyornis pervetus: UCMP 126194. (a=processus acrocoracoideus, Z>=facies articularis clavicularis.)
the Presbyornithidae); the scar for M. scapulohumeralis cranialis
forming a shallow to moderately deep, elliptical depression
(a narrow, deep scar in the Presbyornithidae); the fossa pneumotricipitalis
ventralis small and perhaps pneumatic (a large,
deep, nonpneumatic excavation in the Presbyornithidae); the
scars for Mm. latissimus dorsi posterioris and anterioris are directed
toward a point well distal of where the deltoid crest sets
off from the shaft (directed toward where the crest sets off from
the shaft in the Presbyornithidae) (Figure 4).
In the distal end of the humems, Juncitarsus differs from the
Presbyornithidae in having the attachment area of the anterior
articular ligament of Howard (1929) much more elevated and
lateromedially narrow; the processus flexorius not as ventrally
Juncitarsus Presbyornis
FIGURE 3.—Left scapula in dorsal view. Juncitarsus gracillimus: USNM
468466. Presbyornis pervetus: UCMP 126193 (in mirror image).
(a-craniodorsal margin.)
protmding; probably a well-developed sulcus for M. scapulohumeralis,
which is lacking in the Presbyornithidae; and the
two scars for M. flexor carpi ulnaris on the processus flexorius
distinctly unequal in size (the posterior is considerably larger),
whereas these scars are of about equal size in the Presbyornithidae,
or the anterior is the larger (Figure 5).
ULNA.—I have found no distinctive differences in the proximal
end, maybe due to the poor preservation of the only specimen
of Juncitarsus available. In the distal end, the tuberculum
carpale is short and directed cranially, not clearly craniodistally
as in Presbyornis (proximodistally much longer and blunter in
Telmabates).
RADIALE.—Although generally very similar, Juncitarsus
differs from Presbyornis (the only presbyornithid genus in
which this bone is known) in lacking the deep excavation of the
dorsal side and in having the incisure at the cranial side deeply
cut and not as wide (Figure 6).
CARPOMETACARPUS.—The only proximal end known of
Juncitarsus has the cranial margin of trochlea carpalis (bordering
the anterior carpal fossa) convex, not deeply concave as in
the Presbyornithidae (Figure 7). No difference has been found
in the distal end of the carpometacarpus.
FEMUR.—The femur of Juncitarsus seems to be more robust
than that in the Presbyornithidae. Furthermore, the femoral
neck in Juncitarsus is broader in proximal view; the impressiones
iliotrochanterici show a very different pattern than in the
Presbyornithidae; and the trochlea fibularis is concave, or flat,