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250 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
Presbyornis
FIGURE 7.—Left carpometacarpus of Presbyornis
pervetus, UCMP 126228, in dorsal view.
(a=cranial margin of trochlea carpalis.)
Discussion
Despite their close match in general skeletal morphologies,
Juncitarsus does differ from the Presbyornithidae in several aspects
that can be useful in the identification of fragmentary material.
Given that Juncitarsus is correctly referred to the Phoenicopteridae,
it may not be particularly closely related to the
Prebyomithidae (Ericson, 1997). Rather, the similarities between
the two taxa should be interpreted as symplesiomorphies.
Surely, this also is the explanation of the observed morphological
similarities between the Presbyornithidae and certain other
early Tertiary birds, such as the Graculavidae (Olson and Parris,
1987). Many aspects of the skeletal morphology might thus be
less useful in the reconstmction of the phylogenetic relationships
between these taxa. The similarities do show, however,
that these long-legged forms perhaps share a not much older
common ancestor, and that they are parts of a radiation of late
Mesozoic "shorebirds," as postulated by Martin (1983).
Ericson, Per G.P.
1997. Systematic Position of the Paleogene Family Presbyornithidae
(Aves: Anseriformes). Zoological Journal of the Linnean Society
(London), 121:429-^483.
In prep. The Early Tertiary Presbyornithidae (Anseriformes)—Paleoecology,
Anatomy, and Systematic Revision.
Howard, Hildegarde
1929. The Avifauna of Emeryville Shellmound. University of California
Publications in Zoology, 32:301-394.
Martin, Larry D.
1983. The Origin and Early Radiation of Birds. In A.H. Brush and G.A.
Clark, Jr., editors, Perspectives in Ornithology, pages 291-338.
Cambridge: Cambridge University Press.
Presbyornis
o-
Juncitarsus
FIGURE 8.—Right femur in external view. Juncitarsus gracillimus: USNM 468466 (in mirror image). Presbyornis
pervetus: UCMP 126244. (a=trochlea fibularis.)
Literature Cited
Martin (1983:320) suggested that the supposed radiation of
shorebird-like forms could possibly include "the progenitors of
the entire Tertiary radiation" of birds. This seems less likely,
however, given that many landbirds, such as galliforms, strigiforms,
caprimulgiforms, and cuculiforms, had evolved by the
early Tertiary, some already by the Paleocene (Olson, 1985).
These birds exhibit skeletal morphologies quite different from
the group of "shorebirds" to which Juncitarsus and the Presbyornithidae
belong. If we allow for the time necessary to evolve
these various adaptations, it seems justified to assume that a
few different phylogenetic lineages leading to subclades of
modern neognaths were established by the late Mesozoic. It
would not be very surprising if these lineages eventually prove
to correspond to Olson's (1985:84) tentative division of the
modem birds into the palaeognathous birds, "basal land bird
assemblage," "higher land bird assemblage," and "water bird
assemblage."
Olson, Storrs L.
1985. The Fossil Record of Birds. In D.S. Farner, J.R. King, and KC.
Parkes, editors, Avian Biology, 8:79-238. New York: Academic Press.
Olson, Storrs L., and Alan Feduccia
1980. Relationships and Evolution of Flamingos (Aves: Phoenicopteridae).
Smithsonian Contributions to Zoology, 316: 73 pages.
Olson, Storrs L., and David C. Parris
1987. The Cretaceous Birds of New Jersey. Smithsonian Contributions to
Paleobiology, 63: 22 pages.
Peters, D. Stefan
1987. Juncitarsus merkeli n. sp. stiitz die Ableitung der Flamingos von
Regenpfeifervogeln (Aves: Charadriiformes: Phoenicopteridae).
Courier Forschungsinstitut Senckenberg, 97:141-155.