PDF (Lo-Res) - Smithsonian Institution Libraries

316 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
5mm
B
5mm
FIGURE 3.—Fregata magnificens Mathews (Neognathae). The antorbital area of the skull in A, lateral, and B, dorsolaterocaudal
views. Each scale bar=5 mm. (j=jugal, l=lacrimal, m=maxilla, n=nasal, nf=nasal foramen,
pl=palatine, u=uncinate (lacrimopalatine).)
naths and in nine families representing six neognathous orders,
including Fregatidae (Pelecaniformes), Procellariidae and Diomedeidae
(Procellariiformes), Laridae and Alcidae (Charadriiformes),
Cariamidae (Gruiformes), Accipitridae (Falconiformes),
and Cuculidae and Musophagidae (Cuculiformes)
(Burton, 1970; pers. obs.). Monophyly of this set of taxa is out
of the question, and four of the included orders (Pelecaniformes,
Procellariiformes, Charadriiformes, and Gmiformes)
have been repeatedly considered to be among the earliest neognathous
branches. In addition, strong evidence of the presence
of the uncinate has been found in Hesperomis (Elzanowski,
1991). This suggests that the presence of the uncinate is plesiomorphic
at least for the neomithines and that an ancestral bone
was present in the primitive, pre-neomithine birds.
The origin of the uncinate has remained obscure. Frank
(1954:232) suggested that it is an avian neomorph. Burton
(1970) raised the possibility of its derivation from a ligament
(which is more widespread than the bone) but admitted that this
begs the question of the origin of the ligament. McDowell
(1978) mapped the uncinate to the archosaurian ectopterygoid
because this bone appeared to be the only possible avian homologue
for a reptilian element that lies lateral to the pterygoid
and caudal to the maxilla. Thus far, no intermediate condition
has been found. The oviraptorid ectopterygoid provides at least
a stmctural intermediate between the reptilian ectopterygoid
and the avian uncinate. Whether it is an evolutionary intermediate
remains to be decided in a broader phylogenetic analysis.
The similarities to the avian uncinate cannot be homologous
unless the oviraptorids are more closely related to the ornithurine
birds than is Archaeopteryx because the latter possesses a
typical theropodan, hooked ectopterygoid, which is preserved
in a caudal position in the fifth (Eichstatt) skeleton.
BASIPTERYGOID ARTICULATION.—The pterygoid has a basal
process for the articulation with the cranial base in oviraptorids
(Figure 1), Hesperomis, and the majority of those neognaths
that have a basipterygoid articulation (sensu stricto) as distinguished
from the rostropterygoid articulation of the galliforms
and anatids (Weber, 1993). The basal process is well developed
in many Charadriiformes and some Caprimulgiformes (Steatomithidae,
Caprimulgidae, Nyctibiidae) and in all the Tumi-