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314 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
is separated from the ectopterygoid by a vestigial postpalatine
("palatine") fenestra (Figure 2A). The fenestra leads to a flat
bony pocket, which opens medially by a long fissure between
the ascending wing of the palatine and the ectopterygoid (Figure
2B). Although the palatine/pterygoid contact is not preserved,
there is no indication of the presence of a pterygopalatine
("subsidiary palatine") fenestra between the pterygoid
wing of the palatine and the pterygoid.
The details of pterygoid structure remain unclear due to its
tight contact with or fusion to the adjacent bones. The rostral
end of the pterygoid cannot be precisely distinguished from the
palatine and ectopterygoid but seems to be forked rostrally.
The rostral part of the bone is strongly concave ventrally and
receives the pterygoid wing of the palatine. The caudal part of
the pterygoid has a short wing for the basipterygoid articulation
and a quadrate wing that closely adheres to what has been identified
as the pterygoid ramus of the quadrate (Barsbold et al.,
1990, fig. 10.1 A). The pterygoquadrate articulation, at angles
to the long axis of the pterygoid, is very tight and does not suggest
any mobility.
The ectopterygoid provides a smooth rostral continuation of
the thick lateral margin of the pterygoid. (A large bone in the
type specimen of Oviraptor philoceratops that is attached to
the caudal end of the pterygoid was identified as an ectopterygoid
(Smith, 1992), which is clearly a mistake, the bone probably
being the left quadrate.) The ectopterygoid is oriented vertically,
almost in a parasagittal plane, and its rostral end lies
much more dorsally than does the caudal end (Figure 2A). The
rostral end articulates primarily with the lacrimal and maxilla
and marginally contacts the jugal and the ascending wing of the
palatine (Figure 2). The ectopterygoid is well delimited from
the pterygoid across the ridge, but the suture wanes more medially
(in the trough). The medial margin of the bone is over­
lapped by the palatine. Rostrally, the two bones are separated
by a small postpalatine fenestra, which is well exposed in lateral
view (Figure 2A) but is barely exposed in ventral view (Figure
1).
The lacrimal is oriented transversely, and its cross section
gradually expands from a flattened lateral ridge to a broad medial
base (Figure 2A). Its ventral extremity is irregularly
crenate (Figure 2B).
Comparisons
Characters of the Oviraptoridae (Figures 1, 2; Barsbold et al.,
1990), Caenagnathidae (Figure 5; Sternberg, 1940; Currie et
al., 1993; Sues, 1997), Therizinosauroidea as represented by
Erlikosaurus (Clark et al., 1994), and Omithomimosauria (Osmolska
et al., 1972; Barsbold and Osmolska, 1990) that are
specifically shared with Archaeopteryx (Elzanowski and
Wellnhofer, 1995, 1996), Confuciusomis (Hou et al., 1995),
Gobipteryx (Elzanowski, 1977, 1995), the Odontognathae
(Marsh, 1880; Elzanowski, 1991), and other ornithurine birds
(Jollie, 1957; Elzanowski, 1995) are analyzed below, and their
distribution is summarized in Table 1. All these characters
show the opposite states in the Dromaeosauridae (Colbert and
Russell, 1969; Ostrom, 1969; Sues, 1977; Currie, 1995) and
usually in Allosaurus (Madsen, 1976) and other tetanuran
theropods. The subdivision of birds and, especially, the definition
of Ornithurae, follow Elzanowski (1995).
Unfortunately, very little is known about the jaws of troodontids,
which show some avian similarities in their braincase
(Currie, 1985; Currie and Zhao, 1993). Similar to the troodontids
are jaw fragments of Archaeornithoides (Elzanowski and
Wellnhofer, 1992, 1993), which may in fact represent a juvenile
troodontid. One of the main reasons for describing it as a
separate genus in a family of its own was its tooth stmcture,
TABLE 1.—Potential cranial synapomorphies of the Omithomimosauria (Omim), Therizinosauroidea (Ther),
Oviraptoridae (Ovir), Caenagnathidae (Caen), and birds as represented by Archaeopteryx (Arch), Gobipteryx
(Gobi), and Hesperomis (Hesp). The opposite character states (0) are present in the Dromaeosauridae and the
majority of known theropods. Parentheses indicate that the homology of noted similarities may be open to interpretation.
A=ambiguous character state. See text for complete definitions and discussion of the characters.
Character
1. Palatine with long maxillary process
2. Coronoid absent
3. Inrraramal articulation absent
4. Maxilla with broad palatal shelf
5. Quadrate head bent backwards
6. Palatine with broad pterygoid wing
7. Pterygoid with basal process
8. Ectopterygoid in rostral position
9. Articular and surangular co-ossified
10. Articular with lateral process
11. Articular with medial process
12. Mandibular symphysis fused
13. Jugal bar rod-shaped
14. Ectopterygoid contacts lacrimal
Omim
1
1
1
1
1
0
(1)
A
0
0
0
0
0
7
Ther
0
0
0
0
0
Ovir Caen
1 1
1 1
1 1
1 1
1 ?
1 1
1 ?
1 ?
0 1
1 1
1 1
1 1
1 ?
1 ?
Arch
1
1
1
?
1
1
A
0
0
0
0
0
0
0
Gobi
?
(1)
?
Hesp
1
1
0
1
0
1
1
(1)
1
1
1
(1)
1
(1)