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320 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY their tooth implantation, such as the expanded dental roots and the equal height of the lingual and buccal margins of the dentary (Elzanowski and Wellnhofer, 1995). The teeth of Ichthyornis are usually anchored in separate alveoli, whereas those of the hesperomithids are in a common groove; however, Martin and Stewart (1977) described a mandible of Ichthyornis with teeth in a groove. Avian teeth do not show any close similarity to any known theropod teeth except for the early juvenile teeth of Archaeornithoides (Elzanowski and Wellnhofer, 1993). The teeth of Archaeopteryx and Ichthyornis are similar in having the crowns divided into a straight base and a recurved tip. On the other hand, the teeth of Ichthyornis were reported to have the roots distinctly expanded, as in the hesperomithids (Martin and Stewart, 1977). Unfortunately, the radiographs on which this observation is based have never been published. Dental roots are not expanded in Archaeopteryx (Howgate, 1984; Elzanowski and Wellnhofer, 1996). 1 Entirely toothless jaws evolved independently in the oviraptorosaurs, advanced omithomimosaurs, Confuciusomis and Gobipteryx (these two genera were included in the Enantiornithes by Hou et al., 1995), and the advanced neomithines. An edentulous premaxilla coexists with a dentigerous maxilla and dentary in the therizinosauroids and hesperomithids. It is clear that the reduction of teeth occurred several times independently within the analyzed set of taxa. Discussion Some of the avian characters, such as the toothless beaks of the oviraptosaurs and advanced omithomimosaurs, are certainly convergent and evolved more than once within the set of taxa under comparison. Reduction of teeth is a recurrent theme in vertebrate evolution. There is, however, no reason to expect a pervasive convergence on birds in the cranial morphology of the omithomimosaurs, therizinosauroids, and oviraptorosaurs because their skulls are unlike any avian skull. This is what one could expect as a result of turning a primitive, perhaps Archaeopteryx-like cranial morphology into several highly specialized kinds of jaw apparatus of the gigantic descendants of the ancestors of birds. In terms of jaw function, the oviraptorids are comparable to the dicynodonts (Osmolska, 1976), and the therizinosauroids are convergent on the omithischians in having cheeks (Clark et al., 1994). It seems reasonable, therefore, to suspect that the unique cranial similarities of birds, oviraptorosaurs, therizinosauroids, and omithomimosaurs (Table 1, characters 1-6) are synapo- 1 Editor's Note: This is at variance with Martin and Stewart, elsewhere in this volume, who consider previously published photographs and descriptions to indicate that the teeth of Archaeopteryx do have expanded roots. morphic and thus indicative of the monophyly of a clade composed of these taxa and probably troodontids (Figure 6). This would agree with the phylogeny reconstmcted from 20 cranial and 39 postcranial characters by Russell and Dong (1993), who subdivided the tetanurans into two groups: one that included the dromaeosaurs and camosaurs and one that included the ornithomimosaurs, troodonts, therizinosauroids, and oviraptorosaurs. Most intriguing are four characters (Table 1, characters 10-13) that are shared by the oviraptorosaurs and the ornithurine birds but are absent in Archaeopteryx. These suggest that the oviraptorosaurs branched off after Archaeopteryx and thus represent the earliest known flightless birds. Except for the elongate forelimbs (which become shortened in all flightless forms), the postcranial skeleton of Archaeopteryx does not have any avian traits that would be absent in the oviraptorids (Barsbold 1983a, 1983b). Therefore, if flightlessness had evolved at a stage of avian evolution close to Archaeopteryx, this would be extremely difficult to distinguish from the primary flightlessness of the theropods. Relationships of the oviraptorosaurs have been enigmatic ever since their discovery (Osbom, 1924). The only consensus reached in recent phylogenetic reconstmctions is that the oviraptorosaurs belong in the Coelurosauria, a major clade that gave rise to birds, but their placement within that clade varies considerably (Gauthier, 1986; Barsbold et al., 1990; Holtz, 1996). Evidence for their affinities comes almost exclusively from the postcranial skeleton because the oviraptorid skull is difficult to compare with the skull of any other group of theropods. In contrast, even the highly specialized, edentulous skulls of omithomimosaurs are still clearly identifiable as theropodan. The two cranial characters used by Gauthier (1986) to define the Coelurosauria, namely, the pterygopalatine fenestra and ventral pocket in the ectopterygoid, are absent in the oviraptorids (as well as in the omithurines). Several similarities of the jaws of Hesperomithidae and Ichthyomithidae prove likely to be synapomorphies when analyzed against the plesiomorphic background provided by the theropods and Archaeopteryx. Wetmore (1930) combined the Hesperornifhiformes and Ichthyornithiformes in the superorder Odontognathae, but monophyly of this taxon has never been explicitly suggested because most of their similarities were thought to be primitive. A closer relationship between these two orders is now suggested by the lack of mandibular symphysis, probably due in both taxa to the separation of the tip of the mandible as a predentary bone; the presence and detailed similarities of the intraramal joint; the absence of interdental plates, which is probably correlated with the lingual alveolar margin being flush with the buccal margin; and probably the expansions of the dental roots (fide Martin and Stewart, 1977) and the straight quadrate.
NUMBER 89 321 FIGURE 6. Table 1. -Unresolved polytomy of the avian and three theropod lineages, as suggested by characters 1-6 in Barsbold, Rinchen 1983a. O "ptich'ikh" chertakh v stroyenii khishchnykh dinozavrov [On the "Avian" Characters in the Structure of Predatory Dinosaurs]. Trudy, Sovmestnaya Sovetsko-Mongol 'skaya Paleontologicheskaya Eks peditsiya, 24:96-103. [In Russian.] 1983b. Khishchnyye dinozavry mela Mongolii [Predatory Dinosaurs of the Cretaceous of Mongolia]. Trudy, Sovmestnaya Sovetsko-Mon gol'skaya Paleontologicheskaya Ekspeditsiya, 19:1-117. [In Rus sian.] Barsbold, Rinchen, Teresa Maryanska, and Halszka Osmolska 1990. Oviraptorosauria. In D.B. Weishampel, P. Dodson, and H. Osmol ska, editors, The Dinosauria, pages 249-258. Berkeley: University of California Press. Barsbold, Rinchen, and Halszka Osmolska 1990. Omithomimosauria. In D.B. Weishampel, P. Dodson, and H. Os Buffetaut, Eric molska, editors, The Dinosauria, pages 225-244. Berkeley: Univer sity of California Press. 1992. Remarks on the Cretaceous Theropod Dinosaurs Spinosaurus and Burton, P.J.K. Baryonyx. Neues Jahrbuch fur Geologie und Paldontologie, Monat- shefte. (1992):88-96. 1970. Some Observations on the Os Uncinatum in the Musophagidae. Os trich, supplement, 8:7-13. Literature Cited i' Campbell, Kenneth E., and Eduardo P. Tonni 1981. Preliminary Observations on the Paleobiology and Evolution of Teratorns (Aves: Teratornithidae). Journal of Vertebrate Paleontology, 1:265-272. Clark, James M., Altangerel Perle, and Mark Norell 1994. The Skull of Erlicosaurus andrewsi, a Late Cretaceous "Segnosaur" (Theropoda: Therizinosauridae) of Mongolia. American Museum Novitates, 3115: 35 pages. Colbert, Edwin H., and Dale A. Russell 1969. The Small Cretaceous Dinosaur Dromaeosaurus. American Museum Novitates, 2380: 49 pages. Currie, Philip J. 1985. Cranial Anatomy of Stenonychosaurus inequalis (Saurischia, Theropoda) and Its Bearing on the Origin of Birds. Canadian Journal of Earth Sciences, 22:1643-1658. 1987. Bird-like Characteristics of the Jaws and Teeth of Troodontid Theropods (Dinosauria, Saurischia). Journal of Vertebrate Paleontology, 7:72-81. 1995. New Information on the Anatomy and Relationships of Dromaeosaurus albertensis (Dinosauria, Theropoda). Journal of Vertebrate Paleontology, 15:576-591. Currie, P.J., S.J. Godfrey, and Lev Nessov 1993. New Caenagnathid (Dinosauria: Theropoda) Specimens from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences, 30:2255-2272.
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SMITHSONIAN CONTRIBUTIONS TO PALEOB
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ABSTRACT Olson, Storrs L., editor.
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EARLY WATERFOWL (ANSERIFORMES) AND
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v m SMITHSONIAN CONTRIBUTIONS TO PA
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localities, all of them situated in
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Bone of Sus scrofa Linnaeus, introd
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duboisi are larger than the largest
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8 iver (1897) but afterward were tr
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10 SMITHSONIAN CONTRIBUTIONS TO PAL
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16 Cor. Hum. Uln. Cpm. Fern. Tbt. T
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20 sometatarsus are proportionally
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34 ability in such a way that it ca
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42 2km SMITHSONIAN CONTRIBUTIONS TO
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Site 13 Research Base ENTRANCE Lowe
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48 the last has unusually slender w
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50 Si 5 15i 10- 5- 20 J 15 I 10 f 5
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Comparison of Paleoecological Patte
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NUMBER 89 69 TABLE 1.—Vertebrate
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NUMBER 89 71 Mallorca, probably in
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NUMBER 89 Alcover, J.A. 1989. Les a
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The History of the Chatham Islands'
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NUMBER 89 87 Species Common Name Pe
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NUMBER 89 89 NZA 797,1930,1934 Unco
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NUMBER 89 91 anoramphus spp.), Chat
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NUMBER 89 93 TABLE 2.—Land snails
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NUMBER 89 95 counterparts, with som
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NUMBER 89 population, if such exist
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NUMBER 89 99 FIGURE 11.—Skulls of
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NUMBER 89 101 FIGURE 13.—Lower ma
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NUMBER 89 the Chatham Island Pied O
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NUMBER 89 Locality 9, Western Maung
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NUMBER 89 107 yellowish sand (site
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NUMBER 89 109 ogy. Notornis, supple
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112 SMITHSONIAN CONTRIBUTIONS TO PA
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The Middle Pleistocene Avifauna of
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NUMBER 89 Accordi, B. 1962. La grot
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130 FIGURE 1.—Map showing locatio
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132 Cranium Mandibula Scapula Clavi
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Seabirds and Late Pleistocene Marin
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NUMBER 89 141 METHODS Only strictly
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NUMBER 89 143 FIGURE 2.—Area of s
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NUMBER 89 151 FIGURE 10.—Area of
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NUMBER 89 153 FIGURE 12.—Area of
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NUMBER 89 155 the period studied. T
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NUMBER 89 157 Walker, C.A., G.M. Wr
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164 Vl 620 M 570 £ 520 S 470f •
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166 birds, such as the two species
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170 cional Autonoma de Mexico, for
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174 ated with this specimen, see Mi
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The Fossil Record of Condors (Cicon
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NUMBER 89 179 FIGURE 2.—Geographi
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NUMBER 89 181 FIGURE 5.—Vulturida
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NUMBER 89 183 FIGURE 7.—Referred
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Two New Fossil Eagles from the Late
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NUMBER 89 187 TABLE 1.—Measuremen
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NUMBER 89 189 carpal trochlea relat
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NUMBER 89 191 FIGURE 4.—Holotypic
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NUMBER 89 193 We compared the parat
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NUMBER 89 195 FIGURE 6.—Distribut
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NUMBER 89 197 the Florida State Mus
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A New Genus of Dwarf Megapode (Gall
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NUMBER 89 201 lis hypotarsi along t
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NUMBER 89 203 The fossil is larger
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NUMBER 89 205 Clark, George A., Jr.
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A New Genus and Species of the Fami
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NUMBER 89 209 son with other known
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NUMBER 89 211 FIGURE 1.—Argornis
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NUMBER 89 213 AM AL AM AL AM AL AM
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NUMBER 89 215 caput humeri perpendi
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Selmes absurdipes, New Genus, New S
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NUMBER 89 219 FIGURE 2.—Selmes ab
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NUMBER 89 221 Costae: Deformed frag
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A Fossil Screamer (Anseriformes: An
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NUMBER 89 FIGURE 3.—Chaunoides an
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NUMBER 89 227 B C D FIGURE 6.—The
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NUMBER 89 229 FIGURE 9.—Right tib
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The Anseriform Relationships of Ana
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NUMBER 89 233 Subfamily ANATALAVINA
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NUMBER 89 235 mal was found under t
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NUMBER 89 237 tion, with retroartic
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NUMBER 89 FIGURE 7.—Sternum and p
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NUMBER 89 241 der. The bone is very
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NUMBER 89 243 Eocene records of the
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Presbyornis isoni and Other Late Pa
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NUMBER 89 255 FIGURE 1.—Referred
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NUMBER 89 257 vical vertebrae of th
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NUMBER 89 259 (Olson and Parris, 19
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