ｖｅｒ／化石研究会会誌 ＰＤＦ化／０８０８００７９ 化石研究会誌４１巻１号／本文／５ ２５‐３２ 欧文 2008.09.24 09. 化石研究会会誌 Journal of Fossil Research, Vol.４１（１）,２５-３２（２００８） ［Original report］ Phylogenetic position of Ornithomimosauria in Coelurosauria with comments on the relationship of ornithomimosaurs and alvarezsaurids KOBAYASHI, Yoshitsugu* Abstract The phylogenetic position of Ornithomimosauria within Coerulosauria is discussed. Most of previous phylogenetic analyses suggested that Ornithomimosauria is basal coelurosaur dinosaurs (Tyrannosauridae is the most basal taxon). One study suggested that ornithomimosaurs and alvarezsaurids form a monophyly. This study argues an ornithomimosaurs-alvarezsaurids relationship and supports the idea that they are probably not closely related. Additional information from this study are that two characters for the ornithomimosaur-alvarezsaurid monophyly from the previous study (metacarpals I-III extent of shaft-to-shaft contact 60-70% of shafts and metacarpal I length at least 60% that of metacarapal II) are not supported (roughly 20% contact between metacarpals II and III, less than 50% shaft-to shaft contact in metacarpals I and II in some taxa, and metacarpal I in Harpymimus rougly 50% of metacarpal II). A phylogenetic analysis in this study suggests that the features, supporting a close relationship between ornithomimsoaurs and alvarezsaurids in the previous study are from derived ornithomimids, not primitive forms. Key words： Dinosauria, Coelurosauria, Ornithomimosauria, Alvarezsauridae, phylogeny Introduction ornithomimosaur genera were placed in the Ornithomimosauria are a group of theropod families Harpymimidae (includes Harpymimus) dinosaurs, each of which resembles modern ground and Garudimimidae (includes Garudimimus) (Barsbold, birds in having a beak-like jaw and lightly built body 1981 ; Barsbold and Perle, 1984) from Mongolia with long, slender limbs (Fig. 1). The members of as well as unnamed taxa for Pelecanimimus from this group are best known from the Cretaceous Spain and Shenzhousaurus from China (P!rez- sediments of Laurasia (Osm"lska, 1997). The Moreno et al., 1994 ; Ji et al., 2003). Barsbold first recorded ornithomimosaur is Ornithomimus (1976) coined Ornithomimosauria, which includes velox by Marsh (1890), who established the family Pelecanimimus, Shenzhousaurus, Harpymimidae, Ornithomimidae. Since the establishment of the Garudimimidae, and Ornithomimidae (Barsbold, family, six additional genera from North America 1981; Barsbold and Perle, 1984; P!rez-Moreno (Struthiomimus and Dromiceiomimus)andAsia et al ., 1994) (Fig. 1). The definitions of Ornithomimidae (Archaeornithomimus, Sinornithomimus, Gallimimus, and Ornithomimosauria have been consistent in and Anserimimus) were assigned to it. Non-ornithomimid previous literature (Russell, 1972 ; Barsbold and Accepted : 13th June, 2008 *Hokkaido University Museum, Hokkaido University N 10, W 8, Kita-ku, Sapporo, Hokkaido, 060-0810 Japan E-mail : [email protected] ―25― ｖｅｒ／化石研究会会誌 ＰＤＦ化／０８０８００７９ 化石研究会誌４１巻１号／本文／５ ２５‐３２ 欧文 2008.09.24 09. Outgroups Pelecanimimus Shenzhousaurus Harpymimimus (Harpymimidae) Garudimimus (Garudimimidae) Ornithomimidae Fig. 1. Reconstruction of a Chinese ornithomimid, Sinornithomimus dongi (from Kobayashi and Lü, 2003) and a simplified cladogram of ornithomimosaurs (from Kobayashi and Barsbold, 2004). Osm"lska, 1990 ; P!rez-Moreno et al ., 1994 ; Holtz, includes all ornithomimosaurs from the Late 1994 ; Osm"lska, 1997 ; Holtz, 1998 ; Norell et Cretaceous of North America and Asia except al. , 2002 ; Clark et al ., 2002 ; Hwang et al ., 2002 ; Garudimimus brevipes of Mongolia (Archaeornithomimus, Kobayashi and Lü, 2003 ; Makovicky et al., 2004) Sinornithomimus, Gallimimus, Anserimimus, Struthiomimus, except for Sereno (1997 ; 1998 ; 1999). Dromiceiomimus,andOrnithomimus) (Barsbold Padian et al . (1999) used a node-based definition and Osm"lska, 1990 ; Osm"lska, 1997). In this of Ornithomimosauria : Pelecanimimus and Ornithomimus study, Ornithomimidae is based on a stem-based and all descendants of their most recent common definition as all ornithomimosaurs closer to Ornithomimus ancestor, which is similar to“Ornithomimidae”of Sereno than to Garudimimus. (1998). Based on this definition, Ornithomimosauria includes Pelecanimimus , Shenzhousaurus , Harpymimus , Phylogenetic status of Ornithomimosauria/Ornithomimidae Garudimimus, Archaeornithomimus, Sinornithomimus, in previous studies Gallimimus, Anserimimus, Struthiomimus, Dromiceiomimus, Main phylognetic analyses on Coelurosauria and Ornithomimus.“Ornithomimosauria”of Sereno are Holtz (1998), Sereno (1999), Maryanska et al. (1998) is different from this and is a stem-based (2002), and the Theropod Working Group (Norell et definition (all maniraptoriforms closer to Ornithomimus al ., 2002 ; Clark et al , 2002 ; Hwang et al ., 2002 ; than Neornithes), consisting of Therizinosauridae, Makovicky et al ., 2005 ; Norell et al ., 2006 ; Turner Alvarezsauridae, and“Ornithomimidae”(Sereno, et al ., 2007) and suggested that Ornithomimosauria/ 1999). This inconsistency in terminology is caused by Ornithomimidae are maniraptoriforms, basal to a disagreement in the phylogenetic position Oviraptoridae, Dromaeosauridae, and Aves. Although of Ornithomimosauria/Ornithomimidae within their relationships with other maniraptoriforms (e.g., Coelurosauria. This study compares the difference Troodontidae, Tyrannosauridae, Therizinosauridae, in the phyogentic position of Ornithomimosauria/ and Alvarezsauridae) are inconsistent, the phylogenetic Ornithomimidae within Coelurosauria in previous studies status of Ornithomimosauria/Ornithomimidae is and discusses the relationships of Ornithomimosauria consistent in Maryanska et al. (2002) and the and Alvarezsauridae. Theropod Working Group, which differs from Holtz This study follows the definition of Padian (1998) and Sereno (1999) (Fig. 2). et al. (1999) for Ornithomimosauria because it In Maryanska et al . (2002) and the Theropod is concordant with the traditional usage of Working Group, Ornithomimosauria is placed higher Ornithomimosauria. Ornithomimidae traditionally than Tyrannosauridae but more basal to the rest of ―26― ｖｅｒ／化石研究会会誌 ＰＤＦ化／０８０８００７９ 化石研究会誌４１巻１号／本文／５ ２５‐３２ 欧文 2008.09.24 09. Coelophysidae Dilophosaurus Elaphrosaurus Ceratosaurus Carnotaurus Abelisaurus Spinosauridae Megarosaurus Herrerasaurus ischigualastensis Eustreptospondylus Coelophysis bauri Torvosaurus Allosauroidea A Piatnizkysaurus Tyrannosauridae Afrovenator C Ornithomimosauria Carcharodontosaurus Dromaeosauridae Giganotosaurus Therizinosauria Acrocanthosaurus Archaeopteryx lithographica Neovenator Confuciusornis sanctus Allosaurus Avimimus portentosus Yangchuanosaurus Caudipteryx zoui Sinraptor Chirostenotes pergracilis Monolophosaurus Nomingia gobiensis Gasosaurus "Oviraptor" mongoliensis Proceratosaurus IGM100/42 Dryptosaurus Conchoraptor gracilis Ornitholestes Ingenia yanshini Coelurus Scipionyx Bagaraatan Ornithomimidae Pelecanimimus Tyrannosauridae Compsognathidae Oviraptoridae Caenagnathidae Microraptor Therizinosauroidea Troodontidae Allosaurus fragilis Dromaeosauridae Sinraptor dongi Rahonavis Tyrannosauridae Archaepteryx Coelurus fragilis Alvarezsauridae Dilong paradoxus D Compsognathidae Pelecanimimus polyodon Archaeornithomimus asiaticus Herrerasauridae Harpymimus okladnikovi Ceratosauria Shenzhousaurus orientalis Torvosauridae Garudimimus brevipes B Spinosauridae Struthiomimus altus Allosauridae Gallimimus bullatus Sinraptoridae Ornithomimus edmontonicus Compsognathidae Anserimimus planinychus Ornitholestes Ornitholestes hermanni Deltadromeus Alvarezsauridae Therizinosauridae Therizinosauroidea Alvarezsauridae Oviraptorosauria Ornithomimidae Archaeopteryx lithographica Tyrannosauroidea Jeholornis prima Caudipteryx Sapeornis Caenagnathidae Confuciusornis sanctus Oviraptoridae Yixianornis grabavi Troodontidae Apsaravis uhkaana Dromaeosauridae Troodontidae Aves Dromaeosauridae Fig. 2. Cladograms of theropods from previous phylogenetic analyses : Holtz (1998) (A), Sereno (1999) (B), Maryanska et al. (2002) (C), and Turner et al. (2007) (D). members of Coelurosauria (Turner et al. (2007) Tyrannosauridae, Ornithomimimosauria, the clade of suggested that Compsognathidae is more basal to Oviraptorosauria and Therizinosauroidea, and Ornithomimosauria). Their analyses indicate that the the clade of Dromaeosauridae and higher taxa. differences in interrelationships for higher taxa Although the relationships of these clades are not (especially the position of Oviraptoridae/Oviraptorosauria) resolved, it leaves a possibility of the phylogenetic do not effect on the phylogenetic position of status of Ornithomimosauria as suggested by Ornithomimosauria. Holtz’s study shows unresolved Maryanska et al . (2002) and the Theropod Working polytomy among Troodontidae, Compsognathidae, Group. Sereno’sstudy is completely different from ―27― ｖｅｒ／化石研究会会誌 ＰＤＦ化／０８０８００７９ 化石研究会誌４１巻１号／本文／５ ２５‐３２ 欧文 2008.09.24 09. the other studies. Ornithomimidae is nested within a subequal to that of the lacrimal ornithomimids. clade with Therizinosauridae and Alvarezsauridae, Prefrontal orbital flange is absent in Struthiomimus where this clade is called“Ornithomimosauria”by altus (AMNH 5339). Anterior teeth are smaller than Sereno, and Tyrannosauridae is placed higher than posterior ones in the maxilla in Pelecanimimus. Ornithomimosauria. Chevron height is no greater than twice height of corresponding neural spines in ornithomimids. Relationships of Ornithomimidae and Alvarezsauridae Dentary length relative