THE ANATOMY OF EFFIGIA OKEEFFEAE (ARCHOSAURIA, SUCHIA), THEROPOD-LIKE CONVERGENCE, AND THE DISTRIBUTION OF RELATED TAXA

By S. Nesbitt. 2007

206 citations recorded by the source corpus.

Abstract Effigia okeeffeae is named based on a well-preserved nearly complete skeleton from the Upper Triassic (?Rhaetian) “siltstone member” at Ghost Ranch, northern New Mexico. The skull is described and compared to other suchian and basal archosaurs. The maxilla and premaxilla are edentulous, and a rhamphotheca was possibly present in life. Effigia conclusively indicates that the skull of Shuvosaurus and the postcrania of “Chatterjeea” belong to the same taxon. Furthermore, the close relationship between Shuvosaurus and Effigia indicates that both taxa are nested within the suchian clade and not within Ornithomimisauria. However, the similarity in features in the skull and postcrania of Effigia and ornithomimids suggests extreme convergence occurred between the two clades. A clade containing Arizonasaurus, Bromsgroveia, Poposaurus, Sillosuchus, Shuvosaurus, and Effigia is suggested based solely on shared derived character states. Additionally, a clade (Clade Y) containing Sillosuchus, Shuvosaurus, and Effigia is well supported by further derived character states. The distribution and temporal pattern of members of Group Y suggest that members of Group Y are present in the early Middle Triassic through the Latest Triassic of North America, and one member of the clade, Sillosuchus, was present in South America.

Subfields: Ecology, Evolution, Behavior and Systematics, Paleontology

View Paper: https://www.semanticscholar.org/paper/68eb8a7e1056c6798d2c87358be17a98a81bd989

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Ecology, Evolution, Behavior and Systematics

1. R. Schoch
2. D. Gower
3. M. Ezcurra
4. M. Langer
5. Michael Benton
6. S. Brusatte
7. J. Desojo
8. R. Butler

In Paleontology

1. S. Nesbitt
2. R. Irmis
3. M. Langer
4. M. Ezcurra
5. R. Butler
6. Jorge Ferigolo
7. Michael Benton
8. S. Brusatte

Citations in the corpus

• Best Practices for Justifying Fossil Calibrations (2011, background): “—Nesbitt et al. 2011 conclusively demonstrates that IVPP V 6026 belongs along the stem of Crocodylia (in the clade Pseudosuchia).”
• A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny (2010, background): “On the other hand, in non-dinosaurian archosaurs (e.g. Effigia, Silesaurus, Eucoelophysis, Marasuchus; Nesbitt 2007; Dzik 2003; Sullivan & Lucas 1999; PVL 3036) the distal condyles of the metatarsal II are almost symmetric in dorsal view.”
• The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida) (2010, background): “As discussed by Nesbitt (2007), shuvosaurids share many characters with avemetatarsalian taxa, especially theropod dinosaurs, and these must be interpreted as convergences in the current analysis.”
• Aetosauria: a clade of armoured pseudosuchians from the Upper Triassic continental beds (2013, background): “…is nested within Pseudosuchia, the crocodile lineage of Archosauria; however, the phylogenetic relationships of aetosaurs with other high-level suchians are currently a matter of debate (e.g. Gower & Sennikov 1996; Gower & Walker 2002; Nesbitt 2007, 2011; Brusatte et al. 2010; Desojo et al. 2012).”
• Postcranial Osteology of Azendohsaurus madagaskarensis (?Middle to Upper Triassic, Isalo Group, Madagascar) and its Systematic Position Among Stem Archosaur Reptiles (2015, methodology): “This suite of character states in a highly autapomorphic taxon illustrates a continued theme in recent discovery and descriptions of Triassic archosauromorphs (e.g., Effigia okeeffeae, Nesbitt and Norell, 2006; Nesbitt, 2007): rampant convergence.”
• Postcranial Anatomy of the Rauisuchian Archosaur Batrachotomus kupferzellensis (2009, methodology): “There is a new body of evidence from sacral, pelvic, femoral and osteoderm characters for the monophyly of Nesbitt’s (2005) Clade X that includes Arizonasaurus, Bromsgroveia, Effigia, Poposaurus, Shuvosaurus (=Chatterjeea), and Sillosuchus (see also Alcober and Parrish, 1997; Nesbitt, 2007; Weinbaum”
• The Late Triassic dinosauromorph Sacisaurus agudoensis (Caturrita Formation; Rio Grande do Sul, Brazil): anatomy and affinities (2013, background): “…of the ilium is a taphonomic signature seen in a number of archosaurs, for example Bromsgroveia walkeri (Galton & Walker 1996), Effigia okeeffeae (Nesbitt 2007), Silesaurus-like form (Irmis et al. 2007a), Guaibasaurus candelariensis (Langer et al. 2011) and Silesaurus opolensis (ZPAL AbIII/907/…”
• The anatomy of the basal ornithischian dinosaur Eocursor parvus from the lower Elliot Formation (Late Triassic) of South Africa (2010, unknown): “Nesbitt SJ. 2007.”
• The origin and early radiation of dinosaurs (2010, background): “This period of time, from approximately 235–201 million years ago, witnessed the evolution of several morphologically distinctive archosaur clades that filled a variety of ecological roles (Nesbitt, 2007; Brusatte et al., 2008a; Nesbitt et al., 2010).”
• Macroevolutionary patterns in the evolutionary radiation of archosaurs (Tetrapoda: Diapsida) (2010, background): “Second, one of the great revelations of the recent renaissance in Triassic-Early Jurassic archosaur palaeontology is that dinosaurs and several crurotarsans were strongly convergent on each other (Parker et al. 2005; Nesbitt & Norell 2006; Nesbitt 2007).”