[Palaeontology, 2012, pp. 1–25] THE POSTCRANIAL ANATOMY OF COLORADISAURUS BREVIS (DINOSAURIA: SAUROPODOMORPHA) FROM THE LATE TRIASSIC OF ARGENTINA AND ITS PHYLOGENETIC IMPLICATIONS by CECILIA APALDETTI1*, DIEGO POL2 and ADAM YATES3 1CONICET, Universidad Nacional de San Juan, Museo de Ciencias Naturales, Av. Espana 400 (norte), San Juan, 5400 Argentina; e-mail: [email protected] 2CONICET, Museo Paleontologico Egidio Feruglio, Av. Fontana 140, Trelew, Chubut 9100, Argentina; e-mail: [email protected] 3University of the Witwatersrand, Bernard Price Institute for Palaeontological Research, Private Bag 3, Johannesburg, Gauteng, 2050, South Africa; e-mail: [email protected] *Corresponding author. Typescript received February 2012; accepted in revised form 13 July 2012 Abstract: Basal sauropodomorphs from the Upper Triassic surface of the tibia deflected and facing posterodistally and Los Colorados Formation of north-western Argentina have well-developed pyramidal dorsal process of the posteromedial been known for several decades but most of them are only corner of the astragalus. Several postcranial characters of briefly described. New postrcanial remains of Coloradisaurus Coloradisaurus are exclusively shared with Lufengosaurus, brevis, the most gracile sauropodomorph from this unit, are from the Lower Jurassic of China. The inclusion of this described here and evaluated within a phylogenetic context. information in two recent phylogenetic data sets depicts These materials belong to a single individual and include ele- Coloradisaurus as closely related to Lufengosaurus and well ments of the vertebral column, pectoral girdle, incomplete nested within Plateosauria. Both data sets used indicate forelimb, pelvis and hindlimb. These elements share an auta- strong character support for the inclusion of Coloradisaurus pomorphic feature with the type specimen of Coloradisaurus and Lufengosaurus within Massospondylidae. brevis and provide novel and unique features that diag- nose this taxon, such as pubic apron with semicircular cross- Key words: Triassic, Los Colorados, Sauropodomorpha, section and with a depression on its anterior surface, distal Massospondylidae, Plateosauria, phylogeny. B asal sauropodomorphs were globally widespread includes remains of four sauropodomorph taxa: Riojasau- dinosaurs and dominated the large herbivorous fauna rus incertus (Bonaparte 1972; Bonaparte and Pumares from the Late Triassic until Early Jurassic (Sereno 1997, 1995), Lessemsaurus sauropoides (Bonaparte 1999; Pol and 1999; Galton and Upchurch 2004). In South America, this Powell 2007b), Coloradisaurus brevis (Bonaparte 1978) group includes both basal forms (e.g. Saturnalia, Panpha- and a partially preserved unnamed form (PULR 136, gia and Chromogisaurus) and more derived taxa near to Ezcurra and Apaldetti 2011). the origin of Sauropoda (e.g. Mussaurus, Leonerasaurus; Coloradisaurus brevis was originally named Coloradia Langer et al. 1999; Martinez and Alcober 2009; Pol and brevis (Bonaparte 1978) and later renamed Coloradisaurus Powell 2007a; Ezcurra 2010; Pol et al. 2011). The highest brevis by Lambert (1983) given the genus Coloradia was diversity and abundance of basal sauropodomorphs in the preoccupied. The original description of Coloradisaurus Late Triassic of South America is present in the Ischigual- was mainly based on the skull anatomy of the holotype asto-Villa Union Basin in north-western Argentina. Saur- specimen (PVL 3967), and the presence of isolated postcra- opodomorphs of this basin include the oldest basal nial remains was only briefly mentioned (Bonaparte 1978). sauropodomorphs Panphagia protos (Martinez and Alco- Coloradisaurus was originally referred to Plateosauridae ber 2009) and Chromogisaurus novasi (Ezcurra 2010) from (sensu Galton and Cluver 1976) and more specifically as the Carnian levels of the Ischigualasto Formation (Rogers closely related to Plateosaurus and Lufengosaurus. The affin- et al. 1993; Martinez et al. 2011). The overlying Los Col- ities of Coloradisaurus and Lufengosaurus were supported orados Formation (Norian–Rhaetian; Bonaparte 1972) by subsequent studies, although the phylogenetic position ª The Palaeontological Association doi: 10.1111/j.1475-4983.2012.01198.x 1 2 PALAEONTOLOGY of these two taxa have been regarded as more closely related specified, all the other references are based on the literature to Plateosaurus than to Massospondylus by some authors listed in this table. (Sereno 1999; Galton and Upchurch 2004; Barrett et al. 2005; Upchurch et al. 2007; Martinez 2009), whereas others Anatomical abbreviations. acf, acromial fossa; acp, acromion authors retrieved Coloradisaurus and Lufengosaurus as more process; alp, anterolateral process; apr, pubic apron; ars, articular closely related to Massospondylus than to Plateosaurus surface of metacarpal III; asp, ascending process; cas, concavity (Yates 2003a, 2004, 2007a, b; Smith and Pol 2007; Sertich of the posterior surface of the ascending process; cdf, centrodia- and Loewen 2010; Ezcurra 2010). pophyseal fossa; cf, cuboid fossa; cof, coracoid foramen; cot, cor- acoid tubercle; cn, cnemial crest; D11–D12, dorsal vertebra 11 An articulated postcranial skeleton (PVL 5904, previ- and 12; dep, lateral depression of dorsal centrum; di, diapophy- ously reported as field # 6, Yates 2004, 2007a) discovered sis; dpc, deltopectoral crest; dsp, distal surface of the pubic in the upper section of Los Colorados Formation by Jose´ blade; epi, epipophysis; eps, entepicondylar surface; exf, extensor Bonaparte in 1973 is here described and referred as the fossa; fas, fossa of the base of ascending process; fdp, facet for second known specimen of Coloradisaurus brevis. The descending process of the tibia; fhe, femoral head; gl, glenoid; new information increases our knowledge on the anatomy ias, iliac articular surface; ibl, iliac blade; ilp, iliac peduncle; isp, of Coloradisaurus brevis and contributes to understanding ischial peduncle; it, internal tuberosity; lc, lateral condyle; lco, the relationships of Coloradisaurus within basal sauro- lateral concavity; lt, lesser trochanter; mc, medial condyle; mt, podomorphs. metatarsal; nc, neural canal; nis, notch of the ischial acetabular margin; ns, neural spine; of, obturador foramen; opp, proximal Institutional abbreviations. LV, Museum of Lufeng Dinosaurs, opening of the pubic apron; pa, parapophysis; pap, base of the Jingshan, Yunnan Province, China; PVL, Instituto Miguel Lillo, preacetabular process; pas, pubic articular surface; pcdl, posterior Tucuma´n, Argentina; PVSJ, Museo de Ciencias Naturales, San centrodiapophyseal lamina; pdp, proximal depression of the Juan, Argentina; UFSM, Universidade Federal de Santa Maria, pubic apron; pip, proximal ischial plate; plp, posterolateral pro- Santa Maria, Rio Grande do Sul, Brazil. cess; pmc, posteromedial corner; pocdf, postzygodiapophyseal fossa; podl, postzygodiapophyseal lamina; pof, poplietal fossa; pop, base of the postacetabular process; poz, postzygapophysis; Comparative data. The comparisons with other saur- ppl, pubic plate; prcdf, prezygodiapophyseal fossa; prdl, prezygo- opodomorphs made in the description were based on the previ- diapophyseal lamina; prz, prezygapophysis; ptb, pubic tuberosity; ous publications and on personal observation of specific taxa pup, pubic peduncle; sac, supracetabular crest; rc, radial condyle; detailed in Table 1. Except in those cases where the source is spol, spinopostzygapophyseal lamina; sprl, spinoprezygapophyse- al lamina; sul, sulcus; tfc, tibiofibular crest; tub, rugose tuberosi- TABLE 1. Source of comparative data used in this study. ties of the dorsal end of the scapula; uc, ulnar condyle; 4t, Taxon and source fourth trochanter; I–V, pedal digits I to V. Adeopapposaurus mognai, Martinez 2009 Anchisaurus polyzelus, Yates 2004 SYSTEMATIC PALAEONTOLOGY Antetonitrus ingenipes, Yates and Kitching 2003 Blikanasaurus cromptoni, Galton and Van Heerden, 1998 SAURISCHIA Seeley, 1887 Glacialisaurus antartica, Smith and Pol 2007 SAUROPODOMORPHA von Huene, 1932 Jingshanosaurus xinwaensis, Zhang and Yang 1994 Lessemsaurus sauropoides, Bonaparte 1999; Pol and Powell 2007b Leyesaurus marayensis, Apaldetti et al. 2011 Genus COLORADISAURUS Lambert, 1983 Lufengosaurus huenei, Young 1941 Massospondylus carinatus, Cooper 1981 Type species. Coloradisaurus brevis (Bonaparte, 1978). Melanorosaurus readi, Heerden and Galton 1997; Bonnan and Yates 2007 Diagnosis. As for the type and only species. Panphagia protos, PVSJ 874, Martinez and Alcober 2009 Pantydraco caducus, Yates 2003a; Galton et al. 2007 Plateosaurus engelhardti, Galton 2000, 2001; Moser 2003; Coloradisaurus brevis (Bonaparte, 1978) Yates 2003b Figures 1–16 Riojasaurus incertus, PVL 3808; Bonaparte, 1972 Sarahsaurus aurifontanalis, Rowe et al. 2010 1978 Coloradia brevis Bonaparte, p. 327, figs 1–3. Saturnalia tupiniquim, Langer et al. 1999, 2007; Langer 2003 1983 Coloradisaurus brevis Lambert, p. 102. Seitaad ruessi, Sertich and Loewen 2010 1990 Coloradisaurus brevis Galton, p. 336, figs 15.3G–H, Thecodontosaurus antiquus, Benton et al. 2000 15.4C. Unaysaurus tolentinoi, Leal et al. 2004 2004 Coloradisaurus brevis Galton and Upchurch, p. 234, Vulcanodon karibaensis, Cooper 1984 figs 12.3G–H, 12.5C. Yunnanosaurus huangi, Young 1942 2007a Coloradisaurus brevis Yates, p. 33. APALDETTI ET AL.: POSTCRANIAL ANATOMY OF COLORADISAURUS BREVIS 3 Holotype. PVL 3967. Skull and mandible found in articulation sauropoides, as well as a fragmentary material that represents with the atlas-axis and C3,