ISSN (impreso) 0326-1778 / ISSN (on-line) 1853-6581

HISTORIA NATURAL Tercera Serie Volumen 2 (1) 2012/49-71

COMMENTS ON THE TAXONOMIC DIVERSITY AND PALEOBIOGEOGRAPHY OF THE EARLIEST KNOWN ASSEMBLAGES (LATE –EARLIEST )

Comentarios sobre la diversidad taxonómica y paleobiogeografía de las asociaciones de dinosaurios más antigüas (Carniano tardío-Noriano más temprano).

Martín D. Ezcurra

GeoBio-Center, Ludwig-Maximilians-Universität München, Richard-Wagner-Str. 10 (D-80333), Munich, Germany. [email protected]

Recibido: 26/10/2011 - Aceptado: 19/4/2012

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Abstract. The beginning of dinosaur evolution is currently known based on a handful of upper Carnian– lowermost Norian (232–225 Mya) localities situated in a paleolatitudinal belt of approximately 40–50° S in Argentina, Brazil, Zimbabwe and India. The taxonomic diversity of the oldest known dinosaur- bearing assemblages, included within the Assemblage Zone, is reviewed here. The Brazilian “Teyuwasu barberenarai” is reinterpreted as a nomen dubium representing an indeterminate dinosauriform, the record of cf. Saturnalia from Zimbabwe is considered a basal saurischian and only one of the Indian specimens described by Huene can be unambiguously assigned to Dinosauria. The highest early dinosaur species richness sampled is concentrated in southwestern Pangean assemblages (Argentina and Brazil), with 10 to 11 different described species. By contrast, only one or two species can be currently recognized from the approximately coeval beds of south–central Pangea (Zimbabwe and India), which are much less well sampled. The oldest known dinosaur assemblages appear to have been mostly restricted to subtropical to cool temperate arid areas based on recent paleoclimatological reconstructions. This observation agrees with the hypothesis that the absence of in the upper levels of the of Argentina is related to an increase in humidity in the basin. Accordingly, climatic factors, with humidity as probably the most important, may have controlled the paleobiogeographic distribution of the oldest known dinosaur assemblages. The achievement of a worldwide dinosaur distribution during the latest may have occurred after a global climate change, such as the end of the “Carnian Pluvial Event”, and/or the invasion of more tropical humid climates by dinosaurs.

Key Words. Archosauria, Dinosauria, Triassic, Paleobiogeography, Macroevolution.

Resumen. La temprana evolución de los dinosaurios es conocida actualmente gracias a un número reducido de localidades del Carniano superior-Noriano más inferior (232-225 Ma) de Argentina, Brasil, Zimbawe e India, situadas en un cinturón paleolatitudinal alrededor de los 40-50° S. La diversidad taxonómica de las asociaciones portadoras de dinosaurios más antiguas conocidas, incluidas en la Biozona de Hyperodapedon, es aquí revisada. “Teyuwasu barberenarai” de Brasil es reinterpretado como un nomen dubium de un indeterminado, el registro de cf. Saturnalia de Zimbawe es propuesto como un saurisquio basal y solo uno de los especímenes provenientes de India, descripto por Huene, puede ser asignado de manera no ambigua a Dinosauria. La diversidad taxonómica más rica de dinosaurios está concentrada en asociaciones del suroeste de Pangea, con 10 a 11 especies diferentes (Argentina y Brasil). En contraste, sólo una o dos especies pueden ser reconocidas actualmente en los niveles aproximadamente coetáneos del centro-sur de Pangea (Zimbawe e India), los cuales se encuentran considerablemente menos muestreados. Basados en reconstrucciones paleoclimáticas recientes, las asociaciones de dinosaurios más antiguas conocidas parecen haber estado mayormente restringidas a áreas áridas subtropicales a templadas frías. Esta observación concuerda con la hipótesis de que la ausencia de dinosaurios en los niveles superiores de la Formación Ischigualasto pudo haber estado relacionada con un incremento en la humedad de la cuenca. En consecuencia, los factores climáticos, probablemente con la humedad como el más importante, pudieron haber controlado la distribución paleobiogeográfica de las asociaciones de dinosaurios más antiguas conocidas. El logro de una distribución mundial por parte de los dinosaurios durante el Triásico más tardío pudo haber ocurrido después de un cambio climático global, tal como el fin del “Evento Pluvial Carniano”, y/o la incursión de los dinosaurios en climas tropicales húmedos.

Palabras clave. Archosauria, Dinosauria, Triásico, Paleobiogeografía, Macroevolución.

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INTRODUCTION and a larger Norian dinosaur sample is cu- rrently available (Brusatte et al., 2010; Lan- Dinosaurs were one of the most impor- ger et al., 2010; Ezcurra, 2010a). The latter is tant tetrapod groups of Mesozoic terrestrial particularly evident for Norian outcrops of ecosystems. The oldest representatives of Europe [e.g. Trossingen Formation (=Knoll- the clade come from Upper Triassic beds of enmergel sensu Beutler, 2005), Löwenstein Argentina (Ischigualasto Formation), Brazil Formation (= Stubensandstein sensu Beutler, (Santa Maria Formation), Zimbabwe (Pe- 2005); Fraas, 1913; Huene, 1934; Rauhut and bbly Akose Formation), and India (lower Hungerbühler, 2000; Galton, 2001], Argen- Maleri Formation) (Huene, 1940; Colbert, tina (e.g. Los Colorados and Laguna Colo- 1958, 1970; Reig, 1963; Casamiquela, 1967; rada formations; Bonaparte, 1972; Casami- Bonaparte, 1976; Chatterjee, 1987; Sereno quela, 1977), South Africa (e.g. lower Elliot and Novas, 1992; Rogers et al., 1993; Sere- Formation; Huxley, 1866; Haughton, 1924; no et al., 1993; Raath, 1996; Langer et al., Kitching and Raath, 1984; Olsen and Galton, 1999, 2010; Langer, 2005a; Furin et al., 2006; 1984; Galton and Van Heerden, 1998; Gal- Martínez and Alcober, 2009; Alcober and ton et al., 2005; Butler et al., 2007; Yates, 2003, Martínez, 2010; Brusatte et al., 2010; Ezcu- 2007a, b; Yates and Kitching, 2003) and the rra, 2010a; Cabreira et al., 2011; Martínez et USA (e.g. Chinle Formation; Colbert, 1950, al., 2011). These beds are inferred to be late 1989; Long and Murry, 1995; Hunt et al., Carnian to earliest Norian in age because 1998; Irmis, 2005; Parker and Irmis, 2005; Ir- of biostratigraphical correlations mis et al., 2007; Nesbittet al., 2007, 2009; Sues with the Ischigualasto Formation, which is et al., 2011), which have provided abundant constrained to approximately 232–225 Mya remains of basal sauropodomorphs (with on the basis of radioisotopic data (Rogers the exception of North America) and basal et al., 1993; Langer, 2005a; Furin et al., 2006; neotheropods (with the exception of South Martínez et al., 2011). Almost complete ske- Africa). letons of early dinosaurs have been disco- The new discoveries and continuous vered in Argentina (e.g. , Herrera- work of multiple authors have considera- saurus, : Sereno and Novas, 1992; bly improved the knowledge of the origin Sereno et al., 1993; Martínez et al., 2011) and and early evolutionary radiation of dino- more recently from Brazil (e.g. Saturnalia, saurs in the last two decades. In particular, Pampadromaeus; Langer et al., 1999; Cabreira Brusatteet al. (2010) and Langer et al. (2010) et al., 2011), providing a wealth of anatomi- conducted extensive reviews of the current cal information on the early evolution of the understanding of this issue, and a recently group. However, early dinosaur remains published volume focused on this topic from the Pebbly Arkose and lower Maleri also provided a wealth of new information formations are currently scarce, although (Butler et al., 2011). The present contribu- these formations have been much less ex- tion will focus on a review of the taxono- tensively sampled (Huene, 1940; Colbert, mic diversity of the oldest known dinosaur 1958; Chatterjee, 1987; Raath, 1996; Langer assemblages, including a reappraisal of the et al., 2010; Novas et al., 2011). and systematics of some of their Conversely, mid-late Norian dinosaur- specimens. The latter contributes to a more bearing beds are more common worldwide complete understanding of the macroevo- than those from the Carnian-earliest Norian, lutionary patterns that occurred in the first

HISTORIA NATURAL Tercera Serie Volumen 2 (1) 2012/49-71 HISTORIA NATURAL Tercera Serie Volumen 2 (1) 2012/49-71 51 Ezcurra m. d. ca. 7 million years (late Carnian–earliest known dinosaur-bearing assemblages cu- Norian: Martínez et al., 2011) of dinosaur rrently available worldwide. Indeed, at an evolution. alpha-taxonomic level, the record of South Institutional abbreviations. BSPG, Ba- American Triassic dinosaurs (15 species) re- yerische Staatssammlung für Paläontolo- presents 60% of the total of southern Pangea gie und Geologie, Munich, Germany; G/K, (25 species) and 37.5% of the worldwide (ca. Geological Survey of India, collection G/K; 40 species) species richness. GR, Ghost Ranch Ruth May Museum of The main dinosaur-bearing depocenters of Paleontology, New Mexico, USA; ISI, Geo- South America are the Ischigualasto-Villa logical Studies Unit of the Indian Statisti- Unión Basin in northwestern Argentina and cal Institute, Calcutta, India; MACN-Pv, the Paraná Basin in southern Brazil (Reig, Museo Argentino de Ciencias Naturales, 1963; Colbert, 1970; Sereno and Novas, 1992; Paleontología de Vertebrados, Buenos Ai- Langer et al., 1999). Both basins yielded late res, Argentina; MB, Humboldt Museum für Carnian–earliest Norian dinosaur remains Naturkunde, Berlin, Germany; MCP, Mu- that are among the oldest specimens known seo de Ciencias e Tecnología, Porto Alegre, so far. Brazil; NHMUK, Natural History Museum, Ischigualasto-Villa Unión Basin: Ischigualasto London, UK; SMNS, Staatliches Museum Formation. The lower levels of the Ischigua- für Naturkunde, Stuttgart, Germany; PVL, lasto Formation have been dated to 231.4 ± Fundación “Miguel Lillo”, San Miguel de 0.3 Mya (late Carnian: Rogers et al., 1993; Tucumán, Argentina; PVSJ, Museo de Cien- Furin et al., 2006; Rene et al., 2010) (from a cias Naturales, Universidad Nacional de bentonite ash sampled approximately 20 m San Juan, San Juan, Argentina; PEFO, Pe- above the base of the formation within an trified Forest National Park, Arizona, USA; approximately 700 m thick section: Martí- PULR, Paleontología, Universidad Nacio- nez et al., 2011). A second radioisotopic age nal de La Rioja, La Rioja, Argentina; UCMP, yielded a date of 225.9 ± 0.9 Mya (earliest University of California Museum of Paleon- Norian) for the upper third of the Ischigua- tology, Berkeley, California, USA; UFRGS, lasto Formation (Martínez et al., 2011) (from Universidad Federal de Río Grande do Sul, feldspars sampled approximately 630 m Porto Alegre, Brazil; UFSM, Universidad from the base of the formation within an Federal de Santa María, Santa María, Brazil; approximately 700 m thick section: Martí- QG, Zimbabwe Natural History Museum, nez et al., 2011). A third radioisotopic date Bulawayo, Zimbabwe. of 218 ± 1.7 Mya (middle Norian) was pre- liminary reported by Shipman (2004) (from a single sample within a bed 26 m below DISCUSSION the contact between the Ischigualasto and Los Colorados formation within a section The earliest dinosaur records: late Car- at the eastern extremity of the Ischigualasto nian–earliest Norian assemblages (Hype- Formation that is poorly correlated to the rodapedon Assemblage Zone) rest of the formation: Currie et al., 2009). However, Martínez et al. (2011) considered South America this dating unreliable because of the uncer- The South American record provides un- tainty in the stratigraphic location and the questionably the best sample of the oldest fact that the methodology used to derive it

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has yet to be published in detail. Accordin- the Hyperodapedon AZ are followed here. gly, if the rate of sedimentary deposition of The La Peña, Cancha de Bochas and parts the unit was roughly constant, most of the of the Valle de la Luna members of the Ischi- lower half of the Ischigulasto Formation gualasto Formation have yielded a diverse should be upper Carnian and the upper sample of early dinosaurs (see Martínez et half should be lowermost Norian in age al., 2011), that currently minimally includes (Furin et al., 2006; Martínez et al., 2011). six different species: two herrerasaurians As a result, the Carnian-Norian boundary ( ischigualastensis Reig, 1963; should be located close to the middle of the Sereno and Novas, 1992; Sanjuansaurus gor- Ischigualasto Formation, within the Valle dilloi Alcober and Martínez, 2010), three ba- de la Luna Member (Irmis et al., 2011; Mar- sal sauropodomorphs (Eoraptor lunensis Se- tínez et al., 2011). reno et al., 1993; protos Martínez The lower levels of the Ischigualasto For- and Alcober, 2009; novasi mation (0–300 m) belong to the Hyperoda- Ezcurra, 2010a; note that Eoraptor lunensis pedon Assemblage Zone (AZ) (Chatterjee, has been more commonly interpreted as a 1980; Benton, 1983a; Rogers et al., 1993; basal saurischian or a basal theropod: Sere- Langer, 2005a, b; Langer et al., 2007a; equi- no et al., 1993; Ezcurra, 2006, 2010a; Langer valent to the Scaphonyx--Herre- and Benton, 2006; Irmis et al., 2007; Nesbitt rasaurus biozone of Martínez et al., 2011), et al., 2009a), and the probable basal the- which can be roughly constrained to the ropod Eodromaeous murphi Martínez et al., late Carnian (Martínez et al., 2011). Lucas 2011 (Figure 1). Among these taxa, Herrera- (1998, 2010) and Lucas et al. (2007) propo- saurus ischgualastensis was the most abun- sed an Adamanian age for the Ischigualas- dant predator within the tetrapod assem- to Formation, correlating the South Ameri- blage of the lower Ischigualasto Formation can assemblage with the Adamanian fauna (Martínez et al., 2011). A seventh dinosaur of the North American Blue Mesa Member species from the lower Ischigualasto For- of the Chinle Formation. However, Irmis et mation may be represented by a putative al. (2010, 2011) pointed out that radioisoto- ornithischian preliminarily reported on the pic dates indicate that the North American basis of an isolated cervical vertebra (Haro Adamanian fauna is younger than the Is- and Salinas, 2006). Nevertheless, this report chigualasto Formation. This result falsifies requires a more comprehensive study be- global correlations of the Ischigualasto fore it can be confirmed. Dinosaur remains Formation employing an Adamanian age are currently absent from the upper half and raises strong concerns as to the use of the Ischigulasto Formation, which co- of “land vertebrate faunachrons” for such rresponds to the Exaeretodon and Jachaleria long-range biostratigraphic correlations biozones (upper two-thirds of the Valle de (Irmis et al., 2010). Thus, there is no current la Luna and Quebrada de la Sal members) evidence that Hyperodapedon-bearing for- (Martínez et al., 2011). mations, including the Ischigualasto, San- The ornithischian mertii ta María, Pebbly Arkose, lower Maleri and (P. mertii: Casamiquela, 1967) comes from Sandstone formations, are of the Hoyada del Cerro Las Lajas, southeast substantially different ages (contra Lucas, to Los Palacios, in an area of the Ischigua- 2010). Accordingly, the global correlations lasto Formation that crops out in La Rioja proposed by Langer (2005a, b) employing Province (Casamiquela, 1967; Bonaparte,

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1976, 1997). Bonaparte (1976, 1997) indica- more precise geological or biostratigrahical ted that the holotype and only known spe- information from the Hoyada del Cerro las cimen of Pisanosaurus mertii came from the Lajas locality is available. Thus, the referral middle levels of the Ischigualasto Forma- of Pisanosaurus mertii to the Hyperodapedon tion. However, Martínez et al. (2011) noted AZ should be considered ambiguous based that the stratigraphic correlation between on the currently available evidence. the locality in which Pisanosaurus mertii Paraná Basin: Santa Maria Formation. The was found and the area of the Ischigualas- Hyperodapedon AZ is also documented in to Formation that crops out in the San Juan the upper levels of the Santa Maria Forma- Province is poorly constrained. Furthermo- tion of the Brazilian Paraná Basin (Langer re, in addition to Pisanosaurus mertii, only et al., 2007a), and, as a consequence, this the holotype of the ornithosuchid Venatico- section has been interpreted as coeval with suchus rusconii and a basal crocodylomor- the lower Ischigualasto Formation (Langer, ph specimen were collected in this locality 2005b). The Santa Maria Formation has yiel- (Bonaparte, 1971, 1978, 1982; Ezcurra et al., ded the remains of four different species of 2008), whereas no , cynodont dinosaurs: the herrerasaurid or saurischian specimen was found (J. pricei Colbert, 1970, the basal sauropodo- Bonaparte, pers. comm. 2011). Due to the morphs Saturnalia tupiniquim Langer et al., absence of the latter taxa it is impossible 1999 (based on at least three individuals: to assess lateral correlations between the Langer et al., 1999, 2007b; Langer, 2003), San Juan and La Rioja outcrops of the Is- Pampadromaeus barberenai Cabreira et al., chigualasto Formation on the basis of bios- 2011, and a still undescribed fragmentary tratigraphy (Ezcurra, 2012). As a result, the postcranium (UFSM 11330) of a sauropo- Pisanosaurus-bearing locality is considered domorph more derived and larger than Sa- to occupy an indeterminate stratigraphic turnalia (Da-Rosa et al., 2006). As a result, position within the Ischigualasto Forma- the sauropodomorphs constitute the most tion (Martínez et al., 2011), at least until abundant group within the sampled dino-

Figure 1 - Drawing showing two individuals of the early dinosaur Eoraptor lunensis at the shore of a pool in a river during the deposition of the first half of the Ischigualasto Formation, NW Argentina (ca. 230 Mya). Artwork by Emilio López-Rolandi.

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saur specimens from the Santa Maria For- alterations have probably exaggerated this mation, contrasting with the situation in the robustness (BSPG AS XXV 53). BSPG AS coeval beds of the Ischigualasto Formation, XXV 53 measures 27.6 cm in length as pre- in which the herrerasaurid Herrerasaurus is served. The femoral head is anteromedially the most common dinosaur. directed and appears to be strongly intur- A highly problematic taxon that has not ned (Figure 2A–C). However, it is evident been properly described and reviewed is from the proximal surface of the that the putative basal dinosaur Teyuwasu barbe- the medial half of the femoral head is dis- renai (Figure 2), also known from the Hype- placed ventrally with respect to the rest of rodapedon AZ of the Santa Maria Formation. the bone due to two longitudinal fractures Kischlat (1999) named Teyuwasu barberenai (Figure 2C: lfr), that appears to correspond on the basis of a right femur (BSPG AS to the proximodistally directed parallel rid- XXV 53) (Figure 2A–F) and tibia (BSPG AS ges described by Kischlat (1999). As a re- XXV 54) (Figure 2G–L) that had previously sult, the femoral head appears to be more been assigned by Huene (1938, 1942) to the ventrally located than in life, and the de- “rauisuchian” Hoplitosuchus raui. Kischlat gree to which it is inturned has probably (1999) interpreted Teyuwasu as a robust also been exaggerated. The absence of a dinosaur, but no characters were clearly posterior notch between the femoral head indicated in support of this referral. Ne- and shaft and the apparently proximally vertheless, this author (Kischlat, 1999: 58) located fourth trochanter, with a proximal did describe some putative dinosaurian border above the ventral margin of the features of Teyuwasu, such as a “tibia with a femoral head, bolster this interpretation. cnemial crest and a helicoidal rounded dis- The femoral head is rounded in posterior tal articular surface, which is so developed view, resembling the condition in Stauriko- as to encompass the ascending process of saurus pricei (Bittencourt and Kellner, 2009), the astragalus”. More recent authors have Alwalkeria maleriensis (ISI R306), Tawa hallae considered Teyuwasu barberenai as an inde- (Nesbitt et al., 2009a), and some sauropo- terminate putative early dinosaur (Langer, domorphs such as Efraasia (SMNS 12220, 2004; Langer et al., 2010). 14881), Eucnemesaurus (Yates, 2007a), Rio- The preserved bones of Teyuwasu bar- jasaurus (PVL 3808) and Lessemsaurus (Pol berenai have suffered strong taphonomic and Powell, 2007). By contrast, a femoral alteration, and as a result they are poorly head that is square in outline is observed in preserved (Figure 2). Thus, the interpre- Herrerasaurus ischigualastensis (Novas, 1993; tation of the morphology of these bones PVL 2566), bryansmalli (cast of should be considered tentative. The femur PEFO 10395; GR 226), Saturnalia tupiniqium is preserved in three portions that have (Langer, 2003), neotheropods (e.g. Liliens- been attached with plaster with no direct ternus liliensterni: MB R. 2175; Coelophysis contact between them (BSPG AS XXV 53) rhodesiensis: cast of QG1; Dilophosaurus we- (Figure 2A–D). The perimeters of the sepa- therilli: UCMP 37302), and ornithischians rate fragments of shaft match one another, (e.g. Eocursor: Butler, 2010; Stormbergia: and, as a result, it appears that no or only Butler, 2005; Scutellosaurus: UCMP 130580). a small portion of the femoral diaphysis is The proximal surface of the femoral head missing. The femur appears to have belon- possesses a partially preserved shallow ged to a robust , but the taphonomic longitudinal sulcus (Figure 2E: ls), as also

HISTORIA NATURAL Tercera Serie Volumen 2 (1) 2012/49-71 HISTORIA NATURAL Tercera Serie Volumen 2 (1) 2012/49-71 55 Ezcurra m. d. occurs in silesaurids and basal dinosaurs roposteriorly deep. Only the base of the ti- (Ezcurra, 2006; Nesbitt, 2011). The poor biofibular crest is preserved, but it appears preservation of the proximal surface of the to have extended more posteriorly than the bone prevents an assessment as to whether tibial condyle (Figure 2F). The tibial con- it was straight or curved. The posterior dyle has a straight medial margin and a tuberosity of the femoral head is strongly rounded posterior margin. The fibular con- reduced, resembling the condition of basal dyle is strongly convex in distal view. The dinosaurs (Novas, 1996) and the basal sile- popliteal fossa is moderately deep and the saurid Asilisaurus kongwe (Nesbitt, 2011). anterior extensor groove is absent. The anterior surface of the shaft of BSPG The tibia of Teyuwasu barberenai is also a AS XXV 53, at the level of the ventral mar- very robust bone, with a total length of 26.4 gin of the femoral head, possesses a low cm (BSPG AS XXV 54) (Figure 2I–L). Thus, proximodistally extending structure that it is considerably longer than the tibiae of probably represents the anterior trochanter the known specimens of Saturnalia tupini- (Figure 2A, B, D: at?), which resembles that quim (Langer, 2003) and Eoraptor lunensis of other basal saurischians, such as Herre- (PVSJ 512) (ca. 15 cm), and slightly longer rasaurus ischigualastensis (Novas, 1993) and than that of Staurikosaurus pricei (24.6 cm: Saturnalia tupiniquim (Langer, 2003). The Colbert, 1970). However, it is smaller than trochanteric shelf seems to be absent, as several specimens of Herrerasaurus ischi- occurs in baldwini (Ezcurra, gualastensis (PVL 2566: Reig, 1963; Novas, 2006), Eoraptor lunensis (PVSJ 512), Guaiba- 1993) as well as the still undescribed sau- saurus candelariensis (MCP 2355-PV; UFRGS ropodomorph from Alemoa reported by PV 0725T), Staurikosaurus pricei (Bittencourt Da-Rosa et al. (2006). The cnemial crest is and Kellner, 2009), most sauropodomorphs low and not laterally curved (Figure 2G), (e.g. Plateosaurus, Riojasaurus; Bonaparte, contrasting with the condition widely ob- 1972; Moser, 2003), “gracile” forms of basal served in basal dinosaurs (Irmis et al., 2007; neotheropods (Raath, 1977, 1990), and orni- Nesbitt, 2011). Although only a portion of thischians (e.g. Eocursor: Butler, 2010; Storm- the base of the lateral condyle is preser- bergia: Butler, 2005; Scutellosaurus: UCMP ved, the medial condyle would have been 130580). The fourth trochanter is well de- considerably more posteriorly extended veloped posteriorly, transversely thick and because the posterior tip of the base of the apparently located well proximally in the lateral condyle is positioned considerably shaft (Figure 2B–D), but the latter appears to more anteriorly than the posterior end of be a post-mortem artefact (see above). The the former condyle (Figure 2G). This featu- fourth trochanter appears to be symmetric re resembles the morphology observed in in medial or lateral view, contrasting with the basal dinosauriform lillo- most basal saurischian and sauropodomor- ensis (Sereno and Arcucci, 1994), ornithis- ph dinosaurs (e.g. Herrerasaurus ischigualas- chians (e.g. Pisanosaurus mertii: PVL 2577; tensis: Novas, 1993; Saturnalia tupiniquim: Eocursor parvus: Butler, 2010), Sanjuan- Langer, 2003). However, this condition can- saurus gordilloi (PVSJ 605), some specimens not be assessed confidently because of the of Herrerasaurus ischigualastensis (MACN- poor preservation of the bone and should Pv 18060, holotype of “Ischisaurus cattoi”: be considered tentative. The distal end of Ezcurra, 2012; PVL 2558) and sauropodo- the femur is transversely wider than ante- morphs (e.g. Saturnalia tupiniqium: Langer,

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Figure 2 - Indeterminate dinosauriform “Teyuwasu barberenai”. Right femur (BSPG AS XXV 53) in anterior (A), medial (B), posterior (C), lateral (D), proximal (E) and distal (F) views, and right tibia (BSPG AS XXV 54) in proximal (G), distal (H), anterior (I), medial (J), posterior (K) and lateral (L) views. Scale bar equals 10 cm. Abbreviations. at?, probable anterior trochanter; cc, cnemial crest; fap, facet for the reception of the ascending process of the astragalus; fc, fibular condyle; fh, femoral head; ft, fourth trochanter; lc, lateral condyle; lfr, longitudinal fracture; lg, longitudinal groove; ls, longitudinal sulcus; mc, medial condyle; pf, popliteal fossa; plp, posterolateral process; tc, tibial condyle; tfc, tibiofibular crest.

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2003; Panphagia protos: PVL 874; Chromogi- su barberenai is a strongly inturned femoral saurus novasi: Ezcurra, 2010a). The medial head (Benton, 1990; Ezcurra, 2006; Irmis et condyle is distinctly posteriorly projected al., 2007; Brusatte et al., 2010; Langer et al., with respect to the shaft in lateral and me- 2010). However, as noted above, this cha- dial views. The tibial shaft is straight in racter may well be an artefact related to the lateral and anterior views. The distal end strong taphonomic alterations suffered by of the tibia has an oval outline, being trans- the bones. Accordingly, the assignment of versely wider than anteroposteriorly deep Teyuwasu barberenai to Dinosauria should and lacking a posteromedial ridge (Figure be considered ambiguous. Nevertheless, 2H), as also occurs in basal dinosauromor- Teyuwasu barberenai can be assigned confi- phs (e.g. Marasuchus lilloensis: Sereno and dently to the clade that includes silesaurids Arcucci, 1994; opolensis: Dzik, and dinosaurs based on the presence of a 2003) and herrerasaurids (Novas, 1989). femur with a longitudinal proximal groove, By contrast, in ornithischians (e.g. Pisano- and a reduced posterior tuberosity on the saurus mertii: PVL 2577; Eocursor parvus: femoral head, and the tibia with a postero- Butler, 2010), sauropodomorphs (e.g. Sa- lateral process exceeding laterally the facet turnalia tupiniquim: Langer, 2003; Panpha- for the reception of the ascending process gia protos: Martínez and Alcober, 2009; of the astragalus and with a longitudinal Chromogisaurus novasi: Ezcurra, 2010a) and lateral groove separating the posterolate- neotheropods (e.g. Liliensternus liliensterni: ral process and the facet for the reception MB R. 2175; Zupaysaurus rougieri: Ezcurra of the ascending process of the astragalus and Novas, 2007) the tibia possesses a dis- (Novas, 1989, 1996; Ezcurra, 2006; Langer tinct posteromedial corner in distal view and Benton, 2006; Irmis et al., 2007; Nesbitt, as a result of the presence of such a longi- 2011; considering Pseudolagosuchus major tudinal ridge. The facet for the reception of to be a silesaurid dinosauriform as recove- the ascending process of the astragalus is red by Nesbitt et al., 2010). In addition, the horizontally oriented (Figure 2I: fap) and probable presence of an anterior trochanter anteroposteriorly shallower than half of on the femur and a tibia with asymmetric the depth of the distal end of the bone (Fi- posterior condyles of the proximal end are gure 2H). The posterolateral process of the additional synapomorphies that support distal end of the tibia possesses a convex or more inclusive clades posterior surface and is slightly more late- (Ezcurra, 2006; Nesbitt et al., 2009b). The rally extended than the facet for the recep- lack of clear autapomorphies or a unique tion of the ascending process of the astra- combination of characters, in combination galus, resembling the condition of several with the extremely poor state of preserva- basal dinosauriforms (e.g. Pseudolagosu- tion of the holotype, means that Teyuwasu chus major: PULR 053; some specimens of and Teyuwasu barberenai must be conside- Herrerasaurus ischigualastensis: PVSJ 373). red as nomina dubia that represent an inde- The posterolateral process and the facet terminate dinosauriform with an apparent for the reception of the ascending process robust morphology. of the astragalus are separated by a lateral groove (Figure 2H: lg). The only dinosaurian synapomorphy po- tentially present in the holotype of Teyuwa-

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Africa India Cabora Bassa Basin: Pebbly Arkose Forma- Gondwana formations: lower Maleri Forma- tion. The late Carnian–earliest Norian di- tion. The lower Maleri Formation has been nosaur record in Africa is currently much correlated with the South American Hy- more restricted than in South America perodapedon AZ (late Carnian–earliest No- (Langer, 2005a; Langer et al., 2010). The ol- rian) based on the presence of a faunal as- dest known dinosaur specimen from this semblage dominated by individuals of the continent was reported by Raath (1996), as rhynchosaur Hyperodapedon (= Paradapedon) part of a poorly sampled Triassic tetrapod huxleyi and the cynodont Exaeretodon (Lan- assemblage from the Pebbly Arkose For- ger, 2005a; see Benton, 1983b). Among the mation (Cabora Bassa Basin), lower Zam- diverse tetrapod fauna recovered from this bezi Valley of Zimbabwe. This fauna is do- unit, the only named dinosaur species is minated by individuals of the rhynchosaur Alwalkeria maleriensis, which is known by a Hyperodapedon, and likely pertains to the single specimen that includes a right femur Hyperodapedon AZ (Raath et al., 1992; Lan- and astragalus (Chatterjee, 1987; Remes and ger, 2005b; Langer et al., 2010). Raath (1996) Rauhut, 2005). Alwalkeria maleriensis can be described a fragment of dinosaur femoral considered as a valid species of saurischian, shaft from these beds that probably repre- with an unusual femoral morphology and sents the oldest dinosaur record outside of a more conservative astragalar morphology South America and India. This specimen (Novas et al., 2011). Before the description of was originally interpreted as a “prosauro- Alwalkeria, Huene (1940) reported the first pod” (Raath, 1996), but, more recently, Lan- dinosaur remains collected from the Maleri ger et al. (1999: 515) considered that “the beds of India (Figure 3). Huene (1940) des- morphology of the femoral fragment of the cribed five isolated postcranial bones from unnamed Zimbabwean sauropodomorph the Hyperodapedon-bearing levels of the is almost indistinguishable from that of Maleri Formation, including the distal half Saturnalia, and it would not be surprising of a femur (K. 33/608a) (Figure 3B, E), the if they belonged to the same taxon.” This proximal end of a tibia (K. 33/621a) (Figure specimen is considered here to belong to a 3C, F), and three incomplete dorsal verte- saurischian because of the presence of an brae (K. 33/606b, 621b, G. 281/1a) (Figure asymmetric fourth trochanter, which is not 3A, D). Huene (1940) assigned the smaller pendant as occurs in ornithischians. Howe- dinosaur bones, represented by the femur, ver, the Zimbabwean material closely res- tibia and one of the dorsal vertebrae, to an embles the morphology present in a range indeterminate coelurosaur theropod, whe- of basal saurischians, including Saturnalia reas the two larger dorsal vertebrae were tupiniquim but also Herrerasaurus ischigua- considered to represent a prosauropod lastensis and Staurikosaurus pricei, and no sy- (cf. Massospondylus sp.) based on their si- napomorphies can be identified that allow milarity in size and shape to prosauropod assignment to a more precise phylogenetic vertebrae (Huene, 1940: 38). In particular, a referral. Thus, this specimen is here re-in- Huene (1940: 37) proposed that the small terpreted as representing an indeterminate coelurosaur vertebra and femur “could saurischian dinosaur. well go together” (Figure 3A-B, D-E) and suggested their assignment to the family “Podokesauridae” (with a taxonomic con-

HISTORIA NATURAL Tercera Serie Volumen 2 (1) 2012/49-71 HISTORIA NATURAL Tercera Serie Volumen 2 (1) 2012/49-71 59 Ezcurra m. d. tent similar to that currently understand same locality and “could well go together”. as Coelophysoidea) based on their overall However, it is not clear exactly what Huene resemblance to specimens of “Coelophysis meant by this statement, whether the speci- longicollis” (= Coelophysis bauri). The proxi- mens would belong to a single individual, mal tibia (Figure 3C, F) was interpreted by or to a single species. Nevertheless, the ra- Huene (1940) as belonging to a different tio of the centrum width to the distal femo- taxon of coelurosaur because of its larger ral width ranges between 0.78–0.83 (based size. Subsequently, Colbert (1958) reviewed on the anterior and posterior surfaces of the the tetrapods collected from the Maleri For- centrum, respectively), which is considera- mation and also highlighted the similarities bly higher than ratios found in other basal between the putative coelurosaur remains dinosaur specimens, such as in the holoty- described by Huene (1940) and those of pe and a referred specimen of Herrerasaurus the genus Coelophysis, also suggesting that ischigualastensis (PVL 2566: 0.55–0.67; PVSJ they represented members of “Podokes- 373: 0.37–0.53; considering the first to tenth auridae”. Colbert (1958) did not support dorsal vertebrae measured by Novas, 1993) the interpretation of Huene (1940) that the and the holotype of Coelophysis rhodesiensis proximal end of the tibia belonged to a se- (NHMUK R9584 cast of QG 1: 0.50–0.54; cond coelurosaur form, and instead inter- considering the anterior–middle dorsal preted the putative podokesaurid remains vertebrae measured by Raath, 1977). Accor- as probably representing a single species. dingly, the smaller dorsal vertebra and the However, Colbert (1958) disagreed with distal femur cannot be confirmed as belon- the taxonomic assignment provided by ging to the same individual and should be Huene (1940) for the two larger vertebrae considered independently. and stated that these vertebrae belonged to The smaller vertebra (K. 33/606b; Figure phytosaurs because they matched almost 3A, D) appears to be an anterior or middle exactly in size, shape and general morpho- dorsal because the parapophyses (repre- logy with comparable elements of North sented by the base of the left parapophysis; American parasuchians. Subsequent au- Huene, 1940: plate 10, 5a) are still placed thors followed the taxonomic revision con- on the anteroventral corner of the neural ducted by Colbert (1958) (e.g. Roy Chowd- arch pedicle, resembling the condition ob- hury, 1965). However, Chatterjee (1987) did served in dorsal vertebrae 1–10 of Herrera- not discuss the dinosaur remains described saurus ischigualastensis (Novas, 1993). The by Huene (1940) and they have also been centrum is amphicoelous and considerably ignored by more recent reviews of early di- elongated, being around twice as long as nosaur evolution (e.g. Brusatte et al., 2010; high, as also occurs in several archosauro- Langer et al., 2010; Novas et al., 2011; but morphs (e.g. Malerisaurus langstoni: Chat- see Kutty et al., 2007). terjee, 1986; Effigia okeeffeae: Nesbitt, 2007; Major advances in the understanding of Coelophysis rhodesiensis: Raath, 1977). The early dinosaur anatomy and systematics neural arch possesses well-developed pa- subsequent to the work of Colbert (1958) radiapophyseal and posterior centrodia- invite a re-evaluation of these specimens pophyseal laminae, as also occurs in the here. Huene (1940: 37) indicated that the dorsal vertebrae of a wide array of archo- smaller dorsal vertebra (K. 33/606b) and the sauromorphs (e.g. Tanystropheus conspicuus: distal femur (K. 33/608a) were found in the Wild, 1973; Erythrosuchus africanus: Gower,

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Figure 3 - Putative dinosaur specimens described by Huene (1940) and reviewed by Colbert (1956) from the Maleri beds of central India. (A, D) Archosauromorph partial dorsal vertebra in left lateral (A) and posterior (B) views; (B, E) distal left femur in posterior (B) and distal (E) views; and (C, F) dinosaur proximal right tibia in lateral (C) and proximal (F) views. Scale bar equals 1 cm. Drawings modified from Huene (1940: plate 10). Abbreviations: c, centrum; cc, cnemial crest; fc, fibular condyle; lc, lateral condyle and anterior sulcus; mc, medial condyle; nc, neural canal; pa, parapophysis; pcdl, posterior centrodiapophyseal lamina; pdl, paradiapophyseal lamina; pf, popliteal fossa; tc, tibiofibular crest; tfc, tibiofibular crest.

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2001, 2003; Hypselorhachis mirabilis: Butler Postosuchus kirkpatricki: Nesbitt, 2011) and et al., 2009; Effigia okeeffeae: Nesbitt, 2007; ornithodirans (e.g. Dimorphodon macronyx: Silesaurus opolensis: Piechowski and Dzik, NHMUK 41212-13; chanarensis: 2010; Herrerasaurus ischigualastensis: Novas, PVL 4619; Marasuchus lilloensis: PVL 3871; 1993; Coelophysis rhodesiensis: Raath, 1977). Silesaurus opolensis: Dzik, 2003; Pisanosaurus K. 33/606b does not exhibit any synapo- mertii: PVL 2577; Herrerasaurus ischigualas- morphy of Dinosauria, but the presence tensis: Novas, 1993; Saturnalia tupiniquim: of well-developed neural arch laminae is a Langer, 2003; Liliensernus liliensterni: MB R. feature only recognized in basal archosau- 2175). By contrast, the distal femoral con- romorphs among Triassic tetrapods. Accor- dyles of non-archosaur archosauromorphs dingly, this specimen should be considered are poorly posteriorly projected, such as in as an indeterminate archosauromorph. Tanystropheus conspicuus (Wild, 1973), Male- The distal femur (K. 33/608a; Figure 3B, risaurus langstoni (Chatterjee, 1986),Erythro- E) possesses a slightly transversely expan- suchus africanus (Gower, 2003), Euparkeria ded distal end with respect to the shaft. capensis (Ewer, 1965), Doswellia kaltenbachi The popliteal fossa is deep and extends (Dilkes and Sues, 2009), Vancleavea campi proximally slightly beyond the distal con- (Nesbitt et al., 2009c) and Chanaresuchus bo- dyles of the femur. The anterior margin of napartei (PVL 6244). In addition, the overall the femur is strongly convex in distal view, morphology of K. 33/608a is very similar to lacking an extensor fossa. By contrast, that of Silesaurus (S. opolensis: Dzik, 2003) Alwalkeria maleriensis seems to possess a and almost identical to that observed in medially displaced anterior extensor gro- basal saurischian dinosaurs (e.g. tibial con- ove (ISI R306). Although the anterior sur- dyle with a square outline, rounded fibular face of the distal femur of Alwalkeria male- condyle, concave lateral margin of the ti- riensis is damaged, the morphology and biofibular crest), includingHerrerasaurus is- position of the probable extensor groove chigualastensis (PVSJ 373; Novas, 1993) and closely resembles that of basal neothero- Saturnalia tupiniqium (Langer, 2003). Howe- pods (e.g. Coelophysis rhodesiensis: NHMUK ver, K. 33/608a more closely resembles ba- R9585, cast), suggesting that it is a natural sal saurischians than Silesaurus based on feature. The tibial condyle is strongly pos- the proportionally narrower femur in distal teriorly developed and has a square outline view. K. 33/608a lacks neotheropod featu- in distal view. The tibiofibular crest does res, such as a mediodistal crest or an infra- not project beyond the posterior level of the popliteal ridge. Accordingly, this specimen tibial condyle and curves slightly laterally. is considered here as an indeterminate ar- The fibular condyle possesses a rounded chosaur cf. . If K. 33/608a actually lateral margin in distal view. K. 33/608a can represents a saurischian dinosaur, it would be included within Archosauria because of constitute a second dinosaur taxon from the presence of strongly posteriorly projec- the lower Maleri Formation, distinct from ting distal condyles, resembling the con- Alwalkeria maleriensis. dition of phytosaurus (e.g. Pseudopalatus: The proximal tibia (K. 33/621a; Figure Nesbitt, 2011) but see Nesbitt, 2011 for an 3C, F) possesses a distinct cnemial crest alternative position of phytosaurs outside that curves laterally, as usually occurs in Archosauria, most pseudosuchians (e.g. dinosaurs (e.g. Herrerasaurus ischigualasten- Riojasuchus tenuisceps, Hesperosuchus agilis, sis: Novas, 1993; Panphagia protos: PVSJ 874;

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Saturnalia tupiniqium: Langer, 2003; Pisa- served in the proximal end of the tibia of ba- nosaurus mertii: PVL 2577; Eocursor parvus: sal ornithischians, in which the cnemial crest Butler, 2010; Liliensternus liliensterni: MB is very well developed, the lateral condyle R. 2175). The lateral surface of the cnemial is considerably more projected posteriorly crest seems to lack the longitudinal lip that than the medial condyle and both condyles it is observed in some basal dinosaurs, such are separated by a deep posterior notch (e.g. as Pisanosaurus mertii (PVL 2577), Panphagia Pisanosaurus mertii: PVL 2577; Eocursor par- protos (PVSJ 874) and Liliensternus lilienster- vus: Butler, 2010). Accordingly, K. 33/621a ni (MB R. 2175). The lateral condyle is only most likely represents a basal saurischian differentiated from the cnemial crest by the dinosaur. Unfortunately, there are no over- longitudinal depression that received the lapping bones between K. 33/621a and the anterior border of the proximal end of the holotype of Alwalkeria maleriensis that allow fibula. The medial condyle is slightly more an assessment of whether they represent posteriorly extended than the lateral con- distinct taxa. dyle, resembling the condition of Panphagia The criticisms made by Colbert (1958) of protos (PVSJ 874), but contrasting with the the putative dinosaurian affinities of the more asymmetric proximal condyles pre- large vertebral centra described by Huene sent in Marasuchus lilloensis (Sereno and Ar- (1940) (K. 33/606b; G. 281/1a) are followed cucci, 1994), ornithischians (e.g. Pisanosaurus here. These specimens do not exhibit any mertii: PVL 2577; Eocursor parvus: Butler, sauropodomorph or dinosaurian synapo- 2010), sauropodomorphs (e.g. Saturnalia tu- morphies. As a result, the proximal tibia K. piniqium: Langer, 2003; Panphagia protos: PVL 33/621a is the only specimen described by 874; Chromogisaurus novasi: Ezcurra, 2010a), Huene (1940) that can be unambiguously Sanjuansaurus gordilloi (PVSJ 605) and some referred to Dinosauria. Due to the absence referred specimens of Herrerasaurus ischigua- of overlapping elements between Alwalke- lastensis (PVL 2588 and probably MACN-Pv ria maleriensis and 33/621a, the minimal 18060, holotype of “Ischisaurus cattoi”: Ezcu- sampled dinosaur taxonomic diversity of rra, 2012). The lateral and medial condyles the lower Maleri Formation is currently are separated by a wide posterior groove, restricted to a single species. contrasting with basal ornithischians (e.g. Pisanosaurus: PVL 2577; Eocursor parvus: Butler, 2010) and some neotheropods (e.g. DISCUSSION Gojirasaurus quaxi: Carpenter, 1997) that possess a deep posterior notch separating The taxonomic review conducted here both condyles. A gentle concavity in the of some of the oldest known dinosaur spe- proximal surface of the bone separates the cimens collected from the Hyperodapedon cnemial crest from the posterior condyles in Assemblage Zone bolsters previous obser- medial view. K. 33/621a can be assigned to vations that the richest sampled dinosaur Dinosauria because of the presence of a la- taxonomic diversity is concentrated in terally curved cnemial crest, which has been southwestern Pangean assemblages, with recovered as a dinosaur synapomorphy by 10 to 11 different species (Argentina and recent phylogenetic analyses (Irmis et al., Brazil) (Figure 4A-C). By contrast, only one 2007; Nesbitt, 2011). Within Dinosauria, K. or two species can be currently recognized 33/621a does not match the morphology ob- from approximately coeval beds of south–

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Figure 4 - (A) Paleobiogeographical distribution of the oldest known dinosaur assemblages indicated with black stars during the late Carnian–earliest Norian (Hyperodapedon AZ) (paleomap for 230 Mya downloaded from the Paleobiology Database). Named dinosaur species currently known from the Hyperodapedon AZ of the (B) Ischigualasto Formation, (C) Santa Maria Formation, (D) Pebbly Arkose Formation and (E) lower Maleri Formation. Herrerasaurus ischigualastensis modified from Sereno and Novas (1992); Sanjuansaurus gordilloi modified from Alcober and Martínez (2010); Eodromaeus murphi modified from Martínez et al. (2011); Eoraptor lunensis modified from Sereno et al. (1993); Panphagia protos modified from Martínez and Alcober (2009); Chromogisaurus novasi modified from Ezcurra (2010a); Staurikosaurus pricei modified from Bittencourt and Kellner (2009); Saturnalia tupiniquim modified from Langer and Benton (2006); Pampadromaeus barberanai modified from Cabreira et al. (2011); Alwalkeria maleriensis and Saurischia indet. modified from Langer (2004).

central Pangea (Zimbabwe and India) (Fi- non-dinosaur dinosauriforms (e.g. Siles- gure 4A, D-E), although those units have aurus opolensis: Dzik, 2003; elgi- been much less well sampled than those of nensis: Benton and Walker, 2011; Diodorus Brazil and Argentina. The oldest known di- scytobrachion: Kammerer et al., 2012). This nosaur-bearing assemblages are currently latter observation may indicate a disjunct restricted to outcrops from southern Pan- distribution between dinosaurs and non- gea during the late Carnian–earliest No- dinosaur dinosauriforms during the late rian, in a paleolatitudinal belt of approxi- Carnian–earliest Norian. Nevertheless, it mately 40–50° S (Ezcurra, 2010b) (Figure should be pointed out that these hypothe- 4A). This paleolatitudinal belt appears to ses could be easily rejected if dinosaurs are have included mostly subtropical to cool discovered in beds of that age outside of temparate arid areas during the Late Trias- the 40–50° S paleolatitudinal belt. The pre- sic, according to recent paleoclimatologi- sence of dinosaurs in younger Triassic beds cal reconstructions (Sellwood and Valdes, (middle Norian–Rhaetian) of North Ameri- 2006). In agreement with this observation, ca and Europe has been explained through Martínez et al. (2011) suggested that the ab- a south to north dispersal event (Nesbitt et sence of dinosaurs in the upper levels of the al., 2009a; Irmis, 2011). Thus, the achieve- Ischigualasto Formation could be related to ment of a worldwide dinosaur distribution an increase in humidity through time in during the latest Triassic may have occu- the Ischigualasto-Villa Unión Basin. These rred after a global climate change (e.g. the combined lines of evidence favour the idea end of the “Carnian Pluvial Event”; Simms that climatic factors, with humidity as pro- and Ruffell, 1989; see Roghi et al., 2010) bably the most important, may have con- and/or the invasion of more tropical humid trolled the distribution of the oldest known climates by dinosaurs. dinosaur assemblages. The climatological conditions under which the sediments of the Indian lower Maleri Formation were ACNOWLEDGEMENTS deposited are not completely clear, but it may have had a more humid climate than I thank R. Irmis for his comments on an in northwestern Argentina, southern Brazil early version and R. Butler for his feedback or Zimbabwe (Sellwood and Valdes, 2006: in a late version of the manuscript. Figure 2b, c). By contrast, in humid tropi- The comments and suggestions of M. cal to warm temperate areas of Laurasia, J. Trotteyn and A. Martinelli were highly between 0–30° N, the currently available appreciated and improved the overall qua- tetrapod assemblages have yielded only lity of the manuscript.

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I appreciate the helpful of several people Bonaparte, J.F. 1972. Los tetrápodos del sector that allowed me to study specimens under superior de la Formación Los Colorados. their care: M. Moser (BSPG), N. Klein (MB), Opera Lilloana, 22: 1-183. Bonaparte, J.F. 1976. Pisanosaurus mertii Casa- J. Powell (PVL), E. Vaccari (PULR), A. Kra- miquela and the origin of the . marz and Stella Alvarez (MACN), R. Irmis Journal of Paleontology, 50: 808-820. (UMNH), P. Hollroyd (UCMP), S. Chap- Bonaparte, J.F. 1978. El Mesozoico de América man, L. Steel and P. Barrett (NHMUK), R. del Sur y sus tetrápodos. Opera Lilloana, 26: Martínez and D. Abeldin (PVSJ), C. Mala- 1-596. barba (MCP), A. Da-Rosa (UFSM) and C. Bonaparte, J.F. 1982. Classification of the Theco- dontia. Géobios, Mémoire Spécial, 6: 99-112. Schultz (UFRGS). This research was com- Bonaparte, J.F. 1997. El Triasico de San Juan - La pleted during receipt of PhD funding from Rioja, Argentina y sus dinosaurios. Museo Ar- the Emmy Noether Programme of the DFG gentino de Ciencias Naturales, Buenos Ai- (grant BU 2587/3-1 to Richard Butler). res, 190 pp. Brusatte, S.L., Nesbitt, S.J., Irmis, R.B., Butler, R.J., Benton, M.J. and Norell, M.A. 2010. The REFERENCES origin and early radiation of dinosaurs. Ear- th-Science Reviews, 101: 68-100. Butler, R.J. 2005. The ‘fabrosaurid’ ornithischian Alcober, O.A. and Martínez, R.N. 2010. A new he- dinosaurs of the Upper Elliot Formation rrerasaurid (Dinosauria, Saurischia) from the (Lower ) of South Africa and Leso- Upper Triassic of Ischigualasto Formation of tho. Zoological Journal of the Linnean Society, northwestern Argentina. ZooKeys, 63: 55-81. 145: 175-218. Benton, M.J. 1983a. The age of the . Butler, R.J. 2010. The anatomy of the basal or- New Scientist, 98: 9-13. nithischian dinosaur Eocursor parvus from Benton, M.J. 1983b. Dinosaur success in the the lower Elliot Formation (Late Triassic) of Triassic: A noncompetitive ecological model. South Africa. Zoological Journal of the Linnean The Quarterly Review of Biology, 58: 29-55. Society, 160: 648-684. Benton, M.J. 1990. Origin and interrelationships Butler, R.J., Smith, R.M.H. and Norman, D.B. of dinosaurs. In: Weishampel, D.B., Dodson, 2007. A primitive ornithischian dinosaur P. and Osmólska, H. (Eds.), The Dinosauria. from the Late Triassic of South Africa, and University of California Press, Berkeley, the early evolution and diversification of Or- USA, pp. 11-30. nithischia. Proceedings of the Royal Society B, Benton, M.J. and Walker, A.D. 2011. Saltopus, a 274: 2041-2046. dinosauriform from the Upper Triassic of Butler, R.J., Barrett, P.M., Abel, R.L. and Gower, . Earth and Environmental Science D.J. 2009. A possible ctenosauriscid archo- Transactions of the Royal Society of Edinburgh, saur from the Manda Beds 101: 285-299. of Tanzania. Journal of Vertebrate Paleontology, Beutler, G. 2005. Lithostratigraphie. In: Beut- 29: 1022-1031. ler, G., Hauschke, N., Nitsch, E. and Vath, Butler, R.J., Irmis, R.B. and Langer, M.C. 2011. U. (Eds.), Stratigraphie von Deutschland IV: Preface to ‘Late Triassic Terrestrial Biotas Keuper. Courier Forschungsinstitut Sencken- and the Rise of Dinosaurs’ Special Issue. Ear- berg 253, Frankfurt, pp. 65-84. th and Environmental Science Transactions of Bittencourt, J.S. and Kellner, A.W.A. 2009. The the Royal Society of Edinburgh, 101: 5-9. anatomy and phylogenetic position of the Cabreira, S.F., Schultz, C.L., Bittencourt, J.S., Triassic dinosaur Staurikosaurus pricei Col- Soares, M.B., Fortier, D.C., Silva, L.R. and bert, 1970. Zootaxa, 2079: 1-56. Langer, M.C. 2011. New stem-sauropodo- Bonaparte, J.F. 1971. Annotated list of the South morph (Dinosauria, Saurischia) from the American Triassic tetrapods. Second Gondwa- Triassic of Brazil. Naturwissenschaften, 98: na Symposium, South Africa, 1970: 665-682. 1035-1040.

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Recibido: 22/4/2012 - Aceptado: 25/5/2012

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