ORIGINAL PAPER

New stem-sauropodomorph (Dinosauria, Saurischia)from the Triassic of Brazil

Sergio F. Cabreira & Cesar L. Schultz &

Jonathas S. Bittencourt & Marina B. Soares &

Daniel C. Fortier & Lúcio R. Silva & Max C. Langer

Received: 22 August 2011 /Revised: 7 October 2011 /Accepted: 13 October 2011# Springer-Verlag 2011

Abstract Post-Triassic theropod, sauropodomorph, andornithischian dinosaurs are readily recognized based onthe set of traits that typically characterize each of thesegroups. On the contrary, most of the early members of thoselineages lack such specializations, but share a range ofgeneralized traits also seen in more basal dinosauromorphs.Here, we report on a new Late Triassic dinosaur from theSanta Maria Formation of Rio Grande do Sul, southernBrazil. The specimen comprises the disarticulated partial

skeleton of a single individual, including most of the skullbones. Based on four phylogenetic analyses, the newdinosaur fits consistently on the sauropodomorph stem,but lacks several typical features of sauropodomorphs,showing dinosaur plesiomorphies together with some neo-theropod traits. This is not an exception among basaldinosaurs, the early radiation of which is characterized by amosaic pattern of character acquisition, resulting in theuncertain phylogenetic placement of various early membersof the group.

Keywords Dinosauria, Late Triassic . Santa MariaFormation . Archosauria . Phylogeny

Introduction

Previous to the discovery of Saturnalia tupiniquim, fromthe Santa Maria Formation of southern Brazil (Langer et al.1999), the oldest known members of the sauropodomo-morph lineage were relatively massive, medium to largesized dinosaurs, recovered from Norian aged strata, mainlyin Europe, Argentina, and South Africa (Galton 1990).Since then, an unsuspected diversity of smaller, moregracile stem-sauropodomorphs (sensu Langer 2003) wasrecovered from Carnian deposits of South America,especially from the Ischigualasto Formation, in Argentina.This includes Panphagia protos (Martinez and Alcober2009), Chromogisaurus novasi (Ezcurra 2010), and possi-bly also Eoraptor lunensis (Martinez et al. 2011), formerlynested within Theropoda (Sereno et al. 1993). Here, wereport on a disarticulated but otherwise well-preservedskeleton of a new stem-sauropodomorph from the LateTriassic of southern Brazil (Fig. 1), including most of theskull bones (Fig. 2).

Communicated by: Robert Reisz

Electronic supplementary material The online version of this article(doi:10.1007/s00114-011-0858-0) contains supplementary material,which is available to authorized users.

S. F. Cabreira : L. R. SilvaMuseu de Ciências Naturais,Universidade Luterana do Brasil (ULBRA),Av. Farroupilha 8001,92425-900 Canoas, Rio Grande do Sul, Brazil

C. L. Schultz :M. B. SoaresDepartamento de Paleontologia e Estratigrafia,Instituto de Geociências,Universidade Federal do Rio Grande do Sul (UFRGS),Av. Bento Gonçalves 9500,91540-000 Porto Alegre, Rio Grande do Sul, Brazil

J. S. Bittencourt :M. C. Langer (*)Laboratório de Paleontologia de Ribeirão Preto, FFCLRP,Universidade de São Paulo,Av. Bandeirantes 3900,14040-901 Ribeirão Preto, São Paulo, Brazile-mail: mclanger@ffclrp.usp.br

D. C. FortierDepartamento de Geologia, UFMG,Av. Antônio Carlos 6627,31270-901 Belo Horizonte, Minas Gerais, Brazil

NaturwissenschaftenDOI 10.1007/s00114-011-0858-0

Systematic palaeontology

Dinosauria Owen 1842 sensu Padian and May (1993)Saurischia Seeley 1887 sensu Gauthier (1986)Eusaurischia Padian, Hutchinson & Holtz 1999 sensuLanger (2004)stem-Sauropodomorpha Huene 1932 sensu Salgado et al.(1997; see Langer 2003)Pampadromaeus barberenai new genus and species

Etymology The generic name is derived from the Quechuaword pampa (=plain), in reference to the grassland landscapethat covers parts of Rio Grande do Sul, and dromaeus,variant of Greek δρομεύς (=runner), in reference to theprobable cursoriality of the animal. The specific epithethonors the Brazilian palaeontologist Mário C. Barberena.

Holotype ULBRA-PVT016 (Museu de Ciências Naturais,Universidade Luterana do Brasil, Canoas), disarticulatedpartial skeleton preserved in a single mudstone block(Figs. 1 and 2), including most skull bones, parts of themandible, incomplete vertebral column, and apendicularskeleton (see details of the preserved elements in theElectronic Supplementary Material). Some of the elementswere extracted, but most were only superficially exposed,retaining their original position in the block.

Type locality and horizon Reddish mudstones of theAlemoa Member, Santa Maria Formation, Rosário do Sul

Group (Zerfass et al. 2003), exposed at the site known as“Janner” or “Várzea do Agudo” (53°17′34.20″ W, 29° 39′10.89″ S), located about 2 km west of the town of Agudo,Rio Grande do Sul, Brazil (Fig. 1). Based on the co-occurrence of index fossils such as Exaeretodon andHyperodapedon, the site can be assigned to the upperportions of the Hyperodapedon Assemblage Zone (Langeret al. 2007). Correlation to the better constrained Ischigua-lasto Formation, northwestern Argentina (Martinez et al.2011), suggests a late Carnian age; ca. 230–228 Ma.

Diagnosis It is distinguished from all other well-knownTriassic dinosauromorphs by the following unique combi-nation of character states (see extended diagnosis in theElectronic Supplementary Material): head longer than twothirds of the femoral length, premaxilla with short subnarialprocess, concave ventral margin of the premaxilla–maxillaarticulation, no inset of first premaxillary or dentary tooth,premaxilla and dentary with unserrated mesial-most toothcrowns, most teeth lanceolate with coarse denticles alongthe carinae, sacral vertebrae with dorsoventrally expandedribs, femur with reduced medial tuberosity (“t” in Novas1996; Fig. 3) in the head and well-developed trochantericshelf, epipodium significantly longer than femur.

Description

The premaxilla has a shallow narial fossa, four alveoli, anda subnarial process that does not reach the nasal. On the

Fig. 1 Pampadromaeus barberenai, locality map and skeletal silhouette, showing preserved elements of the holotype (ULBRA-PVT016)

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medial side, the maxillary process of the premaxilla forms ahorizontal shelf below the palatal process of the maxilla.The dorsal and rostral rami of the maxilla meet forming alow, but well-defined angle at the rostral margin of thebone. Reconstruction of the premaxilla–maxilla articulationsuggests that the former is ventrally projected. This isreminiscent of the subnarial gap of theropods, in the sensethat the alveolar margin is bent upwards (Rauhut 2003), butno diastema is evident. The antorbital fossa has a deeprostral depression in a position equivalent to that of thepromaxillary fenestra/foramen described for Zupaysaurusrougieri (Ezcurra 2007), “Syntarsus” kayentakatae(Tykoski 1995), and cf. Dracovenator regenti (Yates2005). This leads to a rostral furrow that apparently opensonto the medial surface of the bone, but no aperture islaterally visible. There are about 20 maxillary toothpositions and six large foramina around the antorbital fossa,the latter of which opens caudally. The lacrimal has a long,nearly vertical ventral ramus, the ventral portion of which isexcavated by the antorbital fossa. The prefrontal lacks a

sheet of bone covering the lacrimal, which is present invarious basal sauropodmorphs, but not in P. protos (Martinezand Alcober 2009). The postorbital forms a pendanteminence over the dorsocaudal border of the orbit, asseen in other basal dinosaurs (Sereno and Novas 1994;Martinez et al. 2011). The squamosal has a strap-shapedventral process, as typical of early sauropodomorphs(Yates 2003). The caudal ramus of the jugal is forkedand not ventrally arched. A medial ridge on the ventralsurface of the pterygoid holds a row of about 15 positionsfor small rudimentary teeth, as previously recognized onlyin E. lunensis and Eodromaeus murphi among dinosaurs(Martinez et al. 2011; Nesbitt 2011).

The dentary bears about 20 tooth positions, extendingfrom the rostral tip of the bone. Medial to the glenoid, thearticular is pierced by the foramen for the chorda tympani,as in Silesaurus opolensis (MCL, personal observation,2007), some dinosaurs (Yates 2005; Nesbitt 2011), andvarious pesudosuchians (Gower 1999). Most tooth crownsin the central portion of the upper and lower rows are

Fig. 2 Pampadromaeus barberenai, ULBRA-PVT016 (holotype),skull elements reversed as needed to left lateral (total skull lengthslightly over 10 cm). a Right premaxilla and maxilla. b Right frontalin ventral view. c Right jugal. d Right prefrontal. e Right postorbitaland left squamosal. f Left parietal in ventral view. g Left pterygoid inventral view. h Left dentary. i Right surangular, angular, articular, and

prearticular in medial view. a Angular; aof antorbital fossa; arartigular; d dentary; emf external mandibular fenestra; en externalnaris; f frontal; l lacrimal; m maxilla; n nasal; nf narial fossa; pparietal; pa prearticular; pf prefrontal; pm premaxilla; pmd “promax-illary” depression; po postorbital; q quadrate; sa surangular; sqsquamosal

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lanceolate, with an expanded base, a convex mesialmargin, and a sigmoidal (convex at the base andconcave apically) or nearly straight distal margin. Moredistal teeth are shorter, but retain this general shape thatis typical of various basal dinosaurs (Barrett et al.2011). There is some imbrication between adjacent crowns,with the mesial edge of the crowns medially overlappingthe distal edge of the tooth mesial to it. Carinae arecoarsely serrated, their denticles forming oblique angleswith the crown margin. The most mesial teeth on bothpremaxilla and dentary are narrower and bear less evidentserrations, as seen in coelophysid theropods (Tykoski andRowe 2004). Mesial dentary teeth of other stem-sauropodo-morphs such as S. tupiniquim (Langer et al. 1999) and P.protos (Martinez et al. 2011) are broader and bear serratedcarinae, but the preserved elements may not belong to thevery tip of the jaw.

The atlantal neurapophysis has a plate-like, dorsallyexpanding epipophysis that does not extend caudal to thepostzygapophysis. Cervical ribs have elongated and straightshafts. As typical of saurischians (Langer and Benton2006), trunk vertebrae have well developed laminationssurrounding the diapophysis, and hyposphene–hypantrumauxiliary articulations. As in many basal dinosaurs (Langer2003; Langer et al. 2011), two vertebrae form the entiresacrum, with ribs attached to the cranial half of therespective centrum. The ribs are dorsoventraly expandedand ventrally connected to one another. The circumscribedintercostal space has a small ventral aperture, medial to thecaudal half of the first centrum, and a large dorsal openingbordered by unexpanded transverse processes. The scapularblade is cranially inclined, and the humerus has a broad

distal end, as typical of sauropodomorphs (Langer andBenton 2006). The ilium has a deep dorsal lamina, but thepreacetabular ala is short and pointed. The long postace-tabular ala bears an evident brevis fossa. The acetabularwall has a nearly straight ventral margin, as seen in S.tupiniquim, Guaibasaurus candelariensis, and P. protos.The femoral head is offset and inturned, with the long axisforming an angle of 40° to the intercondylar line. It has aflat craniolateral surface and subtle medial tubera (Nesbittet al. 2009). The articular surface has well-developedtransverse groove and facies articularis antitrochanterica(Langer 2003). The lateral surface of the proximal portionof the femur has a crescent-shaped dorsolateral trochanter, aknob-like lesser trochanter, and a well-developed trochan-teric shelf. The fourth trochanter expands as an asymmet-rical, sharp flange. The epipodium is nearly 20% longerthan the femur. The cnemial crest of the tibia is craniallyprojected and the lateral condyle is set at the center of thelateral margin of the proximal articulation. Metatarsal I issignificantly shorter than metatarsals II and III.

Phylogenetic analyses and discussion

Phylogenetic analyses (see details in the ElectronicSupplementary Material) based on four recent studies onthe early radiation of dinosaurs (Martinez and Alcober 2009;Ezcurra 2010; Nesbitt et al. 2010; Martinez et al. 2011)unambiguously place P. barberenai on the sauropodomorphstem (Fig. 3), with minor variations that include its sister-taxon relationship to either P. protos, Sauropodomorpha(sensu Langer 2003), or Sauropodomorpha plus S. tupini-

Fig. 3 Simplified phylogeneticrelations of Pampadromaeusbarberenai among basal dino-saurs, based on the analyses ofthe cited matrices (see ElectronicSupplementary Material). Dottedlines and underlinedlettering indicate non-Eusaurischia saurischian grade;gray lines and lettering indicatesauropodomorph lineage; fullblack lines and lettering indicatetheropod lineage. Sauropodo-morpha applied sensu Langer(2003). D Dinosauria, EEusaurischia

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quim. However, despite this recurring position, theaffinities of P. barberenai to sauropodomorphs are notsupported by strong tree statistics, neither by many oruncontroversial anatomical traits. In conjunct, these includethe following: (1) highly homoplastic characters (meanConsistency Index based on the four analyses indicated underbrackets) as lanceolate tooth crowns (0.53) with expandedbases (0.30) that overlap one another (0.26), four premaxillaryteeth (0.47), interpostzygapophyseal notch in proximal tailvertebrae (0.20), humerus longer than or subequal to 0.6 of thefemoral length (0.43), supracetabular crest extensive to thepubic peduncle of the ilium (0.28), proximal femoralarticulation with straight transverse groove (0.28), andproximal portion of the tibia with a cranially displaced fibularcondyle (0.33); (2) characters codified as missing data formost fossil taxa, e.g., medial foramen on the articular (Nesbitt2011); and (3) features with a seemingly more consistentdistribution, such as strap-shaped ventral process of thesquamosal, proximal tail vertebrae with long neural spines,humerus with broad distal end (relative to the length of thebone), and ilium with a subtriangular preacetabular ala andlong pubic peduncle. However, P. barberenai lacks sometypical sauropodomorph traits such as a small head andlonger crowns on the rostral part of the tooth series (Martinezand Alcober 2009). The analyses also revealed numerousautapomorphies for P. barberenai, but most of themcorrespond to homoplastic traits more common to otherdinosauromorph groups, and none is really unique to thattaxon. Theropod features (Rauhut 2003; Tykoski 1995)include concave ventral margin of the premaxilla–maxillaarticulation, unserrated teeth in the rostral tip of the upperand lower jaws, “promaxillary” depression, and deep dorsaliliac lamina. Other putative theropod traits of P. barberenai,such as a “forked” caudal process of premaxilla (Rauhut2003) and a concave caudal margin of the iliac lamina indorsal profile (Tykoski 1995), are also seen in sauropodo-morphs and S. opolensis. Likewise, dinosaur plesiomorphies(Langer and Benton 2006) retained or reverted in P.barberenai include a deep acetabular medial wall withstraight ventral margin and narrow sacral transverse process-es that do not roof the intercostal space. This seems also tobe the case of the palatal teeth, known in early membersof the archosaurs lineage (Nesbitt 2011), putative basalpseudosuchians (Wu and Russell 2001), some pterosaurs(Kellner 2003), and basal dinosauromorphs such asLewisuchus admixtus (JSB, personal observation, 2011),although hitherto unrecognized in dinosaurs other thanE. lunensis and E. murphi.

The outcomes of the phylogenetic analyses (Fig. 3)stress the uncertainties concerning the relationships ofvarious basal dinosaurs. For example, G. candelariensis,E. lunensis, and herrerasaurs appear alternatively basal tothe sauropodomorph-theropod dichotomy or at the base of

either lineage. This most likely results from the ambiguousdistribution of traits, which became characteristic of certaindinosaur clades, among these and other basal dinosaur-omorphs such as S. opolensis, S. tupiniquim, P. protos, E.murphi, and Eocursor parvus. Phylogenetic reconstructionsof basal dinosaurs are further problematical because thosefeatures accumulated over a relatively short period of time(Irmis 2011), in forms with recurring body structure andinferred habits (i.e., medium-sized, bipedal, and omnivo-rous). In fact, the early dinosaur radiation may represent asegment of evolutionary history that is particularly hard toreconstruct, and its poor constraint is not surprising. Onlyadditional finds and, especially, more detailed phylogeneticstudies will facilitate development of a more stableevolutionary framework for the placement of many basaldinosaurs.

Acknowledgments Aspects of this work were funded by ConselhoNacional de Desenvolvimento Científico e Tecnológico, UniversidadeLuterna do Brasil (to S.F.C), and Fundação de Amparo à Pesquisa doEstado de São Paulo (toM.C.L. and J.S.B.). This is contribution no. 25 ofLaboratório de Paleontologia, FFCLRP-USP. Thanks to Luiz FlávioLopes for the photographic work, to Maíra Massarani for the drawing ofFig. 2, and to three anonymous reviewers for their comments.

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Electronic Supplementary Material for:

New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of

Brazil

Sergio F. Cabreira1, Cesar L. Schultz2, Jonathas S. Bittencourt3, Marina B. Soares2,

Daniel C. Fortier4, Lúcio R. Silva1 and Max C. Langer3*

1 Departamento de Biologia. Universidade Luterana do Brasil, ULBRA. Canoas, Rio Grande do Sul, Brazil.

2 Instituto de Geociências, Universidade Federal do Rio Grande do Sul, UFRGS, Brazil.

3 Laboratório de Paleontologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto-SP, 14040-901, Brazil.

4 Departamento de Geologia, UFMG, Belo Horizonte-MG, 31270-901, Brazil.

* Correspondence and requests for materials about the character list and character-taxon matrix presented

below should be addressed to M.C.L. (mclanger@ffclrp.usp.br)

This file includes:

1. Details on the type-material of Pampadromaeus barberenai.

1.1. Block containing the type-material of Pampadromaeus barberenai.

1.2. Anatomical details of ULBRA-PVT016.

2. Character-state scoring for Pampadromaeus barberenai.

3. Extended differential diagnosis of Pampadromaeus barberenai.

4. Details of the parsimony analyses.

5. Character analyses

6. Additional references

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1. Details on the type-material of of Pampadromaeus barberenai.

1.1. Block containing the type-material of Pampadromaeus barberenai. Most of the skeletal remains attributed to P. barberenai were preserved scattered over a single mudstone block, a photograph of which, taken during early stages of preparation (2006) is shown in Fig. S1. In addition, assorted bones were collected from the perimeter of the block, including tail vertebrae, right humerus and ulna, right ilium, tibiae, metatarsals and pedal phalanges. Based on their corresponding size and on the absence of duplicated elements, all these bones are believed to belong to a single individual. Fig. S2 shows a “bone map” of the block.

Fig. S1 Mudstone block containing most of the skeletal remains attributed to ULBRA-PVT016, holotype of P. barberenai (during early stages of preparation) As a whole, the holotype of P. barberenai contains the rostral portion of the right side of the skull, with semi-articulated premaxilla, maxilla (both bearing teeth), lachrymal, and palatine, as well as isolated skull bones: right nasal, frontal, jugal, prefrontal, and

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postorbital, left parietal, squamosal, and quadrate, parts of the braincase (supraoccipital and paroccipital processes), and both pterygoids (incomplete right bone); parts of both mandibuar rami, including left dentary (with teeth) and surangular, and right partial dentary (with teeth) and articulated surangular, angular, prearticular, and articular; incomplete vertebral column including right atlantal neurapophysis, various trunk and tail vertebrae, an articulated two-vertebrae sacrum, various ribs (neck and trunk) and haemal arches; right scapula, partial left scapula, right humerus and ulna; right ilium lacking the ischiadic peduncle, left ilium lacking the postacetabular ala, proximal left ischium, partial left and nearly complete right femora, proximal half of left tibia, right tibial shaft, both fibulae, various metatarsals (including complete left metatarsal I) and pedal phalanges.

Fig. S2 “Bone map” of the mudstone block containing ULBRA-PVT016. Abbreviations: a, right angular; an, right atlantal neural arch; ar, right articular; cr, cervical rib(s); cv, caudal vertebra(e); d, dentaries; f, right frontal; f, femora; ha, haemal arch(es); ind, indeterminate bone; j, right jugal; jb?, lower jaw bone?; la, right lacrimal; mI; left metatarsal I; left ilium; m, right maxilla; n, right nasal; p, left parietal; pa, right prearticular; pal, right palatine; pf, right prefrontal; ph, pedal phalanx; pl?, osteoderm?; pm, right premaxilla; po, right postorbital; pt, pterygoids; q, left quadrate; s, sacrum; sa, surangulars; sc, right scapula; sq, left squamosal; tr, trunk rib(s); tv, trunk vertebra(e). (l) and (r) indicate left and right sides when both bones are preserved

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1.2. Anatomical details of ULBRA-PVT016.

Figs S3-7 depict details of the P. barberenai anatomy (based on its type material).

Fig. S3 P. barberenai (ULBRA-PVT016). Medial view of the rostral portion of the right side of the skull, including premaxilla, maxilla, lachrymal, and palatine (above). Details of the premaxilla (below right). Details of the palatal ramus of the maxilla (below left)

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Fig. S4 P. barberenai (ULBRA-PVT016). Right dentary in lateral view (above). Details of the rostral tip (below right). Details of central teeth (below left)

Fig. S5 P. barberenai (ULBRA-PVT016). Right ilium in medial view

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Fig. S6 P. barberenai (ULBRA-PVT016). Proximal portion of the left femur (lateral view)

Fig. S7 P. barberenai (ULBRA-PVT016). Left pterygoid (ventral view) showing medial a row of rudimentary teeth on the palatal process.

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2. Character-state scoring for Pampadromaeus barberenai. Table S1 depicts the character-state scoring for P. barberenai in the four data-matrices employed in the analyses conducted here. These data-matrices represent different views of early dinosaur evolution: Martinez and Alcober (2009) is based on a previous study by Langer and Benton (2006); Ezcurra (2009) is mostly based on the analysis of Yates (2007); Martinez et al. (2011) stands for a more complete study in preparation by Paul Sereno; Nesbitt et al. (2010) is a multi-authored contribution that was expanded, with nearly equivalent results for ornithosuchians, in Nesbitt (2011).

Table S1: Character-state scoring for Pampadromaeus barberenai. (A=1/2)

Martinez and 001?111??1 ?1?1???0?? ?0011200?? ??????1100 Alcober 2009 ??010??0?1 0????????? ???????012 1100?????? ?1010??0?? ???????? Ezcurra 2010 00???00211 00??1?011? ?0???000?1 000000?110 ?0?0?0??0? 10?1??0??? 10????111? 1????????? ?????????0 ???0000000 0??0010?10 0101000000 ?????????? ?????????1 ??????0?0? 01??001?11 0?01000?00 0000?0??00 00?11?0??0 1????00?10 10??1????? 1?0?1????? ?????????? ?????????? ????001001 11010202?? ?????????? ?????????0 0001111100 11011100?0 0?000????? ?010?????? ?????????? ?????????? ?????????? ??0??0???0 ??210011?? 11?1???? Nesbitt et al. 2010 ?0?1101?01 ??01110000 ?0???????? ?????1?0?? 1?3?00???? ??0??????? ?????????? ??????02?? ??00??0000 ?100?00201 10010????? ?????????? 00000?1??0 01?????10? ?????0???1 ?00?0????? ?????????? ??00001111 ?10??????? 1????????? ?1100?A101 1?01111101 01??0?A??0 00???????? ?????????? ?????????? ?????????? ?????????? ?????????? Martinez et al. 2011 ???00?0111 ??0?0010?1 01?1?0???? ??00?0??00 0?1100???? ???0100??? ?0?1???0?? ????????20 ?0001012?? ?????????? ???????000 1?1?00??0? ?????????? ?????????

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3. Extended differential diagnosis of Pampadromaeus barberenai. Distinguished from all other well-known Triassic dinosauromorphs by the following unique combination of character states: head longer than two-thirds of the femoral length (short head is characteristic of sauropodomorphs; Langer and Benton, 2006), most teeth lanceolate with coarse denticles (unknown in herrerasaurs, Eodromaeus, and basal neotheropods; Martinez et al., 2011), premaxilla with short subnarial process and femur with well-developed trochanteric shelf (the reverse is seen in Eoraptor; Langer and Benton, 2006), concave ventral margin of the premaxilla-maxilla articulation and unserrated mesialmost tooth crowns (known only in some neotheropods; Tykoski and Rowe, 2004), epipodium significantly longer than femur (the reverse is seen in Saturnalia; Langer, 2003), no inset of first premaxillary or dentary tooth (the reverse is seen in silesaurids and sauropodomorphs; Sereno, 2007; Nesbitt et al., 2010; Martinez et al., 2011), deep sacral ribs and femoral head with reduced medial tuberosity (the opposite is seen in Marasuchus and lagerpetids; Novas 1996; Nesbitt et al., 2009). The ilium of Pampadromaeus differs from that of Chromogisaurus (Ezcurre 2010) for its deeper dorsal lamina, less caudally extensive supracetabular crest, and smoother cranial portion of the brevis shelf, whereas its scapula differs from that of Panphagia (Martinez and Alcober 2009) for its slenderer blade and shorter and deeper acromial process. In addition, the articular of Panphagia lacks a well developed foramen for the chorda tympani, medial to the glenoid. 4 - Details of the parsimony analyses.

A series of four parsimony analyses were performed based on the character-taxon matrices of Martinez and Alcober (2009), Ezcurra (2009), Nesbitt et al. (2010), and Martinez et al. (2011). The only modifications, other than the scoring of Pampadromaeus barberenai (Table 1), were those proposed by Bittencourt and Kellner (2009) for Staurikosaurus pricei in the data-matrix of Langer and Benton (2006), incorporated into the matrix of Martinez and Alcober (2009).

The character-taxon matrices were modified in Mesquite v.2.6 (Maddison and Maddison, 2009), and TNT v.1.1 (Goloboff et al., 2003; Goloboff et al., 2008) was employed to perform heuristic/exhaustive searches. Zero length branches were not collapsed. Other parameters (e.g., constrains, additive sequence of characters states) follow the original studies. Bootstrap proportions, “Bremer support” decay indices, and tree statistics were calculated using TNT v.1.1. Bootstrap analyses were conducted with one thousand replicates and the same parameters employed for the primary MPT searches.

4.1. Analysis based on Martinez and Alcober (2009)

An “implicit enumeration” search revealed tree (03) most parsimonious trees (MPTs) with 197 steps, summarized here in a strict consensus tree (Fig. S8). Tree statistics: CI

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(consistency index, excluding uninformative characters) = 0.533; HI (homoplasy index, excluding uninformative characters) = 0.467; RC (rescaled consistency index) = 0.297; RI (retention index) = 0.558.

4.2. Analysis based on Ezcurra (2010). A heuristic search (Addition sequence = random; Branch-swapping algorithm = TBR; 10.000 replicates; hold = 10) revealed four (04) most parsimonious trees with 1,171 steps, summarized here in a strict consensus tree (Fig. S9). Tree statistics: CI (consistency index, excluding uninformative characters) = 0.376601; HI (homoplasy index, excluding uninformative characters) = 0.623399; RC (rescaled consistency index) = 0.255811; RI (retention index) = 0.679262. 4.3. Analysis based on Nesbitt et al. (2010).

A heuristic search (Addition sequence = random; Branch-swapping algorithm = TBR; 10.000 replicates; hold = 10) revealed three (03) most parsimonious trees with 757 steps, summarized here in a strict consensus tree (Fig. S10). Tree statistics: CI (consistency index, excluding uninformative characters) = 0.457181; HI (homoplasy index, excluding uninformative characters) = 0.542819; RC (rescaled consistency index) = 0.321476; RI (retention index) = 0.703170. 4.4. Analysis based on Martinez et al. (2011)

An “implicit enumeration” search revealed five (05) most parsimonious trees (MPTs) with 248 steps, summarized here in a strict consensus tree (Fig. S11). Tree statistics: CI (consistency index, excluding uninformative characters) = 0.613; HI (homoplasy index, excluding uninformative characters) = 0.387; RC (rescaled consistency index) = 0.490; RI (retention index) = 0.799. An unconstrained analysis reveals a set of 10 MPTs of 247 steps, the strict consensus of which shows Silesauridae forming a clade with Heterodontosauridae and Genasaura+Lesothosaurus.

Fig. S8 Strict consensus of 3 MPTs based on the inclusion of Pampadromaeus barberenai in the character-taxon matrix of Martinez and Alcober (2009). Bootstrap proportions and “Bremer support” decay indices are successively indicated for each clade

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Fig. S9 Strict consensus of 4 MPTs based on the inclusion of Pampadromaeus barberenai in the character-taxon matrix of Ezcurra (2010). Bootstrap proportions and “Bremer support” decay indices are successively indicated for each clade

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Fig. S10 Strict consensus of 3 MPTs based on the inclusion of Pampadromaeus barberenai in the character-taxon matrix of Nesbitt et al. (2010). Bootstrap proportions and “Bremer support” decay indices are successively indicated for each clade

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Fig. S11 Strict consensus of 5 MPTs based on the inclusion of Pampadromaeus barberenai in the character-taxon matrix of Martinez et al. (2011). Bootstrap proportions and “Bremer support” decay indices are successively indicated for each clade

5. Character analyses

Tables S2-5 list all unambiguous synapomorphies (recovered using TNT v.1.1) of the least inclusive clade containing Pampadromaeus barberenai in the strict consensus trees of Figs S7-10 (indicated with a black circle). Each line of the tables successively includes: number and definition of the characters in the original studies, direction of the transformation in the present analyses, character state scores for P. barberenai, and number of MPTs that include the synapomorphy. Table S2: Partial synapomorphy list based on Nesbitt et al. (2010).

5 Premaxillary teeth, number: 3(0); 4 (1); 5 (2); 6+ (3); 0 (4). 0>1 1 3 92 Articular, foramen on the medial side: absent (0); present and medial to the

glenoid (1). 0>1 1 3

101 Tooth, crown: not mesiodistally expanded (0); mesiodistally expanded above root in cheek teeth (1).

0>1 1 1

150 Humerus, distal end width: narrower or equal to 30% of humerus length (0); greater than 30% of humerus length (1).

0>1 1 3

216 Femur, proximal surface: rounded and smooth (0); transverse groove that is straight (1); transverse groove that is curved (2).

0>1 1 3

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Table S3: Partial synapomorphy list based on Martinez et al. (2011).

2 External naris, size: small, set within tapered snout end (0); large, expanded narial margin (1). 0>1 ? 5

19 Nasal, posterolateral process: absent (0); present (1). 0>1 ? 4 24 Squamosal, ventral process, shape: transversely compressed flange (0); slender

prong 3 or more times basal width (1). 0>1 1 4

45 Dentary tooth 1, position: terminal (0); inset (1). 0>1 0 2 69 Humerus, deltopectoral crest, length relative to humeral length: 30% or less (0);

35-44% (1); 45% or more (2). 1>2 ? 4

70 Manus, length (longest digit) relative to humerus + radius: 20-30% (0); approximately 40% (1); 50- 70% (2).

2>1 ? 4

76 Manus digit I phalanx 1, rotation of axis through distal condyles: no rotation or slight ventrolateral rotation (0); rotated 45° ventromedially (1); rotated 60° ventromedially (2).

0>1 ? 4

79 Ilium, preacetabular process, shape: tab-shaped (0); strap-shaped (1); subtriangular (2); semicircular (3).

0>2 2 5

81 Ilium, preacetabular process, attachment scar: absent (0); present (1). 0>1 ? 4 90 Ischium, mid shaft, cross-sectional shape: oval or elliptical (0); subtriangular (1). 0>1 ? 5 95 Ischium, antitrochanter, anteroposterior length relative to adjacent length of the

articular surface for the ilium: greater (0); less (1). 0>1 ? 3

122 Astragalus, fibular facet, primary orientation: dorsolateral (0); lateral (1). 0>1 ? 5 125 Astragalus, anteromedial corner, shape (dorsal view): subrectangular (0); anteriorly

projecting at least 25% width of the medial side of the astragalus (1). 0>1 ? 5

Table S4: Partial synapomorphy list based on Martinez and Alcober (2009).

14 Ventral ramus of the squamosal wider (0) or narrower (1) than a quarter of its length 0>1 1 1

24 Maxillary/dentary tooth crowns unexpanded (0) or rostro-caudally expanded at the base (1)

0>1 1 3

26 Lanceolate crowns present in none (0), some (1), or most (2) maxilla/dentary teeth 01>2 2 3 28 Tooth crowns on the rostral quarter of the tooth-bearing areas of the upper and

lower jaws are about the same height (0) or significantly higher than more caudal teeth (1)

0>1 0 1

48 Humerus longer than or subequal to (0), or shorter than 0.6 of (1) the length of the femur

1>0 0 1

50 Humeral distal end is narrower than or equal to (0), or wider than (1) 0.3 of the total length of the bone

0>1 1 1

90 Caudolateral flange of distal tibia short and does not project (0) or projects caudal to the fibula (1)

1>0 ? 2

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Table S5: Partial synapomorphy list based on Ezcurra (2010).

75 Shape of the supraoccipital: diamond-shaped, at least as high as wide (0); semilunate and wider than high (1). 0>1 ? 4

131 Relative elongation of the anterior cervical centra (cervicals 3–5): lengths of the centra less than 2.5 times the height of their anterior faces (0); lengths 2.5–4 times the height of their anterior faces (1); the length of at least cervical 4 or 5 exceeds 4 times the anterior centrum height (2).

0>1 ? 4

142 Postzygodiapophyseal lamina in cervical neural arches 4–8: present (0); absent (1). 0>1 ? 4 143 Laminae of the cervical neural arches 4–8: well developed tall laminae (0); weakly

developed low ridges (1). 0>1 ? 4

184 Length of base of the proximal caudal neural spines: less than (0), or greater than (1), half the length of the neural arch.

0>1 1 4

185 Position of postzygapophyses in proximal caudal vertebrae: protruding with an interpostzygapophyseal notch visible in dorsal view (0); placed on either side of the posterior end of the base of the neural spine without any interpostzygapophyseal notch (1).

0>1 1 4

211 Transverse width of the distal humerus: is less than (0), or greater than (1), 33% of the length of the humerus.

0>1 1 4

252 Length of the pubic peduncle of the ilium: less than (0), or greater than (1), twice the anteroposterior width of its distal end.

0>1 1 4

304 Position of the posterior end of the fibular condyle on the proximal articular surface tibia: anterior to (0) or level with (1), the posterior margin of proximal articular surface.

1>0 0 4

363 Supraacetabular crest of ilium: not extended along the pubic peduncle or only at the base of the peduncle (0); extended along the pubic peduncle as a faint ridge (1); extended along the entire pubic peduncle and contacts the distal end as a well developed crest (2).

1>2 2 4

372 Iliac blade in dorsal view: straight or slightly laterally curved along the whole of its anteroposterior extension (0); strongly laterally curved, with a deeply concave lateral border (1).

0>1 1 4

6. Additional References Bittencourt JS. Kellner AWA (2009) The anatomy and phylogenetic position of the Triassic dinosaur Staurikosaurus

pricei Colbert, 1970 Zootaxa 2079:1–56.

Goloboff PA, Farris JS, Nixon KC (2003) TNT: Tree analysis using new technologies.

http://www.zmuc.dk/public/phylogeny

Goloboff PA, Farris JS, Nixon KC (2008) TNT, a free program for phylogenetic analysis. Cladistics 24:774–786.

Maddison WP, Maddison D R (2009) Mesquite: a modular system for evolutionary analysis. Version 2.6.

http://mesquiteproject.org

Nesbitt SJ (2011) The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades. Bull Am Mus Nat

Hist 352:1–292.

Sereno PC (2007) Basal Sauropodormorpha: historical and recent phylogenetic hypothesis, with comments on

Ammosaurus major (Marsh, 1889). In: Barrett PM, Batten DJ (Eds) Evolution and palaeobiology of early

sauropodomorph dinosaurs. Spec Pap Palaeontol 77:261–289