Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 O:10.1080/08912960601140085 DOI: online 1029-2381 print/ISSN 0891-2963 ISSN [email protected] E-mail: Paleontolo Museo Pol, D. Correspondence: was sauropodomorph basal single a Finally, 1999). parte and 1978), (Bonaparte recognized: incertus and been have Formation taxa Colorados different Los three from known are the tina) and from sauropodomorphs 2005) Unio Basal Villa 2004). 2003, al. et Langer (Leal 1999; tolentinoi al. Unaysaurus et form (Langer in plesiomorphic located of tupiniquim the remains Saturnalia is yielded sauropodomorphs: basins recently the has two these of and of Brazil part southern southern first the The in Tranquilo) continent. El and asto, (Parana from basins beds Triassic different Upper three in so recorded are, exclusively America far, South from sauropodomorphs Basal Introduction Keywords: and sauropodomorphs basal some with shared type the characters than derived (e.g. longer sauropodomorphs times shows basal three taxon approximately other skull this in a absent of of juvenile having classes are as anatomy size larger, which interpreted distinct significantly are skull eusauropods, two specimens are include new The latter the material whereas studied The material. individuals The individuals. young specimens. extremely subadult found of or recently consists material several type and The material individuals. type the of revision of anatomy skull The Abstract 1 POL DIEGO Patagonia of Triassic Late the from Sauropodomorpha) of anatomy Skull Biology Historical nttt iulLlo iulLlo25 a iuld Tucuma de Miguel San 205, Lillo Miguel Lillo, Miguel Instituto ra ertosrsrce oteaia ein(beti oeteh.Dfeecsaogtesuidseieshlsto quadratojugal helps of specimens studied rami and rostral the anterior the among in and changes Differences major teeth). dorsal revealing sauropodomorph, some orbit, basal in this with the in (absent teeth regions. occurring procumbent temporal region to changes slightly apical ontogenetic symphysis, ventral early the mandibular the fenestra at to understand dentary restricted infratemporal of serrations expansion the dorsoventral broad other, of each extension to subperpendicular an of presence OIE,MsoPaleontolo Museo CONICET, ´ Bnpre1971), (Bonaparte -shgaat ai nrhetr Argen- (northwestern Basin n-Ischigualasto arpdmrh,Poarpd,Suooa ontogeny Sauropoda, Prosauropoda, Sauropodomorpha, 1 07 91:125–144 19(1): 2007; , AM .POWELL E. JAIME & usuu patagonicus Mussaurus rmteSnaMraFormation Maria Santa the from rmteCtriaFormation Caturrita the from esmarssauropoides Lessemsaurus ´ usuu patagonicus Mussaurus ioEii eulo v otn 4,Tee,Cuu 10 retn,and Argentina, 9100, Chubut Trelew, 140, Fontana Av. Feruglio, Egidio gico ´ il Unio Villa , ooaiarsbrevis Coloradisaurus q ´ ioEii eulo v otn 4,Tee,Cuu 10 Argentina. 9100, Chubut Trelew, 140, Fontana Av. Feruglio, Egidio gico 07Tyo Francis & Taylor 2007 ´ rmteUprTisi auaClrd omto sdsrbdbsdo a on based described is Formation Colorada Laguna Triassic Upper the from n-Ischigual- Riojasaurus 2 (Bona- ´ ,Tucuma n, h auaClrd omto,a ela several as well as Formation, of Colorada anatomy Laguna in found the skull recently material additional on the based changes Sauropoda. describe patagonicus of further Mussaurus skulls the we in with Here, present similarities some condition noted derived affinities, also prosauropod they suggested although that aspects briefly anatomy several (1979) its discussed of Vince and found material and were this Bonaparte described two fragments them. Additionally eggshell to close association. and eggs close are complete them in specimens of found all these and were complete of remarkably and Some articulated individuals. young cus tina): Argen- (southern Patagonia from described previously 99.Ti ao a on nteLgn Colorada Laguna the Group). Tranquilo in (El Formation found was taxon This 1979). h yemtra pnwhich upon material type The a ecie nldsrmiso ih extremely eight of remains includes described was usuu patagonicus Mussaurus Thecodontosaurus (Dinosauria: ´ 00 Argentina 4000, n , Plateosaurus n ics t ontogenetic its discuss and BnpreadVince and (Bonaparte usuu patagoni- Mussaurus .Teeicuethe include These ). 2 CONICET, Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 ean;PL56,atcltdseeo n almost individuals. and skeleton different articulated 5865, two PVL forelimb remains; least, hindlimb, vertebrae, at cervicodorsal Including skeleton to, articulated belonging partially post-hatchling 4587, 4213, of PVL PVL individuals; remains individual; postcranial post-hatchling disarticulated a postcranial of articulated postcranial partially skeleton disarticulated 4212, PVL several and remains; post- skull and a incomplete of mandibles vertebrae, including remains dorsal individual 4211, PVL hatchling posterior hindlimb; of and pelvis, series articulated individual. and an with post-hatchling ulna, humeri, scapulae, associated a includes postcranium The skull of complete remains postcranial almost 4210, metatarsals; and PVL fibula, tibia, femur, associated vertebrae, dorsal individual including post-hatchling material, postcranial articulated partially a with of jaws and with skull lower partial 4209, region PVL a individual; of post-hatchling elements rostral hindlimb disarticulated and the ulna, radius, humerus, lacking scapula, vertebrae, cervicodorsal skull articulated 4208, PVL material Referred post-hatchling a of skeleton individual. articulated 4068, PVL Holotype 1–7) (Figures 1887 Seeley Saurischia palaeontology Systematic an as interpreted are specimens. juvenile the they of than association although larger significantly material, are type These other. each associated to closely found skeletons articulated partially pcmn rmtePLcleto IsiuoMiguel (Instituto Tucuma collection Lillo, PVL the from specimens 126 usuu patagonicus Mussaurus 1932 Huene Sauropodomorpha iue1 kl n adbeof mandible and Skull 1. Figure .Pl&J .Powell E. J. & Pol D. ´ ) h e aeilcnit fseven of consists material new The n). oaat n ic 1979 Vince and Bonaparte usuu patagonicus Mussaurus MMP 834 nlf aea iw e brvain nAppendix. in abbreviations See view. lateral left in 1813/4) (MPM-PV h ueieseiesaerfre to referred which are upon specimens basis among juvenile the unique forms the is characters it of sauropodomorphs, combination material). this MPM type and As 4587 (PVL (e.g. here described individuals mens post-hatchling of exclusively the material characters of in combination found a an are with asterisk indicated cranial Characters the here. on described based material 1979) original Vince and the from (Bonaparte one emended is diagnosis following The diagnosis Emended Tranquilo 2002). El Marsicano of and age (Stipanicic the Group for 1996), bound Pankhurst upper and an Rapela providing 1993; al. et (Pankhurst hs rntisyedda g f203 of age of an al. Rb-Sr) yielded et rock (Chebli granitoids (whole Formation dating these Leona Radiometric La 1976). the 1999). by of intruded 1998a,b, is granitoids Group the Herbst Tranquilo El which and Furthermore, in Gnaedinger horizon 1995; the above (Norian; Mussaurus and Triassic below the Late on found based be 1995) Herbst to and Jalfin considered formation usually has this of is age unit The 2001). ornithischian Marsicano this In and heterodontosaurid (Baez Tranquilo a 1995). sauropodomorphs of remains Herbst basal yielded El and to Jalfin addition Formation, the 1965; (Herbst to Group Colorada belong of sediments margin southern Laguna These the Colorada. on collected Laguna each were to and associated closely other Argentina. were Province, specimens MPM Cruz The Santa Colorada, Laguna horizon and Locality scapular series, forelimbs. and cervicodorsal girdle a 1813/4, with MPM-PV articulated skull; skull isolated series; 1813/2, cervicodorsal MPM-PV with MPM- articulated individual; skull 1813/1, post-hatchling PV a of skull complete ean eefud(afi n Herbst and (Jalfin found were remains Mussaurus n h e ueiespeci- juvenile new the and ) Dicroidium Mussaurus ^ 2Ma flora Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 iue3 neoaea iwo h nu n adbeof mandible and snout the of Appendix. view patagonicus Anterolateral Mussaurus 3. Figure deep than shorter anteroposteriorly premaxilla the 45 of angle an margin of forming posterodorsally, anterior directed premaxilla characters: of combination elsewhere. treated be will features diagnostic Theits taxon. this of of morphology diagnostic postcranial as therefore considered and be change cannot ontogenetic Vince to and subject (Bonaparte are taxon 1979) this of diagnosis original patagonicus Appendix. in abbreviations See side. of right specimens Post-hatchling inverted 2. Figure otria tagt ota xeso fteinfra- the of orbit the extension underneath of fenestra process rostral temporal descending of straight; end postorbital ramus ventral ventral lacrimal; entire the the lacrimal along of ridge sinus; of thin antorbital a of of lamina presence region (superficial) posterodorsal the lateral covering of anteroposter- absence and narrow straight lacrimal iorly of ramus ventral oslrm fqartjglsbepniua oeach other to subperpendicular quadratojugal of rami dorsal nteatro i ftednay(immediately dentary the of tip anterior the on aa arpdmrhwt h olwn unique following the with sauropodomorph Basal * 8 rsneadral rjce e-ieprocess peg-like projected dorsally a presence ; ihteavoa agn anbd of body main margin; alveolar the with h otrna hrcesicue nthe in included characters postcranial The . * akdycntitda mid-height; at constricted markedly , MMP 834.Seabeitosin abbreviations See 1813/4). (MPM-PV Mussaurus usuu patagonicus Mussaurus n eiinof revision a and * neirand anterior ; ,sulo V 85i etltrlve;B kl fPL41 nltrlview, lateral in 4210 PVL of skull B, view; lateral left in 5865 PVL of skull A, . * ; MMP 834.Seabeitosi Appendix. in abbreviations See 1813/4). (MPM-PV iue4 ota n of end Rostral 4. Figure neirt h rtmniua tooth) mandibular first the to anterior opeesbdl pcmn P-V1813/4. most the MPM-PV on specimen, based largely subadult is complete description skull The Skull Description margins. posterior and anterior their on of serrations part with lanceolate teeth maxillary region); apical posterior the having at (or denticles broad margins developed their weakly distal on sigmoid serrations with lacking teeth margin maxillary anterior and symphysis teeth mandibular gently of end only margin anterior with dorsal fenestra) sigmoid mandibular external to (posterior the rami mandibular of end caudal elongated kl ntm of anatomy Skull usuu aaoiu 127 patagonicus Mussaurus usuu patagonicus Mussaurus * osvnrlyexpanded dorsoventrally ; * premaxillary ; natro view anterior in * o and low ; Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 aea iw e brvain nAppendix. in abbreviations See view. lateral steobt h osledo hsoeigi mildly is opening this of end dorsal The high orbit. dorsoventrally the as as almost is total is fenestra the and infratemporal shaped of The hourglass 2). 45% (Figure approximately length of skull have length (1979) orbital Vince orig- and an Bonaparte specimens by described post-hatchling inally during The length skull subject development). the is to length respect allometry orbital negative the to (since just stage specimens ontogenetic these may subadult of this the for than although evidence larger represent is sauropodomorphs, ratio This other length. in skull total the well- of approximately occupying 30% a large, margins. notably lacks are posterior orbits and and The anterior its subtriangular on and fossa fenestra developed the small antorbital The 55% rather their 1). (Figure is approximately to orbit the is subequal of length and is depth length dorsoventral sauropodomorphs). premaxillae, most anteroposterior the in are by Their (as nares enclosed maxillae and are external nasals, and The posteriorly the large region. tapering notably at temporal orbits, the depth the skull along of dorsoventral its The margin maximum orbits. increases posterior its the continuously towards reaches snout height The length; dorsoventral skull total 1). the of Figure (50% rostrum high and short explicitly 1813/4. to is MPM-PV in corresponds number observed morphology description collection the the the otherwise cases, indicated; such (1979). Vince post-hatchling In and Bonaparte the by or described 1813/1, 4587) specimens PVL (MPM-PV 1813/2, specimens MPM-PV subadult other the on three observed better were characters some However, of Lacrimal 5. Figure 128 h klso h ueieseieshv relatively a have specimens juvenile the of skulls The .Pl&J .Powell E. J. & Pol D. usuu patagonicus Mussaurus MMP 834 in 1813/4) (MPM-PV eg P//21 and BPI/1/5241) of (e.g. of specimens adult specimen In 2004). subadult approximate a carinatus proportions of its those Interestingly, [V20]). 13200, SMNS minor Efraasia the of morphology acute the remarkably resembles condition Thus, This is 3). and margin. snout 1 (Figures pointed alveolar the and of the tip with anteroventral degrees the of 45 The of premaxilla angle 1813/4. the MPM-PV of patagonicus specimen margin the anterior in exposed external dentary, small the a angular. between and have surangular, enclosed mandibles fenestra The mandibular palate exposed occiput. complete a and or preserved narrower have specimens the are available of none Unfortunately, openings post-hatchling 4210). (PVL the laterodorsally the which of (1979), Vince in and condition Bonaparte by the described specimens to contrast anterior exposed, dorsally their in and large only are openings preserved These region. having 4587, are PVL 1813/1 openings MPM-PV and specimens supratemporal the its in The preserved 2). expanded, partially orbit and also and the 1 underneath is (Figures postorbital extending end the region ventral anteroventral by The bordered squamosal. is and expanded hre hnhg,i otatwt h o and low the with sauropodomorphs contrast basal (e.g. other in of posterior condition high, is elongated the process) than nasal ascending to the shorter to anterior ventral and located process surface 63 exposed between 4210). varying (PVL degrees 2), 71 and 4068) (Figure (PVL degrees angle larger cantly of The margin). specimens alveolar the post-hatchling with degrees 90 to 60 other of an angle all forms margin from this differs which (in but sauropodomorphs basal [V20]), 116 V NGMJ 1942; osvnrlmdon fti ein stretimes the three are is at region, located foramina this them, larger. these of of midpoint of one dorsoventral whereas Four small margin. notably to the nares alveolar external of the the a of margin surface anteroventral delimits the lateral from ridge scattered foramina The neurovascular sharp five bears fossa. premaxilla a narial which depressed in 12216) SMNS gracilis of ‘Plateosaurus’ condition the with engelhardti of contrast sauro- premaxilla in basal fossa, the other of patagonicus in body Mussaurus than main The higher subqua- podomorphs). and is BPI/1/4376, shorter premaxilla juvenile the but the in than of longer (i.e. body drangular main the 3967), h aea ufc ftelf rmxlai well is premaxilla left the of surface lateral The h anbd ftepeail ie h laterally the (i.e. premaxilla the of body main The nhsuu polyzelus Anchisaurus BI147;Gwe l 90 use al. et Sues 1990; al. et Gow (BPI/1/4376; SN 30)adrltdfrs(e.g. forms related and 13200) (SMNS sdrce otrdral,frigan forming posterodorsally, directed is MS1268, SMNS unnsuu huangi Yunnanosaurus GPIT18318a, ak eldvlpdnarial developed well a lacks unnsuu huangi Yunnanosaurus ooaiarsbrevis Coloradisaurus Glo 96 P 1883), YPM 1976; (Galton Mussaurus assodlscarinatus Massospondylus ltoarsengelhardti Plateosaurus Massospondylus fasaminor Efraasia GJV116 V NGMJ aeasignifi- a have Plateosaurus Mussaurus (Young (PVL Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 iue7 etifaeprlrgo of Appendix. in region abbreviations See view. infratemporal lateral in Left 1813/4) (MPM-PV 7. Figure Appendix. in abbreviations See 4587. PVL specimen subadult C, 1813/1; MPM-PV and 4587 PVL specimens of on Skull based 6. Figure eilwdhaogislnt n osntse to seem not does latero- and constant length almost its an along external width has the medial of process margin This anterior the nares. of half ventral the h sedn aa rcs ftepeail forms premaxilla the of process nasal ascending The usuu patagonicus Mussaurus ndra iw ,ps-acln pcmnPL41;B eosrcino urtmoa region supratemporal of reconstruction B, 4210; PVL specimen post-hatchling A, view. dorsal in usuu patagonicus Mussaurus retd omn nagewt h lelrmri of margin alveolar the with angle the an forming oriented, laterally end. process anterior overlaps its at tabular process abruptly tapers a and This premaxilla the forms 1). of and the (Figure margin to ramus anterior is ventral ramus ascending rostral the posterior The region. a along antorbital and fossa, extends antorbital process the ramus of the edge rostral forms anterior ramus Its ascending an premaxilla, sauropodomorphs. the contacts basal other in o osbet eemn h rsneo subnarial a of presence in the foramen determine is to it elements so possible two contact, not natural These their from maxilla. displaced slightly the the are dorsally of borders process and ventral nares anterior the The external forms the nasal. of premaxilla over- the margin the of laterally of process process is descending posterior process the by this lapped Dorsally, 1999). (Ser- sauropodomorphs eno non-eusauropod other of condition most the resembling 4), (Figure gradually taper h sedn au ftemxlai subvertically is maxilla the of ramus ascending The of maxilla The kl ntm of anatomy Skull usuu patagonicus Mussaurus usuu patagonicus Mussaurus usuu aaoiu 129 patagonicus Mussaurus . stiait,as triradiate, is Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 130 sal aeanro roetruhwihwould vessels associated which and nerve through maxillary groove the sauropodomorphs passed narrow have basal antorbital a the ridge, the have this of of usually to edge process ventral Medial posterior sharp fossa. the a forms of maxilla 4587. margin PVL juvenile dorsal the the in The preserved on but well observed, is be information region cannot this jugal is precise the with 1813/4 this contact and sutural MPM-PV At overlaps damaged specimen jugal. of maxilla the slightly maxilla of the the end of point, anteroventral process the posterior laterally saur- open- basal the this the shallow to other ing, Posterior a in of 1999). (Sereno as into size opodomorphs posteriorly, continues these the directed and of groove twice foramina neuro- posterior approximately preceding large this most is moderately of The openings six surface alveolar foramina. by lateral the vascular pierced The forms is maxilla. margin process the ventral of its margin Its antorbital the while of margin. limit fossa ventral orbital the forms anterior margin dorsal the towards poster- extending the expanded fossa. at antorbital slightly the lacrimal of is corner the wall odorsal medial contacting this posteriorly of The strongly end 1). (Figure dorsal a anteroposteriorly and narrow forms fenestra markedly antorbital is wall the of medial margin anterior concave this 13200), basal SMNS other in for As (except fossa. antorbital sauropodomorphs the of anteromedial floor the and forming wall lamina a as maxilla dorsally the extends of ramus ascending of The BPI/1/5241). (e.g. individuals young carinatus in present ante- of state specimens is patagonicus these of character Mussaurus region status subadult this this the in reflect However, could of sauropodomorphs broad. surface basal roposteriorly external most the of which the condition (or of from the surface differs the This fossa lateral narrow. at markedly The is antorbital ramus point). ascending deflected this the to is ventral of even ramus midpoint ascending dorsoventral the 12216) saurus 3314, 1883, (e.g. sauropodomorphs brevis adisaurus similarly present A also is in maxilla region. the of ramus deflected ascending oriented nasal this The is overlaps fossa. the antorbital process laterally the the of of of This fifth height dorsalmost margin dorsoventral the 2). along anterior posteriorly (Figure deflected the opening forms post- antorbital 90 the to and close In is degrees angle 1). this however, (Figure specimens hatchling degrees 75 approximately art ta.2005), al. et Barrett h otro au salwtblrprocess tabular low a is ramus posterior The assodlscarinatus Massospondylus .Pl&J .Powell E. J. & Pol D. ’ uegsuu huenei Lufengosaurus ltoarsengelhardti Plateosaurus gracilis BI146)btnti dl specimens adult in not but (BPI/1/4367) PT18318a, GPIT PL36) ncnrs,i otbasal most in contrast, In 3967). (PVL ic h aemrhlg is morphology same the since eaooarsreadi Melanorosaurus nhsuu polyzelus Anchisaurus VPV1 Yug1941; (Young 15 V IVPP BI154)and (BPI/1/5241) MS120 ‘ 13200, SMNS ltoarsengelhardti Plateosaurus fasaminor Efraasia Massospondylus NMQR SMNS Plateo- Color- YPM antb bevd hsmsigsraewas surface missing This unfortunately observed. is be lacrimal contact cannot lacrimal-prefrontal the the therefore of and missing, ramus rostral the for natus described the resembles ridge ridge this dorsolateral of development of The axis skull. longitudinal the the to oblique oriented a crest by dorsal posterolaterally bordered is and anteriorly smooth fossa antorbital and 5). triangular nasal the (Figure of the apex and dorsal maxilla the the forms of lateral ramus contacts ascending the that the process short rostral on a broad has dorsoventrally lacrimal exposed The and 1). (Figure mostly skull the the of bone surface in L-shaped observed an be can of suture specimens available and nasal-frontal nasals the no of the surface Unfortunately, dorsal snout. posterior the the on of posteriorly details surface extends dorsal of and the surface convex on dorsal markedly is The nasal fossa. dorsal the antorbital the subhorizontal of the margin to significantly contributes minor Efraasia ‘ 13200, ihtecniinof condition the with in carinatus as Massospondylus edge dorsal huenei its in participation h arml u oterdcdanteroposterior the reduced fossa, of antorbital the the nasal of apex to dorsal the of of Due extension surface dorsal lacrimal. the of the is margin nasal anterior the the posterior of to process The sutured descending broad preservation. the of during margin off have broken could this been although extension, splint-like the this the has of of contacts None specimens excluding nares. available other external that premaxilla, the the of margin the process extended the from of maxilla is slender process nasal sauro- a posterior the basal as of most In ventrally region nares. this posterior external the podomorphs, of the descending half of dorsal broad the margin of forms a ramus and the sends ascending maxilla the the forms nasal laterally overlaps nasal the that process the point, of this Posterior opening. body to narial the of main margin dorsal ventral the rounded The of nares. of nasal half external the the margin dorsal of the of margin forming anterior surface the premaxilla, lateral the of the acute process an covers as that extends nasal surface process the dorsal Anteriorly, the snout. of the half some of anterior 1813/2. the however, forms MPM-PV 1), nasal from The gathered (Figure be 4587 can information PVL the and of 1813/4 any in this available on currently of specimens not details are Unfortunately, structure 1997). (Witmer h aea ufc ftersrlrmsi a and flat is ramus rostral the of surface lateral The is lacrimal the sauropodomorphs, basal most in As h aasaeepsdi aea iwi MPM-PV in view lateral in exposed are nasals The Se ta.20) h osmda agnof margin dorsomedial The 2004). al. et (Sues IP 5 art ta.20)and 2005) al. et Barrett 15; V (IVPP usuu patagonicus Mussaurus Plateosaurus usuu patagonicus Mussaurus MS126 nwihtenasal the which in 12216, SMNS ’ ltoarsengelhardti Plateosaurus usuu patagonicus Mussaurus gracilis BI143) hscontrasts This (BPI/1/4934). usuu patagonicus Mussaurus PT138,and 18318a, GPIT a nyamarginal a only has assodlscari- Massospondylus . Lufengosaurus . SMNS Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 hsvraini ttemmn ifiutt interpret taxa. lacrimals other to preserved most well difficult for of moment sampling limited the the at given is variation the since of this with information either phylogenetic correlation dimorphism, the Thus, lack size. represent specimen’s characters sexual these to have in or changes seems authors variation most variation individual as noted 2004) al. et species Sues the 1990; al. single et (Gow considered a recently to actually specimens belong these If BPI/1/5241). above-described BPI/1/4779, to carinatus the referred individuals spondylus in the among significantly characters varies ramus preservational to press). due in be (Fedak, might biases corner fossa posteroventral antorbital the these the on of wall of medial a some of absence In found sinus. condition in the resembles antorbital lacrimal posterodorsal the the the characters over of lacking and lamina corner ends, (superficial) dorsal lateral poorly and a ventral narrow, its at anteroposteriorly expanded straight, being, patagonicus 12684, basal saurus other in (e.g. sinus antorbital posterodorsal lateral the the the is sauropodomorphs. covers lacks of area that lacrimal This corner the lamina 5). (Figure as (superficial) fossa laterally extending antorbital exposed wall lacrimal medial the the its reduced of of into extremely end an most dorsal is the and there at midheight Only region. lacrimal’s is dorsal but the 5) (Figure postero- at fossa the absent antorbital the at of developed This corner moderately ventral fossa. antorbital is the wall a this of medial that floor to wall bears posterior medial Anterior the reduced lacrimal forms a length. extends entire lacrimal the the its ridge, region, along ventral ridge and this dorsal sharp its Along its at flares ends. at slightly anteroposteriorly and narrow midpoint markedly is lacrimal of specimens available nicus the in posteriorly. of the observed faces any be to cannot of and however, opening, flat surface seem lacrimal The is posterior not ramus The ventral does lacrimal’s element. lacrimal this the is contact maxilla ventral the displaced, Although its oriented the jugal. slightly the and with to is 1) sutured degrees is (Figure It margin 60 margin of fenestra. alveolar angle maxillary antorbital an posterior forming entire the obliquely, the of forms and margin straight, and narrow as sauropodomorphs. skull, the basal of other surface in dorsal the on exposed probably neetnl,temrhlg ftelcia ventral lacrimal the of morphology the Interestingly, sauropodomorphs basal other with comparison In anteroposteriorly is ramus ventral lacrimal’s The nhsuu polyzelus Anchisaurus h aea ufc ftevnrlrmso the of ramus ventral the of surface lateral The . ltoarsengelhardti Plateosaurus ’ uegsuu huenei Lufengosaurus gracilis h armlsvnrlrmsdfesin differs ramus ventral lacrimal’s the PT18318a, GPIT eg P//36 BPI/1/4934, BPI/1/4376, (e.g. P 83 lhuhthe although 1883, YPM VPV1) in 15), V IVPP MS120 ‘ 13200, SMNS fasaminor Efraasia usuu patago- Mussaurus Mussaurus SMNS Masso- Plateo- rbeso osdrn h yeseiesfor specimens type patagonicus the of relationships phylogenetic the considering the evaluating underscores of which 2002), problems Wilson 1998; Sereno of and (Wilson one synapomorphies is sauropod opening recognized the supratemporal the from is post-hatchling frontals of the exclusion the but the Interestingly, in 4210). 4587) (PVL depression individuals this PVL from 1813/1, excluded the subadult (MPM-PV of the in end specimens fossa supratemporal posterior the end enters the frontal anterior Consequently, the the 6). to these ontogeny, respect (Figure with From during transversely of frontals expand 6A). that the of Figure end seems posterior half; it posterior dorsally specimens, bowed their markedly rather frontals, on have short (which and individuals and specimen narrow post-hatchling condition subadult shape the the the from of The markedly of differ dorsally. frontals 1813/1 MPM-PV the bowed of slightly extension region is dorsal central Their the for that 6). except smooth, (Figure and end flat is caudal surface the laterome- at maximum width their dial specimens having wide than post-hatchling subtriangular, longer and are the elements These of 4210). PVL (e.g. some and 1813/1 orbit the of third anterior the 6). to (Figure up specimens shorter just relatively post-hatchling is extends process the and posterior In the mid- 4210) orbit. the (PVL anteroposterior the specimen, the of this point reaches In almost frontal. prefrontal in the and is prefrontal with right 1813/1 the articulation of MPM-PV tip posterior specimens the 4587, PVL the in determined. be However, cannot frontal the with its contact Therefore, sutural 1813/4. only MPM-PV was in opening preserved orbital would the partially The of that margin process dorsal origin. the posterior form seems its The but anteriorly. at exposed taper completely to crest not is developed process anterior slightly and a narrow rather be bears was to ramus seems ventral covers preserved lacrimal’s partially the only that of surface process caudal or the descending The 6810) (BPI/1/5241). AMNH Fgr C,atog hsrgo sntperfectly frontal not is the region in this notch although a 6C), have developed to (Figure seems more 4587 PVL specimen slightly the that note to engelhardti Plateosaurus 1883, most (e.g. in YPM as sauropodomorphs slot-like than basal rather concave, moderately V 57(iue6)adi a n arw o as not narrow, and flat in is as in and expanded preserved 6C) (Figure is 4587 basal surface PVL other dorsal in as Its triradiate sauropodomorphs. is element This opening 1). orbital (Figure the inside disarticulation, in preserved ohfotl r elpeevdi MPM-PV in preserved well are frontals Both h rna’ riuainwt h otria is postorbital the with articulation frontal’s The h etperna fMMP 834was 1813/4 MPM-PV of prefrontal left The kl ntm of anatomy Skull . assodlscarinatus Massospondylus ltoarsengelhardti Plateosaurus usuu aaoiu 131 patagonicus Mussaurus MS120.I sinteresting is It 13200). SMNS assodlscarinatus Massospondylus usuu patagonicus Mussaurus nhsuu polyzelus Anchisaurus Glo 1984; (Galton BPI/1/5241, Mussaurus Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 rnvreyrte hnpseoaeal Fgr 6). (Figure posterolaterally than oriented rather and transversely differs shorter basal also proportionately 4210 being process PVL most markedly, specimen this post-hatchling of the of in morphology condition The the the sauropodomorphs. of and resembling axis longitudinal the narrow forming skull, with degrees posterolaterally 45 is of oriented angle is an process it and this elongated specimen 1813/1, the In MPM-PV specimens. subadult the in preserved reduced is 6). specimens (Figure concave subadult slightly the and markedly in and enlarged while also is convex, surface speci- fossa this the 4210, supratemporal In PVL men the development. during of markedly floor changes parietals medial the the of of to contribution fifth The one width). frontal’s approximately the is subadult parietal than the in each width (while specimens frontals similar the a of notably surface have dorsal are the elements these parietals of dorsal The the surfaces 6A). (Figure bowed 4210, dorsally The and post-hatchling PVL expanded fossa. the In of supratemporal different. of parietals the is the specimens of parietal of medial wall) morphology the the (or forming edges, deflected floor supratemporal laterally these the and the to delimit ventrally of Lateral and margins region openings. anterior anterior and slightly medial the by more on bounded are ridges developed These surface side. and either dorsal other on ridges each developed narrow to a sutured strongly have sauropod al. are et embryonic They Salgado in eusauropods; 2005). adult present some in (and be fenestra specimens, material to subadult fronto-parietal seems the a or which of post-hatchling the signs either no frontals. the are with articulation There in preserved are of 1813/1 extension posterior reduced prefrontal). a the has which 2003) rnoprea uue u hsstr stransversely cus in is V-shaped interdigitated suture and oriented this oriented posteriorly but suture, a fronto-parietal have 1883) length. (YPM by its of accentuated carinatus most been for have runs transversely suture may fronto-parietal The causes. it preservational and preserved agn(iue6,a nms aa sauropodo- basal most in for as orbital (except dorsal 6), of the morphs the level of (Figure of the edge half margin posterior lateral at the The nasals forms margin. the frontals of orbital to anterior sutured specimens the progressively loosely narrows subadult is frontal and the the 4210), (PVL of mens patagonicus any Mussaurus in observed huangi Yunnanosaurus 132 13200), h otrltrlwn ftepreasi poorly is parietals the of wing posterolateral The MPM-PV of parietals the of halves anterior The h neirotrgo ftefotl antbe cannot frontals the of region anteriormost The (Yates2003), .Pl&J .Powell E. J. & Pol D. ooaiarsbrevis Coloradisaurus BI154)and (BPI/1/5241) usuu patagonicus Mussaurus ltoarsengelhardti Plateosaurus hcdnoarscaducus Thecodontosaurus nteps-acln speci- post-hatchling the In . NM 1 [V20]). 116 V (NGMJ hcdnoarscadu- Thecodontosaurus nhsuu polyzelus Anchisaurus PL36) and 3967), (PVL Massospondylus sstrikingly is (SMNS (Yates huangi of huenei process Lufengosaurus descending At the jugal. posterolaterally patagonicus the end, of is this process this Ventrally, ascending and the process. by markedly overlapped anteromedial tapers the anterior the of process the of margin with continuous posterior descending edge being the the opening, of of orbital most edge forms anterior length post- process in The In equal 4209). process. almost (PVL are anteromedial processes the both approximately as hatchlings is long length as dorsoventral twice Its convex 7). slightly is (Figure surface lateral its and bowed laterally recurved. medially is end this which in of and in condition 13200) straight, (SMNS the is process to this of contrast tip supratem- distal the The posterior of fossa. margin its poral anterolateral while the rounded orbit forms the the edge forms of process margin this pro- posterodorsal of edge is anterior broader. 1813/4 The distally not and longer, MPM-PV robust, more was of portionately post-hatchling process process the anteromedial this with of of comparison specimens end conse- In and, distal preserved. is frontal the the postorbital the In quently, from left skull. disarticulated the the slightly 1813/4, of surface MPM-PV dorsal specimen the onto extends 7). (Figure large surface a fora- lateral smaller its bears on significantly and men a smooth with is main associated The postorbital foramen, P24). the BMNH of and probably 1883 body is YPM (as for 1813/4 case the ontogenetic MPM-PV differ- specimen marked immature of these the a status Thus, represent shows probably size. ences specimen postorbital with the correlation of robustness nisgnrlsaetepootosfudin of found specimens proportions different the caducus shape polyzelus general with Anchisaurus The resembles its element 1813/4 processes. MPM-PV in robust posterior specimen of more and postorbital much descending a sauropo- broader basal is most of domorphs the posterior postorbital (contacting The a squamosal). process and descending jugal), a frontal), to (sutured the process anteromedial an having 7), (Figure V 57 hr toelp h neirpoesof process specimen anterior subadult the the the overlaps in in it where preserved preserved 4587, is PVL but not of 1813/4, end was distal MPM-PV The process 7). (Figure this flat distinctly lateral is its and surface postorbital the of process descending the carinatus h ecnigpoeso h otria salso is postorbital the of process descending The and bowed laterally is process anteromedial The h otria sasedrtiait element triradiate slender a is postorbital The h otro rcs sbodradsotrthan shorter and broader is process posterior The NM 1 V0) and [V20]), 116 V (NGMJ Yts20;BN 2) oee,i the in However, P24). BMNH 2003; (Yates (BPI/1/5241). sntarpl eetdatrol,a in as anteriorly, deflected abruptly not is usuu patagonicus Mussaurus ooaiarsbrevis Coloradisaurus P 83or 1883 YPM IP 15), V (IVPP assodlscarinatus Massospondylus rcs strdt the to (sutured process ltoarsengelhardti Plateosaurus PL56) the 5865), (PVL Thecodontosaurus Massospondylus Yunnanosaurus PL3967) (PVL Mussaurus the Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 56), incertus saurus arpd,btnti te aa sauropodomorphs basal other in not but sauropods, unnsuu huangi Yunnanosaurus odto sas rsn in similar present (BPI/1/5241), A also orbit. is the infratemporal condition underneath the extends an that of producing fenestra corner incised, ascending descending anteroventral markedly the is elongated the to jugal Ventral of the postorbital. process, the surface of posterior instead, process half, the the dorsally dorsal deflected with slightly covering Its degrees is jugal. and 45 posterolaterally the faces of of angle posterodorsally margin buccal an projects forming and this of oriented laterally half ventral faces the The with 5). process contact and 1 sutural (Figures the postorbital along rapidly tapers and the of edge posteroventral tapers fossa. the antorbital reaches jugal jugal the of anterior the end The maxilla element). latter and orbit, the lacrimal overlapping orbital (laterally the the foramen the between small of wedging to a gradually, margin Anterior by posterior the pierced opening. to is close jugal lateral located the The opening. of orbital dorsal the surface of the Its edges anteroventral of 1). the anterior forms and end (Figure and concave posterior maxilla slightly the is the the margin of at of step region process distinct suborbital caudal a the 2). has of (Figure jugal margin bar ventral suborbital thin post- The a and the low forming dorsoventrally the is elongated, In 5865) jugal the PVL a of jugal. and region suborbital 4210 having the (PVL 1), specimens of hatchling Figure length total 4587; is the anteroposterior 25% approximately PVL jugal is that depth the and dorsoventral of 1813/4 (MPM- region PV specimens subadult the suborbital in high The dorsoventrally 2). (Figure (e.g. of sauropodomorphs basal caducus dontosaurus other length speci- of young skull in mens a total proportion shows This to adult usually development. respect the orbit during with the in allometry of smaller size negative be the since the probably condition would of ratio thirds 5). This and 1 two (Figures jugal the of approximately extension anteroposterior occupies 1813/4 (articulating process an quadratojugal). infratemporal the with lacrimal), posterior postorbital), a and the and with maxilla (articulating process the ascending process suborbital with anterior (articulating an by composed element the on facet V-shaped 2). opened (Figure anteriorly squamosal process an this of into end fits posterior the 4210), (PVL PVL and specimens 5865 post-hatchling the In squamosal. the h sedn rcs ftejgli eaieyshort relatively is jugal the of process ascending The MPM-PV specimen the of process suborbital The of jugal The usuu patagonicus Mussaurus eaooarsreadi Melanorosaurus BnpreadPmrs19;ULR 1995; Pumares and (Bonaparte uegsuu huenei Lufengosaurus usuu patagonicus Mussaurus n h oththigspecimens post-hatchling the and ) NM 1 [V20]), 116 V (NGMJ assodlscarinatus Massospondylus sapoiaey0.75 approximately is NQ 34,and 3314), (NMQR IP 15), V (IVPP satriradiate a is Theco- Rioja- saurus le oec te.Ohrbslsauropodomorphs, basal Other as other. subpar- such are each quadratojugal to the allel of processes jugal and brevis adisaurus osntse ocnattedsedn rcs fthe of process descending infratemporal the contact to the seem process not this does specimens, of at post-hatchling the end In midpoint to fenestra. seems dorsoventral and quadrate the the of the to margin attached anterior is process of it ascending expansion The 5865) anterior quadrate. the the of PVL level the (e.g. at abruptly specimens tapers post-hatchling and, the base the its at in forms wide infratemporal is process is the ascending margin The of surface fenestra. anterior margin lateral posteroventral its Its rounded and of concave. body wide main slightly is The jugal. quadratojugal the by the of overlapped process partially been posterior have the would anterior it the of the although of portion 1), margin (Figure ventral fenestra the of infraorbital most along extend extended would the slightly of corner only posteroventral posteriorly. fenestra the and infratemporal 50– approximately degrees of angle 60 an with morphology, ate huenei Lufengosaurus the of corner engelhardti in posteroventral as Plateosaurus extended posteriorly the not is fenestra forms, infratemporal these the In in 1 both readi as Figures (in Melanorosaurus 2), specimens; degrees an post-hatchling and at 80 and other approximately each subadult the to of and The oriented quadratojugal angle are 1). the process of (Figure ascending process the quadrate and jugal process, in the anterior ascending lacking the from of 4587, end disarticulated dorsal PVL the and former 1813/4 MPM-PV the of fenestra. ventral infratemporal the branch the of most of posterior forms margin an quadratojugal the the have and of jugal taxa reduction eusauropod extreme 13200, Derived BPI/1/5241). of bar SMNS (e.g. the infratemporal the that sauropodomorphs the on seems jugal in Mussaurus the it quadratojugal of 1813/4, the extension with MPM-PV contact specimen natural from its disarticulated is region this Although the posteriorly. the that during showing decreases 5865), of character ontogeny this 4210, specimens of 4209, development post-hatchling PVL the the even is (e.g. of in orbit pronounced extension the more underneath the fenestra Interestingly, infratemporal 3967). PVL (e.g. h neirpoesi pitlk rjcinthat projection splint-like a is process anterior The of in preserved partially is quadratojugal The tapers and short markedly is process posterior The kl ntm of anatomy Skull ltoarsengelhardti Plateosaurus ’ gracilis assodlscarinatus Massospondylus snta eeoe si oebasal some in as developed as not is usuu patagonicus Mussaurus PT18318a, GPIT PL36) nwihteascending the which in 3967), (PVL ijsuu incertus Riojasaurus IP 5,hv nintermedi- an have 15), V (IVPP NQ 34,adsauropods. and 3314), (NMQR usuu aaoiu 133 patagonicus Mussaurus assodlscarinatus Massospondylus SN 30)and 13200) (SMNS ltoarsengelhardti Plateosaurus MS120 ‘ 13200, SMNS ooaiarsbrevis Coloradisaurus Fgr 2). (Figure BI154)or (BPI/1/5241) UR56), (ULR Plateo- Color- Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 xoe nayo h vial pcmn of not specimens patagonicus available is the pterygoid of any the in exposed with contact precise the tunately, rsn ntelte forms. latter the in fenestra present infratemporal of the extension of posterior corner posteroventral the the with posteriorly correlated probably being is of instead and quadrate, in as the deflected This dorsal of ridge. the with half dorsoventral continuous vertically, marked extends process slightly convex, is a 5865) PVL bearing in (exposed surface while concave posterior slightly its is flattened surface anterior anteroposteriorly Its 7). (Figure and or wide quadrate lateromedially the of suture). quadrate-quadratojugal wing the enclosed at location anterolateral located (either its the in sauropodomorphs within varies basal which among foramen, quadrate the the of of none specimens Unfortunately, descending available squamosal. the the is of to process and anterodorsally concave and the slightly of quadratojugal process ascending is the to wing anteroventrally surface sutured caudal anterolateral the specimens the specimen post-hatchling this of In the not 5865). of PVL is (e.g. some well surface is in but caudal 1813/4 preserved MPM-PV Its specimen narrower the wing. and in exposed anteriorly pterygoid developed the anterolateral less The than also corresponding lamina. is the anteromedial wing to the quadrate’s dorsal of gently located the edge is is of margin and ventral half concave Its dorsal extension). the dorsoventral along (only wing extending pterygoid the than extensive dorsoventrally (e.g. exceeds length it quadrate the quim which the total in in of than 70% the sauropodomorphs, restricted basal of more most being 65% length, approximately quadrate in occupies present the wing with condition caducus contrasts subtriangular Thecodontosaurus This or 7). (Figure axis semicircular main quadrate the dorsoventrally the to oriented perpendicular of margin axis ventral its major and its having gular, distal its on condyles stout articular a end. the forms bears quadrate squa- the that the of process half of ventral The process mosal. descending the of and process ascending quadratojugal the the anterolateral with other, the articulates that and each wing wing to pterygoid perpendicular or set anteromedial laminae composed is two half dorsal of Its 7). (Figure exposed view is anterior and on squamosal and quadratojugal the from preservational to causes). due be may this (although squamosal 134 h eta afo h udaei outprocess robust a is quadrate the of half ventral The less is quadrate the of wing anterolateral The subrectan- is quadrate the of wing pterygoid The disarticulated is 1813/4 MPM-PV of quadrate The ooaiarsbrevis Coloradisaurus , .Pl&J .Powell E. J. & Pol D. hcdnoarscaducus Thecodontosaurus . ltoarsengelhardti Plateosaurus usuu patagonicus Mussaurus Yts20) h pterygoid The 2003). (Yates PL36) hscharacter This 3967). (PVL ae 03.Unfor- 2003). Yates ; aunlatupini- Saturnalia SN 13200) (SMNS Mussaurus preserve h otro agno h nrtmoa fenestra. (e.g. sauropods infratemporal and (e.g. the theropods of Only margin of posterior midpoint dorsoventral the the to descending sauropo- down narrow extends and This basal process slender other (its a end). which of the in end dorsal that domorphs, of from its dorsal differs 25% of proportion its approximately extension at is anteroposterior broad length and dorsoventral dorsoven- in extension short proportionally tral is process descending squamosal MPM-PV the the ventrally specimen of of region the anterior tapers in the preserved 1813/4, and smooth, As is 7). laterally, (Figure surface concave This articulation. slightly two in these were when squamosal the bones the of of would region anterolateral process exposed surface laterally descending the anterior the to of The correspond been quadrate. thus end the have dorsal slightly of would lamina the and region by concave by This overlapped The laterally divided ventrally. 7). is broadens surface (Figure surface lateral ridge posterior its extended two on dorsoventrally has and facets short, broad, distinct is squamosal the of process fenestra). (along infratemporal exposed the of is margin the squamosal dorsal the of the of surface process an narrow only anterior dorsoventrally Thus, process. and this of elongated length of squamo- the most the along of the sal of surface of dorsal margin process the overlaps posterior postorbital dorsal and post- The the complete fenestra. the along infratemporal is In anteriorly specimen. process a this extends this in has specimens, broken end and hatchling be anterior to postorbital Its the surface. seems the dorsal from fenestra broad of disarticulated lateromedially infratemporal is process the process posterior This of the of 1). margin region of (Figure posterior dorsal edge the the and posterolateral opening the supratemporal forms squamosal of and angle an anterior 6A). (Figure form the degrees squamosal 40 the specimens approximately of these rami and In on descending 4068 preserved. (PVL 5865). complete specimens PVL are been post-hatchling the processes have of two two rami this these in two Fortunately, however, only tetraradiate, usually specimen is process dinosaurs, this basal Among 1813/4. MPM-PV in mentary emt otc ahohri h pcmnMPM-PV specimen not the in do other quadratojugal each contact and preserved to squamosal seem the the of Similarly, remains squamosal, quadratojugal). (i.e. region the quadrate, infratemporal of the disarticulation of the by elements this affected 1813/4) been MPM-PV that have in might noted fragment squamosal be preserved must the in state of it character process However, descending broad squamosal. and short similarly nteseie P-V11/,tedescending the 1813/4, MPM-PV specimen the In the of branch anterior the 1813/4, MPM-PV In h qaoa of squamosal The usuu patagonicus Mussaurus Shunosaurus usuu patagonicus Mussaurus errsuu ischigualastensis Herrerasaurus , Omeisaurus bsdo the on (based hwa show ) sfrag- is ) Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 rcs n h otrvnrlyepsdsraeof surface exposed posteroventrally the and and transverse the deflected process of surface anteriorly exposed ventrally slightly the delimits is margin posterior ectopterygoid in the of (as the region to due posteromedial reduced extensive significantly is be exposure ventral cannot its opening choanal specimen. the this in and observed Its end length). preserved 4210. entire anterior the PVL (along surface palatines specimen medial the the the of by bordered in are contact margins but lateral other to The each seem to close not lie do ramus anterior the of edges and of condition of in than exposure shorter ventral engelhardti and The broader is opening. ramus orbital this rostral the the of of level half the reaching anteriorly extends and quadrate. the observed. of contact be this cannot 4210 flange PVL markedly specimen the rostromedial in is Unfortunately, the pterygoid to posterolaterally the contact extends of and lateromedially ramus narrow quadrate the 1998; sauropodomorph eusauropods Sereno caducus basal dontosaurus the and for and Wilson 2002) commonly except Wilson 1998; is 1995, dinosaurs, processes (Upchurch in these facet around present semicircular ‘hooks’ developed that that basipterygoideal similarly notch the its A of on opened end processes. distal bears posteriorly the with and a articulates pterygoid) margin right posterior the in preserved directed posterolaterally ramus. the quadrate the three (contacting and flange of transverse ectopterygoid), the consisting sutured the palatine), (laterally the bone, ramus to sauropodomorphs, anterior complex The basal branches. a main other is in pterygoid As PVL specimen 4210. post-hatchling the in exposed partially 4068. PVL and of 1813/4 MPM-PV specimens the patagonicus among character in this differences the probably, Most basal sauropodomorphs). of condition infratemporal generalized the the of (resembling fenestra margin posterior the dorsoventral been of the descending midpoint reaches has elongated that squamosal an the region of post- has process this 5865) other which (PVL the preserved in However, specimen in specimen. hatchling than subadult narrower proportionately the is base short, quite its also although is process descending a the 4068), PVL as holotype regarded the of In traditionally character). synapomorphic condition sauropod (a 1813/4 h rnvrepoesetnsltrvnrlyand lateroventrally extends process transverse The h neirrmso h trgi striangular is pterygoid the of ramus anterior The (as base its at broad is ramus quadrate The only are bones) palatal all as well (as pterygoids The usuu patagonicus Mussaurus eaooarsreadi Melanorosaurus assodlscarinatus Massospondylus SN 24) eebigmr the more resembling 12949), (SMNS r u opeevtoa rbesin problems preservational to due are assodlscarinatus Massospondylus Yts20) aea oti facet, this to Lateral 2003). (Yates teps-acln specimen post-hatchling (the NQ 34.Temedial The 3314). (NMQR P//79.Its BPI/1/4779). (BPI/1/4779) Plateosaurus Mussaurus Theco- om h neiradatrmda agn fthe and of concave margins opening. gently anteromedial suborbital and and reduced is anterior concave edge the choanal forms posterior strongly the of anterior Its is edge The opening. posterior palatine the expansion. delimited the half probably medial than of the more is of margin shaft length the which the in 13200) SMNS (e.g. sauropodomorphs is expan- of medial carinatus that shaft the resembles condition of palatine This length sion. The the the expansions). 40% of medial approximately (with and extension constricted lateral markedly anteroposterior the is shaft to its respect of axis and longitudinal skull the This the to 2). oblique (Figure oriented view is ventral in element exposed is 4210 PVL obliterated) completely (or reduced opening. suborbital a the and ectopterygoid-palatine Interestingly, an contact has also the absent. sauropods of ectopter- is palate taxa, the and contact two large ygoid-palatine or notably these is straight fenestra is in suborbital margin anterior Consequently its ectopter- concave. and the absent of is extension ygoid anteromedial the which in and 12949) h odto of condition from markedly the differs forms these of ectopterygoid the readi osaurus 2003), uobtlfnsr xeso)i lopeetin present the also of is carinatus reduction extension) Massospondylus consequent fenestra the suborbital (and palatines suborbital the reduced Thus, the the from palatine. contact fenestra. excluded to the is seems of pterygoid end branch laterally anterior is ante- posteromedial its ectopterygoid this and the of anterior convex of margin the extension of lateral well romedial margin The lateral a branch. the pterygoid sends borders which ectopterygoid of margin medial the the element. projection, anteromedial pterygoid, latter point, developed the the this of of exposure From process ventral the transverse posterior reducing the the to of close lies margin ectopterygoid posterior the reducing The of fenestra. extensive, margin suborbital is the of surface extension ventral the specimen Its post-hatchling 4210. the of PVL palate the on in exposed as other each from 2002)). separated (e.g. well sauropods being than (e.g. sauropodomorphs pterygoid. basal engelhardti most Plateosaurus the in as of other adjacent are each process pterygoid to the quadrate of branches two the these Thus, of base the carinatus h etpltn fteps-acln specimen post-hatchling the of palatine left The iial xaddetpeyodstrdt the to sutured ectopterygoid expanded similarly A is ectopterygoid left the of process medial The kl ntm of anatomy Skull eaooarsreadi Melanorosaurus BPI/1/4779, BI147) u ifr rmohrbasal other from differs but (BPI/1/4779), hcdnoarscaducus Thecodontosaurus NQ 34.Temda rcs of process medial The 3314). (NMQR hnsuu lii Shunosaurus ltoarsengelhardti Plateosaurus usuu aaoiu 135 patagonicus Mussaurus hcdnoarscaducus Thecodontosaurus MS12949, SMNS BI147)and (BPI/1/4779) ltoarsengelhardti Plateosaurus MR31) rather 3314), NMQR Catre n Zheng and (Chatterjee Massospondylus Massospondylus Yts2003), (Yates Melanor- (SMNS (Yates Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 pcmn fsvrlbslsuoooops(e.g. the sauropodomorphs 3967, adult of basal in incertus present several Riojasaurus stage is of it ontogenetic although specimens early 4210, PVL the specimen reflect opening This could anteropos- wide. lateromedially being between and parietal, narrow present teriorly the is and fontanelle supraoccipital slit-like the a margin, this for lii Shunosaurus sauropodo- other in (e.g. plane morphs sagittal the process on dorsal margin extends acute that dorsal the lacking The arched, high. slightly subrectan- as only is wide is as supraoccipital entire twice being the The concave gular, of occiput. developed slightly the surface are on slightly posterior posterolaterally surfaces two a face These and has by ridge. element divided sagittal This surfaces supraoccipital. exposed distinct the has of 4210 PVL most specimen post-hatchling the of specimens available of specimens patagonicus available the Mussaurus basisphenoid–parasphenoid in observed the be of can complex rest no the Unfortunately, of of process. base details into the quadrate of fits pterygoid’s region medial the the the surface on to are facet articular hook-like respect processes the This with to these shaft. expanded two angle of basipterygoid slightly right ends The and a distal basisphenoid. rounded The at other. the set each are of processes body post- basipterygoid from main the ventrolaterally extend the in that and slender processes preserved are elongated These were 4210. PVL specimen basisphenoid hatchling processes the basipterygoid the of of parts Only specimens. patagonicus Mussaurus and triangular the as process). wide is anteromedial of as the twice palatine half (approximately the broad posterior lateromedially of The expansion process. medial elongated acute, narrow, the lateromedially and a anterior is in expansion The this of exposed half anteroposteriorly. is partially palatine expanded the of only markedly end medial The is 4210. PVL it specimen be since cannot region observed this anteroposteriorly. of details expanded further moderately Unfortunately, be to seems h oe a scmltl rsre nseveral in preserved completely is of jaw specimens lower The Mandible 1883). YPM carinatus pondylus 136 ipae otrol ihrsett h skull the to respect slightly with jaw lower posteriorly complete a displaced has 1813/4 MPM-PV h ciia eini lopol ersne nthe in represented poorly also is region occipital The of specimens available the of elements Braincase and anterolaterally directed is process maxillary The hcdnoarscaducus Thecodontosaurus .Pl&J .Powell E. J. & Pol D. ltoarsengelhardti Plateosaurus ltoarsengelhardti Plateosaurus usuu patagonicus Mussaurus Catre n hn 02) except 2002)), Zheng and (Chatterjee BPI/1/5241, L 56, ULR . r isn nms fthe of most in missing are usuu patagonicus Mussaurus ooaiarsbrevis Coloradisaurus Yts20) neirto Anterior 2003). (Yates MS13200, SMNS nhsuu polyzelus Anchisaurus h specimen The . MH6810; AMNH Massos- Only . PVL neooslmri Fgrs1ad3.Ti small This 3). and 1 (Figures their at margin process peg-like anterodorsal a bear and region symphyseal U- broad the 1998). and a Sereno of Wilson 1998; produce 1995, region (Upchurch that symphysis strong shaped anterior eusauropods the the in with along dentaries degrees, contrasts curvature sauropodo- condition basal medial 43 most This approximately of morphs. condition of the angle resembling an of dentaries forming the of patagonicus the view, rami of ventral mandibular 17% In the and respectively. a 27% length, mini- are anteroposterior has and depths maximum 5865 dorsoventral mum dentary; PVL 2). lower and specimen 1 proportionally (Figures post-hatchling specimens of available The the dentaries of stages the of patagonicus condition and high proportionally short the Interestingly, 2000). as al. et such dentaries antiquus those tosaurus high with and comparison caducus basal in Thecodontosaurus short other even relatively 2004), in having al. found et those Allain (including than These 1). larger sauropodomorphs (Figure are length anteroposterior ratios its approximately is of maximum fenestra) 30% edge mandibular anterior The the external of the level the row). of at either or tip (measured tooth its symphyseal dentaries the at the the of of depth of 24% dorsoventral midpoint approximately anteroposter- ior the is at (measured dentaries length anteroposterior depth the dorsoventral minimum The of end. anterior particularly its high, at and The short proportionately specimens). condition and is post-hatchling Bonaparte dentary the the by for noted (1979) characters (as Vince several eusauropods in in present resemble sauropodomorphs, basal and other of those from different incertus Riojasaurus for elongated ( more 6810, forms and other lower in is than instead, half, posterior sauropodo- basal other engelhardti Plateosaurus with (e.g. comparison morphs post-hatchling in the high in observed 4210. only PVL partially which specimen articular), be splenial, can of (e.g. observation mandible elements the the is some precluding view, have lateral description however, in of exposed following material, most and available the specimen This the morphology. of its on Most based 1). (Figure 1 [V20], 116 carinatus h etre r eakbyepne ttheir at expanded remarkably are dentaries The of dentaries The and short rather is jaw lower the of half anterior The hcdnoarscaducus Thecodontosaurus assodlscarinatus Massospondylus BPI/1/4934, em oices nltrontogenetic later in increase to seems PL56)me ttesymphysis the at meet 5865) (PVL hcdnoarscaducus Thecodontosaurus ijsuu incertus Riojasaurus RlyadSucbr 86 Benton 1836; Stutchbury and (Riley usuu patagonicus Mussaurus UR56). (ULR ltoarsengelhardti Plateosaurus unnsuu huangi Yunnanosaurus MS13200, SMNS Yts20)and 2003) (Yates aodsuu naimi Tazoudasaurus P//79,except BPI/1/4779), Yts20)and 2003) (Yates L 6.The 56). ULR Massospondylus Yts2003), (Yates r notably are Mussaurus Mussaurus Thecodon- GJV NGMJ AMNH ; Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 xaso ftesmhssin symphysis the of expansion docus Omeisaurus tupiniquim 2003), (Yates readi rosaurus (e.g. others carinatus Massospondylus 18318a, also GPIT (e.g. is sauropodomorphs engelhardti basal condition saurus some This in ventrally. found is region curved symphyseal the markedly of margin ventral The 1.44). in than 1.25) nicus (i.e. developed less the (e.g. of known expansion in previously only was dorsoventral post- dentaries the of A the end symphyseal in 1.5. dentary); is symphyseal of the expansion ratio this of of 5865 PVL rest ontogeny specimen hatchling the the of along region expansion slightly patagonicus symphyseal decrease Mussaurus the the to since of seems specimens, expansion slightly mature be fully dorsoventral might in condition developed This row less point). tooth the each the at of to axis region perpendicular constricted (measured of dentaries height times 1.4 dorsoventral approximately the is end rostral symphyseal the sauropodomorphs polyzelus basal for most in dentary (except margin as rostral first symphysis, the the the from of posteriorly Thus, displaced tooth. is tooth mandibular to anterior first just located the is and dorsally extends process omnypeeti aa arpdmrh ( caducus sauropodomorphs dontosaurus basal in present is condition This commonly bone. this of edge lateral slightly the the row from inset tooth the towards leaving exposed, laterodorsally concave is dentary the ridge, slightly longitudinal flat, the Above end. and becomes posterior smooth ridge, is it dentaries this the although Below of 3). row, surface longitudinally and lateral the tooth the is 1 to (Figures close dentary the located margin ridge alveolar the marked of slightly a of half by divided surface posterior lateral neurovascular tooth the the the large Along below six row. aligned bears anteroposteriorly and foramina convex slightly dsuu brevis adisaurus 12684, o xedpseiryt omtedra agno the of would margin dorsal branch the form this to posteriorly 1813/4, extend not is MPM-PV surface dentary specimen in preserved the lateral the As surangular. of the end concave by overlapped posterodorsal laterally a The 1). has (Figure and dorsoventrally polyzelus Anchisaurus h aea ufc ftednaisi mohand smooth is dentaries the of surface lateral The h otro hr ftednaysihl expands slightly dentary the of third posterior The , n aa uarpd rnigbten14and 1.4 between (ranging eusauropods basal and hnsuu lii Shunosaurus ijsuu incertus Riojasaurus Camarasaurus ltoarsengelhardti Plateosaurus ae 04.Tedroeta xeso of extension dorsoventral The 2004). Yates ; C 3845). MCP Tn ta.2001), al. et (Tang aunlatupiniquim Saturnalia ijsuu incertus Riojasaurus fasaminor Efraasia MR3314, NMQR V 3967, PVL MS120 ‘ 13200, SMNS ooaiarsbrevis Coloradisaurus Yts2003),(Yates P 1883). YPM .Hwvr h proportional the However, ). Catre n hn 2002), Zheng and (Chatterjee rltv otedorsoventral the to (relative P//94,btasn in absent but BPI/1/4934), ijsuu incertus Riojasaurus UR5)adeusauropods and 56) (ULR MS12684, SMNS hcdnoarscaducus Thecodontosaurus MS13200, SMNS ijsuu incertus Riojasaurus Brachiosaurus fasaminor Efraasia Plateosaurus L 56, ULR usuu patago- Mussaurus and V 3967, PVL Anchisaurus Saturnalia L 56, ULR Melano- ’ , SMNS Plateo- gracilis Theco- Diplo- Color- is ot o,a nms aa arpdmrh (except sauropodomorphs basal for most the in of as axis row, longitudinal tooth the to ventral located 1813/4 be cranioman- MPM-PV would specimen the the of interpretation, articulation this dibular on Based 6810). in articulation present this is at structure cranioman- This similar the a since 8). of articulation, level dibular (Figure the slightly represents foramen probably a point surangular has to posterior posterior surangular millimetres the the four located of bulge developed margin forms of those region, dorsal this in surangular In the process. as coronoid the developed concave well a strongly with of being margin of instead dorsal patagonicus the Mussaurus posterior macronarian of The 1998). in half Sereno development and (Wilson of sauropods degree extreme an as maoianus such eusauropods Omeisaurus some in present also is surangular huangi carinatus pondylus zelus ooaiarsbrevis Coloradisaurus ooodpoesaoetemniua eeta is fenestra, developed mandibular in a the present above having process surangular, coronoid bowed sauro- strongly basal most 2003), the (e.g. This of foramen). podomorphs that surangular resembles to posterior margin the condition of anterior its level (from the anteriorly convex being opening. orbital the of midpoint anteroposterior the level the the overlaps of reaching element maxilla, this the of of process end posterodorsal 1 anterior (Figures The ramus 6). mandibular and the of of half margin posterior dorsal the the forms that element elongated and fenestra. mandibular external the of subvertical margin and straight anterior a forms dentary the processes, mandibular external the the of margin fenestra. of ventral anterior the the process of forming extensive, half posteroventral more much the 5865 facet is PVL dentary 4209, articular specimen PVL the post-hatchling of acute and end the concave preserved In the dentary. a from posteriorly has since extending 1813/4, angular MPM-PV The be specimen to the angular. seems the process the from ventral missing laterally the of overlaps end the posteriormost dentary of the margin end dorsal posteroventral of The the posteriorly that fenestra. of mandibular dentary third a external anterior the has the of post- forms process 5865 the posterodorsal PVL since extended artefact specimen basal is preservational other hatchling however, a in morphology, probably as This fenestra sauropodomorphs. mandibular external h uaglrdra agni etysigmoid, gently is margin dorsal surangular The of surangular The posteroventral and posterodorsal the Between kl ntm of anatomy Skull hcdnoarscaducus Thecodontosaurus YM18) n oalse degree, lesser a to and 1883), (YPM fasaminor Efraasia NM 1 V0) oslybowed dorsally A [V20]). 116 V (NGMJ ltoarsengelhardti Plateosaurus BI147)and (BPI/1/4779) hcdnoarscaducus Thecodontosaurus ltoarsengelhardti Plateosaurus usuu aaoiu 137 patagonicus Mussaurus PL3967), (PVL Tn ta.20)adreaches and 2001) al. et (Tang usuu patagonicus Mussaurus MS164.I otat a contrast, In 12684). SMNS sgnl ocv Fgr 8), (Figure concave gently is Yts20)and 2003) (Yates nhsuu poly- Anchisaurus AN 6810), (AMNH Yunnanosaurus (AMNH salow a is Massos- (Yates Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 etr n om ato h eta agno the contacts of the angular margin The of ventral fenestra. the process mandibular of part external posteroventral forms and the dentary by is element this overlapped lateral Anteriorly, 6). and its 1 (Figures elongated and dorsally convex. deflected markedly entire suran- is slightly surface the the is region, of this gular surface Along lateral process. the retroarticular the articulation, covers craniomandibular surangular the in to absent be Posterior to seems 1883) uaglrfrmnlctdaoeteexternal minor the sauropodomorphs anterior basal (e.g. large other above in The fenestra located 8). mandibular (Figure foramen margin surangular dorsal close surangular, its the to of at midpoint located A anteroposterior is ramus. the foramen mandibular surangular the posterior of noticeable half dorsal the occupies the of tip posterior in (BPI/1/4779). the as process, reaches retroarticular almost suture of end a this posterior along The angular suture. the directed by posteroventrally overlapped is margin surangular ventral of the the of opening, margin this to the Posterior posterior contacts angular). it (where the fenestra mandibular external of the the to midpoint down the ventrally dorsoventral extends this of and of 8) margin (Figure margin posterodorsal opening rounded dorsal suran- the the forms the Posteriorly, gular fenestra. of mandibular post-hatchling thirds external the two the in to restricted posterior is above, fenestra surangular the noted mandibular 5865, PVL specimen of As external most 8). the forms (Figure and of posteroventrally dentary margin the extends dorsal with suture surangular its the along of well natural lies margin in also is surface row. jaw tooth articular the lower its below the and 5865 articulation PVL specimen incertus of Riojasaurus ramus mandibular left of region Appendix. Posterior in 8. Figure 138 h nua of angular The h aea ufc ftesrnua sfltand flat is surangular the of surface lateral The ventral the 1813/4, MPM-PV specimen the In .Pl&J .Powell E. J. & Pol D. assodlscarinatus Massospondylus MS12684, SMNS usuu patagonicus Mussaurus L 6.I h post-hatchling the In 56). ULR nhsuu polyzelus Anchisaurus assodlscarinatus Massospondylus usuu patagonicus Mussaurus BPI/1/4779. slwand low is Efraasia usuu patagonicus Mussaurus YPM . PL56 n V 20,wihi h most the is which 4210), PVL specimens and post-hatchling 5865 the in (PVL preserved premaxillary are the Four 4587). in teeth PVL 1813/4 elements in MPM-PV five preservation in poor or teeth or four missing were to (due there premaxilla if its although clear complete, not be is to seems 1813/4 MPM-PV probably and for Other (except dental elements. elements of 15 numbers larger and have 13 sauropodomorphs basal between had have dentition would upper Sauropo- total The of 1986). character (Gauthier synapomorphic domorpha a constricted base, notably their are at teeth preserved the the All PVL of 4210). (e.g. teeth preserved few well a are only specimens post-hatchling but specimens, preserved well subadult are row. the row is in tooth tooth upper maxillary the dentition of and teeth lower basal Several premaxillary the the among by of hidden characters Most of sauropodomorphs. combination of unique dentition The Dentition or splenial, bones. prearticular, coronoid articular, their of exposed specimens have available none the Unfortunately, caudal of process. the retroarticular reaches the the almost of angular above, end the noted of referred tip As posterior the BPI/1/5241). in and BPI/1/4779, seen A jaw. is of lower the specimens change of of ontogenetic surface exposure lateral reduced similar the mandibular more on angular much the the a of have half specimens ventral the ramusinMPM-PV1813/4.Thepost-hatchling forms of angular in condition convex, bowed carinatus slightly strongly pondylus only the to is the contrast margin laterally overlaps This angular opening, the surangular. this of opening, to margin Posterior dorsal this half. the of ventral edge the its posterior forming the at surangular the h rmxlaytohrwo V 57and 4587 PVL of row tooth premaxillary The MMP 834 nltrlve.Seabbreviations See view. lateral in 1813/4) (MPM-PV aunlatupiniquim Saturnalia assodlscarinatus Massospondylus BI143) ln hsrgo,the region, this Along (BPI/1/4934). usuu patagonicus Mussaurus nhsuu polyzelus Anchisaurus usuu patagonicus Mussaurus C 3845). MCP (BPI/1/4376, P 1883, YPM hw a shows Massos- Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 a oe ohv rnldeae Yts2004). (Yates enamel wrinkled have to noted was sauropodomorphs, developed enamel Camarasaurus the more on sulci much and surface(presenteveninembryonicmaterialof a rugae coarser have with condition taxa these 2002) faintly Wilson although 1998; is in Sereno exclusively and that be (Wilson to eusauropods enamel considered enamel previously wrinkled of was a surface is layer Interestingly, 3). and thick (Figure convex wrinkled a markedly by is covered tooth the of premaxillary leaf- basal surface lateral third symmetrical of The crown. a condition premaxillary shaped have generalized which asymmetry the sauropodomorphs, in This with sigmoid apex. crown’s contrasts is gently the and margin towards proximally concave distal convex markedly The being with shape, edge. comparison in mesial profile specimen and the different complete, the notably is in a margin Only shows distal the apex. 1813/4 crown’s MPM-PV lacks the located to serrations, also this rounded 4587 distally and tooth small PVL two this specimen has margin the of premaxillary in margin first however, the serrations, distal in The (as mesial and serrations tooth). height lack The crown’s to the margins. asymmetry along seems convex distal gently noticeable and is margin half mesial a tooth its proximal having premaxillary between third its rapidly, the root, along of tapers the apex is expanded The with 3). notably crown (Figure contact is The its and at 1813/4. constricted MPM-PV markedly specimen broad four the central has margin a distal has of but serrations. surface serrations, portion lacks apical labial margin the The mesial The element apex. in thickening. this ends which of sharp region, axis apical a the The at exposed. recurved slightly not is of is base the specimen specimen crown so erupted, the post-hatchling partially the is tooth the this from 4210 PVL In missing 1813/4. is MPM-PV second tooth The apex. be crown’s premaxillary to the seems non- towards and is straight base nearly crown’s in margin the at distal present convex markedly Its commonly sauropodomorphs. serrations the and eusauropod convex the thick slightly with is a margin lacks with comparison mesial covered Its in is layer. and enamel large teeth This maxillary rather 3). posterior (Figure exposed is is crown the element only its and of alveolus region its apical from dislocated is 1813/4 PV in present 1986). also procum- condition slightly carinatus are a elements these bent, All teeth). illary ‘ sauropodomorphs basal (only among condition common Plateosaurus h hr rmxlaytohi elpeevdin preserved well is tooth premaxillary third The MPM- specimen the of tooth premaxillary first The ltoarsengelhardti Plateosaurus BI154)adesuoos(Gauthier eusauropods and (BPI/1/5241) ’ rt n alr19) mn basal Among 1994). Naylor and Britt ; gracilis nhsuu polyzelus Anchisaurus PT138 aefiepremax- five have 18318a GPIT MS120 and 13200, SMNS Massospondylus P 1883 YPM ot’ agn si l te sauropodomorphs other all in the as from degrees margin, 45 serra- the tooth’s approximately acute at of and oriented well-developed tions tooth posterior had the teeth maxillary that maxillary shows fourth 1813/4 MPM-PV erupting specimen an ever, the of all in specimens preserved layer available poorly enamel are elements. elements premaxillary their posterior the in The and than of thinner convex is be surface to also half seems lateral is apical The crowns its concave. these and than convex rather distal slightly straight the only of half is proximal margin the particular, less distal In and a margins. mesial small have the have between elements asymmetry to maxillary pronounced The seems serrations. the 4587 of blunt PVL tooth maxillary specimen second the subadult of However, margin 1). shape distal (Figure the in teeth resemble premaxillary and shape, posterior the serrations in lack and mesial margins Their similar size. distal in difference are slight a only 1813/4 having MPM-PV specimen in exclusively 2004). Yates 1986; present con- be previously polyzelus also to was sidered condition post- This posteriormost the two elements). the are for and teeth (except maxillary procumbent 1813/4 all slightly 5865, MPM-PV PVL specimen row. specimen become hatchling tooth maxillary the crowns the along these In robust and Thus, blunt similar. more exten- mesiodistal remains their sion although in posteriorly, decrease teeth height had these two of or crowns have one The teeth. than could additional more not probably dentition but elements maxilla. more maxillary the of complete margin posterior The the The to 5865). close PVL located of is specimen post-hatchling maxilla this left in element the posteriormost (on teeth nine consists maxil- specimens of post-hatchling complete the six in most dentition has the lary 1813/4 while MPM-PV elements, specimen preserved of The 1). specimens (Figure available the 2003). (Yates eusauropods basal in 1883), present of is region crowns apical the the to restricted The serrations 4587). of PVL third presence and 1813/4 in the MPM-PV (present specimens serrations the in broad element weak, this extremely than apex, three crown’s has the pronounced At tooth. less premaxillary are apical its and concavity convexity proximal its sigmoid although also distal shape, is The in tooth the premaxillary 3). fourth Figure overlaps the of element; margin third this laterally of the region crown (since anterior 1813/4 tooth MPM-PV premaxillary specimen is the exposed partly tooth only in and 4587 this PVL in Unfortunately, damaged slightly element. preceding the h he neirotmxlayteho the of teeth maxillary anteriormost three The in exposed partially only is dentition maxillary The to size in similar is tooth premaxillary fourth The kl ntm of anatomy Skull assodlscarinatus Massospondylus YM18)adesuoos(Gauthier eusauropods and 1883) (YPM usuu aaoiu 139 patagonicus Mussaurus usuu patagonicus Mussaurus nhsuu polyzelus Anchisaurus usuu patagonicus Mussaurus BI147) and (BPI/1/4779), Anchisaurus .How- (YPM Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 opie kl n otrna ean (represent- and remains eggs postcranial and the skull and a specimens comprises material associated post-hatchling of closely the The found skulls with was long. the 4587 PVL cm specimens, 10 as catalogued of approximately class are larger which a to belong significantly are eggs). skeletons unhatched the the than (since belong larger species eggs associated this the to that assumption based the mainly upon is interpretation Weishampel This 1979; 1994). usually Horner Vince and and been (Bonaparte have embryos than as rather they individuals young but extremely as not interpreted established, has Vince specimens well these and of been age (Bonaparte individual unhatched fragments The two 1979). eggshell with and association close eggs specimens is in These found specimens cm. 3 were of approximately several a of class with length on first specimens, skull ‘post-hatchling’ The light the by develop- taxon. some represented this the shed of during ment occurring that changes size ontogenetic skull classes main two of includes here described material The Discussion posterior PVL the specimen post-hatchling in the 4211. present of A teeth width. is maxillary mesio-distal leaf-shaped morphology being maximum the are crown, similar its where the denticles region reaches of basal crown the the region the from elements apical absent the of these to teeth In restricted isolated 9). Two margins (Figure serrated bear 2000). also 1813/2 MPM-PV al. specimen et (Benton of tooth Appendix. in maxillary abbreviations See Posterior 1813/2). (MPM-PV 9. Figure 140 h pcmnPL48 n h P material MPM the and 4587 PVL specimen The .Pl&J .Powell E. J. & Pol D. usuu patagonicus Mussaurus pcmn u eoe oslyfltee and flattened dorsally post-hatchling becomes the but in markedly bowed is specimens element dorsally region subadult This and parietal. this the the expanded of in morphology in the changes affect exposed The dorsally individuals. in and supratemporal exposed become broader but The 4210) laterodorsally (PVL specimens length. and post-hatchling the narrow skull are the openings to relative of ontogeny the patagonicus during length and 2005). height al. et Reisz 2004; al. et (Sues Africa carinatus sauropodomorph pondylus basal the for noted recently h eaiesz fteetra ae n antorbital and of nares ontogeny external during the increases of fenestra Similarly, size length. relative skull and total the the maxilla, to a premaxilla, respect bones with the nasal specimens, of post-hatchling enlargement the relative in than longer 2005). 2005; al. Fechner et and Salgado Rauhut 2001; Varrichio other al. 1994; et al. Chiappe 1994; and et 1997; Norell Carpenter 1994; dinosaurs Currie 1975; and of Horner (Dodson ontogeny reptiles commonly the archosaur which region, during temporal vary and changes speci- rostral remarkable the shows juvenile in anatomy collected skull recently The changes young mens. the extremely ontogenetic the to of early individuals condition the the from of occurring some examining h vial aeilof material available The changes Ontogenetic specimens necessary adult the these if provide to belong determine may to and information complete more some and Casamiquela material by This cf. referred to (1980) were locality. elements same postcranial found the were sauropodomorph basal in a of remains skull proximal and tibiae. and distal femora, the vertebral humeri, of on the ends ossification lack between column, complete entire fusion the of along arches of neural and lack centra not forms: are specimens these adult indicate material MPM material the postcranial of available the in characters found found Several preliminary were other. each that with skulls) association close with in the them articulated in of partially (three found seven skeletons includes was and material locality MPM repetition same to The due elements). individuals different of two least at ing rna ean antb ofietyasge to assigned confidently be Mussaurus cannot these and remains fragments few cranial a to restricted the is represent material ping could and of form skulls adult MPM the than larger h eprlrgo ftesulicessi its in increases skull the of region temporal The h otu ntesbdl pcmn srelatively is specimens subadult the in rostrum The nadto oteeseies ag fragmentary large specimens, these to addition In usuu patagonicus Mussaurus ttemmn.Tepscailmtra is material postcranial The moment. the at lhuhisltrmda it decreases width lateromedial its although , Plateosaurus Mussaurus rmteEryJrsi fSouth of Jurassic Early the from notntl,teoverlap- the Unfortunately, . hsmtra ssignificantly is material This . usuu patagonicus Mussaurus . Mussaurus Mussaurus Massos- allows ,as Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 h urtmoa os,a lontdfor of noted carinatus edge also dylus anterior as sharp fossa, a supratemporal depression the incipient forming subadult this emarginated the in the is participates and In from frontal the 4210). the excluded specimens (PVL specimens be fossa post-hatchling shape, to supratemporal the its seems In in frontal supratem- the fossa. changes in participation poral shows its in and also proportions, frontal The ubn rmxlayadmxlaytehwt faint with pro- teeth slightly maxillary symphysis, and mandibular premaxillary cumbent suborbital the the at the of end dentary of anterior of development expansion dorsoventral the ectopter- fenestra, the of of reducing extension branches ygoid 90 anteromedial approximately broad anterior of degrees, angle and an forming dorsal the quadratojugal to the ventral acute fenestra an orbit, infratemporal forming the of directed extension of posterodorsally process jugal ascending the the of presence the include these (e.g. of sauropodomorphs but engelhardti basal saurus sauropods presence other in the in present the shows absent characters on taxon derived information this several potentially new of The anatomy characters will topic. skull we some this lies but to on contribution, relevant point this comment This of briefly scope herein. the described outside specimens the including analysis phylogenetic a through re-evaluated of relationships The Mussaurus of external Relationships the to posterior fenestra. ramus, of mandibular surface increas- lateral mandibular angular the on the anteroposterior the surangular and the to 24%), overlaps to ingly relative 17% the from height length orbit, higher minimum and the shorter (e.g. underneath proportionately fenestra becomes extension infratemporal dentary the postorbital its the and reduces of length, process its descending increases of the midpoint orbit, anteroposterior the extends the prefrontal alveolar reaching the the degrees), posteriorly 75 degrees). with to 90 angle 45 from the margin to (changing changes degrees maxilla orientation the its subadults of 71 ramus to ascending the the Similarly, 63 in from the than the (changing in of vertical specimens margin more post-hatchling remarkably anterior is the which on premaxilla, of changes the development includes ontogenetic the non-adult to due be could the of this condition although 2005), the in noted of fossa supratemporal development the of edge the The along specimens. of subadult gonicus specimens subadult the the of in parietal narrow relatively te hne,hwvr a emr pcfi of specific more be may however, changes, Other oee,de o aeasapemargination sharp a have not does however, , Rize l 2005). al. et (Reisz assodlscarinatus Massospondylus , Mussaurus hcdnoarscaducus Thecodontosaurus usuu patagonicus Mussaurus aeildsrbdhere. described material Mussaurus usuu pata- Mussaurus Rize al. et (Reisz Massospon- .Sm of Some ). edt be to need This . Plateo- hs hrceswith characters these readi saurus (e.g. huangi sauropodomorphs nanosaurus the to basal carinatus restricted distal Other Massospondylus or and region. absent mesial crowns apical tooth on of serrations margins wrinkling, enamel rcse fprea retdtaseslyt the the to fit characters transversally These skull). the oriented wide of posterolateral axis parietal longitudinal lateromedially length, of anteroposterior skull processes its the to of respect region orbit, fossa, the supratemporal temporal the on underneath frontal posterior the fenestra of the participation infratemporal projection with the extensive an angle of producing lower jugal the a of process forming of opening process jugal ascending antorbital the high, and and short region proportionately narial below of surface maxilla lateral oriented, margin subvertically anterior premaxillae con- (e.g. of specimens the plesiomorphic subadult the in a in dition but condition specimens ‘sauropod-like’ these post-hatchling a of Some show change. characters ontogenetic strong to subject patagonicus 2005). al. et Salgado 2001; al. 2005; al. Sauropodo- et et 1997; Chiappe Reisz including 1979; Vince 1995, and 2005), the (Bonaparte McNamara morpha Fechner in and and role Long Rauhut important 1994; and an (Weishampel Horner have groups dinosaur play processes several of 1991; to evolution these suggested McNamara particular, been In and 1994). McKinney the Shubin evolutionary to (e.g. of origin due novelties the in changes heterochrony of ontogenetic ubiquity understanding importance the of underscored have authors Numerous Conclusions the dorsally. and bowed poorly symphysis, margin U-shaped dorsal broad surangular rather angle a acute forming an at than an meeting rami processes, semicircular maxilla), mandibular basipterygoid the the the around the ‘hooks’ that fenestra, with infratemporal facet contact supratemporal the of a enlarged midpoint (lacking the opening reaches that quadratoju- of gal branch a anterior and fossa, narrow rim supratemporal orbital dorsoventrally the the jugal into of posteriorly half the least extending at of forming openings, frontal region infratemporal the and infraorbital antorbital the extensive separating an fossa orbit antorbital with subcircular a (reduced) fenestra, anteriorly antorbital a of the surrounding presence nares, the external note located can we of condition. these neosauropod) instead Among (or sauropodomorphs eusauropod derived basal the most in present nicus sauropodomorphs. h td fdfeetgot tgsof stages growth different of study The of skull the of characters Other kl ntm of anatomy Skull nta,so h lsoopi condition plesiomorphic the show instead, , hw ueossulcaatr htare that characters skull numerous shows hr h rsneo tlatsm of some least at of presence the share ) , nhsuu polyzelus Anchisaurus usuu aaoiu 141 patagonicus Mussaurus , uegsuu huenei Lufengosaurus Mussaurus usuu patago- Mussaurus n derived and , Mussaurus Melanoro- , Yun- Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 nnilspoto h ainlGorpi Society. the by Geographic with National developed collected the project of was support a financial greatly during material al. are et Galton PVL Bonaparte P. The and Barrett, appreciated. these P. regarding Yates, Upchurch, A. earlier Sereno, P. P. Discussions Wilson, of J. Bonaparte, work. J. reading with topics this critical and of providing Clark, versions Jim for Norell, Olsen Mark thank Paul to like would We Acknowledgements as caducus such Thecodontosaurus juveniles to suspected are be that specimens are from sauropodomorphs known primarily basal several since critical of importance be could of issue analysis This sauropodomorphs. phylogenetic basal of in relationships individuals the non-mature of test to useful Mussaurus be sauropodomorphs the only in not Understanding changes would ontogenetic 2004). of Yates pattern and and 2004; Galton Wilson 2002; Upchurch Wilson 1998; 1999; Sereno Sauropoda 1995, 1998; Sereno Upchurch and phylogenetically 1990; sauropodomorphs (Galton varying basal as among been have interpreted taxon this previously in change ontogenetic to subject of patagonicus relationships phylogenetic Mussaurus the ontogenetic critical test be late appropriately also will to the remains Such understand taxon. this of to changes order in needed Mussaurus be thought. previously may than skulls complex sauropodomorph more of evolution the of under- lying processes heterochronic pattern that suggesting al. 2005), et similar (Salgado noted neosauropods derived recently of A ontogeny the was in element). trends developmental this conflicting at anteroposterior of dentary the of extension to relative height symphysis dorsoventral mandibular this in of increase extension rim, anteroposterior ante- bone, the dorsoventral orbital its to its relative decreasing the increasing depth jugal and along extension the roposterior of prefrontal region the infraorbital of posterodorsal the process of the extension postorbital, posterior the the of in increase process enlarge- descending relative the (e.g. derived of skulls more ment subadult a the and in post-hatchlings condition plesiomorphic-like the a in condition showing trend, developmental expanded teeth). fenestra, enlarged and antorbital symphysis, mandibular high dorsoventrally Camarasaurus kl opooyo the of the in morphology similarities some to through Bona- skull due by (1979) Vince originated proposed and first parte been as processes, skull have sauropod paedomorphic the could of morphology features major that hypothesis 142 h rna opooyo h dl tg in stage adult the of morphology cranial The opposite an have to seem however, characters, Other .Pl&J .Powell E. J. & Pol D. scretyukonadnwmtrasare materials new and unknown currently is u lot xlr h oeadinfluence and role the explore to also but eg hr rmxlaadmaxilla, and premaxilla short (e.g. ic ayo h characters the of many since nhsuu polyzelus Anchisaurus Yts20;Fdk2005). Fedak 2003; (Yates Mussaurus ooyeand holotype and ewudlk otakteSubecretarı the thank to like would We References Knoll Langer F. and (NMQR), M. (MNHN). Butler E. Yates (YPM), and (JMG), A. Nuttal and R. Rubidge Feng (BPI), Gauthier B. (MPM), M. Palacios J. Wild M. (USP), (HMN), R. (SAM), (MNRJ), Unwin Kaal Leal D. L. S. and (SMNS), Kellner Xing was A. X. by: (AMNH), (IVPP), Norell material provided M. access (MACN), relevant collection Bonaparte J. the with to thanks Comparisons 1 possible Figures of 4. drawings Carballido. line and J.L. the and conducted Canesa, Gonzalez L. J. by Caffa, D.P.). executed M. was (to Puerta, MPM Fund P. specimens Kade the Annette of the Preparation Roo- and Theodore Fund, (AMNH), sevelt Paleontology this the of of of support Part Division financial the season. with field developed was the project in participation Lecuona their A. and for Pais, Puerta, D. M. Reuil, Mancuso, A. S. Scanferla, Cardenas, A. M. Puerta, P. are We to Group. thankful Tranquilo El in the conducted on project support field and collaboration Padre their Provincial for Museo Molina M.J. the and Province Cruz Santa oaat F 1978. JF. Bonaparte oaat F 91 o tetra Los 1971. JF. Bonaparte and Anatomy 2000. PM. Galton GW, Storrs L, Juul MJ, Benton of osteology Cranial 2005. X-L. Wang P, Upchurch PM, Barrett ornithischian heterodontosaurid A 2001. CA. Marsicano AM, Baez C, Montenat M, Monbaron C, Meyer J, Dejax N, Aquesbi R, Allain oaat F uae A 95 oa or lpie cra primer el sobre Notas 1995. JA. Pumares JF, Bonaparte Evolucio 1999. JF. Bonaparte oaat F ic .17.E alzodlpie iode nido primer del hallazgo El 1979. M. Vince JF, Bonaparte apne .19.Baby 1994. K. Carpenter embryonic An 1994. BG. Naylor BB, Britt ueir.OeaLlon 22:1–183. Lilloana Opera superior). Formacio Vert J England. southwest Thecodontosaurus of 20:71–102. Triassic Paleontol dinosaur Upper the prosauropod from antiquus the of systematics Vert J China. 25:806–822. of Paleontol Republic People’s Yunnan, of Jurassic Lower the huenei Lufengosaurus Ameghiniana Patagonia. of Triassic Upper 38:271–279. the basal from R A dinosaur C Morocco. 2004. of P. Jurassic Taquet Early D, 3:199–208. the Palevol Russell from M, dinosaur sauropod Rochdy P, Richir ooao,Tria Formacio Colorados, la de Plateosauridae dinosaurio Prosauropoda), de e Tria del idae) incertus Riojasaurus 36:115–187. Ameghiniana Sauropodomorpha. 15:327–332. hiniana ioaro Tria Dinosaurios 32:341–349. orsnfraino ioarNtoa ouet In: Monument. National Dinosaur of babies. formation and Morrison eggs Dinosaur 256–264. p K, editors. Press. Carpenter University JR, Cambridge In: Cambridge: Horner Morrison Colorado). KF, Quarry, Jurassic Hirsch Mesa Upper (Dry the Formation from Sauropoda) (Dinosauria, 16:173–182. Ameghiniana Argentina. Patagonia, de Superior ´ o ooao,L ij,Agnia(Tria Argentina Rioja, La Colorados, Los n ´ ioSpro eL ij,Agnia Ameghiniana Argentina. Rioja, La de Superior sico ´ iospro eL ij,Agnia Ameg- Argentina. Rioja, La de superior sico ´ io Suici,Poarpd) Tria Prosauropoda), (Saurischia, sicos ooai brevis Coloradia Dnsui,Poarpd,Melanorosaur- Prosauropoda, (Dinosauria, on Dnsui:Poarpd)from Prosauropoda) (Dinosauria: Young Dryosaurus ´ ´ elsve las de n oo e etrspro ela de superior sector del podos ..e .s.(Saurischia sp. n. et n.g. rmteUprJurassic Upper the from ´ tba rsca en presacras rtebras ´ eCluaof Cultura de a Camarasaurus ´ e de neo ´ Los n ´ ´ ssico sico Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 onrJ,Cri J 94 mroi n entlmorphology neonatal and Embryonic 1994. PJ. Currie JR, Horner ebtR 95 aflr fo flora La 1965. R. Herbst tria flora La 1998b. R. Herbst S, Gnaedinger tria flora La 1998a. R. Herbst S, Gnaedinger In: birds. of origin the and monophyly Saurischian JA. Gauthier o un .13.DefsieRpi-rnn arsha ihre Saurischia, Reptil-Ordnung fossile Die 1932. F. Huene von aaiul M 90 apeecadlgenero del presencia La 1980. RM. Casamiquela hbiG ehr ,Mne .17.Estratigrafı 1976. M. Menzel J, Gebhard G, Chebli a Shunosaurus, of anatomy Cranial 2002. Z. Zheng S, Chatterjee atnP,Ucuc .20.Poarpd.I:Wihme DB, Weishampel In: Prosauropoda. 2004. P. Upchurch PM, Galton o E icigJ,RahM.19.Sul fteprosauropod the of Skulls 1990. MA. Raath JW, Kitching CE, Gow tria flora La 1999. R. Herbst S, Gnaedinger atnP.19.BslSuoooopaPoarpd.In: Sauropodomorpha—Prosauropoda. Basal 1990. PM. Galton dinosaur prosauropod the of anatomy Cranial 1984. PM. Galton of Saurischia) (Reptilia: dinosaurs Prosauropod 1976. PM. Galton of skull and braincase the on information considering New one: T, than Fedak better are heads Two 2005. T. Fedak relative of significance of ecological skulls and Functional Embryonic 1975. P. 2001. Dodson RA. Coria L, Salgado LM, Chiappe n noeyo e pce of species new a of ontogeny and o f 27:45–58. Palaeon- Afr Research. tol Palaeontological for Institute Price Bernard IV. Parte (Patagonia). Cruz 35:33–52. Santa Ameghiniana Pteridospermae. de provincia Tranquilo, 1–55. p 8. Sci Flight Acad of Calif Evolution the Mem and 1986. Birds of Origin The editor. K, Padian 232–258. p Press. California of University Berkeley: nwcln n ecihe oorGo Pala Geol 4:1–361. Monogr Geschichte. babies. und and Entwicklung eggs Dinosaur 312–337. p editors. Press. University JR, Cambridge Cambridge: Horner K, KF, Carpenter In: Hirsch Alberta. and Montana from Lambeosauridae) estratigra y geolo consideraciones con Patagonia, Cruz, Santa provincia ais abig:CmrdeUiest rs.p288–297. p Press. University and Cambridge eggs Dinosaur Cambridge: editors. babies. JR, Horner KF, Hirsch K, Carpenter inSc136:145–169. Soc Zool China. Linn of J Jurassic Middle the from dinosaur sauropod basal I 1:143–158. Bioestrat Paleontol Paleontol Latinoam Arg Congr Congr II Actas Patagonia. Tranquilo, ioara ekly nvriyo aionaPress. Osmo P, California Dodson of University 320–344. p Berkeley: Dinosauria. rnul,poicad at rz(aaoi) at VI. dinosaur Parte (Patagonia). Cruz 36:275–296. Santa Ameghiniana Ginkgoales. de provincia Parte Tranquilo, (Patagonia). Cruz Santa 35:53–65. Ameghiniana Pteridophylla. de V. provincia Tranquilo, Poarpd)e lTria el en (Prosauropoda) WeishampelDB,DodsonP,Osmo Trossin- from skulls 18:139–171. complete Two I. gen/Wu Germany. of Triassic) Plateosaurus 169:1–98. Postilla America. North press. editors. dino- in 77. DJ, sauropodomorph Palaeontology in early Batten Papers Special of PM, saurs., palaeobiology Barrett and In: Evolution sauropo- systematics. for implications domorph and Sauropodomorpha) Saurischia: major Ammosaurus 3):56A. Anchisaurus in growth 293:2444–2446. Science dinosaurs. sauropod titanosaur (Departa- Congreso alrededores VI y Actas Juanita Cruz). Santa La Geolo de Estancia provincia la Deseado, de mento zona la en ´ ioAgnio1:357–373. Argentino gico ¨ t.wt omnso h it elPalaeontol Geol diet. the on comments with rtt. assodlscarinatus Massospondylus ´ Alligator cs pr ilaa12:1–101. Lilloana Opera ficas. sasalsuoo.JVr aeno 5Spl to 25(Suppl. Paleontol Vert J sauropod. small a as rmteKolnegl(ideKue,Upper Keuper, (Middle Knollenmergel the from ´ saH dtr.TeDnsui 2 Dinosauria The editors. H, lska olLn 175:315–355. Lond Zool J . LwrJrsi,Prln Formation; Portland Jurassic, (Lower ´ ´ i el Formacio la de sil iospro el Formacio la de superior sico wni h olcin fthe of collections the in Owen Hypacrosaurus ´ saH dtr.The editors. H, lska ´ ´ ´ iadlGuoEl Grupo del sica iadlGuoEl Grupo del sica iadlGuoEl Grupo del sica ´ ´ oaBlanca, Roca n magmatismo y a eno sr1) (ser ¨eontol (Ornithischia, Plateosaurus nd edition. ´ ´ gicas nEl agF i ,Kn ,ZagG 2001. G. Zhang X, Kang X, Jin F, Tang of skull the On 2004. MA. Raath S, Hinic RR, Reisz H-D, Sues Le 2002. the CA. Marsicano of PN, Evolution Stipanicic Science and dinosaurs. Ontogeny, History, of 1994. evolution animals NH. fossil The Shubin the 1999. of PC. classification the Sereno the On of 1887. Osteology HG. 2005. Seeley LM. Chiappe RA, Coria L, Salgado remains fossil various of description A 1836. S. Stutchbury H, Riley Embryos 2005. MJ. Raath DC, Evans H-D, Sues D, Scott RR, Reisz facial the of development Early 2005. R. Fechner OWM, Rauhut innermost the suites: Monzonite 1996. RJ. Pankhurst CW, Rapela akus J aeaC,MruzM 93 Geocronologı 1993. M. Marquez CW, Rapela RJ, Pankhurst LM, Chiappe R, Barsbold D, Dashzeveg JM, Clark MA, Norell evolution The Heterochrony: 1991. KJ. McNamara ML, McKinney Padian PJ, Currie In: Heterochrony. 1997. KJ. McNamara JA, Long evolution. dinosaur in Heterochrony 1995. KJ. McNamara JA, Long phrhP 95 h vltoayhsoyo arpddinosaurs. sauropod of history evolutionary The 1995. P. Upchurch elL,AeeoSK ele W,D oaAS 04 new A 2004. AAS. Rosa Da AWA, A Kellner SAK, 1999. Azevedo LA, Leal MJ. Benton M, Richter F, Abdala MC, Langer tetrapod Triassic Late continental on Studies 2005. MC. Langer stem- the of anatomy limb hind and pelvic The 2003. MC. Langer afi A ebtR 95 aflr tria flora La 1995. R. Herbst GA, Jalfin opa rmteElo n lrn omtos(Lower formations Clarens 73:239–258. Mus and Carnegie Ann Elliot Africa. South of the Jurassic) from morpha) carinatus Massospondylus 26:1–370. Tria B Serie VIII. Argentina, Diego: Volumen San Argentina. Homology. editor. 249–271. BK, p Press. Hall Academic In: Archetype. 284:2137–2147. 43:165–171. Lond Soc R Proc Dinosauria. named commonly Patagonia. of Cretaceous 50:79–92. Upper Polonica Palaeontologica the Acta from embryos sauropod 2:397–399. of Lond Soc autumn Geol near the Proc Down, Durdham Bristol. in on Conglomerate discovered Magnesian the animals in saurian 1834, distinct three of evolutionary 309:761–763. their Science and B significance. dinosaur Prosauropod Soc Jurassic early an Roy of Proc dinosaur. theropod non-avian 272:1179–1183. a in region Edinburgh Soc 87:193–203. Sci Roy Trans Earth Patagonia. of plutonism Cordilleran hrpddnsu mroadteafiiiso h lmn Cliff 266:779–782. A Flaming Science 1994. the eggs. of MJ. dinosaur affinities Novacek the and A, embryo Perle dinosaur theropod MC, McKenna AR, Davidson Press. Plenum York: New ontogeny. of Academic Diego: 311–317. San p P. Press. dinosaurs. of Encyclopedia editors. K, hetero- 151–168. and p Sons. change and Wiley Evolutionary John York: editor. New chrony. KJ, McNamara In: hlTasRScLn 349:365–390. B Lond Soc R Trans Phil summary]. English with Chinese [In pp. Press, Ocean 128 China Sichuan. Jingyan, from Sauropoda complete Exploracio de Geolo Congreso XII Deseado. del pretroge For- Caturrita the from Parana Planetes mation, (Sauropodomorpha) Terre dinosaur Sci early Paris, Sci Acad R C 329:511–517. (Carnian) Brazil. Triassic southern Upper of the Sci from dinosaur Earth sauropodomorph Am South J Brazil. south in 19:205–218. succession and faunal tupiniquim Saturnalia the of locality type The I. biochronology. Brazil). 23:1–40. Triassic, Paleobios (Late tupiniquim Saturnalia sauropodomorph 32:211–229. rvni eSnaCu Ptgna.Estratigrafı (Patagonia). Cruz Santa de Provincia kl ntm of anatomy Skull ´ ei elsgaiod jura granitoids los de nesis ´ eHdoabrs ca 4:134–141. Actas Hidrocarburos, de n ´ ai,Bai.Zoaa690:1–24. Zootaxa Brazil. Basin, usuu aaoiu 143 patagonicus Mussaurus wn 84(Dinosauria:Sauropodo- 1854 Owen, ´ ´ ´ io Asociacio sico. ioAgnioyI Congreso II y Argentino gico ´ io e oet e Macizo del noreste del sicos iadlguoE Tranquilo, El grupo del sica ´ ioEstratigra xico miarsmaoianus Omeisaurus ´ .Ameghiniana a. ´ nGeolo ´ c ela de fico ´ gica ´ ay ,a Downloaded By: [Pol, Diego] At: 17:51 20 April 2007 ntttoa abbreviations Institutional Appendix 1942. C-C. Young of osteology complete A 1941. C-C. Young 2004. dinosaur, AM. primitive Yates the of species new A 2003. in AM. cavity Yates antorbital the of evolution The 1997. higher-level LM. and Witmer evolution Early 1998. and PC. critique Sereno phylogeny: JA, dinosaur Wilson Sauropod 2002. JA. syndromes, Wilson history Life 1994. JR. Horner DB, Weishampel sauropod K, Padian PJ, of Currie embryology. In: and Growth 1997. relationships Varricchio DJ. phylogenetic The 1998. P. Upchurch 144 rsuooafo h e esa ueg unn ulGeol Bull Yunnan. 22:63–104. Lufeng, China at Soc Beds Red the from Prosauropoda 7:1–53. C) (ser Sinica Palaeontol gigantism nov.). sp. et of (gen. Young evolution the 230:1–58. Postilla and dinosaurs. sauropodomorph dinosaur amongst Paleont sauropod Syst known J dinosaurs. early of systematic 1:1–42. the for cations Thecodontosaurus fossil the Soc 3:1–75. Mem in pneumaticity. Paleontol of Vert reconstruction function the of soft-tissue analysis an in with record study a Paleontol archosaurs: Vert Soc Mem dinosaurs. 5:1–68. sauropod of phylogeny 136:217–276. Soc Linn J Zool analysis. cladistic babies. and eggs 229–243. p Dinosaur Press. editors. University Carpenter Cambridge JR, In: Cambridge: Horner Dinosauria. KF, of Hirsch K, evolution the and heterochrony, Press. Academic 282–288. Diego: p San dinosaurs. of Encyclopedia editors. 124:43–103. Lond Soc Linn J Zool dinosaurs. PTIsiu n uemfu Museum und Institut Johannesburg, Institute, GPIT Price Bernard Africa South Museum, History BPI Natural The England London, Natural of BMNH Museum American USA York, New History, AMNH Pala V nttt iulLlo Tucuma Lillo, Miguel Instituto Argentina Bloemfontein, PVL Museum, National Africa South Museum, NMQR Geological Provincial China Nanjing, J. M. Padre Provincial NGMJ Regional Argentina Museo Gallegos, Rio Molina, Catolica, Universidade MPM Pontificia Museu Brazil Alegre, Porto Ciencias de MCP Argentino Argentina Museo Aires, Buenos Naturales, MACN and Paleontology Vertebrate China of of Republic Institute People’s Beijing, Paleoanthropology, IVPP Germany .Pl&J .Powell E. J. & Pol D. otlge nvria Tu Universitat ¨ontologie, nhsuu polyzelus Anchisaurus unnsuu huangi Yunnanosaurus Suici:Suoooopa n t impli- its and Sauropodomorpha) (Saurischia: ¨ ign Tu bingen, iccc:tesmallest the Hitchcock: gn ts.nv) new a nov.), sp. et (gen. ¨ uegsuu huenei Lufengosaurus elgeund Geologie r ¨ ´ bingen, n, ntmclabbreviations Anatomical MSSatihsMsu fu Museum Staatliches Cape Museum, SMNS African Iziko—South Africa South Town, SAM s nertdprino rw’ margin crown’s of portion unserrated fossa supratemporal use fenestra supratemporal stfo squamosal margin crown’s on stf serrations sq surangular se foramen surangular san ramus rostral lacrimal root saf tooth rra process retroarticular ro quadratojugal rap wing anterolateral quadrate qj qal qquadrate antorbital of wall medial posteroventral quadrate of wing pterygoid pvw prefrontal postorbital of ptq surface lateral on foramen prf postorbital pof po premaxilla fossa antorbital of wall medial pmx posterodorsal parietal pdw nasal par ridge maxilla lateral lacrimal nas mx lacrimal jugal lr lac fenestra infratemporal frontal j itf suture frontoparietal f nares external fps fenestra mandibular external ridge en dorsolateral lacrimal emf dentary surangular dlr of bulge articular den premaxilla of process jugal arb of ascending process ascending dentary apm of process anterior apj angular apd maxilla of process ascending ang fossa antorbital amx fenestra antorbital tooth afo premaxillary third tooth afe premaxillary first 3p 1p Haven, New Museum, Peabody Yale USA. Universidad Naturales, Argentina YPM Ciencias Rioja, Museo La Rioja, La ULR Germany Stuttgart, Stuttgart, fossa ¨ Naturkunde r