Cranial Osteology of Lufengosaurus Huenei Young (Dinosauria: Prosauropoda) from the Lower Jurassic of Yunnan, People's Republic of China

Journal of Vertebrate Paleontology

ISSN: 0272-4634 (Print) 1937-2809 (Online) Journal homepage: http://www.tandfonline.com/loi/ujvp20

Cranial osteology of Lufengosaurus huenei Young (Dinosauria: Prosauropoda) from the Lower Jurassic of Yunnan, People's Republic of China

Paul M. Barrett , Paul Upchurch & Wang Xiao-Lin

To cite this article: Paul M. Barrett , Paul Upchurch & Wang Xiao-Lin (2005) Cranial osteology of Lufengosaurus huenei Young (Dinosauria: Prosauropoda) from the Lower Jurassic of Yunnan, People's Republic of China, Journal of Vertebrate Paleontology, 25:4, 806-822

To link to this article: http://dx.doi.org/10.1671/0272-4634(2005)025[0806:COOLHY]2.0.CO;2

Published online: 02 Aug 2010.

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Download by: [National Science Library] Date: 02 April 2016, At: 18:41 Downloaded by [National Science Library] at 18:41 02 April 2016 BARRETT ET AL.-CRANIAL OSTEOLOGY OF LUFENGOSAURUS 807

(e.g., Rozhdestvensky, 1965). Moreover, differing opinions re- SYSTEMATIC PALEONTOLOGY garding prosauropod interrelationships and classification (e.g., Young, 1941a, b, 1942; Galton and Cluver, 1976; Cooper, 1981) DINOSAURIA Owen, 1842 obscured further the affinities of the Chinese taxa. SAURISCHIA Seeley, 1887 Rozhdestvensky (1965) suggested that all of the prosauropod SAUROPODOMORPHA von Huene, 1932 material from the Lower Lufeng Formation was referable to a PROSAUROPODA von Huene, 1920 single taxon and that the generic- and species-level differences LUFENGOSA UR US Young, 1941a proposed by Young (1941a,b, 1942, 1947b,c, 1951) were the re- (Figs. 1-6) sult of ontogenetic variations that were not taxonomically infor- Species-Lufengosaurus huenei Young, 1941a. mative. Consequently, Rozhdestvensky (1965) regarded Lufen- Type Emended Diagnosis-As for type species (see below). gosaurus magnus, Yunnanosaurus huangi, Y. robustus, and Gy- Distribution-Dull Purplish Beds of the Lower Lufeng For- posaurus sinensis as junior subjective synonyms of L. huenei. mation (Hettangian), Lufeng County, Yunnan Province, Peo- Galton (1976) and Galton and Cluver (1976) initially accepted this in ple's Republic of China. interpretation though, contrast, Steel (1970) retained all referred a second to five taxa as valid Comments-Young (1947b) species entities. Cooper (1981) also followed the con- Most authors have the clusions of the of all Lufengosaurus (L. magnus). regarded Rozhdestvensky (1965) regarding synonymy latter as a junior subjective synonym of the genotype species, L. of Young's Lower but made the additional Lufeng species, sug- huenei (Rozhdestvensky, 1965; Galton, 1990). Here, we base our gestion that as a whole was a Lufengosaurus junior subjec- generic diagnosis solely on the genotype species in order to pro- tive of he a synonym Massospondylus, though maintained spe- mote the stability of the genus. The taxonomic status of L. mag- cific between the South African and Chinese separation forms, nus, and other taxa that have been placed in synonymy with with the latter denoted as M. huenei. Galton Later, however, Lufengosaurus (e.g., Gyposaurus sinensis, Tawasaurus, and Ful- and Yunnanosaurus as distinct (1990) accepted Lufengosaurus genia), will be addressed elsewhere, pending examination of the valid In this L. genera. scheme, magnus and Gyposaurus sinensis relevant type specimens. were listed as junior subjective synonyms of L. huenei, and Y. robustus became a of Y. The junior subjective synonym huangi. LUFENGOSA URUS HUENEI Young, 1941a reasons for these taxonomic amendments were not discussed, however. Lufengosaurus huenei Young, 1941a:3. In addition to the above-mentioned taxa, several other pro- Lufengosaurus huenei Young: Rozhdestvensky, 1965:97. sauropod specimens have been documented from the Lower Lufengosaurus huenei Young: Steel, 1970:54. Lufeng Formation. A badly crushed skull from the Dark Red Massospondylus huenei (Young): Cooper, 1981:804. Beds of Dadi (= Tati in earlier transliterations) was originally Lufengosaurus huenei Young: Galton, 1990:336. described as an early lizard and named Fulgenia youngi (Carroll Lufengosaurus huenei Young: Galton and Upchurch, 2004:234. and but has since been demonstrated to be a Galton, 1977), a skeleton with skull. and This taxon is Holotype-IVPP V15, complete juvenile prosauropod (Evans Milner, 1989). Yunnan Province, as a Locality-Shawan village, Lufeng County, currently regarded junior subjective synonym of Lufengo- of China. saurus huenei and The People's Republic (Evans Milner, 1989; Galton, 1990). Horizon-Dull Beds of the Lower Lufeng Forma- skull of another individual from Dawa Purplish poorly preserved juvenile tion, Lower Jurassic (Hettangian: Luo and Wu, 1994, 1995). Tawa in older was described as Tawasaurus (= transliterations) Emended Diagnosis-(cranial features only). Lufengosaurus minor and referred to the Ornithischia originally (Yang, 1982). can be diagnosed on the basis of the following autapomorphies: work has shown this to be either an inde- Subsequent specimen distinct tuberosity on lateral surface of ascending process of max- terminate or a sub- prosauropod specimen (Sereno, 1991) junior illa; low boss on central portion of jugal at junction of the three of huenei More jective synonym Lufengosaurus (Galton, 1990). jugal processes; prominent boss on dorsal surface of rostrolateral new fieldwork in the Basin recovered an almost recently, Lufeng process of parietal; and presence of ridge on caudal part of lat- skeleton and skull that was complete described as the new pro- eral surface of maxilla. In addition, Lufengosaurus possesses a

Downloaded by [National Science Library] at 18:41 02 April 2016 taxon xinwaensis and sauropod Jingshanosaurus (Zhang Yang, unique combination of character states not present in any other Several other Lower that were 1994). Lufeng specimens origi- basal sauropodomorph (see comparative comments, below). described as nally prosauropods (Simmons, 1965; Young, 1966) Comments-Young (1941a, 1951) included several cranial have now been re-identified as and include sauropod remains, characters in his original diagnosis: skull small and not elongated; the earliest known cranial material review in Bar- sauropod (see triangular external naris; small, but dorsoventrally tall, antorbital rett, 1999). fenestra; orbits round and large; supratemporal fenestra opening several authors have included the Lower taxa Finally, Lufeng dorsally; and teeth weakly compressed and serrated. However, in phylogenetic analyses of the Sauropodomorpha, though few, if all of these features are present in a wide variety of extinct any, of these studies included character codings based on first- archosaurs (e.g. Romer, 1956; Carroll, 1987) and cannot, there- hand examination of the specimens (Galton, 1990; Sereno, 1999; fore, be used to distinguish Lufengosaurus from other dinosaurs. Pisani et al., 2001; Yates 2003a, 2004; Galton and Upchurch, The postcranial skeleton of Lufengosaurus will be described 2004). Some of these analyses place Lufengosaurus in a clade elsewhere. with Plateosaurus and other similar prosauropods, such as Efraa- sia (sensu Yates, 2003b; note that this taxon is referred to as DESCRIPTION AND COMPARISON Sellosaurus in Sereno [1999] and Galton and Upchurch, [2004]) and Coloradisaurus (e.g., Sereno, 1999; Galton and Upchurch, General Comments 2004), supporting Young's original suggestion that Lufengosau- rus was closely allied with these taxa (Young, 1941a), while oth- The following description extends and complements those ers position Lufengosaurus close to Massospondylus and Yun- provided by Young (1941a, 1951). Basal sauropodomorph phy- nanosaurus (Yates, 2003a, 2004). A comprehensive phylogenetic logeny and taxonomy is in a state of flux and there is currently analysis of basal sauropodomorphs that incorporates new char- debate regarding the phylogenetic position of several taxa (e.g., acter information collected first-hand from the Chinese speci- Anchisaurus, Blikanasaurus, and melanorosaurids) and the com- mens will be presented elsewhere. position of the clade Prosauropoda (Sereno, 1999; Benton et al., 808 JOURNAL OF VERTEBRATE PALEONTOLOGY,VOL. 25, NO. 4, 2005

2000; Yates, 2003a, b, 2004; Yates and Kitching, 2003; Galton and caudalmost part of the left nasal process. The remaining portions Upchurch, 2004). Here, skulls of those animals 'traditionally' of the premaxillae are missing and the rostralmost part of the regarded as prosauropods (e.g., Galton. 1990) are used for com- snout is entirely reconstructed. parison with Lufengosaurus. Sources of the comparative data Maxilla-The maxilla is divided into two major processes: a presented below (both from personal observation of material horizontally directed tooth-bearing ramus, and a vertically di- and from the literature) are listed in Table 1. rected ascending process that arises from a point approximately The skull is long and low in lateral view (Figs. 1-2). and is one third of the distance from the rostral end of the bone (Figs. widest transversely at a point dorsal to the postorbitals. In dorsal 1-2). The right maxilla is more complete than the left: the latter view, the skull appears to be very wide relative to that of other is missing most of the rostral part of the tooth-bearing ramus. In prosauropods (Fig. 3), but this feature has probably been accen- lateral view, the tooth-bearing ramus is long, straight, slender, tuated by dorsoventral crushing and incorrect reconstruction of and dorsoventrally convex along most of its length. It is highest the premaxillae. The skull is largely complete, but has suffered anteriorly and gradually tapers towards its posterior termination. some damage in several areas. Both premaxillae and the rostral A minimum of six large vascular foramina are present on the ends of the mandibles are missing and have been reconstructed lateral surface of this ramus, all the openings of which are ori- to the snout a rounded outline in ventral view. How- give broad, ented rostroventrally (with the exception of the caudal-most fo- the orientation of the maxillae as that ever, preserved suggests ramen which is oriented caudoventrally). The right maxilla bears the snout would have been much narrower and in life. At longer a rostrocaudally elongate triangular facet on its lateral surface least some of this damage has resulted from plastic deformation ventral to the external naris and rostral to the base of the of the which has been crushed and just skull, slightly dorsoventrally This area represents the articular surface for has some torsion in of its ascending process. undergone resulting misalignment right the of the and demonstrates that and left-hand sides. The of the in combination maxillary process premaxilla preservation skull, the latter was slender and A low extends along with caused makes the distinction of sutural elongate. ridge damage by crushing, the caudal third of the maxilla, forming the dorsal boundary of a boundaries difficult. Originally, the mandibles were conjoined shallow buccal emargination that was restricted to the caudal with the skull (Young, 1941a), but they were removed later pro- of the element (the rostral section of the tooth row is not viding additional detail on the palate (Young. 1951: Fig. 4). How- part inset: 1-2). Although maxillary ridges are ubiquitous in ever, portions of the left mandible remain adhered to the left side Figs. ornithischians, they are unknown in prosauropods (c.f. Galton, of the skull and the articular region of the right quadrate is this structure is therefore regarded as an autapomorphy of similarly adhered to the right mandible. Several regions of the 1973): Fifteen alveoli are present in the left maxilla, as skull are completely obscured by matrix or by the presence of Lufengosaurits. the more complete right maxilla contained 20 teeth. other cranial elements: the articulated nature of the specimen preserved; The tooth row extends along the entire length of the maxilla and means that the detailed morphology of several bones cannot be the caudalmost maxillary tooth is situated ventral to the orbit. ascertained at present. The part of the main maxillary ramus contacts the The cranial openings are large, giving the skull an open ap- posterior lachrymal, and palatine. The jugal has a long oblique con- pearance. The shape of the external naris cannot be deduced jugal, tact with the dorsal surface of the tapering posterior end of the with certainty, but it is likely to have been considerably larger than has been restored. This is evident from the rostral extent of maxilla and the lachrymal contacts the dorsal surface of the maxilla dorsomedial to the In ventral view, the palatine has a the maxilla which extends almost to the of the jugal. right (Fig. 2), tip broad contact with the caudomedial surface of the maxilla (Fig. 4). snout in the reconstructed skull: the addition of the premaxilla surface of the ramus is flat to increase both skull and The medial tooth-bearing gently would, therefore, substantially length its and a row of sub- naris diameter. In lateral the antorbital fenestra forms an convex dorsoventrally throughout length, view, foramina dorsal to the the orbit is and circular. circular replacement lies immediately approximately equilateral triangle, large These foramina are from each other and the fenestra to have been sub- dental parapet. separated by infratemporal appears rhomboidal interdental The ventral of the lateral in outline. In dorsal the fenes- plates. margin trapezoidal view, supratemporal the maxilla extends farther than that trae have a The internal nares are surface of slightly ventrally sub-triangular outline (Fig. 3). so that much of the tooth root is obscured in outline and are on the medial surface, elliptical rostrocaudally elongate (Fig. 4). They This ventral extension of the lateral bounded the vomers maxillae and in lateral view. maxillary Downloaded by [National Science Library] at 18:41 02 April 2016 by (rostromedially), (laterally) surface maintains a constant height along the length of the max- palatines (caudomedially). illa, and therefore differs from the 'lateral plate' seen in sauro- 1995). Rostrally, the maxillae approach the Dermatocranium and Splanchnocranium pods (Upchurch, vomers, but it is unclear whether they were in direct contact. The Premaxilla-A small, finger-like portion of bone, situated be- medial surfaces of the ascending processes are obscured by ma- tween the nasals on the skull midline, probably represents the trix (Fig. 4).

TABLE 1. Sourcesof comparativedata used in this study

Taxon Source(s) Anchisaurus polyzelus YPM 1883: Galton (1976): Yates (2004) Coloradisaurus brevis Bonaparte (1978) Efraasia minor Galton (1985a): Galton and Bakker (1985); Yates (2003b) Jingshanosaurus xinwaensis Zhang and Yang (1994) Massospondylus carinatus BP/1/4376: BP/l/4779: BP/1/4934: BP/1/5241: SAM-PK-K1314; Gow (1990); Sues et al. (2004) Mussaurus patagonicus Bonaparte and Vince (1979) Plateosaurus spp. AMNH 6810: MB XXIV: Galton (1984, 1985b): Yates (2003b) Riojasaurus incertus ULR 56: Bonaparte and Pumares (1995) Thecodontosaurus caducus BMNH RU P24: Kermack (1984): Yates (2003a) Unaysaurus tolentinoi Leal et al. (2004) Yunnanosaurus huangi NGMJ 004546; Young (1942)

Accession/specimen numbers denote material examined by the authors firsthand: other data were gathered from the literature. species taxonomy of the Upper TriassicGerman prosauropods follows Yates (2003b). BARRETT ET AL.-CRANIAL OSTEOLOGY OF LUFENGOSAURUS 809

pa.b Opening Reconstructed Matrix pa

f p fr . .P0 mx..b. n

bocc pt I.pal I pt q qq mx

sa q pt

mx.r ps Downloaded by [National Science Library] at 18:41 02 April 2016 B j.b FIGURE 1. Skullof Lufengosaurushuenei (IVPP V15) in left lateralview. A, drawingof skull as preserved.B, interpretativeline drawingof skull, showingdamage, reconstruction and positions of sutures/articularsurfaces. Abbreviations: bocc, basioccipital;f, frontal;j, jugal;j.b, jugal boss; 1, lachrymal;I.pal, left palatine;mx, maxilla;mx.b, boss on ascendingprocess of maxilla;mx.r, maxillary ridge; n, nasal;pa, parietal;pa.b, parietalboss; pfr, prefrontal;po, postorbital;ps, parasphenoid;pt, pterygoid;q, quadrate;qj, quadratojugal;r.pal, right palatine;sa, surangular.Scale bar equals 100 mm.

In lateral view, the basal half of the ascending process projects cending process of the maxilla and the anterolateral process of almost vertically from the tooth-bearing ramus, but the dorsal the nasal is an elongate, obliquely inclined contact that lies be- portion curves caudodorsally, as in most prosauropods (with the tween the rostrodorsal margin of the ascending process and the exception of Mussaurus and Yunnanosaurus). In Lufengosaurus, caudoventral margin of the rostrolateral process of the nasal. the degree of curvature differs between the two sides of the skull The caudodorsal part of the ascending process contacts the lach- due to deformation. Galton (1990) and Galton and Upchurch rymal (visible on the left side only, obscured by matrix on the (2004) suggested that the expanded distal end of the ascending right): consequently, the nasal is completely excluded from the process was autapomorphic for Lufengosaurus, but this feature dorsal margin of the antorbital fenestra (in contrast to the situ- has been accentuated by crushing and it is likely that it does not ation in Plateosaurus and Unaysaurus) though it still contributes differ markedly from the situation in other prosauropods (com- to the border of the antorbital fossa (Fig. 1). The rostral surface pare Figs. 1 and 2). The rostroventral margin of the ascending of the ascending process is gently excavated to form part of the process contributes to the border of the external naris (contra caudal and caudoventral margin of the external narial fossa. A Chatterjee and Zheng, 2002). The articulation between the as- large dorsally opening vascular foramen is situated caudal to the 810 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 25, NO. 4, 2005

A pa.b pa Isp Isp Opening Reconstructed • Matrix

par.p pfr Smx.b

j.b Pt mx.r Downloaded by [National Science Library] at 18:41 02 April 2016 B bptept FIGURE 2. Skullof Lufengosaurushuenei (IVPP V15) in rightlateral view. A, drawingof skullas preserved.B, interpretativeline drawingof skull, showing damage, reconstruction, and positions of sutures/articular surfaces. Abbreviations: bocc, basioccipital; bpt, basipterygoid process; ept, epipterygoid;f, frontal;j, jugal;j.b, jugal boss; 1, lachrymal;Isp, laterosphenoid;mx, maxilla;mx.b, boss on ascendingprocess of maxilla;mx.r, maxillaryridge; n, nasal;pa, parietal;pa.b, parietalboss; par.p, paroccipital process; pfr, prefrontal;po, postorbital;pt, pterygoid;q, quadrate;r.pal, right palatine;sq, squamosal.Scale bar equals 100 mm.

external naris, anterolateral to the base of the ascending process. of the antorbital fossa. Anchisaurus displays a third condition in The caudoventral corner of the ascending process is excavated, which the medial lamina extends along the entire length of the forming a small 'medial lamina' that comprises the rostral and antorbital fossa, but does not appear to extend a significant dis- rostroventral boundaries of a shallow antorbital fossa (Figs. 1-2), tance dorsally. A medial lamina appears to have been absent in as also occurs in Efraasia, Thecodontosaurus, Riojasaurus, and Jingshanosaurus, Mussaurus, and Yunnanosaurus. Finally, ap- Massospondylus. In contrast, the medial laminae of Coloradi- proximately one-third of the distance from the base of the as- saurus (A. M. Yates, pers. comm., March 2005), Unaysaurus and cending process, a prominent boss arises from the lateral surface Plateosaurus are much more extensive, forming a thin sub- of the bone (Figs. 1-2). This boss does not appear to be pathological triangular sheet that arises from the ascending process and the in origin as it is present on both sides of the skull and has a smooth, rostral half of the ventral margin of the antorbital fossa, with the finished bone surface. Other prosauropods lack this boss, which result that the antorbital fenestra is restricted to the caudal half is interpreted herein as an autapomorphy of Lufengosaurus. Downloaded by [National Science Library] at 18:41 02 April 2016 812 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 25, NO. 4, 2005

A D Opening Isp Reconstructed Matrix sq po j f par.p t

bpt

bocc - . Pt pal

bt pt Downloaded by [National Science Library] at 18:41 02 April 2016

sa b t

FIGURE 4. Skull of Lufengosaurus huenei (IVPP V15) in palatal view. A, drawing of skull as preserved. B, interpretative line drawing of skull, showing damage, reconstruction, and positions of sutures/articular surfaces. Abbreviations: bocc, basioccipital; bpt, basipterygoid process; bt, basal tuber; ect, ectopterygoid; f, frontal; j, jugal; Isp, laterosphenoid; mx, maxilla; pal, palatine; par.p, paroccipital process; po, postorbital; pt, pterygoid; q, quadrate; qj, quadratojugal; sa, surangular; sq, squamosal; t, teeth; v, vomers. Scale bar equals 100 mm. Note the sulcus on the ventral surface of the basisphenoid and the system of ridges that radiates over the ventral surface of the pterygoid.

Lachrymal-The lachrymal consists of an elongate main shaft, cesses form a structure that resembles an inverted 'L'-shape oriented caudoventrally with respect to the skull roof, and a (Figs. 1-2). In lateral view, the shaft is slightly bowed rostrally rostrally oriented dorsal process (though much of the latter is along its length and forms the caudal, and part of the dorsal, obscured by the nasals and prefrontals). Together these pro- margin of the antorbital fenestra rostrally and the majority of the BARRETT ET AL.-CRANIAL OSTEOLOGY OF LUFENGOSAURUS 813

rostral orbital rim caudally. The shaft has a sub-oval to sub- expanding laterally once more as it approaches its contacts with triangular cross-section and terminates in a ventral expansion. the nasal and prefrontal. Caudal to its widest point, the frontal is This area is expanded both transversely and especially rostro- also emarginated, forming long curved contacts with the postor- caudally relative to the main part of the shaft, forming a sub- bital caudolaterally and the parietal caudomedially. Junctions triangular articular region, whose apex is oriented medially. This between the prefrontal and frontal and between the postorbital expansion contacts the jugal ventrally. A distinct ridge extends and frontal are marked by low but distinct ridges. The surfaces of dorsoventrally along the rostral edge of the shaft, bounding a the frontals are gently concave dorsally, though the latter feature shallow excavation on the rostral surface of the bone. This ridge may be the result of crushing. A complex interdigitating suture is prominent and in the ventral third of the bone forms part of (situated caudally) and a longitudinally extending midline ridge the 'medial lamina' that comprises the posterior rim of the ant- mark the position of the junction between the two frontals. The orbital fossa. Similar laminae are present in Coloradisaurus, rostral limit of the frontals cannot be determined accurately due Massospondylus, Plateosaurus, Thecodontosaurus, Riojasaurus, to damage, but may have extended transversely from a point and Efraasia. This contrasts with Anchisaurus, Mussaurus, Yun- approximately level with the midpoints of the prefrontals, in nanosaurus, and Jingshanosaurus, in which the ventral part of dorsal view. In both dorsal and lateral views, the frontal makes the lachrymal lamina is absent. In Riojasaurus, Anchisaurus, and only a small contribution to the orbital margin (contra Young, Coloradisaurus the rostrodorsal boundary of the lachrymal 1941a), as in Plateosaurus. In all other prosauropods, the frontal forms a significant contribution to the medial lamina; however, makes a much greater contribution to the dorsal orbital margin. this section of the lamina is not present in Lufengosaurus or The frontal is excluded from the supratemporal fenestra by other prosauropods. contact between the rostrolateral wing of the parietal and the The lachrymal foramen is large and situated in the dorsal half rostrodorsal process of the postorbital, though it does contribute of the bone. The dorsal process extends rostrally, in lateral view, to a small, shallow supratemporal fossa (equivalent to the 'oval tapering as it does so. The junction between the dorsal process depression' mentioned by Young, 1941a). Similar supratemporal and the main part of the shaft is a robust area that is expanded fossae are also present in Thecodontosaurus, Massospondylus, transversely to the same extent as the expansion at the ventral Riojasaurus, Efraasia, Unaysaurus, and Plateosaurus. Ventrally, end of the shaft. The rostral part of the dorsal process is sand- a well-defined crest extends longitudinally along much of the wiched between the rostrolateral process of the nasal and the length of the frontal, curving first medially and then laterally as ascending process of the maxilla, while the caudal part of the it does so. The areas medial and lateral to this crest are gently process is clasped by the prefrontal. In dorsal view, the lachrymal concave both transversely and rostrocaudally. At the caudal makes a very small contribution to the skull roof (Fig. 3). There margin of this crest a small facet is present for articulation with is no contact between the lachrymal and frontal (contra Young, the laterosphenoid. 1941a). Parietals-The main bodies (dorsomedial portions) of the pa- Prefrontal-The prefrontal forms the rostrodorsal half of the rietals are damaged and partially reconstructed so it is not pos- orbital rim (Figs. 1-2). In dorsal view, it is an elongate, strap- sible to tell whether they were fused or sutured on the midline, shaped element that is gently convex both rostrocaudally and or if a pineal foramen was present (Fig. 3). Similarly, the suture transversely (Fig. 3). The medial and lateral margins of the pre- between the central part of the parietal and frontal is difficult to frontal are sub-parallel and almost straight-sided, while the cau- locate, due to cracking of the bone surfaces. Laterally, a gently dal margin is strongly rounded. Rostrally, the prefrontal gives bowed, stout process arises from the rostrolateral corner of the rise to a ventrolaterally oriented process with a sub-triangular main body of the parietal: the rostral margin of this process outline in lateral view. This process overlaps the caudal part of contacted the caudal margin of the frontal. Distally, this rostro- the lachrymal and extends a short distance onto the caudomedial lateral process articulates with the caudal part of the rostrodorsal surface of the latter, partially obscuring the junction between the process of the postorbital: together these bones form the rostral lachrymal dorsal process and shaft. The main body of the pre- margin of the supratemporal fenestra. A distinct, rounded boss frontal has an extensive overlapping contact with the frontal, of bone (noted as a 'bony protuberence'; Young, 1941a:4) is which borders it caudally and medially, and its rostral process present on the dorsal surface of the rostrolateral process (Fig. 3). contacts the nasal. The presence of this feature on both sides of the skull indicates

Downloaded by [National Science Library] at 18:41 02 April 2016 Galton (1990; Galton and Upchurch, 2004) suggested that the that it is not an artefact. Moreover, this symmetry and the fin- large prefrontals could be regarded as an autapomorphy of ished appearance of the bone suggest that this structure is not Lufengosaurus. However, this character is difficult to use in prac- pathological in origin. This feature is unknown in other prosau- tice as the proportions of the prefrontals in Lufengosaurus can- ropods and is here regarded as an autapomorphy of Lufengo- not be accurately compared to either total skull length or frontal saurus huenei. The remainder of the dorsal surface of the ros- length due to incompleteness. Moreover, due to plastic defor- trolateral process is gently concave along its length, and this mation of the skull, the right prefrontal is significantly longer curved surface merges smoothly into the lateral surface of the than the left, confounding the use of prefrontal proportions in a main parietal body, which forms the medial margin of the supra- diagnosis. The prefrontals of several other prosauropods, includ- temporal fenestra. This lateral surface is rostrocaudally short and ing Massospondylus, Yunnanosaurus, and Anchisaurus, are also concave both dorsomedially and anteroposteriorly: it merges narrow, elongate and strap-like in dorsal view, suggesting that into the elongate caudolateral process caudally. The latter was caution should be exercised regarding the use of 'large prefron- misidentified as the conjoined postparietal (= interparietal) and tals' as an autapomorphy of Lufengosaurus. However, the pre- tabular by Young (1941a). This caudolateral process articulates frontals of Lufengosaurus clearly differ from those of Thecodon- with the squamosal laterally and the supraoccipital posteriorly: tosaurus and Plateosaurus, which have a sub-triangular outline in the caudal margins of the parietals form an acute rim of bone in dorsal view, and from those of Coloradisaurus and Efraasia, occipital view. The dorsal surface of the parietal, where pre- which are very short rostrocaudally. served, is slightly vaulted caudally. The junctions between the Frontals-The frontals are sub-trapezoidal, transversely parietals and underlying braincase elements (laterosphenoid, broad plates that are longer rostrocaudally than they are wide prootic, etc.) are obscured by matrix. transversely. In dorsal view, they reach their greatest transverse Postorbital-Young (1941a) suggested that separate postfron- width at a point approximately one-third of the distance from the tal and postorbital bones were present, with the former compris- caudal margin (Fig. 3). Rostral to this point, the lateral margin ing a triradiate bone lying caudodorsal to the orbit and the latter becomes strongly emarginated to form the orbital rim, before present as a short, splint-like element situated between the post- 814 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 25, NO. 4, 2005

frontal and jugal. However, these structures are actually parts of The quadratojugal consists of two principal rami: a rostral a unitary postorbital: there is no separate postfrontal (contra ramus that contacts the jugal and a dorsal ramus that overlaps Young, 1941a), as is also the case in all other dinosaurs (Sereno the lateral wing of the quadrate (Fig. 1). These rami diverge from and Novas, 1994). each other at an angle of approximately 450 in lateral view and The postorbital is a triradiate bone with a long ventral process define the caudoventral margin of the infratemporal fenestra and with shorter rostrally and caudally directed dorsal processes. (see also Young, 1941a:plate 1, fig. 1A). The rostral ramus tapers In lateral its ventral view, and rostral processes form most of the towards its tip and was dorsoventrally narrow: a small section of caudal and caudodorsal orbital rim, while the ventral and caudal this process is still present on the left hand side of the skull. It define rostrodorsal of the processes margins infratemporal fe- articulates with the dorsal, rather than ventral, margin of the nestra The ventral is and (Figs. 1-2). process elongate slender, jugal (contra Young, 1941a). The dorsal ramus tapers along its to its termination and tapering gradually curving slightly rostrally length and extends along the lateral surface of the quadrate as it does so. Its caudal has a margin long obliquely inclined shaft: however, it is not possible to determine if there was a contact with the of the In transverse postorbital process jugal. contact with the squamosal. A small section of the caudoventral cross-section, the ventral is in its ventral process sub-triangular part of the left quadratojugal is still present, attached to the part, with the apex of this approximately equilateral triangle lateral surface of the quadrate. Young's original figure of the pointing medially. skull (ibid:plate 1, fig. 1A) indicates that the caudoventral part of In lateral view, the rostrodorsal process is well developed, the quadratojugal was an extensive, dorsoventrally expanded, and In dorsal strap-like, tapers rostrally. view, this process is sheet-like structure, similar to that of Plateosaurus and substan- divided into two articular regions (Fig. 3). The laterally situated tially different from the more slender quadratojugals of other articulation is elongate and extends rostromedially, terminating prosauropods. in a broadly rounded tip: it overlaps the frontal, so that the caudodorsal corner of the orbit is actually roofed by the latter. Squamosal-The left squamosal is missing and has been restored, whereas the element is almost The smaller, stouter, medially positioned articular surface of the right complete (Fig. 2). The is a tetraradiate bone of a small rostrodorsal process contacted the rostrolateral processes of the squamosal large consisting main that rise to rostral, ventral, caudoventral, and parietal, excluding the frontal from the supratemporal fenestra body gives caudomedial rami. A but rostral ramus is (see above). The lateral surface of the postorbital lacks the short, robust, over- prominent rugosity present in some individuals of Plateosaurus. lapped extensively by the postorbital. In contrast, the ventral ramus has a stout base, but is and to a blunt The caudodorsal process is shorter than the other two postor- elongate tapers tip. This ramus extends the dorsal bital processes and tapers caudally to a sharp tip. The latter fits along part of the lateral surface of into a laterally situated sulcus on the postorbital process of the the quadrate shaft. A small sulcus for the M. adductor mandibu- squamosal, forming a 'V'-shaped contact between these two lae superficialis is formed at the junction between the ventral and bones. rostral rami. The caudoventral ramus is stout and sub-triangular Jugal-The jugal consists of three rami: a robust rostrallv di- in outline and terminates in a sharp tip that extends to a point rected maxillary process; a short caudodorsally oriented postor- just below the level of the quadrate head. It contacts the paroc- bital process, and a caudally directed quadratojugal process cipital process caudally. The rostral and caudoventral rami form (Figs. 1-2). The left jugal is slightly crushed. Laterally, the sur- the boundaries of the quadrate cotylus. Finally, the caudomedial face of the jugal is dorsoventrally convex, while the medial sur- process of the squamosal is short and slender, and contacts the face is dorsoventrally concave. The postorbital ramus is rela- parietal medially (Fig. 3). tively short, tapers to a sharp point dorsally, and terminates be- Quadrate-The quadrate consists of a robust shaft that gives low postorbital mid-height. In contrast, the maxillary ramus is rise to a lateral wing, which articulates with the quadratojugal, stout and robust. It is directed slightly dorsally as well as ros- and a medial wing that contacts the pterygoid (Figs. 1-2, 4). trally, tapers rostrally and has extensive sloping contacts with the Proximally, the head of the quadrate is obscured as it is bound caudodorsal surface of the maxilla ventrally and the ventral por- tightly into an articular fossa composed of the ventral and caution of the lachrymal dorsally. The caudally projecting quadra- doventral processes of the squamosal. The shaft of the quadrate tojugal ramus is elongate and strap-like and diverges from the is slightly bowed anteriorly in lateral view and its caudal margin ramus at an Downloaded by [National Science Library] at 18:41 02 April 2016 postorbital angle of approximately 500 (though this is thickened into a ridge-like structure. Distally, the shaft ex- angle may have been reduced by crushing), as in Mussaurus, pands both transversely and rostrocaudally to form the articular Massospondylus, and Jingshanosaurus. In contrast, these pro- surface that contacts the mandible. This articular region is di- cesses diverge at angles of approximately 90' in Plateosauruis, vided into lateral and medial condyles, with the lateral condyle Coloradisaurus, and Thecodontosaurus, and 600 in Riojasaurus situated dorsal to the medial one, and the medial condyle the and Yunnanosaurus. At the junction of the three jugal rami a larger of the two in terms of articular surface area. The distal end low, rounded boss of bone is present (Figs. 1-2). This feature is of the quadrate extends ventral to the level of the maxillary tooth present on both jugals suggesting that it is not pathological in row, resulting in a significant offset for the craniomandibular origin. As this feature is absent from other we prosauropods, joint (Fig. 1). propose that this represents an autapomorphy of Lufengosaurus. The two wings of the quadrate are set at an angle of slightly The dorsal margin of the maxillary ramus provides a small con- less than 900 to each other and are separated by a deep, rostral tribution to the ventral margin of the orbit, while the postorbital fossa. The lateral surface of the quadratojugal wing is gently and quadratojugal rami delimit the rostroventral corner of the concave both rostrocaudally and dorsoventrally. As this process infratemporal fenestra. descends from the quadrate head the surface twists slightly cau- Quadratojugal-The specimen originally included both dally so that the dorsal part of the lateral surface faces laterally quadratojugals but, subsequent to Young's (1941a) description, and the ventral half of the lateral faces slightly caudally. As a the right element seems to have become completely separated result, the caudal surface of the quadrate appears to be shallowly from the rest of the skull and its whereabouts is unknown. Nev- excavated along its length, with the excavation bounded by the ertheless, its extent can be determined, in part, from the shape of quadrate shaft medially (Fig. 5). The medial surface of the the articular surfaces present on the quadrate. The left element quadratojugal process is convex dorsoventrally. The pterygoid is badly damaged caudoventrally: comparisons with Young's wing of the quadrate extends rostrally and is overlapped exten- original figures and photographs indicate that a large section of sively by the pterygoid. Presence/absence of a quadrate foramen the main body of the bone is missing. could not be determined. Downloaded by [National Science Library] at 18:41 02 April 2016 816 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 25, NO. 4, 2005

(he may also have misinterpreted the rostral portion of this area magnum (Fig. 5). Lateral to this eminence and dorsal to the as a caudal continuation of the vomers, leading him to suggest contact with the opisthotic, the bone is transversely concave. that the vomers extended to the posterior margin of the internal Each of these concavities bounds a low, raised area that would nares: see below). have been the site of insertion for the neck musculature. Imme- Epipterygoid-The right epipterygoid is preserved in life po- diately ventral to this region are two prominent sub-crescentic sition. In lateral view, it is an elongate, sub-triangular element processes, which form the dorsolateral borders of the foramen that extends almost vertically from its ventral contact with the magnum and represent the proatlantal facets. The occipital plate pterygoid towards the skull roof (Fig. 2). The base of the element is steeply inclined with respect to the long axis of the skull and is is rounded and rostrocaudally expanded. whereas dorsally it oriented at about 450 to the horizontal, though this orientation tapers to a narrow point. has been exaggerated by the dorsoventral crushing of the skull Ectopterygoid-The ectopterygoid (= transversum in Young and it is likely that the occipital plate would have been more [1951]) is missing from the right side of the skull but is present on vertically oriented in life. No post-temporal opening is present the left (Fig. 4). Though the left element is still partially encased (contra Young, 1941a): the opening present on the right-hand in matrix, it appears to be a gently curved, strap-shaped bone side of the occiput is not a genuine feature of the skull, but was that attaches laterally to the jugal via a small anteroposteriorly caused by breakage and displacement of parietal and supraoc- short process. From here the bone curves ventrally and posteri- cipital. orly to articulate with the dorsal surface of the pterygoid. In Exoccipital-opisthotic-The exoccipital and opisthotic are ventral view, the junction between the pterygoid and ectoptery- fused into a single element that comprises the paroccipital pro- goid appears to run anteroposteriorly along the transverse flange cess: boundaries between the two elements cannot be deter- of the pterygoid such that the ectopterygoid makes up a small mined (contra Young, 1941a). The element labelled as an exoc- portion of the anterolateral part of this process. The ventral cipital by Young (1941a:fig. 5) is the proatlantal facet of the surface of this section is flat to mildly concave and lacks the deep supraoccipital (see above). Only the right paroccipital process is excavation seen in Thecodontosaurus. The maxilla, palatine, and preserved (Fig. 5): that on the left is entirely reconstructed. It ectopterygoid bound a small sub-orbital fenestra that is filled projects laterally from the foramen magnum and becomes dor- with matrix on the left-hand side of the skull. soventrally constricted in its central portion before expanding Palatine-In ventral view, the palatine consists of two parts: a again at its distal end. The distal end is slightly thickened an- maxillary process and a sheet-like main body. The maxillary pro- teroposteriorly and curves slightly caudally at the point where it cess is a broad-based, stout, rostrocaudally elongate projection contacts the squamosal. The tip of the process is reconstructed. that contacts the caudomedial surface of the maxilla (Fig. 4). As The exoccipital part of the process forms the lateral border of the this process extends medially, it first constricts and then expands foramen magnum. Unfortunately, these elements are too poorly rostrocaudally to merge with the main body of the palatine. In preserved to reveal the position of any nervous or vascular fo- ventral view, the main body of the palatine is largely obscured by ramina. its contacts with the pterygoid (along most of its length) and the Basioccipital and Basisphenoid-The ventral margin of the vomer (rostrally), but is visible as a thin strip of bone extending foramen magnum is composed of the basioccipital. The basioc- rostromedially from the maxillary process. The main body is set cipital condyle is sub-crescentic in posterior view and is convex at an angle to the maxillary process and extends dorsomedially dorsoventrally and transversely (Fig. 5). It is set on a very short towards the midline, so that the palatine body is oriented at neck and projects directly caudally, extending almost parallel to approximately 80' to the horizontal. The palatine forms much of the long axis of the skull (Fig. 4). The dorsal surface of the the caudomedial margin of the internal naris and meets the vo- basioccipital condyle is excavated. Immediately ventral to the mer rostromedially along a short contact. Dorsally. the surface of condyle, the neck merges into the basal tubera. The junction the main body of the palatine is largely obscured by matrix, but between the basioccipital and basisphenoid can still be traced: where visible it is a smooth, flat, dorsomedially inclined sheet. the basal tubera are made up of equal contributions from each of Lufengosaurus lacks the ventral palatine peg that is present in these elements. The basal tubera are short, sub-triangular pro- Plateosaurus. cesses that are ventrolaterally directed (Figs. 4-5). A deep sub- Vomer-The vomers are rostrocaudally elongate. straight. circular depression separates the basal tubera rostrally and cov- rod-like elements that extended to the midline of the ers the caudoventral surface of the basisphenoid (contrasting Downloaded by [National Science Library] at 18:41 02 April 2016 parallel skull (Fig. 4). They are sub-triangular in transverse cross-section with the absence of this recess in Thecodontosaurus). The ros- and form the rostromedial margin of the internal nares. Cau- troventral part of the basisphenoid (between the bases of the dally, they taper to a thin rod that contacts the palatines laterally. basipterygoid processes) is gently concave transversely. The ba- They also appear to contact the pterygoids caudomedially. sipterygoid processes are short, ventrally and slightly laterally Young (1951) suggested that the vomers projected caudally to a directed projections that arise from the base of the basisphenoid point approximately level with the caudal border of the internal close to its junction with the parasphenoid. They are sub-circular nares, but this is not the case. in transverse cross section, extend sub-parallel to each other and do not diverge markedly (Fig. 4). The processes are not con- Braincase nected to each other by a transverse wall of bone, in contrast to the condition present in Plateosaurus. The ventral and lateral views of the braincase were not avail- Parasphenoid-Only a short section of the parasphenoid is able when Young (1941a) originally described the specimen, but visible (Fig. 1). It appears to be sub-triangular in cross section later preparation provided some new information (Young, 1951). proximally, but the distal part is encased in matrix. Dorsally, it is Nevertheless, many details of braincase anatomy are still ob- excavated by a longitudinal groove. The exposed part of the scured by matrix and most of the sutures between these elements parasphenoid is horizontally oriented and the rostrum is situated are untraceable. ventrally with respect to the occipital condyle, showing that the Supraoccipital-The supraoccipital is a sub-triangular plate- braincase is relatively deep or 'stepped,' as in Plateosaurus and like bone that extends to cover the dorsal half of the occipital Coloradisaurus. region of the skull (Figs. 3, 5). It contacts the parietals dorsally. Laterosphenoid-A small element located on the right hand A low, rounded eminence extends dorsoventrally along the mid- side of the braincase is probably the laterosphenoid. It is a line of the bone from its junction with the parietals to the junc- wedge-shaped bone in lateral view, consisting of a squat, sub- tion with the exoccipitals and the dorsal border of the foramen rectangular main body that gives rise to a stout, finger-like pro- BARRETT ET AL.-CRANIAL OSTEOLOGY OF LUFENGOSAURUS 817

cess rostrally. The latter curves slightly laterally as it extends coronoid eminence is prominent and is approximately twice the rostrodorsally and is sub-triangular in transverse cross-section. A height of the tooth-bearing part of the mandible. It is composed sharp ridge divides the lateral surface of the laterosphenoid into of the dentary (rostrally) and the surangular (caudally) and rises two parts: a small laterodorsally facing surface and a larger lat- to an acute apex in lateral view. eral portion. No cranial foramina can be identified. Dentary-In lateral view, the tooth-bearing portion of the dentary is dorsoventrally shallow and maintains an almost con- Mandible stant height along its length (Fig. 6). Caudally, the dentary in- creases in dorsoventral height, reaching its greatest development The left and right mandibles are both broken anteriorly and close to its contact with the bones. the sections of the dentaries are teeth are post-dentary Rostrally, large missing. Only eight lateral surface is but more a marked in the of the left 16 tooth smoothly convex, caudally present preserved part dentary: posi- that extends the and are visible in the mandible. In addi- ridge develops caudodorsally along dentary, tions better-preserved right results the caudal of the tooth row the dorsal of the caudal of the left mandibular in part becoming medially tion, margin part inset. This in combination with a similar on the ramus is also the ddrsal of the has been feature, ridge damaged: part surangular maxilla forms the of a small buccal emar- broken off and remains adhered to the ventral margin of the (see above), boundary left-hand side of the skull The mandible exhibits a gination. Ventral to the ridge, the dentary ramus is pierced by (Fig. 1). right several nutritive foramina. At the is small external mandibular fenestra that is bounded rostrally and large mid-length, dentary in with the axis of the rostroventrally by the dentary, caudodorsally by the surangular, sub-elliptical cross-section, long ellipse oriented the into two and caudoventrally by the angular (Fig. 6). However, most of the dorsoventrally. Caudally, dentary splits a caudodorsal that contacts the margin of the external mandibular fenestra is not composed of processes, process surangular and a caudoventral that contacts the finished bone and it has probably been enlarged by damage. An process angular. the is convex its external mandibular fenestra is not present on the left-hand side Medially, dentary dorsoventrally along length. of the skull, though there is a depression in this region and the No interdental plates are visible. The Meckelian canal is closed surrounding bones have been displaced: this might indicate that medially, at least in the preserved portion of the dentary: its a fenestra was present, but that it was very small. caudal aperture can be seen in the internal mandibular fenestra. The medial surfaces of the mandibles are obscured by the Intercoronoid-There is some indication of a rostrocaudally presence of the armature for the skeletal mount: moreover, elongate intercoronoid, situated ventral to the tooth row on the many of the sutures between the mandibular elements are indis- dorsomedial surface of the right mandible (see also Young, tinct. However, it can be seen that the large internal mandibular 1951:fig. 11.3). However, this area is covered by the mount ar- fenestra is walled laterally by the dentary, surangular, and angu- mature and further details are not available. lar, and medially by the dentary, prearticular, and angular. This Angular-This is a large strap-like element that makes up the opening leads into the Meckelian canal. ventral portion of the posterior part of the jaw ramus (Fig. 6). It Strong ventral curvature of the surangular and angular, rela- is arched dorsally and tapers posteriorly to its termination. It has tive to the dentary, has produced a significant ventral offset in a broad contact with the surangular, dorsally; rostrally, it has an the position of the craniomandibular joint with respect to the almost vertical contact with the dentary. The ventral-most por- dentary tooth row, as also seen in Plateosaurus, Unaysaurus, tion of the angular is visible in medial view. Coloradisaurus, and Efraasia. The distal part of the right quad- Surangular-In lateral view, the surangular is dorsoventrally rate is adhered to the right mandibular glenoid (Fig. 6). The deepest at the level of the coronoid eminence (Fig. 6). As the

A Downloaded by [National Science Library] at 18:41 02 April 2016

Positionof armature Opening d.r Reconstructed

ang d

B emf FIGURE 6. Right mandibleof Lufengosaurushuenei (IVPP V15) in lateralview. A, drawingof skull as preserved.B, interpretativeline drawing of skull,showing damage, reconstruction, and positionsof sutures/articularsurfaces. Abbreviations: ang, angular;d, dentary;d.r, dentaryridge; emf, externalmandibular fenestra; q, quadrate;sa, surangular.Scale bar equals 100 mm. 818 JOURNAL OF VERTEBRATE PALEONTOLOGY,VOL. 25, NO. 4, 2005

bone extends caudally it decreases in height, describing a gentle Accessory elements sigmoidal curve as it does so. Firstly, the surangular expands dorsoventrally to form the posterior part of the coronoid emi- Young (1941a) described an almost complete right sclerotic nence. It then extends caudoventrally and narrows dorsoven- ring, but this was removed during preparation and its where- trally as it approaches the jaw joint before tapering farther cau- abouts is unknown. No hyoid apparatus was preserved with the dally and turning slightly dorsally to form the retroarticular pro- skull and the stapes is unknown. cess. The retroarticular process is sub-triangular in cross section and has a shallowly concave dorsal surface. It is relatively long DISCUSSION and finger-like, and projects caudally beyond the level of the posterodorsal corner of the skull. Suggested Synonymy of Lufengosaurus and Yunnanosaurus The lateral surface of the surangular is smoothly convex dorsoventrally in its ventral half, but the dorsal margin of the bone Rozhdestvensky (1965) suggested that Lufengosaurus huenei is oriented almost transversely to form the thickened dorsal mar- was the only valid prosauropod from the Lower Lufeng Forma- gin of the coronoid eminence: these two areas of the surangular tion. and that all of the other prosauropod taxa named by Young are separated by a distinct change of slope. A small vascular (or (including Yunnanosaurus huangi, Y. robustus, Gyposaurus sin- nervous) foramen is present on the rostral margin of the coro- ensis, and Lufengosaurits magnus) were junior subjective syn- noid eminence. onvms of L. huenei. Under this scheme, the various specific- and Prearticular-The prearticular is exposed in medial view. The generic-level differences identified by Young were dismissed as caudal part is a block-like element. There appears to be an elon- size-related characters and it was stated that the type specimens gate anterior process, but most of the latter is obscured by the of each taxon could be accommodated within an ontogenetic armature for the skeletal mount. The prearticular comprises the series of L. huenei. However, Rozhdestvensky's (1965) analysis medial portion of the caudal part of the mandible, forming the is flawed in several respects and detailed re-examination of the support for the articular. type specimens of both Lufengosaurus and Yunnanosaurus dem- Articular-The articular is a small block-like element that lies onstrate substantial, taxonomically informative differences be- immediately dorsal to the prearticular and contacts the surangu- tween these two genera. Here, this discussion will be limited to lar laterally and ventrally. It is sub-triangular in dorsal view, with comparisons between the crania of Lufengosaurus and Yunnano- the apex of the triangle pointing caudally. The rostral margin of sautrus: the postcrania of these genera will be re-described in the mandibular cotyle is formed from a sharp ridge. The dorsal detail elsewhere. surface of the articular is gently concave both rostrocaudally and In his discussions of ontogenetically variable characters, Rozh- transversely. destvensky (1965) frequently used discussion of phylogeny to the characters he used to individuals. Dentition polarize recognize juvenile For example, Rozhdestvensky (1965) noted that the upper jaw of In general, the teeth are not well preserved: many are broken Yunnanosaurus huangi overhangs the front end of the lower jaw apically and the mesial and distal margins are often obscured by and he suggested that this character state resembled that in close apposition and No teeth are which he considered to be dinosaur ancestors glue. premaxillary preserved. "pseudosuchians', The maxillary teeth are longest apicobasally in the portion of the (in fact, the situation in Yunnanosaurus probably results from maxilla immediately ventral to the ascending process (Fig. 1). post mortem deformation of the skull). Similarly, the configura- Caudal to this point the teeth decrease in length. In addition, the tion of the upper temporal bar in Y. huangi (which is deflected tooth crowns decrease in mesiodistal width caudally. The teeth ventrally relative to the skull roof: Young, 1942) was interpreted are closely packed and display an en echelon arrangement. They as a 'primitive' pseudosuchian-like feature. As these character are lanceolate and labiolingually compressed and the crowns are states resembled the situation in an older and, therefore, more slightly expanded mesiodistally with respect to the root (there is primitive taxon (in Rozhdestvensky's view) these were inter- a constriction between crown and root, but cingula are absent). preted as the juvenile states for these characters. However, this The crowns are almost symmetrical in labial view and display method of determining the ontogenetic status of an individual is little or no recurvature. In mesial and/or distal view. the crowns unreliable as shared features between 'ancestors' and juveniles are curved The crowns are of derived taxa result from a number of different factors, Downloaded by [National Science Library] at 18:41 02 April 2016 slightly lingually. apicobasally longer may than mesiodistally wide. The labial surface of the crowns is me- including symplesiomorphy, homoplasy, and heterochrony, siodistally convex, while the lingual surface is concave in the rather than representing a recapitulated ontogenetic sequence. same direction. Neither surface exhibits any grooves or ridges Moreover, it would only be possible to choose between these and the enamel is smooth, lacking ornament. No genuine wear various alternative scenarios if the taxa involved were in a phy- facets are present-all of the apical wear present can be attrib- logenetic framework: the latter did not form a part of Rozh- uted to breakage (wear surfaces are irregular, rather than destvensky's analysis. Consequently, these two cranial characters smooth). Close examination reveals that denticles were present do not support Rozhdestvensky's contention that Y. huangi is a on the mesial and distal margins of the maxillary tooth crowns, juvenile Lufengosaurus. but individual denticles are not well preserved: they are often Three other features of Yunnanosaurus huangi could be inter- missing or abraded. This damage may have occurred during preted as ontogenetically controlled characters: the holotype preparation as Young (1941a) describes the teeth as coarsely specimen of Y. huangi is smaller than that of Lufengosaurus serrated. huenei (IVPP V15) and possesses a relatively larger orbit and a Dentary teeth are identical to those in the maxilla in terms of smaller number of teeth (Rozhdestvensky, 1965). All of these both morphology and preservation. The teeth in the caudal parts features are generally accepted as features indicative of juvenil- of the dentaries are oriented a little mesiodorsally, but this has ity in dinosaurs (e.g., Varricchio, 1997). However, although the probably been accentuated by crushing of the skull, which could snout of IVPP V15 is incomplete (hampering proportional com- have displaced these teeth forwards. parisons), it appears that the orbit of this individual is at least as In most respects, the dentition of Lufengosaurus is similar to large, proportionally, as that of Y. huangi. In the latter, the maxi- that of other prosauropods, but can be easily distinguished from mum diameter of the orbit is equivalent to approximately 30% of that of Jingshanosaurus, in which the mesial maxillary teeth are total skull length, whereas in IVPP V15 this value is approxi- strongly recurved, and from Yunnanosaurus, in which the teeth mately 34% (though in reality this figure is likely to be slightly are sub-cylindrical and non-denticulate. lower, due to incorrect reconstruction of the premaxillae: see BARRETT ET AL.-CRANIAL OSTEOLOGY OF LUFENGOSAURUS 819

above). Consequently, overall differences in size and tooth num- current re-description (see Appendix). It is conceivable that such ber remain as the only potential juvenile features of Y. huangi. modifications will have an impact on the results of cladistic Nevertheless, detailed comparison between the skulls of Yun- analyses, perhaps affecting hypotheses of the relationships of nanosaurus and Lufengosaurus reveals many significant differ- Lufengosaurus and/or other sauropodomorph taxa. To test this ences between them, of which none can be attributed to onto- possibility, we have re-run the analyses of Sereno (1999), Yates genetic changes on the basis of current evidence: and Kitching (2003), and Galton and Upchurch (2004) using both the data-sets and versions that include lacks a whereas this fea- original updated 1) Yunnanosaurus supratemporal fossa, modified for Appendix). The results ture is in codings Lufengosaurus (see present Lufengosaurus; of these are summarised below. A medial lamina is absent in whereas both analyses 2) Yunnanosaurus, Sereno data-matrix consists of 32 and contributions to the lamina are (1999)-Sereno's (1999) maxillary lachrymal pres- characters for nine and two outgroups ent in ingroup prosauropods Lufengosaurus; and His analysis found six most parsi- The of lacks the (Theropoda Sauropoda). 3) quadratojugal Yunnanosaurus prominent monious trees of 34 A deletion of caudoventral seen in (MPTs) length steps. posteriori expansion Lufengosaurus; three unstable taxa (Ammosaurus, 'Griposaurus' (= 'Gyposau- The and teeth of Yunnanosaurus are cylin- 4) maxillary dentary rus' sinensis), and Coloradisaurus) produced a single topology in drical and non-denticulate, in contrast to the more 'typically which Lufengosaurus is the sister taxon to Plateosaurus + Efraa- prosauropod' lanceolate and coarsely serrated teeth of Lufen- sia (forming a plateosaurid clade). These plateosaurs form the gosaurus; to + Yunnano- The bar is relative to the sister-group massospondylids (Massospondylus 5) upper temporal deflected ventrally while is at the base of the Prosau- skull roof the fe- saurus), Riojasaurus placed in Yunnanosaurus, exposing supratemporal A of Sereno's data, using the branch- nestra in lateral view. In the ropoda. re-analysis original Lufengosaurus, upper temporal and-bound search in PAUP 2004) replicated bar the same as the skull 4.0b10 (Swofford, lies in approximately plane roof, these results the fenestra in lateral view. exactly. obscuring supratemporal The same search was then applied to a revised version of Yunnanosaurus lacks the cranial of 6) autapomorphies Lufen- Sereno's data, in which 61 % of the cranial characters of Lufen- gosaurus (see above). gosaurus were modified in line with our new observations on the the same. These differences in cranial anatomy are clearly sufficient to holotype skull, but with all other conditions remaining 24 MPTs of warrant taxonomic separation of Yunnanosaurus and Lufengo- An analysis of this revised dataset produced length unstable taxa saurus: we therefore reject the proposed synonymy of these taxa. 36 steps. A posteriori deletion of three (Ammo- saurus, 'Griposaurus', and Coloradisaurus) produced two distinct one identical to that found by Sereno (1999), Suggested Synonymy of Lufengosaurus and Massospondylus topologies, and one in which Plateosaurus and Lufengosaurus swap positions Cooper (1981:696) stated that "besides geographic separation (Fig. 7). there is little to distinguish Lufengosaurus from Massospondylus Yates and Kitching (2003)-Yates and Kitching produced a and the writer is of the opinion that these two taxa are conge- data-matrix consisting of 212 characters for 19 ingroup basal neric, and Lufengosaurus is regarded as a junior subjective synonym of Massospondylus." However, Cooper (1981) provided no discussion of this suggestion and did not propose any poten- Theropoda tial character states that would support this assertion, although he did suggest that differences in limb proportions could be used as a basis for specific separation between the South African Mas- sospondylus carinatus and M. huenei (ibid:804). Nevertheless, Sauropoda contrary to Cooper's unsupported assertion, Massospondylus and Lufengosaurus can be distinguished on the basis of numer- ous cranial features, which strongly suggest that they are distinct genera (see Table 1 for sources of comparative data). Riojasaurus Downloaded by [National Science Library] at 18:41 02 April 2016 1) The parasphenoid rostrum of Massospondylus projects rostrally from a point level with the basioccipital condyle, whereas in Lufengosaurus the parasphenoid is ventrally offset Yunnanosaurus with respect to the condyle. 2) In Massospondylus, the frontal makes a significant contribution to the orbital rim, whereas this contribution is small in Lufengosaurus. Massospondylus 3) Massospondylus lacks the four proposed autapomorphies of Lufengosaurus (see above). 4) Lufengosaurus lacks the cranial autapomorphies of Masso- spondylus, such as the 'knob and ridge' system present on the Plateosaurus lachrymal and prefrontal of the latter (see Sues et al., 2004, for a full list of Massospondylus cranial autapomorphies). Consequently, the synonymy of these two genera is rejected. Efraasia

Systematics Lufengosaurus has been included in a number of recent cladistic analyses of prosauropod, or basal sauropodomorph, rela- Lufengosaurus tionships (e.g., Sereno, 1999; Yates, 2003a, 2004; Yates and FIGURE 7. One of two MPTs obtained from analysisof the Sereno Kitching, 2003; Galton and Upchurch, 2004). Many of the char- (1999) sauropodomorphdataset incorporating revised cranialcharacter acter codings for this taxon should be modified in the light of the codings for Lufengosaurus.See text for furtherdetails. 820 JOURNAL OF VERTEBRATE PALEONTOLOGY.,VOL. 25, NO. 4, 2005

sauropodomorphs and two outgroup taxa (Herrerasaurus and Ancestor Neotheropoda). Their original analysis yielded five MPTs of Ammosaurus length 449 steps. These five topologies are identical except that Blikanasaurus occupies different positions among the basalmost Anchisaurus sauropods. Lufengosaurus is the sister taxon to Massospondylius, and together with Coloradisaurus and Plateosaturus form a Camelotia monophyletic Prosauropoda. Lessemsaurus A branch-and-bound search, using PAUP 4.0b10 (Swofford. 2004), has been applied to a revised version of this dataset. in Melanorosaurus which 33% of the Lufengosaurus cranial characters have been modified. The results are identical to those described above, Riojasaurus that MPT has increased six to except length by steps 455, perhaps Coloradisaurus reflecting increased character conflict within the dataset. Galton and Upchurch (2004)-Galton and Upchurch (2004) Plateosaurus produced a dataset consisting of 137 characters for 23 ingroup basal sauropodomorphs and one outgroup (hypothetical 'Ances- Efraasia This two MPTs of 279 tor'). analysis yielded length steps. These Euskelosaurus two MPTs are identical except for the position of Massospondy- lus. Lufengosaurus is the sister taxon to "Gyposaurtussinensis', Massospondylus and these two taxa form the sister group of a clade containing Euskelosaurus, Efraasia, and Plateosaurus. Application of the Gyposaurussinensis Heuristic search in PAUP 4.0b10 (Swofford. 2004) reproduced Lufengosaurus this result exactly. A Heuristic search has been applied to a revised version of the Yunnanosaurus Galton and Upchurch (2004) data matrix in which 44% of Lufen- gosaurus cranial characters have been modified. This yielded five Jingshanosaurus MPTs of 280 length steps (Fig. 8). These trees display some Mussaurus interesting differences with regard to those found originally by Galton and Upchurch (2004). In particular. Mussaulrutsand Jing- Saturnalia shanosaurus have moved to a position close to the base of the Prosauropoda; Lufengosaurus + 'Gyposaurus' sometimes cluster Thecodontosaurus with Yunnanosaurus; is more related to Massospondylus closely Barapasaurus Plateosaurus than is Lufengosaurus; and Coloradisaurus now lies within the Euskelosaurus + Plateosaurus + Efraasia clade. Shunosaurus Conclusions-It is clear from the above that there is little Vulcanodon consensus regarding the phylogenetic relationships of Lufengo- and this saurus, situation has not been changed by revision of the Kotasaurus cranial characters of this taxon. All analyses agree that Lufen- gosaurus lies within a monophyletic Prosauropoda (i.e., it is Blikanasaurus more closely related to Plateosaurus than to Sauropoda). How- FIGURE 8. Strict consensus tree of the five MPTs obtained from ever, the taxa that constitute Prosauropoda, and the rela- analysis of the Galton and Upchurch(2004) sauropodomorphdataset tionships within this clade, remain controversial. Nevertheless, with revised charactercodings for the skull of Lufengosaurus.See text revision of Lufengosaurus cranial characters has had some inter- for discussion. esting effects. First, in all three analyses, the updated Lufengo- saurus data have resulted in an increase of MPT length, suggest- that character conflict has increased. Downloaded by [National Science Library] at 18:41 02 April 2016 ing Second, in two of the fication of character for those analyses (Sereno, 1999; Galton and Upchurch, 2004), the number codings published phylogenetic analyses that include this taxon: the impact of these changes on of MPTs has increased and new topologies are proposed. It character evolution within will be might seem unfortunate and unexpected that more accurate Sauropodomorpha explored in more detail the character coding should result in increased conflict and alongside phylogenetic analysis mentioned poorer above. topological resolution. However, the current study represents the first in a series of of the Chinese re-descriptions prosauropod CONCLUSIONS taxa, and an evaluation of the importance of new data should perhaps be postponed until revised information on Lufengosau- Contrary to previous suggestions (Rozhdestvensky, 1965; Gal- rus (postcrania), 'Gyposaurus', and Yunnanosaurus has been ton, 1976: Galton and Cluver, 1976; Cooper, 1981) the Chinese processed and incorporated into phylogenetic analyses. Further- prosauropod genus Lufengosaurus can be distinguished from all more, it will also be important to synthesise the different char- other known prosauropods. Although all previous cranial diag- acter-sets proposed by Yates and Kitching (2003) and Galton nostic features of huenei (Young, 1941a; Galton, Lulfengosaurus and Upchurch (2004) before a full assessment of the relation- 1990) are shown to be invalid, the taxon can be diagnosed on the ships of Lufengosaurus and other Chinese prosauropods is at- basis of four cranial autapomorphies: in addition, it can be fur- tempted. For the present, we can conclude that Lufengosaurus is ther distinguished by the presence of unique combinations of closely related to Plateosaurus, Coloradisaurus, Ynlnanosaurus, character states present in isolation in other prosauropods. The and Massospondylus, but there is little agreement concerning the functions of the cranial bosses of Lufengosaurus are unclear at relationships among these taxa. present, but the presence of a short ridge on the lateral surface A full re-analysis of sauropodomorph interrelationships lies of the maxilla may indicate that the fleshy cheek of this animal outside the scope of this work and will be presented elsewhere (cf. Galton, 1973) may have been more extensive than in other (PU, PMB, and P. M. Galton, unpublished data). Nevertheless, prosauropods, which only possess the corresponding ridge on the re-examination of the type skull of Lufengosaurus allows clari- dentary. BARRETT ET AL.-CRANIAL OSTEOLOGY OF LUFENGOSAURUS 821

The Chinese prosauropodfauna has been neglected, despite Dong, Z-M. 1992. The Dinosaurian Faunas of China. Springer-Verlag, its obviousimportance in understandingearly dinosaur evolution Berlin, 188 pp. and Detailed re-examinationof the skull has Evans, S. E., and A. R. Milner. 1989. Fulgenia, a supposed early lizard ecology. holotype as a 32:223-230. revealed numerouserrors in the interpretationsof previous au- reinterpreted prosauropod dinosaur. Palaeontology thors with this Fang, X-X., Q-P. Long, L-W. Lu, Z-X. Zhang, S-G. Pan, Y-M. Wang, dealing both the anatomy and systematics of X-K. and Z-W. 2000. Middle, and Jurassic and the to character Li, Cheng. [Lower, Upper taxon, resultingchanges the codingof many subdivision in the Lufeng region, Yunnan Province]; pp. 208-214 in states clearly impact on the phylogeneticposition of Lufengo- Editorial Committee of the Proceedings of the Third National saurus and on our understandingof characterevolution among Stratigraphical Congress of China (eds.), Proceedings of the Third basal sauropodomorphsas a whole. Revision of the skull of National Stratigraphical Congress of China. Geological Publishing Lufengosaurus,the first prosauropodtaxon to be named from House, Beijing. [Chinese] the Lower Lufeng Formation,represents the first step towards Galton, P. M. 1973. The cheeks of ornithischian dinosaurs. Lethaia 6: re-evaluationof this poorly understooddinosaur fauna. 67-89. Galton, P. M. 1976. Prosauropod dinosaurs (Reptilia: Saurischia) of Postilla 169:1-98. ACKNOWLEDGMENTS North America. Galton, P. M. 1984. Cranial anatomy of the prosauropod dinosaur Pla- PMB and PU thankour colleaguesat the IVPP and NGMJfor teosaurus from the Knollenmergel (Middle Keuper, Upper Triassic) I. Two skulls from with their help and hospitality during our stays in China: Zhou of Germany. complete Trossingen/Wtirtt. comments on the diet. et Palaeontologica 18:139-171. Zhonghe,Zhou Xiao-Dan and Xu Xing deservespecial mention, Geologica as do the collections staff at IVPP. We are also to the Galton, P. M. 1985a. Cranial anatomy of the prosauropod dinosaur Sel- grateful losaurus gracilis from the Middle Stubensandstein (Upper Triassic) of the Jurassic the Natural zur Royal Society London, Foundation, of Nordwtirttemberg, West Germany. Stuttgarter Beitrige EnvironmentResearch Council, the CambridgePhilosophical Naturkunde, Series B 118:1-39. Society and the PalaeontologicalResearch Fund (NaturalHis- Galton, P. M. 1985b. Cranial anatomy of the prosauropod dinosaur Pla- tory Museum)for fundingthis research.We are especiallygrate- teosaurus from the Knollenmergel (Middle Keuper, Upper Triassic) ful to Debbie Maizels for her excellent drawings of the skull. P. of Germany. II. All the cranial material and details of soft part et 19:119-159. M. Galton and A. M. Yates provided helpful reviews of the anatomy. Geologica Palaeontologica P. M. 1990. Basal manuscript. S. E. Evans (University College London) is thanked Galton, Sauropodomorpha-Prosauropoda; pp. 320-344 in. D. B. P. Dodson, and H. Osm6lska (eds.), for discussion and J. Robinson (NHM) is thanked for checking Weishampel, the for errors. We thank the for The Dinosauria (1st Edition). University of California Press, Berkeley. Appendix typographic following P. M., and R. T. Bakker. 1985. The cranial anatomy of the pro- access to in their care: S. Kaal and R. Smith Galton, specimens (SAM); sauropod dinosaur "Efraasia diagnostica,"a juvenile individual of Sel- M. Raath (BPI); Zhou Xiao-Dan (NGMJ); M. Norell and C. losaurus gracilis from the Upper Triassic of Nordwiirttemberg, West Mehling (AMNH); A. Arcucci (ULR); W.-D. Heinrich (MB); Germany. Stuttgarter Beitrhge zur Naturkunde, Series B 117:1-15. and C. Chandler (YPM). Translations were made by W. Downs Galton, P. M., and M. A. Cluver. 1976. Anchisaurus capensis (Broom) (Fang et al., 2000) and D. A. Russell (Rozhdestvensky, 1965) and and a revision of the Anchisauridae (Reptilia, Saurischia). Annals of obtainedcourtesy of the Polyglot Paleontologistwebsite (http:// the South African Museum 69:121-159. in www.uhmc.sunysb.edu/anatomicalsci/paleo). Galton, P. M., and P. Upchurch. 2004. Prosauropoda; pp. 232-258 D. B. Weishampel, P. Dodson, and H. Osm61lska(eds.), The Dino- of California Press, LITERATURE CITED sauria (2nd Edition). University Berkeley. Gow, C. E. 1990. 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APPENDIX

Revised character codings for Lufengosaurus in the data matrices of Sereno (1999), Yates and Kitching (2003), and Galton and Upchurch (2004). See text for details of the analyses.

Character 5 10 15 20 25 30 35 40 Sereno (1999) 0?111 ?1111 11121 1111? ??11? 1?101 ?0 Yates and Kitching (2003) 10?01 ??0?1 11110 ??000 10101 10110 10100 0??11 Galton and Downloaded by [National Science Library] at 18:41 02 April 2016 Upchurch (2004) 10?1? ???10 ?10?? 11111 ?00?1 1?01? ?1?11 ?11?0 Character 45 50 55 60 65 70 75 80 Yates and Kitching (2003) 01200 ?0100 ?01?1 ????1 10?0? 10110 00??? 00010 Galton and Upchurch (2004) 01,?10 1?100 00000 11000 00100 1?000 01100 00001 Character 85 90 95 100 105 110 115 120 Yates and Kitching (2003) 01??? 0?010 10000 000?0 01100 0?011 10001 11010 Galton and Upchurch (2004) 11011 10001 10001 10010 1011? ??000 01001 01000 Character 125 130 135 140 145 150 155 160 Yates and Kitching (2003) 11010 00001 11111 12110 12121 10011 00010 10021 Galton and Upchurch (2004) 010?0 0??11 11001 1? Character 165 170 175 180 185 190 195 200 Yates and Kitching (2003) 10100 01010 01100 00111 01011 01000 001?1 00011 Character 205 210 Yates and Kitching (2003) 12210 01010 02

In the Sereno (1999) matrix, the following cranial characters were recoded: character 1 was changed from '?' to '0'; characters 2, 6, 20-22, and 25 were changed from '1' to '?'; characters 27 and 31 were changed from 'O' to "?':and characters 28 and 30 were changed from '0' to '1'. In the Yates and Kitching (2003) matrix, the following cranial characters were recoded: character 6 was changed from '2' to '?'; characters 7, 63, and 65 were changed from '1' to '?': characters 9. 16. 54. and 58-59 were changed from 'O' to '?': characters 2 and 39 were changed from '0' to '1'; characters 20 and 24 were changed from '1' to 'O';character 43 was changed from to '2'; characters 18-19, 27, 34-35, 45, 50, and 62 were changed from '?' to '0'; and characters 48 and 55 were changed from '?' to '1'. "1' Finally, in the Galton and Upchurch (2004) matrix, the following cranial characters were recoded: characters 3, 5, 7-8, 11, 14-15, 21, 24, 31, 36, and 39 were changed from '1' to '?'; characters 10 and 22 were changed from '1' to '0'; characters 18 and 38 were changed from '?' to '1'; and characters 30, 33, and 43 were changed from '0' to '?'