integrating ichnofossil and body fossil records to...

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Paleobiology, 31(3), 2005, pp. 400–423

Integrating ichnofossil and body fossil records to estimatelocomotor posture and spatiotemporal distribution of earlysauropod dinosaurs: a stratocladistic approach

Jeffrey A. Wilson

Abstract.—Fossil vertebrate distributions are typically based on body fossils, which are often poorlysampled at the margins of their true temporal and spatial ranges. Because vertebrate ichnofossilscan be preserved in great abundance and in different environments than vertebrate body fossils,inclusion of ichnofossil data may improve sampled ranges. However, if ichnofossils are to serve asan independent source of distributional data, then their attribution to a body fossil group (i.e.,trackmaker identification) cannot rely on temporal and spatial coincidence. Ichnofossils identifiedby synapomorphies can act as an independent source of distributional data that can modify spatial,temporal, and character distributions, which in turn may influence hypotheses of locomotor evo-lution.

In this paper I evaluate the spatial, temporal, and character distributions of early sauropod di-nosaurs by using a combined ichnofossil and body fossil data set. Sauropod ichnofossils supple-ment the spatiotemporal distributions of early sauropods and provide important information onearly sauropod foot posture that is rarely preserved or can only be inferred from body fossils. Thepresence of derived features in early-appearing ichnofossils challenges previous hypotheses ofcharacter transformation, implying either parallelism, reversal, or ghost lineages.

Stratocladistics can be used to resolve conflicting character and temporal distributions from bodyfossils and ichnofossils. Stratocladistic analysis of a combined ichnofossil and body fossil data setsuggests a richer, more widely distributed diversity of early sauropods than currently recognizedin body fossils and suggests that several locomotor characters originated much earlier than impliedby body fossils.

Jeffrey A. Wilson. Museum of Paleontology & Department of Geological Sciences, University of Michigan,1109 Geddes Road, Ann Arbor, Michigan 48109-1079. E-mail: [email protected]

Accepted: 24 September 2004

Introduction

Sauropod dinosaurs are the largest animalsknown to have walked on land. Their terres-trial capabilities are evident from the mor-phology of sauropod limb and axial bones(Mantell 1850; Phillips 1871; Hatcher 1901,1902; Riggs 1904; Bakker 1971; Coombs 1975),but most strikingly in the sauropod footprintrecord (Bird 1944; Farlow 1992; Lockley et al.1994). In addition to providing evidence of theterrestrial capabilities of sauropods, foot-prints provide temporal, spatial, and characterdata that can inform hypotheses of sauropodlocomotor evolution.

Spatiotemporal distributions based on sau-ropod ichnofossils and body fossils overlap,but some strata and areas are recorded by onlyone of these sources. This partial disjunctionbetween ichnofossil and body fossil data setsindicates that no one source provides the besthypothesis of sauropod distributions. The im-

port of ichnofossils on sauropod distributionsis especially relevant early in sauropod his-tory, when body fossils are rare and fragmen-tary (Lockley et al. 1994). In addition to spa-tiotemporal information, early sauropod ich-nofossils provide information about locomo-tor posture that often cannot be discernedfrom the earliest body fossils, which rarelypreserve manual and pedal remains. For ex-ample, the Middle Jurassic Shunosaurus(Zhang 1988) is the earliest appearing sauro-pod that preserves complete manual and ped-al remains. Because sauropods had alreadyevolved a fairly stereotyped manus and pes bythe Middle Jurassic, the timing and nature ofthe transformation leading to this basic sau-ropod foot plan cannot yet be inferred frombody fossils. However, recently described LateTriassic and Early Jurassic sauropod ichnofos-sils may provide insight into early sauropodlocomotor evolution, suggesting a Triassic or-igin for certain features that do not appear in

401EARLY SAUROPOD DISTRIBUTIONS

FIGURE 1. Simplified cladogram indicating the phylo-genetic relationships amongst saurischians as wellas phylogenetic taxonomy within Sauropodomorpha(based on Gauthier 1986; Sereno 1998, 1999; Wilson andSereno 1998). Sauropodomorpha and its two constituentsubgroups are arranged into a ‘‘node-stem triplet’’ (Ser-eno 1998) that nests the stem-based groups Sauropodaand Prosauropoda within the node-based group Sau-ropodomorpha. As shown by the gray tone, the stem-based groups (Prosauropoda or Sauropoda) include allsauropodomorphs more closely related to the referencetaxon within the clade (Plateosaurus or Saltasaurus) thanto the reference taxon within the opposing clade (Sal-tasaurus or Plateosaurus). By this definition, all sauro-podomorphs are either sauropods (represented by tonesmore dark than light), prosauropods (represented bytones more light than dark), or their common ancestor(represented by white line).

the body fossil record until the Middle Juras-sic.

The spatiotemporal distribution and loco-motor posture of early sauropods are dis-cussed below. First, I discuss the definition,ancestry, and content of Sauropoda. Second, Ievaluate sauropod spatiotemporal distribu-tions by using a combined ichnofossil andbody fossil data set. Third, I compare the tem-poral distribution of locomotor characters pre-served in early sauropod ichnofossils with theappearance of those same characters as im-plied by recent phylogenetic analyses of bodyfossils. Fourth, I use stratocladistic analysis toreconcile conflicting body fossil and ichnofos-sil distributions. And last, I propose a revisedchronology for early postural changes withinSauropoda.

Sauropoda: Definition,Ancestry, and Content

The concept of ‘‘sauropod’’ has remainedrelatively unchanged since the taxon was in-troduced by Marsh in 1878. This may be due,in part, to the morphological gap separatingsauropods from other sauropodomorphs.That is, perception of a sauropod ‘‘body plan’’relies on the absence of intermediate formsthat possess some, but not all, sauropod fea-tures. There were no ‘‘near-sauropod’’ sauro-podomorphs hypothesized to bridge this mor-phological gap until the recent discovery andreinterpretation of several Late Triassic forms.To provide a nomenclatural context for thediscussion that follows, the phylogenetic def-inition, hypothesized ancestry, and impliedcontent of Sauropoda are briefly discussed be-low.

Definition. Although the earliest cladisticanalyses of Sauropoda did not specify a phy-logenetic definition for the group (Russell andZheng 1993; Calvo and Salgado 1995; Up-church 1995, 1998), more recent analyses haveadopted a definition of Sauropoda as a stem-based group that includes all sauropodo-morphs more closely related to Saltasaurusthan to Plateosaurus (Sereno 1998; Wilson andSereno 1998; Wilson 2002; Upchurch et al.2004). This definition is mirrored by a stem-based definition for Prosauropoda that usesthe same reference taxa: all sauropodomorphs

more closely related to Plateosaurus than toSaltasaurus (Sereno 1998). These two stem-based clades comprise the node-based Sauro-podomorpha, which includes Plateosaurus, Sal-tasaurus, and all descendents of their most re-cent common ancestor (Sereno 1998). Thisnode-stem triplet configuration of phyloge-netic definitions (Fig. 1) implies that (1) anysauropodomorph must be either a sauropod, aprosauropod, or their common ancestor; (2)any taxon more closely related to one refer-ence form than the other must be a sauropo-domorph; and (3) any taxon with equal affin-ity to these two reference forms is either theirancestor or not a sauropodomorph.

Ancestry. The closest relatives to sauro-pods have been sought amongst small- to me-dium-sized sauropodomorphs common inUpper Triassic and Lower Jurassic horizons.Their stratigraphic distribution in rocks pre-dating the then-known sauropods led Huene(1920) to coin the taxon ‘‘Prosauropoda’’ forthese ‘‘before sauropods.’’ As stratigraphical-ly older sauropods and younger prosauro-pods were discovered, however, temporaloverlap precluded placement of prosauropodsen toto as the direct ancestors of Sauropoda

402 JEFFREY A. WILSON

(Charig et al. 1965). Since then, both tradition-al (Galton 1990) and cladistic (Sereno 1999;Benton et al. 2000; Galton and Upchurch 2000,2004) analyses of sauropodomorph relation-ships have suggested that prosauropods forma monophyletic group. Although the strengthof these claims varies between analyses, nu-merous synapomorphies of Prosauropodahave been proposed. Among these are severaldiscrete characters that include a premaxillarybeak, a highly modified first manual digit,and an hourglass-shaped proximal metatarsalII (Sereno 1999). Prosauropod monophyly wascontested by Yates (2001, 2003), who disband-ed prosauropods into a paraphyletic array ofsequential outgroups to Sauropoda. More re-cently, Yates has proposed a more moderatehypothesis that recognizes a monophyleticcore of prosauropods (including Plateosaurus)flanked basally by primitive forms and api-cally by sauropod-like forms (Yates and Kitch-ing 2003; Yates 2004). Applying the phyloge-netic definitions of Sereno (1998) to this to-pology, the monophyletic core that includesPlateosaurus should be called Prosauropoda,the derived sauropod-like forms should be in-cluded in Sauropoda, and taxa resolved asoutgroups to those clades should be excludedfrom Sauropodomorpha. For the purposes ofthis analysis, I will assume a monophyleticProsauropoda that includes genera acceptedas such by all recent cladistic analyses (Sereno1999; Yates and Kitching 2003; Yates 2004; Gal-ton and Upchurch 2004). Theropoda and Or-nithischia will be considered sequential out-groups to Sauropodomorpha (Fig. 1). Theco-dontosaurus (Yates 2003) and Saturnalia (Langeret al. 1999), whose phylogenetic affinities re-main controversial, were not included in thisanalysis. The focus group for this analysis,then, will include sauropods and near-sauro-pod sauropodomorphs identified by Yates (Ya-tes 2003, 2004; Yates and Kitching 2003).

Content. The sauropod ‘‘body plan’’ com-prises numerous osteological characters thatsupport the monophyly of Sauropoda and itssubgroup Eusauropoda (Upchurch 1995,1998; Wilson and Sereno 1998; Wilson 2002).Owing to its morphological distinctiveness,the taxonomic content of Sauropoda is uncon-troversial for all Jurassic and Cretaceous sau-

ropodomorphs (although lower-level affinitiesare controversial for some). However, the af-finities of five Upper Triassic–Lower Jurassicsauropodomorphs (Blikanasaurus, Anchisaurus,Antenonitrus, Melanorosaurus, Lessemsaurus)have received attention because they are hy-pothesized to possess some, but not all, sau-ropod body plan characters (Bonaparte 1999;Yates 2003, 2004; Yates and Kitching 2003).

Galton and van Heerden (1985, 1998) de-scribed the partial hindlimb of the Upper Tri-assic (Carnian–Norian) sauropodomorph Bli-kanasaurus cromptoni, which they considered‘‘an early experiment in the direction of heavi-ly-built quadrupedal saurischians, but. . . noton the evolutionary line that gave rise to theSauropoda’’ (1985: p. 511). Some recent cladis-tic analyses, however, have resolved Blikana-saurus as more closely related to sauropodsthan to prosauropods (Upchurch et al. 2002,2004; Yates 2003, 2004), but this hypothesis isnot yet strongly supported. Yates and Kitch-ing (2003: p. 1757) excluded Blikanasaurus fromtheir analysis because of its topological insta-bility, and Blikanasaurus possesses at least onehypothesized synapomorphy of prosauro-pods (hourglass-shaped proximal metatarsalII [Sereno 1999]). Although there are featuresthat seem to support sauropod affinities forBlikanasaurus, many of these are proportionalmeasures that could be related to body size(e.g., relative length of metatarsus, breadth ofmetatarsals I and V). Although I will provi-sionally treat Blikanasaurus as a basal sauro-pod in the discussion below, further inquiryinto its phylogenetic position is required.

The small, facultatively bipedal Anchisaurusis usually considered part of a monophyleticProsauropoda (Sereno 1999; Galton and Up-church in press), but a recent review of the ho-lotypic and referred remains has suggestedsauropod affinities (Yates 2004). In the lattercontext, the small body size of Anchisauruswas interpreted as a reversal in the overalltrend toward large body size in Sauropodo-morpha (Yates 2004: Fig. 14). Although Yates(2004) reported a relatively high decay index(5) for the node positioning Anchisaurus at thebase of Sauropoda, its Early Jurassic (Pliens-bachian–Toarcian) age implies a 20-million-year ghost lineage preceding its appearance in


the fossil record. Implied stratigraphic debtand character evidence supporting its prosau-ropod affinities (Sereno 1999; Galton and Up-church 2004) cast doubt on the hypothesis thatAnchisaurus is a sauropod.

Yates and Kitching (2003: p. 1753) recentlydescribed the new genus Antenonitrus on thebasis of a partial postcranial skeleton from theUpper Triassic (Norian) of South Africa thatthey suggest represents the ‘‘earliest knownsauropod.’’ If the holotype constitutes a singleindividual, then the limb proportions suggesta quadrupedal pose for Antenonitrus. In fact,most of the features linking Antenonitrus tosauropods are proportional features; few dis-crete characters support this relationship. Iwill provisionally treat Antenonitrus as a po-tential sauropod, but the association amongthe holotypic remains and characters evidenc-ing this affinity require further evaluation.

The Upper Triassic Melanorosaurus (Haugh-ton 1924) from South Africa is an enigmaticsauropodomorph that is traditionally placed,along with the South American genus Rioja-saurus, in Melanorosauridae (Galton 1985),widely regarded as a sauropod-like family ofprosauropods (Galton 1990; Bonaparte andPumares 1995; van Heerden and Galton 1997).However, Yates (2003) and Yates and Kitching(2003) have recently suggested that Melanoro-saurus is a true sauropod. This assessment isbased in part on the shape of the femoralshaft, which lacks the mediolateral sigmoidcurvature typical of saurischians. However,the constituency of the holotype remains con-troversial (Haughton 1924; van Heerden1979), and referral of better-preserved re-mains to the genus (van Heerden and Galton1997; Welman 1999) must await restudy of theholotype.

The South American Upper Triassic (upperNorian) genus Lessemsaurus (Bonaparte 1999)was named on the basis of several presacraland sacral neural arches and associated pre-sacral centra from the Los Colorados Forma-tion of La Rioja, Argentina. Although Bona-parte (1999: p. 133) referred Lessemsaurus tothe prosauropod family Melanorosauridae, hegrouped it with the sauropods Lapparentosau-rus and Volkheimeria as having vertebrae of the‘‘sauropodo primitivo’’ type. He based this on

the height of the dorsal neural spines, pres-ence of an infrapostzygapophseal fossa ondorsal neural arches, and the presence of a‘‘supraneural’’ constriction below the postzy-gapophyses (Bonaparte 1999: p. 134). Al-though no presacral features diagnose Sauro-poda, three were resolved as synapomorphiesof Eusauropoda by Wilson (2002: Appendix3): opisthocoelous cervical centra, mid-cervical neural arches taller than height ofposterior centrum face, and dorsal neuralspines broader transversely than anteropos-teriorly. Unfortunately, none of these featurescan be adequately scored in Lessemsaurus. Cer-vical centra are part of the holotype of Lessem-saurus, but Bonaparte (1999) did not commenton the morphology of their articular faces. Thecervical neural spines do not appear elongaterelative to the presumed height of the centra,which were associated but not articulated(Bonaparte 1999: Fig. 13B). Bonaparte men-tions that the dorsal neural spines are trans-versely thick, but did not provide measure-ments or figures that allow comparison ofneural spine dimensions. Thus, despite su-perficial similarities, as yet there is no strongevidence that Lessemsaurus is a sauropod. Itwill be regarded here as an indeterminate sau-ropodomorph pending discovery of morecomplete skeletal remains.

Spatiotemporal Distribution ofEarly Sauropods

Until recently, sauropod body fossils andichnofossils were known only from Jurassicand Cretaceous sediments. This distributionwas inconsistent with the Late Triassic firstappearances of the sauropod sister lineagesProsauropoda and Theropoda (Figs. 1, 2)(Gauthier 1986). The 15–20-Myr missing inter-val preceding the first appearance of sauro-pods in the fossil record was recently reducedby the discovery of Late Triassic sauropodbody fossil taxa, including Isanosaurus and asecond, unnamed form (Buffetaut et al. 2000,2002), Antenonitrus (Yates and Kitching 2003),and Blikanasaurus (Upchurch et al. 2002, 2004;Yates 2003).

Well before the discovery of these body fos-sils, however, trackways from the Upper Tri-assic of North America were described and at-


FIGURE 2. Temporal and spatial distributions of early sauropods and related theropod (Herrerasaurus, Eoraptor),prosauropod, and ornithischian (Pisanosaurus) dinosaurs. Tracks and trackways are represented by gray bars; bodyfossils are represented by black bars. The age of the Kota Formation is not resolved beyond Early Jurassic; the Kotasauropods Barapasaurus and Kotasaurus have been placed in the middle of that range. Abbreviations: AF, Africa; AS,Asia; AU, Australia; EU, Europe; IN; India; MA, Madagascar; NA, North America; SA, South America. Abbrevia-tions for geological stages are from Benton 1993, and timescale is based on Gradstein et al. 1999.

tributed to the ichnotaxon Tetrasauropus (Lock-ley 1986; Conrad et al. 1987). Despite theirsimilarity to Jurassic and Cretaceous sauro-pod trackways, Tetrasauropus was not identi-fied as such by traditional methods of track-maker identification, which rely on pheneticsimilarity and coincident spatial and temporaldistributions of body fossils and ichnofossils.It was not until after the discovery of Isano-saurus body fossils that Tetrasauropus track-ways were attributed to a sauropod trackmak-er, which ‘‘reflects the convention of using os-teological evidence as the ultimate arbitor [sic]in deciding at least the temporal, if not thespatial, range of major vertebrate groups’’(Lockley et al. 2001: p. 189). (As Lockley et al.[2001: p. 185] noted, the North American Te-trasauropus trackways differ from the holotyp-ic Tetrasauropus trackway from South Africa,which Rainforth [2003: p. 829]) considers ‘‘in-compatible with dinosaurian pedal struc-

ture.’’ Here and elsewhere, ‘‘Tetrasauropus’’ re-fers to the North American trackways de-scribed by Lockley et al. [2001], which may bereferred to a different ichnogenus.)

Ichnofossils are an important source of spa-tiotemporal information for tetrapods becauseof their abundance (one trackmaker can makemany tracks) and their preservation in envi-ronments distinct from those preserving bodyfossils (Lockley 1991; Lucas 2003). AlthoughMesozoic mammals remain notable excep-tions, perhaps because of their small body sizeand relatively indistinct manual and pedalskeleton, ichnofossils enhance distributionaldata (Lockley and Foster 2003). Ichnofossils,however, can extend distributions based onbody fossils only when trackmaker identifi-cation is spatially and temporally indepen-dent. In contrast to traditional methods thatrely on phenetic similarity and temporal andspatial coincidence, synapomorphy-based


trackmaker identification (Olsen 1995; Carra-no and Wilson 2001) relies on the recognitionof osteological synapomorphies from track-way evidence. Synapomorphy-based track-maker identification frees tracks from precon-ceived distributions based on body fossils, adistinction especially relevant to early sauro-pod distributions because (1) a lengthy miss-ing interval precedes the first appearance ofbody fossils, and (2) the sauropod manus andpes are characterized by numerous synapo-morphies that facilitate their identificationfrom trackways. Below, I discuss the spatialand temporal distributions of early sauro-pods, based on combined body fossil and ich-nofossil data.

Temporal Distribution. The earliest knowndinosaur skeletal remains are preserved inMiddle to Late Triassic sediments of the Is-chigualasto Formation of northwestern Ar-gentina, which have been radiometrically dat-ed at 228 Myr B.P. (Rogers et al. 1993) (Fig. 2).Represented in the Ischigualasto fauna are thebasal ornithischian Pisanosaurus (Casamiquela1967) and the saurischian theropods Herrera-saurus (Reig 1963) and Eoraptor (Sereno et al.1993). Sauropodomorpha first appears ap-proximately 5 Myr later in the Carnian ofMadagascar (Flynn et al. 1999), Africa (Dutuit1972), South America (Langer et al. 1999), andNorth America (Chatterjee 1984; Sereno 1991).Theropod trackways of Anisian–?Ladinianage (ca. 238 Ma; Demathieu 1990) suggest aneven earlier divergence for Theropoda andSauropodomorpha (Carrano and Wilson2001).

An Upper Triassic (Carnian) first appear-ance for Sauropoda is suggested by both bodyfossil and ichnofossil remains, but both re-quire confirmation. As mentioned above, thepartial hindlimb of the Upper Triassic (Car-nian) Blikanasaurus preserves several featuresof Sauropoda (Yates 2003, 2004; Yates andKitching 2003; Upchurch et al. 2004), some ofwhich may be body size-related. Likewise,tracks from the lower Upper Triassic (Carni-an) Portozuelo Formation of west-central Ar-gentina may possess sauropod synapomor-phies (see below), but their identification re-mains tentative (Marsicano and Barredo2004).

The oldest definitive sauropod fossils arethe Tetrasauropus trackways preserved in theChinle Group of western North America,which are Norian–Rhaetian in age (ca. 210 Ma;Lockley et al. 2001). Other Upper Triassictrackways from South Africa (Pentasauropus,Sauropodopus, Tetrasauropus [Ellenberger 1972])and eastern North America (Agrestipus[Weems 1987]) do not appear to preserve di-agnostic sauropod features and cannot yet bereferred to that group. Slightly younger?Rhaetian strata in Thailand preserve thefragmentary remains of Isanosaurus (Buffetautet al. 2000) (Fig. 2). Isanosaurus may be morederived than the Toarcian Tazoudasaurus (Al-lain et al. 2004) and the probably Toarcian Vul-canodon (Raath 1972; Yates et al. 2004), whichis generally considered the most primitivesauropod (Wilson 2002: Fig. 13, Table 13).

Sauropod ichnofossils are preserved inLower Jurassic sediments in Italy (Dalla Vec-chia 1994), Poland (Gierlinski 1997), and Mo-rocco (Ishigaki 1988). The two Europeantrackways are preserved in slightly older (Het-tangian, ca. 206–202 Ma) horizons than are theMoroccan trackways (Pliensbachian, ca. 195–190 Ma). Still younger sauropod body fossilsare known from Lower Jurassic horizons of In-dia (Barapasaurus [Jain et al. 1975]; Kotasaurus[Yadagiri 2001]) and China (Kunmingosaurus[Zhao in Dong 1992]; Gongxianosaurus [He etal. 1998]; ‘‘Lufeng sauropod’’ [Barrett 1999]).Of these early sauropod body fossils, only Go-ngxianosaurus preserves complete pedal re-mains. The first complete sauropod skeleton isShunosaurus, from Middle Jurassic sedimentsof China (Zhang 1988), which also preserveother sauropods (e.g., Datousaurus). Ichnofos-sils from the Middle Jurassic (Bathonian) ofEurope (Santos et al. 1994; Day et al. 2002)provide the first record of the derived sauro-pod subgroup Neosauropoda. These wide-gauge trackways have been attributed to titan-osaur trackmakers (Wilson and Carrano 1999).Neosauropod body fossils first appear in theCallovian of Kirghizia (Ferganasaurus [Alifan-ov and Averianov 2003]) and persist through-out the remainder of the Jurassic and Creta-ceous.

Figure 2 identifies several intervals duringwhich no definitive sauropods have been re-


corded, including the Aalenian, Sinemurian,and intervals preceding the Carnian. Until re-cently, a lengthy missing interval (about 20Myr) spanned the Carnian, Norian, andRhaetian ages, between the first appearance ofprosauropods and the appearance of the firstsauropods. However, the recent discoveries ofIsanosaurus, Antenonitrus, and Tetrasauropus, aswell as the reinterpretation of Blikanasaurushave begun to bridge this temporal gap. Like-wise, a Toarcian gap was filled recently by thediscovery of Tazoudasaurus (Allain et al. 2004)and the revised Toarcian age for the Vulcano-don beds (Yates et al. 2004), which were pre-viously considered to be ?Hettangian (e.g.,McIntosh 1990; Wilson and Sereno 1998).

Spatial Distribution. The spatial distribu-tion of early sauropod body fossils is restrict-ed to fairly small areas in southern, central,and eastern Pangea (Fig. 3, black-filled cir-cles). Sauropod body fossils from uppermostTriassic sediments of Thailand (Isanosaurusand an unnamed form) and Lower Jurassicsediments of China (Gongxianosaurus, ‘‘Lufengsauropod’’) delimit a northeastern area, bodyfossils from the Upper Triassic and Lower Ju-rassic of southern Africa (Antenonitrus, Blikan-asaurus, Vulcanodon) and the Lower Jurassic ofIndia (Barapasaurus, Kotasaurus) delimit asouthern area, and a single body fossil fromthe Lower Jurassic of Morocco (Tazoudasaurus)forms a central area. If we accept that Sauro-poda is a monophyletic group that includesthese body fossils, and that sauropods couldnot cross the Tethys Sea, then this distributionsuggests that sauropods previously inhabitedthe intervening land area. Thus, body fossilssuggest that early sauropods may have beenpresent in Madagascar, central Africa, easternNorth America, western Europe, and the Mid-dle East. These data, however, do not implythat early sauropods were present in Austra-lia, Antarctica, South America, or westernNorth America. Recently, Gillette (2003: p.687) interpreted the distribution of sauropodbody fossils as suggesting an ‘‘initial geograph-ic distribution limited to southeastern Asia’’ fol-lowed by an Early Jurassic ‘‘[e]xpansion of dis-tribution. . . through southern Laurasia andeastern Gondwana’’ and later ‘‘geographic ex-pansion in the Middle Jurassic to include Aus-

tralia and South America, but not North Amer-ica’’ until the Late Jurassic. Although this inter-pretation appears consistent with body fossildata, incorporation of ichnofossil data yields adifferent pattern of early sauropod distribu-tions.

Sauropod footprints confirm the predictionthat sauropods inhabited land areas withinthe area enclosed by sauropod body fossils,and they extend the geographical range ofearly sauropods to western North Americaand possibly South America (Fig. 3, white-filled circles). Combined ichnofossil and bodyfossil data indicate that sauropods achieved abroad east-west distribution (western NorthAmerica to eastern Asia) by the Late Triassicand extended their range to Africa, Europe,India, and southern South America by the Ear-ly Jurassic. Later body fossils indicate that sau-ropods attained their broadest geographicdistribution by the Middle Jurassic, when theyalso occupied both Madagascar (Lapparento-saurus [5‘‘Bothriospondylus’’] [Ogier 1975; seealso Buffetaut 2003]) and Australia (Rhoetosau-rus [Longman 1926]) (Fig. 2). The only majorcontinental landmass that has not yet pro-duced sauropod fossils is Antarctica. Howev-er, because sauropods have been recoveredfrom each of the landmasses adjoining Ant-arctica during the Middle Jurassic (India, Aus-tralia, southern Africa, southern South Amer-ica, Madagascar), it is likely that sauropodswere present on Antarctica by that time.

Distribution of Morphological Features

The quadrupedal posture and distinctivemanus and pes skeletons of sauropods havefacilitated identification of their footprints inthe fossil record since Bird’s (1941) discoveryof sauropod trackways in the Early Creta-ceous of Texas, which were later named Bron-topodus birdi in his honor (Farlow et al. 1989).The sauropod manus and pes skeleton andtheir corresponding impressions in sauropodichnotaxa such as Brontopodus share numeroussimilarities (Fig. 4), including several syna-pomorphies of Sauropoda and its subgroups(Table 1). The ability to observe these syna-pomorphies varies with preservation of thetrackway. Whereas several features can be ob-served in coarsely preserved footprints (e.g.,


FIGURE 3. Geographic distribution of early sauropod fossils mapped onto paleogeographic reconstructions of theEarth during the Late Triassic (Rhaetian–Norian–Carnian, 220 Ma) and Early Jurassic (Sinemurian, 200 Ma). Black-filled circles represent body fossils; white-filled circles represent ichnofossils. Late Triassic body fossils includeBlikanasaurus (South Africa; Galton and van Heerden 1985), Antenonitrus (South Africa; Yates and Kitching 2003),and Isanosaurus (Thailand; Buffetaut et al. 2000); Late Triassic ichnofossils include Tetrasauropus (U.S.A.; Lockley etal. 2001) and an unnamed form from the Portozuelo Formation (Argentina; Marsicano and Barredo 2004). EarlyJurassic body fossils include Vulcanodon (Zimbabwe; Raath 1972; South Africa; Yates et al. 2004), Tazoudasaurus (Mo-rocco; Allain et al. 2004), Barapasaurus (India; Jain et al. 1975), the ‘‘Lufeng sauropod’’ (China; Barrett 1999), andGongxianosaurus (China; He et al. 1998), and Early Jurassic ichnofossils include unnamed forms from Holy CrossMountains (Poland; Gierlinski 1997), Lavini di Marco (Italy; Dalla Vecchia 1994), and Atlas Mountains (Morocco;Ishigaki 1988). Paleogeographic reconstructions are based on Smith et al. 1994.

large body size, digitigrade manus, spreadingpes), some features can be identified only intrackways (e.g., quadrupedal stance, wide-gauge posture) or finely preserved tracks (e.g.,shaft width of metatarsal I . metatarsals II–IV). One of the more conspicuous features as-sociated with sauropod trackways is the heel

impression, which may be regarded as a ‘‘re-ciprocal illuminant’’—a soft tissue featurepreserved in trackways that have been attri-buted to a certain trackmaker by other means(Carrano and Wilson 2001: p. 571). The pres-ence of a well-marked heel trace in all sauro-pod trackways thus far identified indicates


FIGURE 4. Sauropod manus, pes, and footprints. A, B, Brachiosaurus. Right manus in proximal (A) and anterior (B)views. C, F, ?Brontopodus. Right manus print (C) and right pes print (F), oriented relative to the trackway midline(arrow). Modified from Thulborn 1990: Fig. 6.16f. D, E, Apatosaurus. Right pes in proximal (D) and dorsal (E) views.Modified from Gilmore 1936: Figs. 25, 27, 28. A–C from Wilson and Sereno 1998: Fig. 22. Roman numerals indicatedigit numbers. Scale bar, 10 cm for A, B, D, and E; C and F not to scale.

that a fleshy pad supported the pes, a featurethat may be related to the acquisition of aspreading metatarsus and semi-digitigradepedal posture (Wilson and Sereno 1998). Assuch, presence of a heel impression can beused as a synapomorphy that identifies a eu-sauropod trackmaker.

Trackway features suggest that Brontopodustrackways were made by a titanosauriformsauropod, perhaps a saltasaurid (sensu Wil-

son 2002; Wilson and Upchurch 2003). Be-cause these Early Cretaceous trackways do notpredate the estimated origin of Titanosauri-formes (Late Jurassic) or Saltasauridae (EarlyCretaceous), Brontopodus does not modify thehypothesized temporal distributions of titan-osauriforms, saltasaurids, or their definingsynapomorphies (Table 1). However, MiddleJurassic trackways preserving saltasaurid fea-tures (Santos et al. 1994; Day et al. 2002) alter


TABLE 1. Synapomorphies of Sauropoda and its subgroups that can be identified in the trackways of Brontopodusbirdi (Fig. 4C,F). The asterisk indicates a ‘‘reciprocal illuminant’’—a soft tissue feature associated with trackwayssecurely identified by osteological synapomorphies. Synapomorphies are based on Wilson 2002 and referencestherein; trackway features are modified from Carrano and Wilson 2001. Osteological features for Neosauropodahave been resolved as eusauropod synapomorphies by Upchurch (1998).

Clade Osteological character Trackway feature

Sauropoda Columnar, obligately quadrupedalposture

Quadrupedal tracks

Large body size Large track sizeEusauropoda Manual phalangeal count reduced Short digit impressions

Minimum shaft width of metatarsal Iexceeds those of metatarsals II–IV

Digit I more deeply impressed thanothers

Semi-digitigrade pes Metatarsals spreading in pes printPedal ungual IV reduced/absent No pedal ungual IV printSickle-shaped pedal unguals II, III

*Pes supported by heel pad

Pedal ungual II, III impressionsdeep, sickle-shaped

Heel traceBarapasaurus 1 more derived

taxaLaterally directed pedal unguals Pedal ungual prints offset laterally

Neosauropoda Metacarpus bound

Metacarpus forming 2708 arc

Anteroposteriorly narrow manusprint that lacks digit divergence

Tightly arched manus printTitanosauriformes Femoral shaft deflected medially Wide-gauge tracksSaltasauridae Femoral distal condyles offset 108

relative to shaftWide-gauge tracks

Femoral midshaft, transverse diame-ter at least 185% anteroposteriordiameter

Wide-gauge tracks

existing distributions because they predatethe hypothesized origin of both Titanosauri-formes and Saltasauridae. Either these line-ages appeared earlier than the body fossil re-cord shows, or their defining characters ap-peared homoplastically in earlier sauropods.Thus, if trackways are attributed to body fos-sil clades through the use of synapomorphies,then any diagnostic trackway that extends thetemporal distribution of a body fossil clade al-ters the distributions of characters, taxa, orboth.

Late Triassic (Fig. 5) and Early Jurassic (Fig.6) trackways outside the spatiotemporal rangedelimited by body fossils can be referred toSauropoda on the basis of osteological syna-pomorphies. Because few appendicular syna-pomorphies of or within Sauropoda are esti-mated (on the basis of body fossils) to haveevolved before the Early Jurassic, these earlyappearing trackways have the potential tomodify either character distributions or tem-poral distributions. There are three resolutionsto distributional conflicts implied by ichnotaxabearing characters that appear outside the tem-

poral range of body fossil clades they diagnose(Fig. 7) (Carrano and Wilson 2001):

1. parallelism—the ichnotaxon is not a memberof the body fossil clade, but represents anas-yet-undiscovered body fossil thatevolved the character independently;

2. reversal—the ichnotaxon is more primitivethan both the body fossil clade diagnosedby the feature and its body fossil outgroups(which lack the feature), and the characterdiagnoses the clade including all four butwas lost in the body fossil outgroups;

3. synapomorphy—the ichnotaxon is a memberof the body fossil clade, extending the tem-poral range of the body fossil clade, all lat-er-appearing body fossil outgroups, andthe character.

Resolution of conflicting ichnological andbody fossil distributions as either parallelismor reversal results in modification of previouscharacter distributions, whereas resolution ofthis conflict as synapomorphy results in mod-ified temporal distribution of taxa. The distri-bution of several locomotor characters among


FIGURE 5. Late Triassic sauropod footprints. A, B, Tetrasauropus trackways from the Upper Triassic (Chinle Group)of Cub Creek (A) and Peacock Canyon (B), Colorado (from Lockley et al. 2001). C, Possible sauropod trackwaysfrom the Portozuelo Formation (Carnian) of Argentina (modified from Marsicano and Barredo 2004). This photo-graph was not taken from directly above tracks; relative sizes are distorted (upper tracks appear smaller than lowerones). Abbreviations: rm, right manus print; rp, right pes print. Scale bar, 50 cm for A, 10 cm for B.

FIGURE 6. Early Jurassic sauropod footprints. A, Trackway from the Pliensbachian of the Atlas Mountains, Morocco(based on Farlow 1992: Fig. 2a–b). B, Trackway ROLM 28 from the Hettangian of Lavini di Marco, Italy (based onDalla Vecchia 1994: Fig. 2); C, Manus-pes pair of ?Parabrontopodopus from the Hettangian of the Holy Cross Moun-tains, Poland (based on Gierlinski 1997: Fig. 1b). The trackways from Morocco (A) and Italy (B) are oriented relativeto the trackway midline, which could not be determined for the Polish specimen (C). Abbreviations: lm, left manusprint; lp, left pes print; rm, right manus print; rp, right pes print. Scale bar, 10 cm.


FIGURE 7. Three resolutions to the conflict in characterand taxon distributions from body fossil and ichnofossildata. In this example, the early appearance in an ich-

←

nofossil (IF) of a derived morphological feature (*)known to be absent in the later-appearing body fossils(BF1 and BF2) but present in a derived body fossil (BF3)can be resolved three ways. Parallelism (1) interprets theichnofossil as basal to the body fossils and resolves thefeature as evolving in parallel in the ichnofossil andbody fossil 3. Reversal (2) also interprets the ichnofossilas basal to the body fossils, but instead resolves the fea-ture as a synapomorphy of all four taxa that was re-versed in two of the body fossils. Synapomorphy (3) in-terprets the ichnofossil as an early appearing member ofthe BF3 lineage, which implies three ghost lineages. Res-olutions (1) and (2) imply homoplasy but no additionalghost lineages; resolution (3) implies additional ghostlineages (dark gray bars) but no homoplasy. Vertical dis-tances reflect hypothetical age differences. Pale graybars indicate ghost lineages implied by body fossils;dark gray bars indicate ghost lineages implied by ich-nofossils. Black indicates the derived condition; whiteindicates the primitive condition.

early sauropod body fossils and ichnofossils isdiscussed below. In each case, resolution of thecombined data results in ad hoc claims of ho-moplasy, ghost lineages, or both. Synapomor-phies are based on recent studies of sauropodsystematics (Upchurch 1998; Wilson and Ser-eno 1998; Wilson 2002).

Quadrupedal Posture. Determination of lo-comotor posture in extinct tetrapods typicallyrelies on indirect evidence derived from skel-etal remains. Primary among these are inter-membral indices, but relative trunk lengthand qualitative assessments of the robustnessof forelimb elements are also used. Trackwaydata, in contrast, offer direct evidence of lo-comotory posture, but generalizations basedon them are not without ambiguity. In orderfor them to be useful indicators of locomotorbehavior, trackways should be interpreted inthe context of behavioral variation (is thetrackway representative of ‘‘typical’’ track-maker behavior?), taphonomic variation (istrackway morphology altered by preserva-tion?), and taxonomic variation (is the track-maker ‘‘typical’’ of the larger taxon it repre-sents?).

In some cases, osteological and trackwaydata offer an unambiguous determination oflocomotor posture. Theropods are consideredobligate bipeds because their forelimbs are nomore than 40–50% of hindlimb length, theirslender manus bears narrow, sickle-shapedunguals, and only bipedal trackways have


been attributed to the group. Osteological andichnological data are similarly compelling forthe locomotor posture of most sauropods,which have relatively elongate forelimbs (atleast 70% hindlimb length) and only quadru-pedal trackways attributed to them.

In contrast, these data are ambiguous forthe locomotory posture of prosauropods,whose phylogenetic affinities affect the polar-ity of basal sauropod characters (see ‘‘Ances-try’’ above). Many prosauropods have hind-limb and trunk proportions intermediate be-tween those of theropods (bipeds) and sau-ropods (quadrupeds), which may suggest anintermediate locomotory posture (Huene1926; Galton 1976, 1990, 2000; Cooper 1981;van Heerden 1997). Trackways attributed toprosauropods exhibit both bipedal (e.g., Pseu-dotetrasauropus [Ellenberger 1972], Otozoum[Rainforth 2003]) and quadrupedal locomo-tion (e.g., Navahopus [Baird 1980]; cf. Otozoum[Lockley and Hunt 1995: Figs. 4.17–4.19; Lock-ley and Meyer 2000: Fig. 4.3]). It is not yet clearwhether these tracktypes represent one ormore prosauropod trackmakers, each capableof two locomotor modes (i.e., a facultative bi-ped), or two prosauropod trackmakers, eachcapable of a single locomotor mode (i.e., a bi-ped and a quadruped).

The nearest outgroups to Dinosauria, Lag-erpeton and Marasuchus, are regarded as biped-al (Sereno and Arcucci 1993, 1994), as are the-ropods. The sauropodomorphs Saturnalia andThecodontosaurus, which have been regardedas either basal prosauropods or outgroups toSauropodomorpha, are likewise considered tobe bipedal (Langer et al. 1999; Yates 2001).Thus, Dinosauria and Saurischia are primi-tively bipedal (Carrano 2000). Sauropodomor-pha was probably primitively bipedal, but theancestral state is contingent on relationshipswithin Prosauropoda and the locomotor pos-ture assigned to basal prosauropods.

Sometime after their hypothesized diver-gence from Theropoda and Prosauropoda238–228 Myr ago (see above ‘‘Spatial Distri-bution’’), sauropods acquired an obligate qua-drupedal stance. If the Upper Triassic Anten-onitrus is shown to be a sauropod and an as-sociated individual, then its relatively robust,elongate forelimb suggests that it is the earli-

est quadrupedal sauropod body fossil. TheLower Jurassic Barapasaurus, Gongxianosaurus,and Vulcanodon are the first definitive sauro-pod body fossils for which a quadrupedalpose can be inferred. The earlier appearing,Upper Triassic Isanosaurus is too fragmentaryto determine its locomotor posture.

North American Tetrasauropus trackways(Figs. 2, 5A,B), which are coeval with the bodyfossil Antenonitrus, suggest that sauropodquadrupeds evolved before the Upper Triassic(Norian). Even older trackways from the Por-tozuelo Formation of Argentina (Figs. 2, 5C)record a quadruped in the Carnian (ca. 225Ma), 5–10 Myr before the appearance of An-tenonitrus and approximately 25 Myr beforethe appearance of a definitive quadrupedalbody in the Lower Jurassic. However, as Mar-sicano and Barredo (2004) noted, the presenceof manus prints in these trackways is irregularand the trackmaker may have been a faculta-tive, rather than an obligate, quadruped.

Semi-Digitigrade Pes. Acquisition of aspreading pes with metatarsals oriented near-ly horizontally is a synapomorphy for Eusau-ropoda (Upchurch 1995), a clade that includesall sauropods but the basalmost forms Vulcan-odon, Tazoudasaurus, Gongxianosaurus, Anten-onitrus, and Blikanasaurus. Wilson and Sereno(1998: p. 41) hypothesized that the morphol-ogy of the eusauropod tarsus and pes sug-gested a ‘‘semi-digitigrade’’ foot posture, inwhich the relatively short metatarsals (;1/4tibia length) were oriented nearly horizontallyand supported by a fleshy heel pad (Fig. 4D–F). Non-eusauropods such as Vulcanodon andGongxianosaurus, in contrast, have a relativelyelongate metatarsus (.1/3 tibial length) thatresembles those of prosauropods and thero-pods.

In the absence of qualifying terms, ‘‘semi-digitigrady’’ does not have explicit meaningin existing classifications of tetrapod locomo-tor posture. Specifically, ‘‘digitigrady’’ refersto a range of postures intermediate betweenthe extremes of ‘‘plantigrady,’’ in which themetatarsals and phalanges are oriented hori-zontally and contact the substrate, and ‘‘un-guligrady,’’ in which the metatarsals are ori-ented nearly vertically and only the distal-most phalanges contact the substrate (Carra-


no 1997: p. 78). By this definition, thesauropod pes is digitigrade but closer to theplantigrade extreme than the unguligrade ex-treme. Somewhat confusingly, the specializedfoot posture of hippopotamids, rhinocerotids,and proboscideans, in which a fleshy pad sup-ports the pes, has been termed ‘‘sub-unguli-grade’’ because the penultimate and ungualphalanges contact the substrate (Carrano1997: Fig. 1B, Appendix 1). Although the hy-pothesized sauropod hind foot posture is insome ways similar to ‘‘sub-unguligrady’’ (viz.the fleshy heel pad), the metatarsus is not heldvertically as in sub-ungulates, nor are the non-ungual phalanges hypothesized to be held offthe substrate. For the purposes of this discus-sion, the term ‘‘semi-digitigrady’’ will be ap-plied to the foot posture hypothesized for Eu-sauropoda.

Body fossils provide unambiguous supportfor the hypothesis that a semi-digitigrade pesoriginated in Eusauropoda, which first ap-pears in the Lower Jurassic, and was absent ineusauropod outgroups, which first appear inthe Upper Triassic. Although the earliest eu-sauropod is Sinemurian–Pliensbachian in age(Kunmingosaurus), a semi-digitigrade pes isfirst documented in the Middle Jurassic (Ba-jocian) Shunosaurus. These hypothesized tem-poral and character distributions are chal-lenged by semi-digitigrade pes impressionspresent in Upper Triassic Tetrasauropus track-ways (Fig. 5A,B) and Lower Jurassic sauropodtrackways (Fig. 6). Additionally, Upper Tri-assic trackways from the Portozuelo Forma-tion (Fig. 5C) seem to indicate an even earlierorigin for semi-digitigrade pedal posture, al-though the unguals appear to be directed me-dially rather than laterally (see ‘‘Laterally Di-rected Pedal Unguals’’ below). Conflicting ich-nological and osteological estimates for thefirst appearance of semi-digitigrady in sau-ropods can be reconciled in one of three ways(Fig. 7). Semi-digitigrady either (1) evolved inparallel in Eusauropoda and in Upper Triassicand Lower Jurassic trackmakers, (2) diagnosesall sauropods but was reversed in Vulcanodonand Gongxianosaurus, or (3) implies that UpperTriassic and Lower Jurassic trackmakers areeusauropods. Resolutions (1) and (2) acceptthe stratigraphic data at face value and inter-

pret the trackmakers as the basalmost sauro-pods, outgroups to Vulcanodon and Eusauro-poda. As such, these two resolutions representequally parsimonious solutions to an ambig-uous character distribution: resolution (1) de-lays transformations, and a semi-digitigradepes is assumed to have been acquired in par-allel in the trackmakers and Eusauropoda,whereas resolution (2) accelerates transfor-mations, and a semi-digitigrade pes is as-sumed to evolve at the base of the clade andlater reverse in non-eusauropod body fossilssuch as Vulcanodon. Alternatively, resolution(2) could imply that the hind foot posture ofnon-eusauropod body fossils has not been in-terpreted correctly, and that the feature diag-noses Sauropoda and has not reversed. Arecent study of skeletal remains referred toPlateosaurus has inferred a less digitigradeposture than traditionally posited for prosau-ropods (Sullivan et al. 2003), which may implythat some prosauropods had a more sauro-pod-like pedal posture. This preliminary re-sult underscores the need for additional in-vestigation into osteological correlates of footposture. Resolution (3) accepts the characterdata at face value, interpreting the Upper Tri-assic and Lower Jurassic trackmakers as eu-sauropods. In this scenario, the early appear-ance of the ichnofossils suggests a Late Tri-assic origin for Eusauropoda and a 50-Myrmissing lineage prior to the Bajocian appear-ance of Shunosaurus, the earliest eusauropodwith a demonstrably semi-digitigrade pes.

Reduction of Manual Phalanges. Prosauro-pods retain the primitive manual phalangealcount of 2*-3*-4*-3–2, in which the first threedigits bear unguals (noted by asterisks). The-ropods, too, retain the primitive phalangealcomplement on the first three digits but apo-morphically reduce the outer two digits for a2*-3*-4*-0–0 count (Sereno and Novas 1992).All eusauropods, in contrast, are character-ized by a shortened manus in which each digitbears two or fewer phalanges, and only thepollex bears an ungual (Wilson and Sereno1998; Fig. 4B). The second ungual attributed tothe manus of Ferganasaurus, which is now lost,has been interpreted as a misassociation (Al-ifanov and Averianov 2003: p. 364). Reductionof manual phalanges, however, remains an


ambiguous synapomorphy of Eusauropoda,because their outgroups do not preserve com-plete manual remains (e.g., Vulcanodon, Go-ngxianosaurus). Although osteological evi-dence for reduction of manual phalanges doesnot appear until the Middle Jurassic (Shuno-saurus), it likely evolved much earlier, as sug-gested by older, but more derived eusauro-pods such as Barapasaurus (Lower Jurassic),which does not preserve a complete manus.

Manual phalangeal reduction can be iden-tified in well-preserved trackways, such asthat of the Cretaceous ichnogenus Brontopodus(Fig. 4C). The manus print is complete, butthere is no indication of individual digits orunguals. However, the degree of reductioncannot be ascertained in even exceptionallywell preserved sauropod forefoot impres-sions, because they do not preserve phalan-geal impressions. This may in itself indicatethe extreme phalangeal reduction in eusau-ropods. Lower Jurassic trackways suggest thatearly sauropods possessed a reduced set ofmanual phalanges similar to those of MiddleJurassic eusauropods. Manual impressionspreserve neither evidence of free digits norungual impressions (Fig. 6). The three smallconvexities on the outer margin of one manualprint (Fig. 6A), do not appear in others andmay be preservational defects. Upper TriassicTetrasauropus trackways, in contrast, appear tobe more primitive in this character than bothShunosaurus and the Lower Jurassic trackmak-ers. The presence of free digits is indicated bythe consistent appearance of extensions fromthe central, fleshy portion of the manus (Fig.5A). However, the number of phalanges re-tained cannot be determined. The absence ofsimilar extensions in other North AmericanTetrasauropus trackways (Fig. 5B) suggests ei-ther a difference in preservation or the pres-ence of a second, more derived sauropod pre-sent in the Upper Triassic. Likewise, the Up-per Triassic Portozuelo trackways do not pre-serve evidence of manual digits and resemblethose of Lower Jurassic trackways.

Trackway evidence suggests that manualphalangeal reduction began prior to the Low-er Jurassic, perhaps even the Upper Triassic.

Laterally Directed Pedal Unguals. Barapasau-rus and more derived sauropods evolved ped-

al unguals that are deflected laterally relativeto the long axis of each digit and of the footitself. This conspicuous feature derives fromchanges in the shape of the articular facet ofthe ungual, as well as asymmetry of the bladeof the ungual (Wilson and Sereno 1998). Thisfeature can be detected in partial pedes andeven in isolated unguals. The presence of lat-erally directed pedal unguals is an unambig-uous synapomorphy because the basal sauro-pods Vulcanodon, Tazoudasaurus, Gongxianosau-rus, and Shunosaurus—each of which preservepedal unguals—appear to retain the primitivecondition (but further documentation of thiscondition is required [Wilson and Sereno1998: p. 44]). The presence of this feature canbe easily determined in well-preserved track-ways (Fig. 4F) but may be more difficult to de-tect as preservation quality declines. UpperTriassic Tetrasauropus trackways (Fig. 5A,B)clearly preserve impressions of pedal ungualsdeflected laterally relative to the axis of thepes. Likewise, Lower Jurassic footprints fromPoland preserve ungual impressions that areonly slightly laterally directed from the axis ofthe pes, but their orientation relative to the di-rection of travel cannot be determined (Fig.6C). Lower Jurassic trackways from Moroccoand Italy do not bear ungual traces and can-not be scored for this feature (Fig. 6A,B). TheUpper Triassic Portozuelo trackways (Fig.5C), in contrast, preserve ungual impressionsthat are oriented medial to the axis of the pesand line of travel.

The early appearance of laterally directedpedal unguals in Upper Triassic Tetrasauropustrackways predates the first osteological evi-dence of this feature in the Lower Jurassic Bar-apasaurus. This conflict can be resolved as ei-ther (1) parallelism, (2) reversal, or (3) syna-pomorphy. Each of these resolutions requiresad hoc hypotheses of either homoplasy orghost lineages. Parallelism implies that Tetra-sauropus evolved laterally directed pedal un-guals independent of the clade uniting Bara-pasaurus and other sauropods. Reversal im-plies that laterally directed pedal unguals di-agnoses the clade including Tetrasauropus andmore derived sauropods, but was reversed inintervening basal sauropods. Synapomorphyresolves Tetrasauropus as a member of the clade


uniting Barapasaurus and more derived sau-ropods and implies ghost lineages for severaltaxa.

Digitigrade Manus. In sauropods with adigitigrade manus, the metacarpus is ar-ranged vertically, and the five metacarpals aresubequal in length and tightly appressedproximally (Fig. 4B). The manus contacts thesubstrate at the metacarpal-phalangeal jointand creates an abbreviated forefoot print (Fig.4C). Some sauropods are also characterized bywedge-shaped proximal metacarpal headsthat articulate in a tight arc of approximately2708 (Fig. 4A), a tubular arrangement of themetacarpus that results in a tightly archedforefoot print (Fig. 4C). Upchurch (1998) con-sidered these two features (digitigrade ma-nus, tubular metacarpus) to be correlated anddiagnostic of all sauropods preserved withmanual remains (i.e., Eusauropoda). More re-cently, Bonnan (2003: pp. 599, 610–611) furthersuggested that a digitigrade, tubular metacar-pus is phylogenetically linked to the acquisi-tion of a quadrupedal posture, and that thesethree correlated features will be shown tocharacterize all sauropods once manual re-mains are known for basal forms. In contrast,Wilson and Sereno (1998) and Wilson (2002)regarded the digitigrade manus and tubularmetacarpus as independent features that arepresent in neosauropods but absent in morebasal forms such as Shunosaurus (Zhang 1988:Fig. 49, Pl. 14) and Omeisaurus (He et al. 1988:Figs. 47–48; Pl. 14, Figs. 4–6), whose metacar-pals appear to have poorly defined interme-tacarpal articular surfaces that were onlyslightly arched (;908) in articulation.

Upper Triassic Tetrasauropus trackwaysfrom North America (Fig. 5) and Lower Juras-sic trackways from Italy, Poland, and Morocco(Fig. 6) document sauropod trackmakers witha digitigrade manus, identified by an antero-posteriorly narrow manus print that lacks dig-it divergence (Table 1). However, unlike morederived sauropods (Fig. 4C), the manus printsappear to be only slightly arched. Althoughmore and better-preserved trackways are re-quired to confirm this, the presence of one fea-ture (digitigrade manus) and the absence theother (tightly arched metacarpus) in thesetrackways suggests they are independent

(Wilson and Sereno 1998; Wilson 2002). Al-though quadrupedal posture and digitigrademanus are present in these early trackways,this does not provide evidence that these char-acters are correlated. If we accept the characterscoring of Wilson and Sereno (1998), in whichShunosaurus and Omeisaurus are regarded asprimitive (i.e., manus not digitigrade), thenthe early appearance of a digitigrade forefootposture in Tetrasauropus and Lower Jurassictrackways can be interpreted as either (1) par-allelism, (2) the early appearance of digiti-grade foot posture in non-neosauropods withsubsequent reversals, or (3) the early appear-ance of Neosauropoda. Parallelism impliestwo independent origins of the digitigrademanus posture, whereas reversal implies thatintervening taxa have reverted to a primitiveforefoot posture. Synapomorphy resolves Te-trasauropus and Lower Jurassic trackmakers asneosauropods and implies several ghost line-ages. However, if we accept the Upchurch(1998) and Bonnan (2003) interpretations ofShunosaurus and Omeisaurus as having the de-rived, digitigrade forefoot posture, then track-way evidence suggests that digitigrade fore-foot posture evolved in the Triassic and char-acterized all sauropods more derived than Te-trasauropus. These early sauropods, however,had not yet evolved the tightly arched ar-rangement of metacarpals diagnostic of neo-sauropods.

Using Stratocladistics to ResolveConflicting Distributions

In the preceding section, I attempted to re-construct individual character transforma-tions by using data from both ichnofossils andbody fossils. In each case, ichnofossil andbody fossil character and temporal distribu-tions were nonoverlapping, so hypotheses ofcharacter transformation required ad hoc hy-potheses of character change (homoplasy) orof stratigraphic intervals in which taxa werenot sampled (ghost lineages). The optimalcharacter transformation minimizes both ofthese. I have suggested that for a given topol-ogy, only three alternate hypotheses of char-acter transformation exist for conflicting ich-nological and body fossil data—parallelism,reversal, and synapomorphy (Fig. 7). The


number of ad hoc hypotheses implied by eachof the three possible transformations can bedetermined, and the transformation implyingthe fewest ad hoc claims can be chosen for asingle character and a given topology. How-ever, when several characters are consideredsimultaneously, such as the locomotor char-acters discussed here, minimizing ad hoc hy-potheses amongst multiple character transfor-mations quickly becomes intractable. More-over, these additional character data and tem-poral data should be allowed to influence thecladistic topology itself, and a general methodis required. Stratocladistics is the only methodof phylogenetic inference that explicitly selectsthe tree or trees that minimize both characterdebt and stratigraphic debt (Fisher 1992, 1994;Fisher et al. 2002).

Methods. No computer program is yetavailable that evaluates character data andstratigraphic data together. Stratocladisticanalysis usually employs two programs, aparsimony algorithm that finds the shortesttree or trees given a character-taxon matrix(e.g., PAUP* [Swofford 2001]) and a programthat tracks changes in a multistate, polymor-phic character (e.g., MacClade 4.0 [Maddisonand Maddison 2000]). Protocol for stratoclad-istic analysis has been presented elsewhere(Fisher 1992; Polly 1997; Fox et al. 1999; Blochet al. 2001; Bodenbender and Fisher 2001) andwill only be summarized here. The first stageof stratocladistic analysis proceeds as doesstandard cladistic analysis. That is, operation-al taxonomic units are scored for charactersand this information is coded into a character-taxon matrix. A parsimony algorithm such asPAUP* obtains the shortest tree or trees thatexplain this character information. The secondstage of stratocladistic analysis begins withthe cladistically shortest tree (or trees), whichMacClade converts to a phylogenetic tree bythe addition of a stratigraphic character (typ-ically the last character in the matrix) not in-cluded in the cladistic analysis. The length ofthe phylogenetic tree identical to the cladistictopology is the ‘‘stratigraphically augmentedtreelength,’’ which is the starting point fromwhich shorter trees are sought using the‘‘make ancestor’’ tool in MacClade. Becausestratocladistics compares trees with zero-

length branches (i.e., ancestors), it is impor-tant to include autapomorphies in the char-acter-taxon matrix. The shortest phylogenetictree isomorphic with the shortest cladistic treecan be shortened further by evaluating alter-nate topologies, either by manual branchswapping or the ‘‘Search Above’’ tool inMacClade, or by searching in PAUP* for alltrees below the ‘‘debt ceiling’’ implied by thestratigraphically augmented treelength.

Stratocladistic analysis of early sauropodand sauropod-like taxa evaluated 172 mor-phological characters and a single stratigraph-ic character in three ichnofossils and 12 bodyfossils (see Appendix online at http://dx.doi.org/10.1666/03047.S1). Terminal taxaincluded all relevant Upper Triassic and Low-er Jurassic sauropods, as well as three of theichnofossils discussed above (the Portozueloform [Argentina], Tetrasauropus [U.S.A.], theLavini di Marco form [Italy]; Figs. 5, 6). Manyof the terminal taxa have been included in pre-vious analyses (e.g., Upchurch 1995, 1998;Wilson and Sereno 1998; Wilson 2002), but Go-ngxianosaurus, Isanosaurus, Tazoudasaurus, andthe ichnofossils have not. Morphological char-acters included only those characters resolvedas synapomorphies or autapomorphies atnodes basal to Neosauropoda, as well asuniquely derived autapomorphies (Wilson2002: Appendices 2–4). I have emended scor-ings to accommodate recently described ma-terials of Omeisaurus (Tang et al. 2001), Ma-menchisaurus (Ouyang and Ye 2002), and Bar-apasaurus (Bandyopadhyay et al. 2003). Thestratigraphic character scores the presence ofa terminal taxon in any of the 14 Triassic andJurassic stratigraphic stages from the Anisianto the Oxfordian. Because no sauropods inthis analysis are preserved in two stages (Lad-inian, Aalenian), these states were not codedand did not contribute to total debt. The re-maining 12 stratigraphic stages were coded ascharacter states 0–9 and A or B. The amper-sand symbol (&) denotes polymorphism, inwhich a taxon occupied multiple stratigraphiclevels; the forward slash (/) indicates uncer-tainty, in which a taxon occupies one of sev-eral possible stratigraphic levels (Maddisonand Maddison 2000). Character polarity was


FIGURE 8. Cladistic results. A, Single most parsimoni-ous tree produced in analysis of body fossil taxa only.Treelength equals 214 steps, Consistency Index, exclud-ing uninformative characters 5 0.81, Retention Index 50.86; numbers in parentheses at nodes indicate decay in-dices greater than 1. B, Strict consensus of two trees pro-duced in an analysis of body fossils and ichnofossils(square brackets). Several basal taxa can be resolvedfrom Eusauropoda, whose interrelationships are uncer-tain. Treelength equals 218 steps, Consistency Index, ex-cluding uninformative characters 5 0.80, Retention In-dex 5 0.86. C, Adams consensus of two most parsimo-nious trees in B.

determined by successive outgroups to Sau-ropoda (Prosauropoda, Theropoda).

Results. Cladistic analysis of the 12 bodyfossil ingroup taxa produced a single tree(Fig. 8A). The Upper Triassic and Lower Ju-rassic forms Blikanasaurus and Antenonitruswere resolved as the basalmost sauropods, butthis analysis does not test the possibility thatthey are prosauropods, which remains anopen question (see above, ‘‘Content’’). Rather,this analysis assumes they are sauropods andexamines their affinities within the group. Go-ngxianosaurus, Isanosaurus, Tazoudasaurus, andVulcanodon were resolved as sequential out-groups to Eusauropoda. The basal portion ofthe topology was the most poorly supported(decay indices 5 1), but the derived, eusau-ropod portion of this topology is better sup-ported. Addition of three ichnofossils to thisingroup resulted in two equally parsimonioustrees, a strict consensus of which preserves therelationships of eusauropod outgroups butprovides no resolution within Eusauropoda(Fig. 8B). The Portozuelo and Tetrasauropusichnotaxa were resolved as proximate out-groups to Eusauropoda, and the Lavini diMarco ichnotaxon was in an unresolved po-sition within Eusauropoda. An Adams con-sensus tree offers more resolution, retaining asingle polytomy at the base of Eusauropodabetween Shunosaurus, the Lavini di Marco ich-notaxon, and a clade of more derived eusau-ropods (Fig. 8C).

The Adams consensus tree (Fig. 8C) wasused as the best cladistic tree in the strato-cladistic analysis, with the Lavini di Marcotrackmaker positioned as the most primitiveeusauropod. Addition of the stratigraphiccharacter resulted in a phylogenetic tree 36steps longer than the cladistic topology. Anisomorphic phylogenetic tree two steps short-er could be created by making Prosauropodaand Barapasaurus ancestors, and a tree 14 stepsshorter was discovered by three rearrange-ments of terminal taxa: (1) the Portozuelo andTetrasauropus trackmakers were placed basalto Isanosaurus, (2) Gongxianosaurus was mademore derived than Isanosaurus, and (3) theLavini di Marco trackmaker was made moreprimitive than Tazoudasaurus. Thus, the opti-mal stratocladistic solution is 16 steps shorter


FIGURE 9. Stratocladistic results for basal sauropod body fossils and ichnofossils (square brackets) with hypoth-esized optimizations for locomotor characters discussed in text. This phylogenetic hypothesis implies two homo-plastic characters. Semi-digitigrade pedal posture was lost in Vulcanodon, and laterally directed pedal claws evolvedin parallel in Tetrasauropus and Barapasaurus plus more derived sauropods. Abbreviations for geological stages arefrom Benton 1993; timescale is based on Gradstein et al. 1999.

than the phylogenetic tree implied by the cla-distic topology. Two equally parsimoniousstratocladistic trees differ in the position of Pa-tagosaurus relative to Omeisaurus, Mamenchi-saurus, and Neosauropoda; Theropoda, thePortozuelo trackway, Gongxianosaurus, and Is-anosaurus can be made ancestors without aug-menting treelength. By using the ‘‘CharacterTrace’’ function in MacClade, transformationsfor each of the locomotory synapomorphiesdiscussed above could be examined. The phy-logenetic tree presented in Figure 9 shows theoptimization of the locomotor synapomor-phies discussed above, each of which is im-plied to originate earlier than in the cladisticresult (Table 2).

Early Sauropod Foot Posture

Tetrasauropus and other early trackways notonly record the presence of sauropod track-

makers in time and space, but they also recordthe presence of character states and have thepotential to revise the hypothesized timing oftheir appearance in the fossil record. Morpho-logical features in early sauropod ichnofossilssuggest the early acquisition of several syna-pomorphies whose osteological distributionsare restricted to body fossil subgroups thatappeared later in time (Table 2, Fig. 9).

The Upper Triassic (Carnian) PortozueloFormation trackways from Argentina record asauropod-like trackmaker with a quadrupedalposture, digitigrade manus, and semi-digiti-grade pes much earlier than these features ap-pear in body fossils. If the Portozuelo track-maker is a sauropod, as these features suggest,it implies that many hallmark sauropod lo-comotor features appeared at the beginning ofthe Upper Triassic. The early appearance of


TABLE 2. Estimated temporal origin for several sauropod synapomorphies based on body fossils and ichnofossils.Differences between these estimates are tallied at right; in all cases the origin based on ichnology precedes thatbased on osteology. The two entries for the ‘‘digitigrade manus’’ character reflect alternate interpretations of Shu-nosaurus and Omeisaurus. Upchurch (1998) scored them as derived and resolved digitigrady as a synapomorphy ofEusauropoda; Wilson and Sereno (1998) scored them as derived and resolved digitigrady as a synapomorphy ofNeosauropoda. Because the age of Barapasaurus is not agreed upon, a range of ages was used. Stage name abbre-viations are as in Figure 2 (based on Benton 1993); timescale based on Gradstein et al. 1999. Abbreviation: Myr,million years.

Character Body fossil Ichnofossil Tally

Quadrupedal posture Antenonitrus Late Triassic (Nor) Portozuelo trackway Late Trias-sic (Crn)

9 Myr

Semi-digitigrade pes Barapasaurus Early Jurassic (Sin–Toa)

Portozuelo trackway Late Trias-sic (Crn)

22–44 Myr

Reduction of manualphalanges

Barapasaurus Early Jurassic (Sin–Toa)

Lavini di Marco trackway EarlyJurassic (Het)

2–24 Myr

Laterally directed pedalunguals


Tetrasauropus trackway Late Tri-assic (Nor)

13–35 Myr

Digitigrade manus (Up-church 1998)


Portozuelo trackway Late Trias-sic (Crn)

22–44 Myr

Digitigrade manus (Wil-son and Sereno 1998)

Atlasaurus Middle Jurassic (Bth) Portozuelo trackway Late Trias-sic (Crn)

57 Myr

quadrupedal posture in the Portozuelo track-ways slightly predates their appearance in thebody fossil Antenonitrus (Table 2) but does notimply homoplasy. The early evolution of adigitigrade manus in the Portozuelo and Te-trasauropus trackmakers and the absence ofsauropod trackways indicating a more hori-zontal forefoot posture is consistent with thehypothesis that Shunosaurus and Omeisauruspossessed a digitigrade manus (Upchurch1998; Bonnan 2003). If correct, then a 22–44-Myr difference between the appearance of thefeature in ichnofossils and body fossils is im-plied (Table 2). Likewise, the presence of asemi-digitigrade pes in the Portozuelo and Te-trasauropus trackmakers implies this featureevolved nearly 22–44 Myr earlier than recog-nized in body fossils and was reversed or mis-interpreted in Vulcanodon. Neither the Porto-zuelo nor the Tetrasauropus trackmakers ap-pear to have possessed reduced manual pha-langes, which are interpreted to have evolvedlater in time, with the appearance of the Lavinidi Marco trackmaker in the Hettangian. Tetra-sauropus preserves laterally directed pedal un-guals, but the absence of this feature in later-appearing but more derived forms such as Ta-zoudasaurus, Vulcanodon, and Gongxianosaurusimplies that this feature was acquired in par-allel with the clade including Barapasaurus andmore derived sauropods.

Thus, by the early Late Triassic sauropodshad relatively small forefeet that were held ina nearly vertical, digitigrade posture in whichthe five weight-bearing digits were arrangedin a gentle arch. Distinctive projections fromthe forefoot print indicate an initial stage ofphalangeal reduction in which vestigial digitsare retained. In contrast, the relatively largepes was held in a nearly horizontal, semi-dig-itigrade pose that was supported by a large,fleshy heel. The pes retained four relativelylarge pedal unguals that were oriented alongthe digital axis. This basic eusauropod limbposture was modified in later sauropod sub-groups, which developed a U-shaped manus,reduced the number of manual phalanges,and evolved laterally directed pedal unguals.

Conclusions

The deep history, broad distribution, andmorphological sophistication of Late Triassicand Early Jurassic trackways suggests a richerdiversity of early sauropods than currentlyappreciated. Whereas phylogenetic appraisalsof sauropod descent recognize relatively fewcladogenic events prior to the origin of Neo-sauropoda in the Late Jurassic, preservation ofsauropod trackways and body fossils across awidespread area implies a diverse early sau-ropod fauna thus far absent from the bodyfossil record. The advanced locomotor anato-


my of these early sauropod trackmakers in-dicates that several signature locomotor fea-tures likely evolved during the 10–15-Myr in-terval preceding the appearance of Tetrasau-ropus and Isanosaurus in the fossil record.These results underscore the importance ofichnofossils to understanding vertebrate dis-tribution and locomotor evolution.

Acknowledgments

This manuscript was improved by criticalcomments from P. Barrett, M. Bonnan, M. Car-rano, D. Fisher, and G. P. Wilson. I am gratefulto G. Gierlinski, F. Lando, M. Lockley, and C.Marsicano for discussion of published and un-published sauropod footprints. I also thank P.Galton, P. Upchurch, and A. Yates for allowingme to discuss their manuscripts still in press.

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cham

ber

(0);

abse

nt

(1).

33.

Cor

onoi

d,s

ize:

exte

nd

ing

tod

orsa

lm

arg

inof

jaw

(0);

red

uce

d,n

otex

ten

din

gd

orsa

lto

sple

nia

l(1

);ab

sen

t(2

).34

.To

oth

row

s,sh

ape

ofan

teri

orp

orti

ons:

nar

row

lyar

ched

,an

teri

orp

orti

onof

toot

hro

ws

V-s

hap

ed(0

);br

oad

lyar

ched

,an

teri

orp

orti

onof

toot

hro

ws

U-s

hap

ed(1

);re

ctan

gu

lar,

toot

h-b

eari

ng

por

tion

ofja

wp

erp

end

icu

lar

toja

wra

mi

(2).

35.

Toot

hro

ws,

len

gth

:ext

end

ing

toor

bit

(0);

rest

rict

edan

teri

orto

orbi

t(1

);re

stri

cted

ante

rior

tosu

bn

aria

lfo

ram

en(2

).

36.

Cro

wn

-to-

crow

noc

clu

sion

:ab

sen

t(0

);p

rese

nt

(1).

37.

Toot

hcr

own

s,or

ien

tati

on:a

lig

ned

alon

gja

wax

is,c

row

ns

do

not

over

lap

(0);

alig

ned

slig

htl

yan

tero

lin

gu

ally

,too

thcr

own

sov

erla

p(1

).38

.To

oth

crow

ns,

cros

s-se

ctio

nal

shap

eat

mid

-cro

wn

:ell

ipti

cal

(0);

D-s

hap

ed(1

);cy

lin

dri

cal

(2).

39.

En

amel

surf

ace

text

ure

:sm

ooth

(0);

wri

nk

led

(1).

40.

Mar

gin

alto

oth

den

ticl

es:p

rese

nt

(0);

abse

nt

onp

oste

rior

edg

e(1

);ab

sen

ton

bot

han

teri

oran

dp

oste

rior

edg

es(2

).41

.D

enta

ryte

eth

,nu

mb

er:m

ore

than

20(0

);17

orfe

wer

(1).

42.

Pre

sacr

alb

one

text

ure

:sol

id(0

);sp

ong

y,w

ith

larg

e,op

enin

tern

alce

lls,

‘‘ca

mel

late

’’(1

).43

.P

resa

cral

cen

tra,

pn

eum

atop

ores

(ple

uro

coel

s):a

bse

nt

(0);

pre

sen

t(1

).44

.C

erv

ical

vert

ebra

e,n

um

ber

:9or

few

er(0

);10

(1);

12(2

);13

(3);

15or

gre

ater

(4).

45.

Cer

vic

aln

eura

lar

chla

min

atio

n:

wel

ld

evel

oped

,w

ith

wel

l-d

efin

edla

min

aean

dco

els

(0);

rud

imen

tary

;d

iap

oph

yse

alla

min

aeon

lyfe

ebly

dev

elop

edif

pre

sen

t(1

).46

.C

erv

ical

cen

tra,

arti

cula

rfa

cem

orp

hol

ogy

:am

ph

icoe

lou

s(0

);op

isth

ocoe

lou

s(1

).47

.C

erv

ical

pn

eum

atop

ores

(ple

uro

coel

s),s

hap

e:si

mp

le,u

nd

ivid

ed(0

);co

mp

lex,

div

ided

byb

ony

sep

ta(1

).48

.A

nte

rior

cerv

ical

cen

tra,

hei

ght/

wid

th:l

ess

than

1(0

);ap

pro

xim

atel

y1.

25(1

).49

.M

id-c

erv

ical

cen

tra,

ante

rop

oste

rior

len

gth

/h

eigh

tof

pos

teri

orfa

ce:2

.5–3

.0(0

);.

4(1

).50

.M

id-c

erv

ical

neu

ral

arch

es,h

eigh

t:le

ssth

anth

atof

pos

teri

orce

ntr

um

face

(0);

gre

ater

than

that

ofp

oste

rior

cen

tru

mfa

ce(1

).51

.M

idd

lean

dp

oste

rior

cerv

ical

neu

ral

arch

es,c

entr

opre

zyg

apop

hy

seal

lam

ina

(cp

rl),

shap

e:si

ng

le(0

);d

ivid

ed(1

).52

.P

oste

rior

cerv

ical

and

ante

rior

dor

sal

neu

ral

spin

es,s

hap

e:si

ng

le(0

);bi

fid

(1).

53.

Dor

sal

vert

ebra

e,n

um

ber

:15

(0);

14(1

);13

(2);

12(3

);11

(4);

10or

few

er(5

).54

.D

orsa

ln

eura

lsp

ines

,bre

adth

:nar

row

er(0

)or

mu

chbr

oad

er(1

)tr

ansv

erse

lyth

anan

tero

pos

teri

orly

.55

.A

nte

rior

dor

sal

cen

tra,

arti

cula

rfa

cesh

ape:

amp

hic

oelo

us

(0);

opis

thoc

oelo

us

(1).

56.

Mid

dle

and

pos

teri

ord

orsa

ln

eura

lar

ches

,an

teri

orce

ntr

opar

apop

hy

seal

lam

ina

(acp

l):a

bse

nt

(0);

pre

sen

t(1

).57

.M

idd

lean

dp

oste

rior

dor

sal

neu

ral

arch

es,p

rezy

gop

arap

oph

yse

alla

min

a(p

rpl)

:ab

sen

t(0

);p

rese

nt

(1).

58.

Mid

dle

and

pos

teri

ord

orsa

ln

eura

lar

ches

,sp

inod

iap

oph

yse

alla

min

a(s

pd

l):a

bse

nt

(0);

pre

sen

t(1

).59

.M

idd

lean

dp

oste

rior

dor

sal

neu

ral

arch

essp

inop

ostz

yg

apop

hy

seal

lam

ina

(sp

ol)

shap

e:si

ng

le(0

);d

ivid

ed(1

).60

.M

idd

lean

dp

oste

rior

dor

sal

neu

ral

arch

es,s

pin

odia

pop

hy

seal

lam

ina

(sp

dl)

and

spin

opos

tzy

gap

oph

yse

alla

min

a(s

pol

)co

nta

ct:a

bse

nt

(0);

pre

sen

t(1

).61

.M

idd

lean

dp

oste

rior

dor

sal

neu

ral

spin

es,s

hap

e:ta

per

ing

orn

otfl

arin

gd

ista

lly

(0);

flar

edd

ista

lly,

wit

hp

end

ant,

tria

ng

ula

rla

tera

lp

roce

sses

(1).

62.

Mid

dle

and

pos

teri

ord

orsa

ln

eura

lar

ches

,‘‘i

nfr

adia

pop

hy

seal

’’p

neu

mat

opor

eb

etw

een

acd

lan

dp

cdl:

abse

nt

(0);

pre

sen

t(1

).63

.Sa

cral

vert

ebra

e,n

um

ber

:th

ree

orfe

wer

(0);

fou

r(1

);fi

ve(2

);si

x(3

).64

.Sa

cru

m,s

acri

cost

alyo

ke:a

bse

nt

(0);

pre

sen

t(1

).65

.Sa

cral

vert

ebra

eco

ntr

ibu

tin

gto

acet

abu

lum

:nu

mb

ers

1–3

(0);

nu

mb

ers

2–4

(1).

66.

Cau

dal

tran

sver

sep

roce

sses

:per

sist

thro

ugh

cau

dal

20or

mor

ep

oste

rior

ly(0

);d

isap

pea

rby

cau

dal

15(1

);d

isap

pea

rby

cau

dal

10(2

).67

.F

irst

cau

dal

cen

tru

m,a

rtic

ula

rfa

cesh

ape:

flat

(0);

pro

coel

ous

(1);

opis

thoc

oelo

us

(2);

bico

nve

x(3

).68

.A

nte

rior

cau

dal

cen

tra

(exc

lud

ing

the

firs

t),a

rtic

ula

rfa

cesh

ape:

amp

hip

laty

anor

pla

tyco

elou

s(0

);p

roco

elou

s(1

);op

isth

ocoe

lou

s(2

).69

.A

nte

rior

cau

dal

neu

ral

arch

es,p

resp

inal

lam

ina

(prs

l):a

bse

nt

(0);

pre

sen

t(1

).70

.A

nte

rior

cau

dal

neu

ral

arch

es,p

osts

pin

alla

min

a(p

osl)

:ab

sen

t(0

);p

rese

nt

(1).

71.

An

teri

orca

ud

altr

ansv

erse

pro

cess

es,p

roxi

mal

dep

th:s

hal

low

,on

cen

tru

mon

ly(0

);d

eep

,ext

end

ing

from

cen

tru

mto

neu

ral

arch

(1).

72.

An

teri

oran

dm

idd

leca

ud

alce

ntr

a,ve

ntr

allo

ng

itu

din

alh

ollo

w:a

bse

nt

(0);

pre

sen

t(1

).73

.C

erv

ical

rib

,tu

ber

culu

m-c

apit

ulu

man

gle

:gre

ater

than

908

(0);

less

than

908,

rib

ven

trol

ater

alto

cen

tru

m(1

).74

.‘‘

Fork

ed’’

chev

ron

sw

ith

ante

rior

and

pos

teri

orp

roje

ctio

ns:

abse

nt

(0);

pre

sen

t(1

).75

.‘‘

Fork

ed’’

chev

ron

s,d

istr

ibu

tion

:dis

tal

tail

only

(0);

thro

ugh

out

mid

dle

and

pos

teri

orca

ud

alve

rteb

rae

(1).

76.

Ch

evro

ns,

‘‘cr

us’

’br

idg

ing

dor

sal

mar

gin

ofh

aem

alca

nal

:pre

sen

t(0

);ab

sen

t(1

).77

.C

hev

ron

s:p

ersi

stin

gth

rou

ghou

tat

leas

t80

%of

tail

(0);

dis

app

eari

ng

byca

ud

al30

(1).

78.

Pos

ture

:bip

edal

(0);

colu

mn

ar,o

blig

atel

yqu

adru

ped

alp

ostu

re(1

).79

.Sc

apu

lar

acro

mio

np

roce

ss,s

ize:

nar

row

(0);

broa

d,w

idth

mor

eth

an15

0%m

inim

um

wid

thof

blad

e(1

).80

.H

um

eral

del

top

ecto

ral

atta

chm

ent,

dev

elop

men

t:p

rom

inen

t(0

);re

du

ced

toa

low

cres

tor

rid

ge

(1).

81.

Hu

mer

ald

ista

lco

nd

yle

s,ar

ticu

lar

surf

ace

shap

e:re

stri

cted

tod

ista

lp

orti

onof

hu

mer

us

(0);

exp

osed

onan

teri

orp

orti

onof

hu

mer

alsh

aft

(1).

82.

Hu

mer

ald

ista

lco

nd

yle

,sh

ape:

div

ided

(0);

flat

(1).

83.

Uln

arp

roxi

mal

con

dy

le,s

hap

e:su

btr

ian

gu

lar

(0);

trir

adia

te,w

ith

dee

pra

dia

lfo

ssa

(1).

84.

Uln

arp

roxi

mal

con

dy

lar

pro

cess

es,r

elat

ive

len

gth

s:su

beq

ual

(0);

un

equ

al,a

nte

rior

arm

lon

ger

(1).

85.

Uln

arol

ecra

non

pro

cess

,dev

elop

men

t:p

rom

inen

t,p

roje

ctin

gab

ove

pro

xim

alar

ticu

lati

on(0

);ru

dim

enta

ry,l

evel

wit

hp

roxi

mal

arti

cula

tion

(1).

86.

Rad

ial

dis

tal

con

dy

le,s

hap

e:ro

un

d(0

);su

brec

tan

gu

lar,

flat

ten

edp

oste

rior

lyan

dar

ticu

lati

ng

infr

ont

ofu

lna

(1).

87.

Hu

mer

us-

to-f

emu

rra

tio:

less

than

0.60

(0);

0.60

orm

ore

(1).

88.

Car

pal

bon

es,n

um

ber

:th

ree

orm

ore

(0);

two

orfe

wer

(1).

89.

Car

pal

bon

es,s

hap

e:ro

un

d(0

);bl

ock

-sh

aped

,wit

hfl

atte

ned

pro

xim

alan

dd

ista

lsu

rfac

es(1

).90

.M

etac

arp

us,

shap

e:sp

read

ing

(0);

bou

nd

,wit

hsu

bp

aral

lel

shaf

tsan

dar

ticu

lar

surf

aces

that

exte

nd

hal

fth

eir

len

gth

(1).

91.

Met

acar

pal

s,sh

ape

ofp

roxi

mal

surf

ace

inar

ticu

lati

on:g

entl

ycu

rvin

g,f

orm

ing

a90

8ar

c(0

);U

-sh

aped

,su

bte

nd

ing

a27

08ar

c(1

).92

.M

etac

arp

alI

dis

tal

con

dy

le,t

ran

sver

seax

isor

ien

tati

on:b

evel

edap

pro

xim

atel

y20

8p

roxi

mod

ista

lly

(0)

orp

erp

end

icu

lar

(1)

wit

hre

spec

tto

axis

ofsh

aft.

93.

Man

ual

dig

its

IIan

dII

I,p

hal

ang

eal

nu

mb

er:2

-3-4

-3-2

orm

ore

(0);

red

uce

d,2

-2-2

-2-2

orle

ss(1

);ab

sen

tor

un

ossi

fied

(2).

94.

Man

ual

ph

alan

xI.

1,sh

ape:

rect

ang

ula

r(0

);w

edg

e-sh

aped

(1).

95.

Man

ual

non

un

gu

alp

hal

ang

es,s

hap

e:lo

ng

erp

roxi

mod

ista

lly

than

broa

dtr

ansv

erse

ly(0

);br

oad

ertr

ansv

erse

lyth

anlo

ng

pro

xim

odis

tall

y(1

).96

.P

elv

is,a

nte

rior

brea

dth

:nar

row

,ili

alo

ng

eran

tero

pos

teri

orly

than

dis

tan

cese

par

atin

gp

reac

etab

ula

rp

roce

sses

(0);

broa

d,d

ista

nce

bet

wee

np

reac

etab

ula

rpro

cess

esex

ceed

san

tero

pos

teri

orle

ng

thof

ilia

(1).

97.

Iliu

m,i

sch

ial

ped

un

cle

size

:lar

ge,

pro

min

ent

(0);

low

,rou

nd

ed(1

).98

.Il

iac

blad

ed

orsa

lm

arg

in,s

hap

e:fl

at(0

);se

mic

ircu

lar

(1).

99.

Pu

bic

apro

n,s

hap

e:fl

at(s

trai

ght

sym

ph

ysi

s)(0

);ca

nte

dan

tero

med

iall

y(g

entl

eS-

shap

edsy

mp

hy

sis)

(1).

100.

Isch

ial

blad

e,le

ng

th:m

uch

shor

ter

than

(0)

oreq

ual

toor

lon

ger

than

(1)

pu

bic

blad

e.10

1.Is

chia

ld

ista

lsh

aft,

shap

e:tr

ian

gu

lar,

dep

thof

isch

ial

shaf

tin

crea

ses

med

iall

y(0

);bl

adel

ike,

med

ial

and

late

ral

dep

ths

sub

equ

al(1

).10

2.Is

chia

ld

ista

lsh

afts

,cro

ss-s

ecti

onal

shap

e:V

-sh

aped

,for

min

gan

ang

leof

nea

rly

508

wit

hea

chot

her

(0);

flat

,nea

rly

cop

lan

ar(1

).10

3.Fe

mor

alfo

urt

htr

och

ante

r,d

evel

opm

ent:

pro

min

ent

(0);

red

uce

dto

cres

tor

rid

ge

(1).

104.

Fem

oral

less

ertr

och

ante

r:p

rese

nt

(0);

abse

nt

(1).

105.

Fem

oral

mid

shaf

t,tr

ansv

erse

dia

met

er:s

ub

equ

alto

(0),

125–

150%

,or

(1)

atle

ast

185%

(2)

ante

rop

oste

rior

dia

met

er.

106.

Fem

oral

dis

tal

con

dy

les,

rela

tive

tran

sver

sebr

ead

th:s

ub

equ

al(0

);ti

bial

mu

chbr

oad

erth

anfi

bula

r(1

).10

7.T

ibia

lp

roxi

mal

con

dy

le,s

hap

e:n

arro

w,l

ong

axis

ante

rop

oste

rior

(0);

exp

and

edtr

ansv

erse

ly,c

ond

yle

sub

circ

ula

r(1

).10

8.T

ibia

lcn

emia

lcr

est,

orie

nta

tion

:pro

ject

ing

ante

rior

ly(0

)or

late

rall

y(1

).10

9.T

ibia

ldis

talp

oste

rove

ntr

alp

roce

ss,s

ize:

broa

dtr

ansv

erse

ly,c

over

ing

pos

teri

orfo

ssa

ofas

trag

alu

s(0

);sh

orte

ned

tran

sver

sely

,pos

teri

orfo

ssa

ofas

trag

alu

sv

isib

lep

oste

rior

ly(1

).11

0.F

ibu

la,p

roxi

mal

tibi

alsc

ar,d

evel

opm

ent:

not

wel

lm

arke

d(0

);w

ell

mar

ked

and

dee

pen

ing

ante

rior

ly(1

).11

1.F

ibu

la,l

ater

altr

och

ante

r:ab

sen

t(0

);p

rese

nt

(1).

112.

Fib

ula

rd

ista

lco

nd

yle

,siz

e:su

beq

ual

tosh

aft

(0);

exp

and

edtr

ansv

erse

ly,m

ore

than

twic

em

idsh

aft

brea

dth

(1).

113.

Ast

rag

alu

s,sh

ape:

rect

ang

ula

r(0

);w

edg

e-sh

aped

,wit

hre

du

ced

ante

rom

edia

lco

rner

(1).

114.

Ast

rag

alu

s,fo

ram

ina

atb

ase

ofas

cen

din

gp

roce

ss:p

rese

nt

(0);

abse

nt

(1).

115.

Ast

rag

alu

s,as

cen

din

gp

roce

ssle

ng

th:l

imit

edto

ante

rior

two-

thir

ds

ofas

trag

alu

s(0

);ex

ten

din

gto

pos

teri

orm

arg

inof

astr

agal

us

(1).

116.

Ast

rag

alu

s,p

oste

rior

foss

ash

ape:

un

div

ided

(0);

div

ided

byve

rtic

alcr

est

(1).

117.

Dis

tal

tars

als

3an

d4:

pre

sen

t(0

);ab

sen

tor

un

ossi

fied

(1).

118.

Met

atar

sus,

pos

ture

:bou

nd

(0);

spre

adin

g(1

).11

9.M

etat

arsa

lI

pro

xim

alco

nd

yle

,tra

nsv

erse

axis

orie

nta

tion

:per

pen

dic

ula

rto

(0)

oran

gle

dve

ntr

omed

iall

yap

pro

xim

atel

y15

8to

(1)

axis

ofsh

aft.

120.

Met

atar

sal

Id

ista

lco

nd

yle

,tra

nsv

erse

axis

orie

nta

tion

:per

pen

dic

ula

rto

(0)

oran

gle

dd

orso

med

iall

yto

(1)

axis

ofsh

aft.

121.

Met

atar

sal

Id

ista

lco

nd

yle

,pos

tero

late

ral

pro

ject

ion

:ab

sen

t(0

);p

rese

nt

(1).

122.

Met

atar

sal

I,m

inim

um

shaf

tw

idth

:les

sth

an(0

)or

gre

ater

than

(1)

that

ofm

etat

arsa

lsII

–IV

.12

3.M

etat

arsa

lI

and

Vp

roxi

mal

con

dy

le,s

ize:

smal

ler

than

(0)

orsu

beq

ual

to(1

)th

ose

ofm

etat

arsa

lsII

and

IV.

124.

Met

atar

sal

III

len

gth

:mor

eth

an30

%(0

)or

less

than

25%

(1)

that

ofti

bia.

125.

Met

atar

sals

III

and

IV,m

inim

um

tran

sver

sesh

aft

dia

met

ers:

sub

equ

alto

(0)

orle

ssth

an65

%(1

)th

atof

met

atar

sals

Ior

II(1

).12

6.M

etat

arsa

lV

,len

gth

:sh

orte

rth

an(0

)or

atle

ast

70%

(1)

len

gth

ofm

etat

arsa

lIV

.

127.

Ped

aln

onu

ng

ual

ph

alan

ges

,sh

ape:

lon

ger

pro

xim

odis

tall

yth

anbr

oad

tran

sver

sely

(0);

broa

der

tran

sver

sely

than

lon

gp

roxi

mod

ista

lly

(1).

128.

Ped

ald

igit

sII

–IV

,pen

ult

imat

ep

hal

ang

es,d

evel

opm

ent:

sub

equ

alin

size

tom

ore

pro

xim

alp

hal

ang

es(0

);ru

dim

enta

ryor

abse

nt

(1).

129.

Ped

alu

ng

ual

s,or

ien

tati

on:a

lig

ned

wit

h(0

)or

defl

ecte

dla

tera

lto

(1)

dig

itax

is.

130.

Ped

ald

igit

Iu

ng

ual

,len

gth

rela

tive

top

edal

dig

itII

un

gu

al:s

ub

equ

al(0

);25

%la

rger

than

that

ofd

igit

II(1

).13

1.P

edal

dig

itI

un

gu

al,l

eng

th:s

hor

ter

(0)

orlo

ng

er(1

)th

anm

etat

arsa

lI.

132.

Ped

alu

ng

ual

I,sh

ape:

broa

der

tran

sver

sely

than

dor

sove

ntr

ally

(0);

sick

lesh

aped

,mu

chd

eep

erd

orso

ven

tral

lyth

anbr

oad

tran

sver

sely

(1).

133.

Ped

alu

ng

ual

II–I

II,s

hap

e:br

oad

ertr

ansv

erse

lyth

and

orso

ven

tral

ly(0

);si

ckle

shap

ed,m

uch

dee

per

dor

sove

ntr

ally

than

broa

dtr

ansv

erse

ly(1

).13

4.P

edal

dig

itIV

un

gu

al,d

evel

opm

ent:

sub

equ

alin

size

tou

ng

ual

sof

ped

ald

igit

sII

and

III

(0);

rud

imen

tary

orab

sen

t(1

).13

5.[V

ulc

anod

onau

tap

omor

phy

:mar

ked

dor

sove

ntr

alfl

atte

nin

gof

the

un

gu

als

ofp

edal

dig

its

IIan

dII

I.]

136.

[Shu

nosa

uru

sau

tap

omor

phy

:str

ap-s

hap

edp

tery

goid

.]13

7.[S

huno

sau

rus

auta

pom

orp

hy:a

nte

rior

por

tion

ofth

eax

ial

neu

ral

spin

ep

rom

inen

t.]

138.

[Shu

nosa

uru

sau

tap

omor

phy

:‘‘p

ostp

arap

ophy

ses’

’on

pos

teri

ord

orsa

lve

rteb

rae.

]13

9.[S

huno

sau

rus

auta

pom

orp

hy:t

erm

inal

tail

clu

bco

mp

osed

ofat

leas

tth

ree

enla

rged

,co-

ossi

fied

cau

dal

vert

ebra

ew

ith

two

der

mal

spin

es.]

140.

[Bar

apas

auru

sau

tap

omor

phy

:pos

teri

ord

orsa

lve

rteb

rae

wit

hsl

it-s

hap

edn

eura

lca

nal

.]14

1.[P

atag

osau

rus

auta

pom

orp

hy:c

erv

ical

vert

ebra

ew

ith

elon

gat

ece

ntr

opre

zyg

apop

hyse

alla

min

aean

d‘‘

hoo

ded

’’in

fra-

pre

zyg

apop

hyse

alco

els.

]14

2.[P

atag

osau

rus

auta

pom

orp

hy:a

nte

rior

dor

sal

vert

ebra

ew

ith

elon

gat

ece

ntr

opos

tzy

gap

ophy

seal

and

pos

tzy

god

iap

ophy

seal

lam

inae

.]14

3.[P

atag

osau

rus

auta

pom

orp

hy:t

ran

sver

sely

nar

row

thir

dsa

cral

vert

ebra

.]14

4.[P

atag

osau

rus

auta

pom

orp

hy:p

roxi

mal

hu

mer

us

wit

hm

edia

nri

dg

eon

pos

teri

oras

pec

t.]

145.

[Om

eisa

uru

sau

tap

omor

phy

:max

illa

ryas

cen

din

gra

mu

sw

ith

dor

sove

ntr

ally

exp

and

edd

ista

len

d.]

146.

[Om

eisa

uru

sau

tap

omor

phy

:dis

talm

ost

cau

dal

chev

ron

sfu

sed

toan

teri

orm

ost

por

tion

ofve

ntr

alce

ntr

um

.]14

7.[M

amen

chis

auru

sau

tap

omor

phy

:acc

esso

ryp

rezy

god

iap

ophy

seal

lam

ina

inan

teri

ord

orsa

lve

rteb

rae.

]14

8.[M

amen

chis

auru

sau

tap

omor

phy

:‘‘f

orke

d’’

chev

ron

sin

mid

-cau

dal

reg

ion

wit

han

teri

oran

dp

oste

rior

pro

ject

ion

sor

ien

ted

less

than

458

toea

chot

her

.]14

9.[M

amen

chis

auru

sau

tap

omor

phy

:uln

aw

ith

ante

rior

arm

ofp

roxi

mal

con

dy

len

earl

yon

e-h

alf

the

len

gth

ofsh

aft.

]15

0.[M

amen

chis

auru

sau

tap

omor

phy

:fem

ur

wit

hm

edia

lly

exp

and

edti

bial

con

dy

le.]

151.

[Mam

ench

isau

rus

auta

pom

orp

hy:p

roxi

mal

hal

fof

fem

oral

shaf

tbr

oad

erth

and

ista

lh

alf.

]15

2.[N

eosa

uro

pod

aau

tap

omor

phy

:su

pra

tem

por

alfe

nes

trae

sep

arat

edby

twic

elo

ng

est

dia

met

erof

one

sup

rate

mp

oral

fen

estr

a.]

153.

[Neo

sau

rop

oda

auta

pom

orp

hy:p

tery

goid

pal

atin

era

mu

sw

ith

step

ped

dor

sal

mar

gin

.]15

4.[N

eosa

uro

pod

aau

tap

omor

phy

:bas

isp

hen

oid

/b

asip

tery

goid

rece

ss.]

155.

[Neo

sau

rop

oda

auta

pom

orp

hy:e

xter

nal

man

dib

ula

rfe

nes

tra

clos

ed.]

156.

[Neo

sau

rop

oda

auta

pom

orp

hy:m

arg

inal

toot

hd

enti

cles

abse

nt

onb

oth

ante

rior

and

pos

teri

orm

arg

ins

ofcr

own

.]15

7.[N

eosa

uro

pod

aau

tap

omor

phy

:ch

evro

ns

lack

‘‘cr

us’

’br

idg

ing

dor

sal

mar

gin

ofh

aem

alca

nal

.]15

8.[N

eosa

uro

pod

aau

tap

omor

phy

:car

pal

bon

esnu

mb

ertw

oor

few

er.]

159.

[Bli

kan

asau

rus

auta

pom

orp

hy:fi

bula

wit

hen

larg

ed,o

void

,ven

trom

edia

lly

orie

nte

dd

ista

lar

ticu

lar

surf

ace.

]16

0.[A

nten

onit

rus

auta

pom

orp

hy:v

entr

alri

dg

eon

hyp

osp

hen

esof

dor

sal

vert

ebra

e.]

161.

[Ant

enon

itru

sau

tap

omor

phy

:hu

mer

us

dee

psu

lcu

sad

jace

nt

the

late

rod

ista

lm

arg

inof

the

del

top

ecto

ral

cres

t.]

162.

[Gon

gxia

nosa

uru

sau

tap

omor

phy

:cor

acoi

dfo

ram

enab

sen

t.]

163.

[Isa

nosa

uru

sau

tap

omor

phy

:fem

ur

wit

hsi

gm

oid

fou

rth

troc

han

ter.

]16

4.[L

avin

id

iM

arco

auta

pom

orp

hy.]

165.

[Tet

rasa

uro

pus

auta

pom

orp

hy.]

166.

[Por

tozu

elo

auta

pom

orp

hy.]

167.

[Pro

sau

rop

oda

auta

pom

orp

hy:d

enta

ryto

oth

1in

set.

]16

8.[P

rosa

uro

pod

aau

tap

omor

phy

:man

ual

dig

itI-

ph

alan

x1,

axis

thro

ugh

dis

tal

con

dy

les

rota

ted

608

ven

trol

ater

ally

.]16

9.[P

rosa

uro

pod

aau

tap

omor

phy

:met

atar

sal

IIp

roxi

mal

arti

cula

rsu

rfac

eh

ourg

lass

-sh

aped

.]17

0.[T

her

opod

aau

tap

omor

phy

:in

tram

and

ibu

lar

join

tp

rese

nt.

]17

1.[T

her

opod

aau

tap

omor

phy

:cer

vic

alep

ipop

hyse

sp

ron

g-s

hap

ed.]

172.

[Th

erop

oda

auta

pom

orp

hy:i

nte

rnal

cav

itat

ion

ofce

ntr

aan

dlo

ng

bon

esw

ell

dev

elop

ed.]

173.

Stra

tig

rap

hic

char

acte

r:A

nis

ian

(0);

Car

nia

n(1

);N

oria

n(2

);R

hae

tian

(3);

Het

tan

gia

n(4

);Si

nem

uri

an(5

);P

lien

sbac

hia

n(6

);To

arci

an(7

);B

ajoc

ian

(8);

Bat

hon

ian

(9);

Cal

lov

ian

(A);

Oxf

ord

ian

(B).

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