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doi:10.1144/SP315.18 2009; v. 315; p. 255-269 Geological Society, London, Special Publications

Martin G. Lockley, Richard T. McCrea and Masaki Matsukawa

for a global radiationthe basal Cretaceous of SE Asia and North America: implications Ichnological evidence for small quadrupedal ornithischians from

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Ichnological evidence for small quadrupedal ornithischians

from the basal Cretaceous of SE Asia and North America:

implications for a global radiation

MARTIN G. LOCKLEY1*, RICHARD T. MCCREA2 & MASAKI MATSUKAWA3

1Dinosaur Tracks Museum, University of Colorado at Denver, Campus Box 172, PO Box 173364,

Denver, CO 80217-3364, USA2Peace Region Palaeontology Research Centre, Box 1540, Tumbler Ridge,

B.C. V0C 2W0, Canada3Department of Environmental Sciences, Tokyo Gakugei University, Koganei, Tokyo,

184-8501, Japan

*Corresponding author (e-mail: [email protected])

Abstract: Tracks of small quadrupedal ornithischians with five manual and four pedal digits havebeen recorded from sedimentary rocks near the Late Jurassic–Early Cretaceous (Tithonian–Berriasian) boundary in NE Thailand and British Columbia. These are compared with largertracks of gracile, quadrupedal ornithopods from the earliest Cretaceous of Spain and smallertracks of a quadruped of unknown age from Zimbabwe. The Thai and Canadian tracks aresimilar to the Early Jurassic (Liassic) ichnogenus Anomoepus and the small ornithopod tracksfrom the Late Jurassic of Spain. They are the only known post-Liassic ornithischian tracks inwhich up to five discrete manus digit impressions are clearly visible. Based on strong heteropody(manus much smaller than pes) in all cases we infer an ornithopod trackmaker rather than anotherornithischian. The scattered, but widespread earliest Cretaceous occurrence of this ichnotaxon,herein assigned to Neoanomoepus perigrinatus ichnogen. and ichnosp. nov., on the basis of typematerial from Canada, suggests that these hitherto unknown earliest Cretaceous ichnofaunasmay represent a radiation of small basal ornithopods (pes length less than 15 cm), appearingbefore the widespread radiation of large ornithopods (pes length up to 60 cm or more) later inthe Neocomian (Valanginian–Barremian), Aptian–Albian and Late Cretaceous. The primitivecondition of the trackmaker is indicated by the pedal and manual morphology, which consists offour and five digits respectively that are not enclosed by well-developed fleshy padding or integu-ment. In contrast, all larger Cretaceous ornithopod tracks, mostly from post-Berriasian strata, haveonly three pedal digits enclosed in fleshy pads and a manus in which all functional digits arereduced and enclosed by substantial flesh.

Trackways of small ornithopod dinosaurs arestill comparatively rare. The most famous, and first-described, example of a trackway with what appearsto be unequivocal ornithopod or basal ornithischiancharacteristics (five-toed manus and four-toed pes)is the well-known Early Jurassic ichnogenusAnomoepus (Hitchcock 1848; Lull 1953; Olsen &Rainforth 2003). This ichnogenus (Fig. 1) is wellknown from the early Jurassic of the eastern USAand may be abundant in southern Africa (Ellenber-ger 1972) but was, until recently, relatively poorlyknown from other regions such as the westernUSA (Lockley & Hunt 1995; Lockley & Gierlinski2006), Europe (Avanzini et al. 2001; Gierlinski1991; Gierlinski et al. 2004; Lockley & Meyer2000) and Australia (Thulborn 1994). Anomoepusis characterized, in well-preserved examples,by a four-toed pes, sometimes with metatarsal

impressions, and a five-toed manus. In manycases, however, Anomoepus is hard to identifywith confidence unless both manus and pes tracksare found (Lockley & Gierlinski 2006). In manycases the trackmaker was progressing bipedally,and hallux (digit I of the pes) is inconspicuous andmay not be impressed. Moreover, if not well pre-served it may be difficult to distinguish Anomoepustracks from a number of other tridactyl or tetradactyldinosaur footprints. However, there may be someclues to the ornithischian affinity of incompleteAnomoepus or Anomoepus-like ichnites in thegeneral configuration of the trackway. As indicatedby Lockley (1999), ornithopods typically, indeedconsistently, have trackways that are relativelywide in comparison with those of theropods andconsistently take shorter steps, with shorter(wider) pes tracks that toe inward.

From: BUFFETAUT, E., CUNY, G., LE LOEUFF, J. & SUTEETHORN, V. (eds) Late Palaeozoic and Mesozoic Ecosystemsin SE Asia. The Geological Society, London, Special Publications, 315, 255–269.DOI: 10.1144/SP315.18 0305-8719/09/$15.00 # The Geological Society of London 2009.

Despite this distinctive combination of charac-ters there are few known examples of post-EarlyJurassic tracks that have been assigned unequivo-cally to Anomoepus. Moreover, with the possibleexception of the enigmatic, presumed heterodonto-saurid track Delatorrichnus from the Middle Juras-sic of Argentina (Casamiquela 1964), there is onlyone reported example of a Late Jurassic ornithopodtrack that reveals quadrupedal progression. This is ahitherto undescribed specimen from the Late Juras-sic of Asturias (Garcıa Ramos et al. 2006; Lockleyet al. 2009). Dinehichnus is the only other formallynamed Late Jurassic track attributed to an

ornithopod (Lockley et al. 1998). It is not until theCretaceous that we find abundant ichnologicalevidence of quadrupedal and bipedal ornithopodsin many regions including Asia (You & Azuma1995; Lockley & Matsukawa 1998). However,most of the larger quadrupedal forms had a hoof-likemanus without clear separation of the digit traces.Other than the Cretaceous material describedherein, the only other footprints of small quadrupe-dal ornithopods, with distinct digit impressions,hitherto named from the Early Cretaceous areHypsiloichnus (Stanford et al. 2004). All othertracks of quadrupedal Cretaceous ornithopods

Fig. 1. Type Anomoepus from the Early Jurassic of New England (after Olsen & Rainforth 2003, fig 19.5). (a) Anidealized composite of walking pes and sitting manus and pes with metatarsal impressions; (b, c) composite trackwaysshowing quadrupedal and bipedal impressions, respectively. rm, right manus; rp, right pes; lm, left manus; lp,left pes; t, tail.

M. G. LOCKLEY ET AL.256

indicate much larger trackmakers whose hand andfoot morphology bears little or no resemblance tothat of the Anomoepus trackmaker.

Trackways of large ornithopod dinosaurs arefairly well known in the Cretaceous. Most, how-ever, are large with three well-padded pes impres-sions indicating the derived condition typical ofiguanodontids or hadrosaurs (e.g. Iguanodontipus,Sarjeant et al. 1998). Some indicate quadrupedalprogression, but in such cases the manus is revealedto be a relatively small sub-circular to oval hoof-likeimpression that rarely reveals any differentiationof digit traces.

Only recently have reports emerged of Cretac-eous trackways that evidently represent small quad-rupedal ornithopods that exhibit the primitive,Anomoepus-like, condition of four pedal and fivemanual digits (Fig. 2). These discoveries have beenmade in such widely divergent localities as Thailand(Buffetaut & Suteethorn 1993; Le Loeuff et al. 2002;Matsukawa et al. 2006), Zimbabwe (Lingham-Soliar & Broderick 2000) and Canada (this study).Other distinctive ornithopod morphotypes have

been recorded from Spain (Perez-Lorente et al.1997). The primary purpose of this paper there-fore is to describe these Cretaceous examples indetail and discuss their ichnotaxonomic status.A secondary objective is, where possible, to placethe tracks in their biostratigraphic, palaeobio-geographical and palaeoecological context anddiscuss the extent to which they may shed light onthe timing of the Early Cretaceous ornithopodradiation.

Track material and geological context

Thailand specimens

Tracks that closely resemble the Canadian speci-mens are known from the Phra Wihan Formationof NE Thailand at a site known as Hin Lat PaChad (Buffetaut & Suteethorn 1993; Le Loeuffet al. 2002; Matsukawa et al. 2006). The tracksoccur at a single isolated locality in a jungleregion. The outcrop consists of a single bedding

Fig. 2. Locality map showing the type locality for Neoanomoepus periginatus ichnogen. et ichnosp. nov. in BritishColumbia, and the occurrence of other probable Neoanomoepus or Neoanomoepus-like ichnites from Thailand,Zimbabwe, Spain and Canada.

TRACKS OF SMALL ORNITHISCHIANS 257

plane of about 25 m � 10 m with 10 trackwaysmostly trending from north to south (Fig. 3). Asnoted by Buffetaut & Suteethorn (1993, p. 77),some trackways ‘sometimes show a small, appar-ently tridactyl manus impression lateral to the pesimpression . . . [which] . . . together with thegeneral shape of the footprints suggest that theymay have been left by ornithischians’. We agreewith this interpretation generally, but note that thepes tracks sometimes show faint impressions ofthe hallux and are therefore tetradactyl, and that atleast one manus track is also tetradactyl, and maybe interpreted as pentadactyl.

Le Loeuff et al. (2002, p. 291) considered themanus tracks ‘reminiscent’ of Anomoepus interme-dius and A. scambus, but they stopped short ofapplying these names to the illustrated material(Le Loeuff et al. 2002, fig. 4). According to Olsen& Rainforth (2003), A. intermedius is a synonymof A. scambus, which is the only recognizableichnospecies in the ichnogenus Anomoepus.However, Lockley & Gierlinski (2006) disputedthe claim that the ichnogenus is monospecific.

The Thai material was re-examined byMatsukawa et al. (2006), who illustrated two track-ways (Fig. 3) with both manus and pes footprintsdemonstrating that in some cases the former arepentadactyl and the latter tetradactyl. In that paper,Matsukawa et al. (2006) reproduced a previouslyunpublished map of the site in which 10 trackwayswere numbered. Comparison of these two maps(Fig. 3a and b), which use the same numberingscheme, reveals that trackways 3, 5, 6 and 9 arenot included because they were covered by sedimentat the time they were studied by Matsukawa et al.(2006). Moreover trackways 3, 5 and 6 are probablycontinuations of other trackways such as 1, 4 or7. Nevertheless, these trackways (1, 4 and 7) allhave associated manus impressions (Fig. 3c–e),whereas other trackways (e.g. 2 and 3) indicatebiped progression on a functionally tridactyl pes,probably attributable to ornithopods. The possibilitythat some tridactyl tracks are theropodan cannot bediscounted. One large tetradactyl track, with curveddigit impressions, may be attributable to a crocdodi-lian (Fig. 3f).

Fig. 3. Tracks from the Hin Lat Pra Chad site in Thailand (after Matsukawa et al. 2006). (a) Preliminary mapproduced in local field guide with numbered trackway segments 1–10. Trackway 1 may be a continuation of 4, and 6may be a continuation of 7. (b) Detailed map of northern section showing trackways 1, 2, 4, 7, 8 and 10 (with detailof 10), current ripple vector, and source of track replicas (University of Colorado at Denver 214.54–58) and Phu KumKao Dinosaur Museum (PKKDM) replica. (c) Composite of ornithischian manus (M)–pes (P) set from trackway 1,showing 4 pes and 5 manus digit impressions. (d) Detail of trackway 7 also showing 4 pes digit impressions. (e) Detail oftrackway 4. (f) Detail of large track (trackway 8). All track detail scale bars 10 cm.


The Phra Wihan Formation is considered asNeocomian in age, or may be Berriasian. The prob-able age for the Phra Wihan Formation given byBuffetaut & Suteethorn (1993) is Late Jurassic.However, in a later paper (Buffetaut et al. 1997),they gave a revised age of early Cretaceous (Berria-sian–Barremian) based on palynomorphs (Raceyet al. 1994, 1996). This age estimate, followed byLe Loeuff et al. (2002) and Matsukawa et al.(2006), is further supported by Racey & Goodall(2009).

Canadian specimens

Well-preserved and diagnostic small ornithischianichnites are herein reported from the coal-bearingMist Mountain Formation of the Elk Valley Coalregion in SE British Columbia, Canada. About twodozen clear tracks are preserved as natural castson the underside of a sandstone slab of about 3 m2

(Figs 4–6). In total almost 100 tracks may be dis-cerned by careful observation of the specimen,mould and replica under controlled lighting con-ditions. Several trackway segments are discernible,including at least three with three or more consecu-tive manus–pes sets (Fig. 5, Table 1). The precisestratigraphic location from which the tracks orig-inate is not known. However, the approximatelocation, within the Fording River Coal mine, isknown, and all the strata in the mine are Tithonianto Berriasian. The tracks are thought to originatefrom the Berriasian part of the section. The predo-minant lithology in this region is a coal-bearingsequence consisting of grey mudstones and silt-stones with intercalated buff-coloured sandstoneand coals (Bustin & Smith 1993). Tracks are

abundant and include a variety of tridactyl tracksattributable to bipedal theropods, bipedal ornitho-pods and possibly water- or shore-birds (McCrea& Buckley 2005a). A few isolated sauropod tracksand one trackway have also been recorded(McCrea et al. 2005). As many as 80 track-bearingspecimens have been set aside as outdoor displaysnear the mine entrance and more than a dozen speci-mens have been replicated for scientific study (seereference to specimens below). Plant fossils arealso abundant, and locally moulds of freshwaterunionid or unionid-like clams can be found.

The discovery of this important slab appears toconfirm the report of Currie (1989, p. 294), whosuggested that a trackway of a tridactyl biped,with inward pes rotation, from the Mist MountainFormation, British Columbia, could be ‘identifiedas Anomoepus’. However, this trackway, in theTyrrell Museum (TMP 85.105.1), reveals no diag-nostic manus tracks. Nevertheless, Currie’s identifi-cation was prescient given the quadrupedaltrackway with manus traces described herein.

Institutional abbreviations for replicas used inthe systematic descriptions (below) are FGM forFraser–Fort George Regional Museum, BritishColumbia; and CU for the University of Coloradoat Denver, Dinosaur Tracks Museum.

Trackways from Spain

Although there are a number of reports of track-ways of quadrupedal ornithopods from the EarlyCretaceous of Spain, and other parts of Europe,North America and Asia, almost all examplesother than those cited above refer to large trackswith well-rounded manus impressions in which

Fig. 4. Photograph of large Neoanomoepus track-bearing slab (field number A48) from Mist Mountain Formation,British Columbia. It should be noted that the tracks are preserved as natural casts. (Compare with Fig. 5.)


Fig. 5. Map of large track-bearing slab (field number A48) from Mist Mountain Formation, British Columbia.(Compare with Fig. 4, but note reversal to show non-natural cast aspect.) Trackway A is holotype for Neoanomoepus(see Figs 6 and 8). Details of trackways A–C are shown in Figure 8. Replica of complete slab in Fraser–Fort GeorgeRegional Museum (FGM 002.01.20).

Fig. 6. Photograph of the manus–pes set R1 from trackway A, the holotype of Neoanomoepus (FGM 002.01.20 and CU199.22) (compare with trackway A of Fig. 5).


individual manual digit traces are not differentiatedor discernible. One exception of possible interest isthe Tithonian–Berriasian ornithopod trackwayreported by Perez-Lorente et al. (1997) from LasCerradicas, Spain (see Lockley & Meyer 2000,fig. 8.4; Lockley & Wright 2001). This example isselected because it was, previously, the smallestand earliest described trackway of a quadrupedalornithopod from the Cretaceous. One of us(M.G.L.) had the opportunity to observe thesetracks and obtain accurate scale tracings (Fig. 7),which compare favourably with the largest track-ways of Dinehichnus from the Late Cretaceous ofNE Arizona. (Fig. 7). We present only a brief com-parative analysis below, as the site is currently underinvestigation by others (see Acknowledgements).We conclude that in several respects the Cerradicastracks are intermediate in character between Dine-hichnus tracks and larger ornithopod tracks suchas Iguanodontipus (Sarjeant et al. 1998). The ichno-taxonomic interpretation of these tracks is proble-matic for several reasons. The pes tracks areelongate and segmented with sharp claw traces,which make them morphologically convergentwith theropod tracks, and similar to the recentlydescribed ichnogenus Asianopodus (Matsukawaet al. 2005). Furthermore, the Cerradicas pestracks, which average about 22–23 cm in length,are considerably larger than the examples describedfrom Canada and Thailand; however, they retainsome of the primitive characteristics of Anomoepus,such as discrete phalangeal pads and relatively sharpclaw traces. However, there is no trace of a hallux

on the pes. Likewise, the manus is not robust androunded or oval as in most large iguanodontid andhadrosaurid tracks, but is instead gracile andelongate with a rhomboidal shape, lacking clearlydifferentiated digit impressions, although bluntdigit tip traces are inferred.

Trackways from Zimbabwe

Lingham-Soliar & Broderick (2000) reportedan enigmatic dinosaurian trackway from theMesozoic Dande Sandstone Formation, whichis broadly dated as ?Early Jurassic to Mid-Cretaceous. This ichnite might be consideredsimilar to Delatorrichnus (G. Gierlinski, pers.comm.). The trackway consists of 10 small pestracks (about 5 cm long) and corresponding smallmanus tracks (2–3 cm long) associated with eightof the 10 pes tracks (Fig. 8). In this regard thetracks are similar in size to the smallest of the Thai-land trackways. A second trackway consists of fiveor six small pes tracks, also about 5 cm long, withno associated manus.

Lingham-Soliar & Broderick (2000) suggestedthat the tracks might be similar to the Late Triassicichnogenus Atreipus because of the tridactyl manusand pes. As stated above, there are very few track-ways attributable to small quadrupedal dinosaurs,or dinosaur relatives. Indeed, prior to the discoveryof the previously unnamed Thailand specimens(Le Loeuff et al. 2002; Matsukawa et al. 2006)and the Canadian tracks herein assigned to Neoano-moepus, the only small quadrupedal tracks that

Table 1. Measurements for standard trackway parameters for three Neoanomoepus trackways from theMist Mountain Formation

Track number Pes L:W Manus L:W Step Stride Pace Ang.

A R 1 (19.0):9.8 4.2:6.4 – – –A L 2 12.0:10.5 4.0:4.4 29.4 55.0 142A R 2 10.0:13.7 4.1:4.8 27.3 – –B R 1 19.2:10.7 3.5:5.0 – – –B L 1 (14.2):11.7 (4.5):(7.0) 36.1 52.5 107B R 2 (14.5):13.5 3.0:5.5 25 44.0 90B L 2 13.0:11.0 3.0:5.5 32.5 54.3 132B R 3 ? 14.8:11.4 2.5:(3.5) 26.3 48.7 135B L 3 ? 12.0:11.0 4.7:6.8 28.5 57.2 143B R 4 ? 11.5:10.5 5.1:6.6 31.6 – –C R 1 (16.0): – – – – –C L 1 13.9:10.5 3.8:6.1 32.3 47.0 109C R 2 16.0:9.8 2.5:5.4 25.5 37.0 115C L 2 16.1:11.4 – 19.5 – –

Mean – – 31.1 49.5 122

L, length; W, width; Pace Ang., pace angulation for pes. Step measurements given for pes in row corresponding to completed step. Stridefor pes given in row between two left or right footprints forming stride. Tracks with prefix A are from holotype trackway: those with Band C prefixes are paratypes (L, left; R, right). Brackets refer to measurements of tracks that are poorly, or incompletely, preserved.


had been confidently attributed to ornithischiantrackmakers were Anomoepus, Delatorrichnus andHypsiloichnus. The Late Triassic ichnogenusAtreipus (Olsen & Baird 1986) is also considereddinosaurian (ornithischian) by some researchers,but may also be attributed to a non-dinosaurian arch-osaur (Thulborn 1990, and citations therein). Forthese reasons a Late Triassic or Early Jurassic agefor the Zimbabwe material was considered prob-able. However, the age of the Dande Sandstone For-mation is poorly known, and could be Cretaceous in

part. Possible trackmakers such as the heterodonto-saurids survived until the earliest Cretaceous.

Systematic ichnology

General observations

Anomoepus (Hitchcock 1848), from the LowerJurassic of the Connecticut Valley region, is oneof the best-preserved examples of a distinctivedinosaur track. It forms the basis of the family

Fig. 7. (a) Trackway of quadrupedal ornithopod trackway from Cerradicas, Spain, based on CU Denver tracingT 1189, compared with (b) large and small bipedal Dinehichnus trackways, from the Late Jurassic of NE Arizona(Lockley et al. 1998).


Anomoepodidae, which Lull (1953) attributed to anornithopodan trackmaker. This ichnofamily orig-inally contained only one ichnogenus (Anomoepus),which was traditionally considered to containseveral ichnospecies (Lull 1953). However, Olsen& Rainforth (2003) considered that all ichnospecieswithin North America may be accommodated in A.scambus (however, for alternative views, seeLockley (2005) and Lockley & Gierlinski (2006)).The ichnogenus Moyenosauripus (Ellenberger1974) has also been considered a synonym of Anom-oepus by some workers (Olsen & Galton 1984;Olsen & Rainforth 2003), but a distinct ichnogenusby others (Gierlinski 1991; Lockley & Gierlinski2006).

Anomoepus ichnospecies vary in size from about5 to 15 cm (length of standing pes: sensu Lull 1953);that is, the length of the pes with hallux but withoutmetatarsus impressions. However, metatarsusimpressions are relatively common in Anomoepus.Olsen & Rainforth (2003, fig 19.18) identified onespecimen that has a foot length of 19 cm (seeLockley 2005, fig. 2; Lockley & Gierlinski 2006).Among the features that distinguish thebest-preserved material are the presence of a

anteriomedially directed hallux and a distinctivepattern of double creasing between the digital padimpressions of the pes (see Lull 1953, figs 60, 62–67; Olsen & Rainforth 2003, figs 19.4–19.5).Some specimens also reveal distinctive skinimpressions consisting of fine circular tuberclesthat are very regular in size and shape, as seen, forexample, on specimen 48/1 in the Hitchcock collec-tion. The manus impression, according to Lull(1953), also exhibits five digit impressions with dis-tinct digital pad traces. The step is relatively shortand the axis of digit III of the pes rotates inwards.Left and right tracks are clearly distinguishable,with a moderately wide trackway (about twice aswide as footprint width) and pes pace angulationvalues of between 1308 and 1508 (Fig. 1).

Although some specimens in the Hitchcock col-lection show the fine clear detail indicated by Lull(1953) in his line drawings, most do not. Forexample, there are many trackways of Anomoepusthat indicate bipedal progression, and even wheremanus impressions are preserved it is hard to seeall five digit impressions as clearly as Lull’s draw-ings indicate. These deficiencies are rectified tosome extent by the work of Olsen & Rainforth

Fig. 8. From left to right: comparison between ornithischian trackways from Zimbabwe, Thailand and Canada. Alldrawn to same scale. Detail of holotype trackway of Neoanomoepus (far right) consists of a trackway segment of threemanus–pes sets (1–3; preserved as replica FGM 002.01.20a and also as replica CU 199.22). Manus–pes sets numbered4–7 include representative tracks from trackways B and C (compare with Fig. 5).


(2003), whose illustrations are a great improvementon Lull’s artwork. One also does not see the peshallux impression (digit I) in many tracks, andmany also do not show metatarsal impressions.Such variability is to be expected in a largesample and can be attributed to variable preser-vation and/or variability in mode of progression.

When we compare these classic Liassic Anom-oepus tracks with those found in the basal Cretac-eous sequences of British Columbia and Thailandthere are clearly some distinctive similarities.The tracks fall in the same general size range(between about 5 and 12 cm pes length) withshort steps, inward rotation of pes digit III andpace angulation values averaging about 1408.However, the tracks are also different in anumber of respects. Most notably, despite goodpreservation in multiple examples, the tracksappear to lack discrete digital pad impressions oneither the pes or the manus, in most cases. Thiscould be attributed to preservation, but given thatthe much smaller manus tracks show all five digitimpressions, a phenomenon rarely seen in theHitchcock collections, Lull’s artwork notwithstand-ing, we interpret this as a primary feature. It hasbeen noted that many dinosaur track types reveala trend of increased fleshiness with time (Lockley1999, 2000; Lockley et al. 2000). Thus, it is mostparsimonious to infer that the lack of discrete padimpressions separated by double creases, as inAnomoepus, is a primary feature of morphological,and hence ichnotaxonomic significance. It alsoappears that in Cretaceous material from Canadaand Thailand the hallux is directed more anteriome-dially and may also be more anteriorly situated thanin the type material of Anomoepus. Also, despitetheir depth, which is generally greater than EarlyJurassic Anomoepus, the Cretaceous tracks alsoconsistently lack full metatarsus impressions inmost cases. This suggests that the Cretaceousforms may have been more digitigrade than basalornithischians. It is for these reasons that wepropose a new ichnogenus: Neoanomoepus, accom-modated in the ichnofamily Anomoepodidae.

Another feature of the Cretaceous trackways isthat they appear to represent quadrupedal pro-gression in a majority of cases despite the smallsize of the sample in comparison with the Jurassicmaterial. Although it is debatable whether thisshould be considered a significant factor in formalichnotaxonomy, on balance, the distinctionbetween biped and quadrupeds is generally takento be of prime importance in ichnotaxonomicdescriptions. Regardless of opinion on this issue itis worth pointing out that quadrupedal progressionappears to be more common among Cretaceousornithopods than among their Jurassic ancestors,and in this sense the tendency towards becoming

facultative quadrupeds is significant if notabsolutely diagnostic.

Systematic descriptions

Ichnofamily Anomoepodidae Lull 1953Emended Gierlinski 1991

Ichnogenus Neoanomoepus ichnogen. nov.(Figs 4–6, 8)

Diagnosis. Small trackway of a quadruped with tet-radactyl pes larger than pentadactyl manus. Pes axisinwardly rotated and pes digit I short and anterome-dially directed. Manus outwardly rotated and situ-ated lateral to pes digit III or IV. Step short andtrackway irregular.

Ichnospecies Neoanomoepus perigrinatus ichnosp.nov. (Figs 4–6, 8, Table 1)

Description. Small trackway of a quadruped withtetradactyl, slightly elongate pes (mean length13.2 cm excluding short heel or metatarsal trace;mean width 11.1 cm), which is much larger thanthe pentadactyl manus (mean length 3.6 cm; meanwidth 6.0 cm). Pes axis inwardly rotated between10 and 258 from trackway mid-line and pes digit Ishort and anteromedially directed. Manus outwardlyrotated and situated lateral to pes digit III or II.Step and stride short (mean step 31.1 cm and meanstride 49.5 cm for three trackways on type slab;see Table 1). Trackway, trackway width and paceangulation irregular. Mean pace angulation 1228(range 90–1438, n ¼ 8). Trackway width greaterfor manus (mean 27.2, range 19.5–34.8 cm) thanfor pes (mean 24.5 cm, range 19.3–34.2 cm, n ¼ 6).

Etymology. Meaning ‘new Anomoepus’ thattravelled widely.

Type material. Holotype- and paratype-bearingoriginal slab still in field on ‘crown’ land, butmould and replica of complete slab in Fraser–FortGeorge Regional Museum (FGM 002.01.20).Trackway A is designated as the holotype trackway(FGM 002.01.20a), with an additional replica ofholotype trackway A (CU 199.22) in the Universityof Colorado at Denver, Dinosaur Tracks Museum.Trackway B is designated as a paratype trackway(FGM 002.01.20b), with additional replica of track-way B (CU 199.23) in the University of Colorado atDenver, Dinosaur Tracks Museum.

Type locality. Elk Valley Coal region, SE BritishColumbia, Canada.

Type horizon and age. Mist Mountain Formation,Berriasian.


Distribution and probable affinity

of Neoanomoepus

Various workers have attributed Anomoepus to abasal ornithischian trackmaker or more specificallyto an ornithopod. However, there are no knownEarly Jurassic ornithopod trackmakers withsplayed manus digits that would fit the Anomoepusmanus footprint. Compelling ichnological evidenceof ornithischian affinity in either the Jurassic or theCretaceous generally depends on the occurrence ofquadrupedal trackways, because tracks made bybipeds are generally less diagnostic. A distinctioncan be made between ornithischian tracks thatdisplay marked heteropody (pes much larger thanmanus), which are usually attributed to basalornithischians and ornithopods, and those with lesspronounced heteropody (pes and manus moreequal in size), which are usually attributed to thyreo-phorans or ceratopsians. Based on this general dis-tinction, Neoanomoepus seems to be of ornithopodaffinity because basal ornithischians are notrecorded in the Cretaceous, whereas ornithopodare present and diverse.

At present very few tracks of quadrupedalornithischians are known from the Jurassic. Anom-oepus, rare Delatorrichnus and an unnamed trackfrom Asturias, Spain, are the only quadrupedaltrackmakers with strong heteropody so far reported.Thus we infer that there is a significant gap in thedistribution of Anomoepodidae between the earlyJurassic and the early Cretaceous. Jurassic ornithi-schian tracks that demonstrate less heteropody suchas an unnamed trackway from the Early Jurassic ofFrance (Le Loeuff et al. 1999) or Deltapodus(Whyte & Romano 2001) from the Middle Jurassicof England, and a similar unnamed form from theLate Jurassic of Spain (Garcıa-Ramos et al. 2004;Gierlinski & Sabath 2009), are still poorly knownand mostly without accepted ichnotaxonomies.

Canadian type Neoanomoepus occurs in stratathat are well dated as Berriasian. Likewise, similartrackways from Thailand, which we herein refer toas Neoanomoepus sp., have also been assigned aBerriasian age. Such correlations may be coinciden-tal but they may also indicate an early Cretaceousornithischian radiation. As noted above, this infer-ence arises from the scarcity of small Anomoepus-like quadrupedal ornithischian traces in the Middleand Late Jurassic, followed by a pronounced EarlyCretaceous radiation of ornithopods, many ofwhich, based on tracks, were quadrupedal. Thus,the appearance of Neoanomoepus in the earliestCretaceous suggests that the Early Cretaceous radi-ation of ornithopods, and ornithischians in general,involved small as well as large species. Recent dis-coveries in British Columbia indicate that‘Anomoepodidae-like’ tracks (Fig. 9) also occur in

the Gorman Creek Formation of Valanginian agestratigraphically above the Mist Mountain For-mation (McCrea & Buckley 2005b, 2006). This sup-ports the inference of diverse ornithopodichnofaunas becoming more prevalent in the earlyCretaceous.

For a comprehensive review of available ichno-logical evidence it is necessary to compare Neo-anomoepus with other purported ornithopod orornithischian tracks made by small bipeds, or quad-rupeds that exhibit extreme heteropody. The onlytracks that fall in this category are Early–MiddleJurassic Delatorriichnus tracks (Casamiquela1964; Gierlinski et al. 2004) and Dineichnus foot-prints (Lockley et al. 1998) from the Late Jurassic.The latter ichnogenus has been attributed to a dryo-morph trackmaker (Fig. 7). Hypsiloichnus from theEarly Cretaceous, as the name implies, is inferred tobe of hypsilophodontid origin (Stanford et al. 2004).There are significant morphological differences inall these cases. Delatorriichnus possesses a tridactylmanual print reminiscent of heterodontosaurid mor-phology. Dinehichnus has no trace of a functionalpes digit I, and no manus impressions, whereasNeoanomoepus has a short pedal digit I and smallpentadactyl manual impressions. Hypsiloichnusdiffers from both these ichnogenera in having amore elongate pes, longer pedal digit I and verysmall manual impressions (Fig. 10); however, it isnot known from a trackway sequence. These differ-ences help justify the different ichnogenus designa-tions, and suggest that Neoanomoepus was not madeby either the trackmaker of Delatorriichnus,Dineichnus or Hypsiloichnus.

The unnamed trackmaker from the Cerradicassite in Spain has a pedal morphology and inwardrotation similar to large Dinehichnus (Lockleyet al. 1998), which in turn is similar to Asianopodus(Matsukawa et al. 2005). The elongate foot, sharpclaw traces and phalangeal pad segmentation ofthe Cerradicas tracks means that they could easilybe mistaken for a theropod if it were not for the pre-sence of manus tracks. However, the inward rotationof the pes and rounded symmetric heel pad, whichare also features of Dinehichnus tracks are typicalof ornithopods.

As indicated above, the inner pes digit (I) of thetrackmakers of Neoanomoepus and Hypsiloichnus(Fig. 10) was long enough to make contact withthe substrate, although this was not the case withthe maker of Dinehichnus tracks. A well-developedhallux (digit I) is typical of the primitive conditionseen in basal ornithischian, basal thyreophoransand basal ornithopods, as well as in hypsilo-phodontids (Weishampel et al. 2004), which mayhave included the maker of anomoepodid tracks(Olsen & Rainforth 2003). In contrast, the lack ofa pes hallux in more derived large ornithopods


(iguanodontids and hadrosaurs) and their tracks andin some other ornithischians (ankylosaurs) is wellknown (Weishampel et al. 2004). The track recordsupports this by showing that small forms inferredto be ornithopods retained the primitive digit I. Incontrast, traces of this digit are never found inlarge ornithopod tracks, although they are commonin many other ornithischian tracks. This shows thatthe track and bone records consistently provide evi-dence of the reduction of pes digit I in some cladesof large ornithopods and among some otherornithischian tracks.

The track record is also helpful in showing us thesignificant reduction of manual digits I and V amongornithopods. However, we know of no examplesof track evidence for such significant reductions

among other ornithischians. In the Early Cretac-eous, the manus tracks of Neoanomoepus, theCerradicas specimens (Perez-Lorente et al. 1997)and various iguanodontid tracks such as Iguanodon-tipus (Sarjeant et al. 1998), Caririchnium (Leonardi1984; Lockley 1987; Lockley & Wright 2001),Amblydactylus (Currie & Sarjeant 1979) and Hadro-sauropodus (Lockley et al. 2004) show clearevidence of the reduction of digits I–V to producepronounced heteropody in comparison with otherornithischian tracks. Associated with this smallmanus we see an amalgamation of digits II, III andIV into an integument whose distal end made hoof-like impressions. In short, as the trackmakersbecame larger their feet became more fleshy. Suchmorphological shifts are size-related and involve a

Fig. 9. ‘Anomoepodidae tracks’ from the Gorman Creek Formation (Valanginian) British Columbia. It shouldbe noted that these tracks, unlike those from the Mist Mountain Formation, show metatarsal traces and one showsphalangeal pad impressions on pes digit III.


shortening of distal phalangeal elements while theproximal elements (metatarsals and metacarpals)lengthen in compensation.

This trend of reduction in number of digits,coupled with reduction of distal elements, and ashortening and broadening of the foot is notunique to ornithopods. It has been noted in the saur-ischian clade (Lockley 1999, 2001; Lockley et al.1997) and even parallels the evolution of the footin Tertiary ungulates, notably the equids. Thus, thetrend in Early Cretaceous ornithopods, whethersmall, intermediate or large sized, is towardsgreater, functional digitigrady.

Available ichnological information for pre-sumed ornithopods generally supports this trend.Thus, Early Jurassic Anomoepus shows the highestincidence of metatarsal impression (pes planti-grady) and pentadactyl manus traces. YoungerLate Jurassic and Early Cretaceous tracks show anumber of trends towards digit reduction andgreater digitigrady. In smaller Cretaceous ichnotaxasuch as Neoanomoepus and Hypsiloichnus such

trends are not pronounced. Traces of a functionaldigit I indicate minimal digit reduction and attestto a primitive, more-plantigrade condition similarto Anomoepus, although without strong evidenceof plantigrady in metatarsal posture. The other‘derived’ trend is more pronounced and involvesthe conspicuous reduction of lateral digits I and Vin both the pes and manus. Digit I reduction in thepes is confirmed by body fossils (Weishampelet al. 2004). Although, based on skeletal evidence,manus digit reduction is less pronounced, manustraces are nevertheless highly diagnostic becauseof the evidence of extreme digitigrady. This ismost pronounced in intermediate- and large-sizedspecies, which developed a small hoof-like manus.

The similarity between Early Jurassic Anomoe-pus and Early Cretaceous Neoanomoepus trackssuggests iterative radiations of small ornithopodson at least two occasions, although during theearly Cretaceous there was a major radiation oflarge ornithopods. We infer that these evolutionaryevents left a discernible ichnological record oftrackways attributable to both quadrupeds andbipeds that are best attributed to ornithopodsrather than to other ornithischians. Despite the con-vergence suggested by the names and descriptions,the tracks from these two periods (near theTriassic–Jurassic and Jurassic–Cretaceous bound-aries; at about 208 and 145 Ma, respectively) canbe differentiated on minor morphological grounds.

These occurrences suggest two acme zonesrepresenting significant radiations some 60–65 Maapart. In this regard the track record is consistentwith the skeleton record of an earliest Cretaceousradiation of ornithopods involving both smallclades such as the hypsilophodontids and largeclades such as the iguanodontids (Weishampelet al. 2004). This convergence of the skeletal andichnological records inspires confidence in theutility of both for recording macro-evolutionarytrends.

We thank V. Suteethorn, Geological Survey Division,Department of Mineral Resources, Bangkok, Thailandfor help with access to the Hin Lat Pa Chad site and thetrackway replicas from that location. The opportunity tomake preliminary observations at the Las Cerradicas track-site was provided to one of us (M.G.L.) by the staff ofDinopolis (Teruel). The site is currently being studied byF. Perez-Lorente (La Rioja) and J. I. Canudo (Zaragoza),and for this reason we limit our interpretations to confirm-ing the published record through direct observation of thetracks illustrated in Figure 7 herein. The opportunity toresearch the Mist Mountain Formation tracks was madepossible by a Jurassic Foundation Grant to R.T.M. andsupport from S. George Pemberton. We thankG. Gierlinski (Polish Geological Institute, Warsaw) andJ. Le Loeuff (Musee des Dinosaurs, Esperaza, France)for their helpful review of the manuscript.

Fig. 10. A Hypsiloichnus manus and pes set: modifiedafter Stanford et al. (2004).


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