A diverse, high-latitude ichnofauna from the Late Cretaceous Wapiti Formation, Alberta, Canada

Cretaceous Research 41 (2013) 256e269

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A diverse, high-latitude ichnofauna from the Late Cretaceous Wapiti Formation, Alberta, Canada Federico Fanti a, *, Phil R. Bell b, Robin L. Sissons b a b

Dipartimento di Scienze della Terra e Geologico-Ambientali, Alma Mater Studiorum, Università di Bologna, via Zamboni 67, 40126 Bologna, Italy Pipestone Creek Dinosaur Initiative, 10001 84th Ave, Clairmont, Alberta T0H 0W0, Canada

a r t i c l e i n f o

a b s t r a c t

Article history: Received 26 July 2012 Accepted in revised form 30 December 2012 Available online 4 February 2013

The Wapiti Formation in west-central Alberta preserves one of the most diverse Late Cretaceous terrestrial track records yet identified in Canada. At least seven morphotypes are recognized and attributed to mammals, small reptiles or amphibians, tyrannosaurids, medium-sized theropods, hadrosaurids, and ankylosaurs. Most tracks occur isolated on slump blocks associated with latest Campanian (Wapiti Formation unit 4) exposures found along Pipestone Creek and Red Willow River. With the possible exception of hadrosaurids, tracks provide some of the most compelling evidence for the occurrence of such taxa within the Wapiti Formation ecosystem. The apparent absence of ceratopsian tracks is surprising considering their bones are abundantly preserved in nearby monodominant bonebeds. The overall faunal signal represented by the Wapiti Formation trackmakers is typical of and consistent with other coeval assemblages in similar environments. The Wapiti Formation tracks, combined with the known fossil bone record, provide another data point in a growing palaeobiogeographical picture of the dinosaur faunas of high-latitude northwestern North America during the Late Cretaceous. Ó 2013 Elsevier Ltd. All rights reserved.

Keywords: Tracks Late Cretaceous Wapiti Formation Alberta ichnofauna High-latitude

1. Introduction Tracks and trackways provide an alternate means to body fossils for reconstructing a palaeocommunity (Lockley, 1986). These are especially important for stratigraphic intervals where body fossils are lacking or rare (Lockley, 1991). In Canada, currently published dinosaur track-bearing formations are limited to Cretaceous deposits in Alberta, British Columbia and the Yukon (Long et al., 2000; Gangloff and May, 2004). The oldest Cretaceous Canadian dinosaur ichnofauna comes from the Berriasian Mist Mountain Formation in southeastern British Columbia and includes well-preserved small ornithischian ichnites (Lockley et al., 2009), sauropod (McCrea et al., 2005a) and bird tracks (McCrea and Buckley, 2005). In addition, the Valanginian Gorman Creek Formation along the Narraway River in northeastern British Columbia, close to the Alberta border includes large ankylosaur, both small and large sized-theropod, and small ornithopod tracks (Currie, 1989; Sampson and Currie, 1996). The middle Albian ichnofauna of the Gates Formation near Grande

Institutional abbreviations: TMP, Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada; UALVP, University of Alberta, Edmonton, Alberta, Canada; GPRC, Grande Prairie Regional College, Grande Prairie, Alberta, Canada. * Corresponding author. Tel.: þ 39 051 2094565; fax: þ39 051 2094522. E-mail addresses: [email protected] (F. Fanti), [email protected] (P.R. Bell), [email protected] (R.L. Sissons). 0195-6671/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cretres.2012.12.010

Cache (west-central Alberta) includes abundant nodosaurid (Tetrapodosaurus) as well as undetermined theropod and ornithopod trackways (McCrea and Currie, 1998; McCrea et al., 2001; McCrea and Sarjeant, 2001; McCrea, 2000a, b; 2003). Aptian tracks were reported by Currie (1989) from the Gething Formation exposed along Peace River Canyon in northern Alberta (McLearn, 1923, 1931; Sternberg, 1931, 1932; Currie and Sarjeant, 1979; Currie, 1981, 1983, 1995), but these tracksites were flooded upon the construction of the Peace Canyon Dam in 1979. Similarly, dinosaur tracks (Tetrapodosaurus ichnosp., and small theropod) and bird tracks (Aquatilavipes swiboldae, and a still unnamed ichnotaxon) have been reported from the AptianeAlbian Gething, and Boulder Creek formations in British Columbia (McCrea and Currie, 1998; Buckley and McCrea, 2009). In west-central Alberta, a large sandstone slab (TMP 1994.183.1) collected from the Cenomanian Dunvegan Formation preserves dinosaur footprints with skin impressions referable to the ichnogenus Tetrapodosaurus (McCrea et al., 2001; Tanke, 2004). Finally, McCrea (2003) reported a diverse in situ ichnofauna from the Cenomanian Dunvegan deposits near Tumbler Ridge (British Columbia), which includes well-preserved ornithopod, theropod, and ankylosaur tracks. To date, tens of localities near the Albertae British Columbia border are known for producing isolated and poorly preserved dinosaur footprints: for a detailed account of dinosaur tracksites localities in northwestern British Columbia and west-central Alberta we refer readers to Currie (1989), McCrea and

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Currie (1998) and McCrea (2003). By comparison, dinosaur tracks from the Upper Cretaceous are less numerous and are restricted to Campanian strata of southern Alberta, in particular from the Oldman, St. Mary River, Dinosaur Park, and Horseshoe Canyon formations (Sternberg, 1926; Currie, 1989; McCrea et al., 2005b; Therrien et al., 2011), all of which are known primarily for their rich vertebrate assemblages. These formations include footprints of primarily ornithopods (probably hadrosaurids) and rare medium-sized theropods while lacking tracks of other common taxa known from skeletal material, such as ceratopsids and tyrannosaurids. The purpose of this study is to document track-bearing localities and their associated ichnofauna from the Late Cretaceous (Campaniane Maastrichtian) Wapiti Formation of west-central Alberta. Although the first vertebrate fossils from the Wapiti Formation were described more than half a century ago (Sternberg, 1951), the Wapiti vertebrate fauna is yet poorly understood. A limited number of outcrops and difficult terrain have exacerbated problems of low fossil yield, especially in relation to the rich, contemporaneous beds of the Horseshoe Canyon and Dinosaur Park formations in southern Alberta. Despite these challenges, ichnological evidence collected from a number of localities within the Peace Region of west-central Alberta (Fig. 1) support previous assertions of a diverse highlatitude vertebrate fauna (Fanti and Miyashita, 2009). 2. Stratigraphic and paleontological context The Wapiti Formation, which crops out extensively in westcentral Alberta and northeastern British Columbia (Fig. 1), incorporates exclusively non-marine successions that represent a time interval from lower Campanian to upper Maastrichtian (Fanti and Catuneanu, 2009). As such, it is temporally equivalent to the Belly River Group (Foremost, Oldman, and Dinosaur Park formations), the Bearpaw Formation, and the Edmonton Group (Horseshoe Canyon, Whitemud, and Battle formations) of southern and central Alberta. The Wapiti Formation is also contemporaneous with several Upper Cretaceous deposits elsewhere in North America, including the Prince Creek and lower Cantwell formations (Alaska), Mesa Verde Formation (Wyoming), the Two Medicine and Judith River formations of Montana, North Horn Formation of Utah, and the Fruitland, Kirtland, and Ojo Alamo formations of New Mexico, all known for their abundance of fossil vertebrates and high diversity of dinosaur taxa (Fanti and Catuneanu, 2009). The Wapiti Formation provides a continuous record of terrestrial sedimentation (and therefore associated faunas) at times when western North America was the object of significant inland shifting of the coastline related to large scale transgressive events of the Western Interior Seaway (Fanti and Miyashita, 2009; Fanti and Catuneanu, 2010). In addition, during the Late Cretaceous Wapiti Formation deposits accumulated at a latitude of approximately 65 north, thus associated faunal and ichnological assemblages are representative of high latitude settings (Scotese, 1991; Brinkman, 2003; Fanti and Miyashita, 2009). In the last thirty years, field activities in the Grande Prairie region resulted in the discovery of several important fossil localities. These include ceratopsian-dominated bonebeds, hadrosaur skeletons, isolated teeth and bones ascribed to tyrannosaurs, troodontids, nodosaurs, and ankylosaurs, as well as microvertebrate sites, insect body fossils, and megaplants (Tanke, 2004; Currie et al., 2008; Fanti and Miyashita, 2009; Bell et al., 2013, in press). 3. Methods Molds of minute tracks collected at the Red Willow Falls locality (TMP 2002.66.12, 2003.66.02, 2003.66.06, UALVP 53473) were made in order to produce 3D digital models of specimens for a more

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objective interpretation. Data used to generate 3D models were acquired with a laser scanner (Zsnapper portable, ViALUXÒ) with a 0.2 mm resolution and accuracy 40 mm. Data were processed at the Dipartimento di Scienze Biologiche, Geologiche e Ambientali (Bologna, Italy) using RapidformÒ (alignment of the scans) and SurferÒ (for contour-line and depth-color image analysis). Larger specimens described herein were accessed via Crown and/or County land (precise GPS coordinates available from the University of Alberta Laboratory of Vertebrate Palaeontology or at the Royal Tyrrell Museum of Paleontology). Where specimens could not be collected (due to their size or other logistical issues), they were measured and photographed in situ. All other specimens are housed at the aforementioned repositories. Standard track parameters include: footprint length (FL), footprint width (FW), digit length (L) for digits (sensu Leonardi, 1987) and interdigital angles (angle of divarication, a) between digits (sensu Thulborn, 1990). 4. Tracksite descriptions 4.1. Red Willow Falls The Red Willow River provides some of the most continuous exposures of the Wapiti Formation unit 4, which is characterized by fining-upward successions of levees, overbank deposits, bentonitic beds and frequent, lenticular coal seams which, in spite of thicknesses that locally exceed 1 m, pinch out within a 5 km range. Channel bodies are commonly interbedded with typical floodplain deposits such as lenticular, organic-rich, carbonaceous mudstones and crevasse-splay fine-grained sandstone and siltstone (Fanti and Catuneanu, 2009). A variety of fossils have been recovered from the unit 4 deposits exposed along the Red Willow River from the AlbertaeBritish Columbia border in the west, to the Red Willow Falls locality in the east (Fig. 1). Identifiable elements include a rich collection of associated hadrosaur cranial and postcranial elements, tyrannosaurid teeth, leaves, megaplants, as well as well-preserved tridactyl footprints (Tanke, 2004; Bell et al., in press). Relevant to this study, palynology (Dawson et al., 1994) and diagnostic hadrosaur elements referable to Edmontosaurus sp. (UALVP 53549, UALVP 53722; P.R. Bell, unpubl. data), support a late Campanian age for all fossils collected from the Red Willow Falls locality. Despite the fact that most footprints collected in the area are not referable to a specific track-bearing layer, well-preserved exposures of channel bodies along the east flank of the Red Willow valley document in situ trampled surfaces (Tanke, 2004). Tracks commonly occur at the base of sandy layers that sharply overly fine-grained, muddy, tabular beds that accumulated in water-saturated intra-channel deposits. Tracks commonly preserve minute (<5 mm) polygonal mudcracks, which have been often misinterpreted in old local reports for skin impressions. 4.2. Red Willow River Despite the fact that major bonebeds have so far only been located along the Wapiti River and Pipestone Creek, exposures of Wapiti Formation deposits along the entire drainage system of the Red Willow River are particularly rich in vertebrate remains (Fig. 1). All beds are referred to upper unit 4 and lower unit 5 of the Wapiti Formation, which are stratigraphically separated by the Red Willow Coal Zone (sensu Fanti and Catuneanu, 2009, 2010); palynological and sedimentological data (Dawson et al., 1994; Fanti and Catuneanu, 2009, 2010) document that the Campaniane Maastrichtian boundary (70.6 Ma, Ogg et al., 2004) lies within the Red Willow Coal Zone. Fluvial deposits include fine-grained channel sandstones, tabular coal seams interbedded with dark gray, carbonaceous mudstone, and minor bentonitic layers. The co-

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Fig. 1. A. Locality map showing extent of the Wapiti Formation in the Grande Prairie region of west-central Alberta, and tracksite localities discussed in the text. B. Schematic column of the Wapiti Formation and correlative deposits of southern Alberta showing the stratigraphic occurrence of main tracksites and fossil-bearing strata.

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occurrence of levee and overbank deposits suggests deposition on a low gradient alluvial plain characterized by high freshwater table and abundant vegetation. Fossil remains collected from the Red Willow River valley include an associated hadrosaurine skeleton (Bell et al., in press), both associated and isolated hadrosaur cranial and postcranial elements, ceratopsian bones, Champsosaurus elements (TMP 1989.92.2), rare turtle shell fragments, and well preserved deciduous leaves and silicified logs. Isolated dinosaur ichnites have been found along much of Red Willow River and overall in several localities of the Grande Prairie district. In situ ichnite occurrences are known exclusively from the Red Willow River and in particular from flat, tabular, laterally continuous sandstones exposed primarily during low water conditions. True tracks range from a few millimeters to more than 25 cm in depth. Tanke (2004) reported two localities with in situ trackways and isolated footprints. Both localities have been relocated and prospected in 2011 and 2012 by the authors but no tracks were found, likely as a result of unfavorable water conditions.

2008 and references therein)(Fig. 1). Wapiti Formation deposits that crop out along the Pipestone Creek are representative of the lower Wapiti unit 4: in particular, a volcanic ash located above the bonebed level yielded an age of 73.25  0.25 My (Eberth, in Currie et al., 2008), roughly equivalent to the maximum transgression of the Bearpaw Sea in central and southern Alberta (Baculites compressus zone, 73.4 My, Fanti and Catuneanu, 2009). Vertical facies alternation is typical of levee to overbank deposits, with interbedded fining-upward sequences bounded by channel-base erosional surfaces. At the top of the overbank deposits are paleosols, amber-rich coal seams, and soft, light green to yellow bentonites. The same stratigraphic architecture can be observed in several outcrops along the entirety of Pipestone Creek and near its mouth on the north flank of the Wapiti River. Taphonomic data and large amounts of coalified plant fragments within the fossil-bearing deposits at Pipestone Creek indicate an alternation of wet, pond-like environments with sandy distributary channels. Hadrosaur and isolated ceratopsian remains have been collected in several localities near the mouth of the creek.

4.3. Pipestone Creek

5. Systematic ichnology

The Pipestone Creek Pachyrhinosaurus bonebed is located approximately 1 km upstream from its confluence with the Wapiti River, less than 25 km SW of the city of Grande Prairie (Currie et al.,

5.1. Incertae sedis Ichnogen. et sp. indet

Fig. 2. Small tetrapod tracks from the Red Willow Falls locality. Photograph, line-drawings, color-coded surface, and contour-line map with 0.1 cm of equidistance of A) TMP 2002.66.12, B) TMP 2003.66.02, C) TMP 2003.66.06, and D) UALVP 53473. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

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Description: Three isolated tetradactyl tracks (TMP 2002.66.12, TMP 2003.66.02, and UALVP 53473) preserved as natural casts were collected from slumped sandstone slabs at the Red Willow Falls locality (Fig. 2AeC). TMP 2002.66.12 displays four slender, slightly divergent digit impressions that are subequal in length (Fig. 2A). The track measures 1.6 cm in length and 2.4 cm in width. Digit I and II nearly overlap, whereas the divarication angle between digit IIeIII is 33 , and digit IIIeIV is 31. Digits I and IV are slightly shorter and more divergent with respect to digits II and III. The tips of all digits are slightly pointed without an expanded termination, but otherwise have sub-parallel lengths. No phalangeal pads or claw impressions were observed. The proximal edges of the medial digits (I and II) are more deeply impressed than the lateral ones. TMP 2003.66.02 is larger than TMP 2002.66.12 (length 2.4 cm; width 3.6 cm) with four slender and divergent digit impressions (Fig. 2B). Digit I is the shortest (1.5 cm), whereas digits II, III, and IV are subequal in size ranging between 2.1 and 2.2 mm in length. Digits II and III are straight, central and parallel. Divarication angles between digits IeII is 54 , digits IIIeIV is 60 , and digits IeIV is 125 . With the exception of digit II, which has a distally pointed terminus, all digits have slightly rounded terminations. Digits I, II, and IV preserve partial phalangeal pad impressions, but lack clear ungual/ claw impressions. UALVP 53473 measures 1.9 cm in length and 1.6 cm in width. This well-preserved track displays four almost straight digits with reduced divarication angles. Digits II and III are the best preserved, showing fairly rounded and slightly enlarged distal ends with respect to the rest of the digit, and no claw impression. Although the preservation of digits I and IV is poor, it is possible to notice a decrease in length from digit II to IV, thus digit II representing the longest in the track. The divarication angle between digit I and IV is 85 , between I and II is 40 , and between III and IV is 30 , whereas digits II and III are nearly parallel. The palm is rounded, relatively wide, and well impressed in the sediment. Discussion: Because the aforementioned tetradactyl tracks are isolated (not part of a trackway), potential identifications are severely hampered, especially as a variety of traces (such as invertebrate feeding traces) can closely mimic vertebrate tracks (as in the Scoyenia ichnofacies of continental softgrounds; see Buatois and Mangano, 1995, 2004; Krapovickas et al., 2009; Melchor et al., 2010). Trace fossils that consist of horizontal structures made by deposit-feeding organisms, tubular locomotion traces, possible fin markings (c.f. Undichna), and sediment flow-related scratch marks have been observed in the finer fluvial deposits exposed along the Red Willow River. Moreover, small tetrapod tracks bear other similarities that may be problematic to differentiate from each other, especially when dealing with isolated traces. Nevertheless, on the basis of available data from specimens TMP 2002.66.12 and 2003.66.02, these isolated tracks are considered to be vertebrate tracks characterized by curved, elongated and divergent digit impressions, and relatively high digit divarication angles. Similarly, UALVP 53473 is here interpreted as a tetradactyl track, with a clear impression of the palm and shallow, rounded impressions of the tips of digit II and III. Tracks were most likely left on a soft or waterlogged substrate (semi-terrestrial to wet substrate, sensu Silva

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et al., 2008). The size of the Red Willow Falls tracks indicates the track maker(s?) was a small tetrapod, but insufficient diagnostic data prevents referral to a specific group. However, a comparison with fossil and present day traces (Fig. 3) similar in size, morphology, and environmental setting, permit discrimination of some potential trackmakers. The manus prints of modern toads and bullfrogs are comparable in size and share several morphological characters with TMP 2002.66.12, TMP 2003.66.02, and UALVP 53473. Manual digits are relatively slender, with a rounded distal end and lack claw marks. However, anuran tracks differ from the Red Willow tracks in having widely splayed digits; divarication angle between digit I and IV is commonly higher than 130 and up to 180e200 , and a typical relatively wide divarication angle between digit II and III (>50 ) (Halfpenny, 2000; Murie and Elbroch, 2005). In addition, digit IV is usually longer than digits IeIII and prominently postero-laterally oriented. To date, no fossil evidence of frogs has been reported from the Wapiti Formation. Lacertoid reptiles tracks are relatively well represented in the fossil record worldwide, but nearly exclusively from the Permiane Triassic interval (Haubold et al., 1995; Swanson and Carlson, 2002; Ptaszynski and Niedzwiedzki, 2004; Silva et al., 2008; Valentini et al., 2008 and references therein). Lizard-like manual tracks may greatly differ from pedal ones, and are either tetra- or pentadadctyl. Digit imprints are long, slender and overall similar in length, with acute hypices. Divarication angles between digits is quite variable (depending primarily on the substrate), with frequently curved distal extremities and widely diverging external digits. In comparison, the digits of TMP 2002.66.12 and 2003.66.02 are shorter, more robust and rounded, with no acute distal termination. Similarly, UALVP 53473 has relatively shorter digits with sub-rounded terminations, and a broad palm impression. Squamate fossils from the Wapiti Formation include the borioteiioidean lizards Socognathus uniscuspis and Kleskunsaurus grandeprairiensis (Fanti and Miyashita, 2009; Nydam et al., 2010), known from the swampy deposits of Wapiti Formation unit 3. With a skull length of approximately 1 cm, such lacertilians reptiles would have represented a possible track maker. Crocodilian manus tracks are characterized by long and slender digits with clear ungual or claw impression and widely diverging digits (Lockley and Meyer, 2004 and references therein). Despite the fact that manual tracks are commonly larger in average size, footprints of comparable size with those discussed here have been reported from the Lower Cretaceous of Spain (Fuentes Vidarte and Meijide Calvo, 1999). Compared with the Red Willow tracks, both fossil and modern crocodilian manual tracks have more slender digits, acute hypices and, on average, larger divarication angles between digits (see also Lockley and Meyer, 2004; Lockley et al., 2004a). Ichnotaxonomy of turtle tracks is still highly debated and controversial, and several ichnotaxa are considered as nomen dubium (Moratalla et al., 1995; Avanzini et al., 2005). Tracks left by modern turtles and similarly those in the fossil record referred to these trackmakers share the combination of a distinctive sub-circular shape with not always evident claw marks (Avanzini et al., 2005; Fiorillo, 2005; Fuentes Vidarte et al., 2003; Contessi and Fanti, 2012). The lack of such characters in the Wapiti Formation tracks exclude turtles from possible trackmakers.

Fig. 3. A), TMP 2002.66.12; B) TMP 2003.66.02; C) TMP 2003.66.06; D) UALVP 53473; EeF) American toad [Bufo americanus] and bullfrog [Rana catesbeiana] manual track (Murie and Elbroch, 2005); G) Rhynchosauroides retroversipes from the Upper Triassic of Brazil (Silva et al., 2008); H) modern lizards track (Murie and Elbroch, 2005); IeJ) fossil salamander manual tracks ascribed to the genus Ambystomichnus from the Eocene and Paleocene of Wyoming (Foster, 2001); K) modern California newt [Taricha torosa] manual track (Murie and Elbroch, 2005); L) Crocodylopodus meijidei from the Early Cretaceous of Spain (Fuentes Vidarte and Meijide Calvo, 1999); M) American alligator (Murie and Elbroch, 2005); N) manus of the possible marsupial Duquettichnus kooli from the Aptian of British Columbia (Sarjeant and Thulborn, 1986); O) mammal tracks ascribed to Schadipes sp. from the Maastrichtian Laramie Formation of Colorado (Lockley and Foster, 2003); P) modern Pika [Ochonta princeps] manual track (Murie and Elbroch, 2005).

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Finally, the occurrence of small amphibian tracks in the fossil record after the Permo-Triassic interval is extremely limited and represented by a single Campanian and a few Eocene and Paleocene localities of North America (Peabody, 1954; Denton and O’Neill, 1998; Foster, 2001). Known manus tracks are tetradactyl and overall minute, with relatively short and slender digits. The tips of all digits are rounded and, depending on preservation and substrate hardness, slightly enlarged relative to the rest of each digit. As in extant taxa, digit I is the shortest and digit III is the longest. Fossil tracks are relatively larger in size compared to the majority of modern taxa. Average divarication angle between digit I and IV in modern taxa is 120 (Halfpenny, 2000; Murie and Elbroch, 2005), whereas in the fossil record it varies between 100 and 125 (Foster, 2001). In addition, the absence of claw marks, a deeper impression of the proximal section of the medial digits relative to the lateral ones (as observed in TMP 2002.66.12) as well as rounded digits tips (as in UALVP 53473) have been considered diagnostic features for amphibians, in particular of salamanders (Peabody, 1954; Hunt et al., 1990; Foster, 2001). Although salamander tracks are greatly underrepresented in the fossil record to date, useful data for comparison are provided by detailed studies on present-day newts, documenting relationships between trackmakers and substrate characteristics (Brand, 1979, 1992, 1996). Tracks from the Red Willow Falls area share several morphological characteristics with those of present day western newts (Taricha torosa, Brand, 1996, figure 5), including overall shape, slender digits with rounded terminations, and divarication angles between digits. Available data do not permit referral of TMP 2002.66.12, TMP 2003.66.02, and UALVP 53473 to a specific track maker, nor to a known ichnogenus. However, we refrain from assigning such tracks to crocodilian and anuran tetrapods. Similarly, although lacertilian tracks share several morphological characters with tracks described here, differences in digit divarication angles, digit termination (rounded vs pointy tips, absence of claw marks), and palm impression do not support an attribution to this group of small reptiles, with the possible exception of TMP 2003.66.02. On the contrary, several features, such as wide palm impression, digit morphology, deeper impression of medial digits, and divarication angles between digits, indicate affinities between TMP 2002.66.12 and UALVP 53473 with salamander-like amphibian tracks (see also Melchor and Sarjeant, 2004; Stimson et al., 2012, figure 4). To date, no salamanders have been reported from the Wapiti Formation, although lissamphibians are well documented in the Upper Cretaceous of North America (Denton and O’Neill, 1998; Gardner, 2000, 2003; Holman, 2006), where they are represented by four families (Sirenidae, Amphiumidae, Batrachosauroididae, and Scapherpetontidae; Holman, 2006). Pending further research on microvertebrates and more complete trackways from the Wapiti deposits, tracks described here may represent the first evidence in North America of salamanders in a Late Cretaceous high-latitude ecosystem.

5.2. Mammalia Ichnogen. et sp. indet Description: TMP 2003.66.06 is a small, well preserved, pentadactyl footprint, measuring 1.5 cm in length and 1.6 cm in width (Fig. 2D). Digits IIeV are straight, subequal in length with three phalangeal impressions preserved on digits II, III and IV. Digit V is more slender than digits IIeIV with no clear phalangeal impression. Digits IIeIV also preserve a sharp distal termination. Digit I (hallux) is shorter (0.6 cm long) than the other digits and slightly laterally directed with no clear phalangeal impression. Distal digit terminations are slightly pointed; the palm impression (proximal part of

metatarsus) is relatively sharp-edged, rounded and also represents the deepest section of the track. Discussion: The digital morphology and ichnophalangeal formula of TMP 2003.66.06. is consistent with the phalangeal formula 2-3-33-3 of mammalian manus tracks (Leonardi, 1987; Lockley and Foster, 2003). In contrast, lizards/lacertilians have a phalangeal formula of 2-3-4-5-3 (Leonardi, 1987; Russell and Bauer, 1988; Avanzini et al., 2010). In addition, the palm impression of the foot and consequent plantigrade posture distinguishes TMP 2003.66.06 from other small tracks recovered at the Red Willow Falls locality, which display a more lacertilian-like digitigrade or semi-digitigrade posture. A comparison with other modern and fossil tracks suggests mammalian rather than lacertilian affinities (Fig. 3; Brown et al., 1995; Halfpenny, 2000; Murie and Elbroch, 2005). For these reasons TMP 2003.66.06 is attributed to a small mammalian track maker. Unequivocal mammal tracks from the Cretaceous are extremely rare in the fossil record: reports from North America (Sarjeant and Thulborn, 1986; Sarjeant, 2000; McCrea and Sarjeant, 2001; Stanford and Lockley, 2002; Lockley and Foster, 2003) represent to date the sole record of such traces worldwide (see also McCrea et al., 2004 for discussion). Such studies document rare mammalian tracks in association with a diverse vertebrate ichnofauna in well-vegetated, water rich paleoenvironments. Similar conditions characterized by a diverse dinosaur ichnofauna and a low-gradient and waterlogged alluvial plain with abundant vegetation, have been proposed for the Wapiti Formation unit 4 deposits that crop out at the Red Willow Falls locality (Fanti and Catuneanu, 2009). Two isolated teeth from the unit 3 deposits exposed at the Kleskun Hill locality represent the sole occurrence of mammals from the Wapiti Formation (Fanti and Miyashita, 2009); these teeth have been referred to a generic multituberculate (TMP 2004.23.2) and to a pediomyid marsupial (TMP 2004.23.1) (Fox and Scott, 2010). 5.3. Theropods Description: Two theropod morphotypes have been identified from the Wapiti Formation representing ‘medium-’ and ‘large’sized trackmakers. ‘Medium’-sized tracks are represented by three natural casts (convex epirelief) found on a large slab at the Gloria Locke locality, on the north bank of the Red Willow River (Fig. 4): the sandy slab remains in the field and is visible only under low water conditions. Tracks are up to 30 cm in length with a maximum width of 33.8 cm, with an average foot length/foot width ratio (FL/ FW) of 0.88. Divarication between digits II and IV is variable but notably high (74 , 138 , and 130 respectively). The rounded heel forms a prominent bulge on the posterior part of the foot in the two tracks (tracks A and B, Fig. 4) where digit ?II is attached. In track B, there is a constriction between the heel and the base of digit III. Digits are robust and are only weakly tapered. Despite water wear on the slab, it is possible to distinguish digital and terminal ungual pads. These tracks are also unusual in that track A and track B, here both interpreted as right tracks based on the inward rotation of the distal end of digit III, are nearly touching heel-to-toe, whereas track C, possibly a left print, is anteriorly offset by less than half a foot length from track B. The slab possibly represents a section of an in situ trampled surface with tracks left in a relatively soft, sandy sediment by multiple individuals. UALVP 53475 is a large tridactyl natural cast track (convex epirelief) from the Red Willow Falls locality (Fig. 5). Elongate and narrow claw impressions are evident on digits II and III; however, the block is sheared across the distalmost end of digit IV, preventing observation of the claw impression on that digit. The hypex between digits II and III is anterior to that between digits III and IV. The heel impression is asymmetrical and bilobed, with a marked

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Fig. 4. Uncollected theropod footprints from the Red Willow River. Note that both tracks A and B appear as a right pes footprint. L, footprint length; W, footprint width; D , divarication angle between digits.

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Fig. 5. Isolated tyrannosaurid track (UALVP 53475) from the Red Willow Falls locality. A) photograph; B) interpretive illustration, and C) associated divarication angles between digits.

hypex at the base of digit II and III. The maximum length of the track is 49 cm, and is 51 cm wide. Discussion: Asymmetry of the hypex, relatively narrow digits, and variably-present impressions of the terminal unguals are all hallmarks of theropod trackmakers (Lockley and Hunt, 1995; Lockley et al., 2011a). Division of the aforementioned tracks into ‘medium’ and ‘large’ is purely subjective and is not necessarily reflective of taxonomic affinity. Nevertheless, the largest track described here (UALVP 53475) is equivalent in size todand in some cases larger thandthe pedes of the largest penecontemporaneous theropods (Albertosaurus, Gorgosaurus, Daspetosaurus; Farlow, 2001). Lockley et al. (2011b) also noted strong mesaxony (where digit III projects far beyond the remaining digits) as characteristic of tyrannosaurid tracks. In all of these features, UALVP 53475 closely matches the description of a large, presumably tyrannosaurid track maker. Large ornithopod tracks, which in some cases can resemble large theropods, can be differentiated by their notably wider, typically ovoid digit impressions, absence of claw impressions, greater symmetry, and tracks that are wider than long (Lockley and Hunt, 1995). Tyrannosaurids from the Wapiti Formation are represented by undiagnostic shed teeth and a 40 cm long tyrannosauroid metatarsal from the Wapiti River (TMP 2005.066.0047). Therefore it is not possible to confidently assign UALVP 53475 to any given genus (or ichnogenus).

the Red Willow Falls site measuring 53 cm long and 61 cm wide. The digit impressions are broad with rounded terminations, and the posterior margin of the heel is bilobed, although it is relatively straight or rounded in other specimens (UALVP 53016). In some specimens (UALVP 53478, UALVP 53500) there is a marked crease fully or partially separating digits II, III, and IV.

5.4. Ornithopods Description: UALVP 53500 (Fig. 6A and B) is the best-preserved track and is exemplary of this morphotype, although many other large tridactyl tracks have been identified from the Wapiti Formation (UALVP 53016, 53026, 53723, 53478, 53500, 53501) (Fig. 7Ce F). UALVP 53500 is an isolated natural cast (convex epirelief) from

Fig. 6. Isolated Hadrosauropodus pes tracks from Red Willow Falls. A, B, UALVP 53500; C, D, UALVP 53501; E, UALVP 53016; F, UALVP 53723; G, fragmentary track showing parallel scratch marks (UALVP 53026). 10 cm scale applies to G only.

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Fig. 7. Partial Hadrosauropodus pes track (UALVP 53478) with skin impressions (A, B). Dark gray is main track; light gray denotes overprinted track and slide areas. Crosshatching indicates broken surfaces; C, scale scratch marks on the heel region (large rectangle in B); D, skin impressions on digit III (small rectangle in B); E, enlargement of skin impressions outlined in D. Scale ¼ 10 cm.

A second tridactyl track (UALVP 53478) from Pipestone Creek preserves skin impressions in at least three areas (Fig. 7). The best skin impressions occur along the lateral and anterior (distal) margins of digit III. In these areas, the scales are raised polygons (3e5 sided), measuring 2e3 mm in diameter. The lengths of the sides of each polygon are variable, and consequently the overall morphology of the scales (even between scales with the same number of sides) is variable. The posterior margin of the heel and digit IV preserve abundant parallel striae in the sediments posterior to the main part of the pes, and in some cases extend posteriorly beyond the heel of the pes, which we interpret as scale scratch marks. In the area posterior to digit II, additional parallel striae interpreted as scale scratch marks are 3e4 mm wide, whereas posterior to the heel the scratch marks are 2 mm wide. Discussion: Isolated tracks of large ornithopods are the most commonly encountered dinosaurian ichnites in the Wapiti Formation, all of which have been recovered from unit 4 or the lowest part of unit 5. In situ trackways have not been observed, but a large transported block containing well preserved hadrosaur tracks was

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noted by Tanke (2004) from the Gloria Locke locality; however, these are only visible under low water conditions. Large ornithopod tracks are characterized by wide, typically ovoid digit impressions, and roughly symmetrical tracks that are wider than long (Lockley and Hunt, 1995). However, a detailed study of Late Jurassic theropod footprints from the Lastres Formation of Spain by Avanzini et al. (2012) demonstrated that deep theropod underprints in soft sediment may result in broad tracks closely resembling ornithopod footprints. Therefore, ichnotaxonomic interpretations must be treated with caution. Ichnotaxonomy of purported hadrosaurid tracks was reviewed by Lockley et al. (2004b), who demonstrated the extent of confusion regarding identification of the many traces cited in the literature. As a result, relatively few tracks of Late Cretaceous age are of probable hadrosaurid origin, which those authors refer to Hadrosauropodus. The only described ichnospecies, H. langstoni, comes from the CampanianeMaastrichtian St. Mary River Formation in southern Alberta (see also Currie et al., 1991), although Hadrosauropodus tracks were also identified from the Lance Formation in Wyoming (Lockley et al., 2004b). H. langstoni is characterized by sub-symmetrical pes tracks that are wider than long, with a wide, bilobed heel, and digits with teardrop-shaped pads, which are separated from the larger metatarsophalangeal pad by well-defined creases (Lockley et al., 2004b). Large ornithopod tracks from the Wapiti Formation are virtually indistinguishable from Hadrosauropodus tracks described by Lockley et al. (2004b). Track lengths show a range of sizes that are probably indicative of different age classes rather than taxonomic differences (although a taxonomic signal cannot be ruled out entirely). However, as most tracks are isolated occurrences, there is no ichnological evidence as yet suggestive of gregarious behavior in the Wapiti Formation trackmakers. Skin impressions associated with UALVP 53478 identify this footprint as a true track (not an underprint). Although incomplete, the absence of claw impressions and broad, ovate digits more closely resemble the tracks of large ornithopods than of theropods. Skin impressions are known from a small number of Late Cretaceous hadrosaurid tracks (Currie et al., 1991; Lockley et al., 2004b). The association between parallel striae and true skin impressions (i.e. polygonal scales) on UALVP 53478 (Fig. 8) leaves no doubt as to the formation of parallel scratch marks on dinosaur tracks (Difley and Ekdale, 2002; Currie et al., 2003; Avanzini et al., 2012) (Fig. 7G). Moreover, the size and shape of scales in UALVP 53478 are consistent with scales observed on other hadrosaurid tracks (Currie et al., 1991; Lockley et al., 2004b), and associated with skeletal remains (Brown, 1916; Bell, 2012). Although the sample size is small,

Fig. 8. Tetrapodosaurus track from the Wapiti Formation. Manual ichnite (TMP 2004.97.1) from Pipestone Creek (photo courtesy of D.H. Tanke).

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the consistent morphology of pedal skin impressions is notable because scale morphology differs markedly across the body of some hadrosaurids (Bell, 2012). Basement-scales on the body (exclusive of the pes) attain a diameter up to and sometimes exceeding 10 mm. In contrast, no hadrosaurid skin impressions (including those on tracks) from the toe pads have scales >3.5 mm. However, scales on the posterior part of the metatarsophalangeal pad can be somewhat larger (up to 5 mm). 5.5. Ankylosauridae Tetrapodosaurus isp Description: TMP 2004.97.1, recovered from Pipestone Creek, is an isolated pentadactyl ichnite (convex epirelief), which identifies it as a manus track (Fig. 8). Digits IeIV are short, robust and roughly triangular in outline, whereas digit V is comparatively gracile with a rounded terminus. The digits ‘fan out’ from the center of the track, so much so that digits I and V are posteriorly facing relative to digit III. The ‘heel’ is a concave arc. The maximum width between digits I and V is approximately 41 cm. Discussion: McCrea et al. (2001) discussed the identification of pentadactyl tracks attributable to ankylosaurids and ceratopsians. Those authors considered several features diagnostic of ankylosaurid tracks (Tetrapodosaurus), namely: 1. Reduced digit V; 2. Posteriorly oriented digits I and V; and 3. Prominent digit I. In contrast, ceratopsid tracks (Ceratopsipes) are characterized by: 1. Reduced digits IV and V; 2. Less well-defined digit impressions; 3. Digit I not as pronounced as Tetrapodosaurus; and 4. More transverse (wider than long) manus. Based on these observations, TMP 2004.97.1 closely matches the manus of Tetrapodosaurus. McCrea et al. (2001) also argued that the pedal digit impressions are short and broad in ceratopsians compared to ankylosaurs, and Lockley et al. (2001) described ceratopsian pedal traces with digits I and II that are longer than II and IV, neither of which is the case in the Wapiti Formation specimen. We therefore identify the Wapiti Formation pedal trace also as an ankylosaur. Canadian occurrences of Tetrapodosaurus have been reported from the Gething Formation (AptianeAlbian) of British Columbia, the Gates Formation (lower Albian) of Alberta, and the Dunvegan Formation (Cenomanian) of Alberta and northeastern British Columbia (Currie, 1989; McCrea and Currie, 1998; McCrea et al., 2001). TMP 2004.97.1 is therefore the youngest ankylosaur track reported from Canada, although contemporaneous ankylosaur tracks have also been documented from the U.S. and Mongolia (Ishigaki, 1999; McCrea et al., 2001). Ankylosaur remains from the Wapiti Formation are extremely rare, represented only by a nodosaurid scute (TMP 2005.66.46) and tooth (Fanti and Miyashita, 2009), which come from units 4 and 3, respectively. Tetrapodosaurus tracks have been interpreted as nodosaurid in origin based on osteology of the manus and pes (McCrea and Currie, 1998; McCrea et al., 2001). Therefore, we conclude that only nodosaurids have been thus far identified from the Wapiti Formation. 6. Discussion Late Cretaceous dinosaur and other vertebrate track assemblages are notably underrepresented in North America. A significant exception is represented by a number of track-bearing localities from Upper Cretaceous deposits of Alaska, from which have been reported theropod, hadrosaur, neoceratopsian, therizinosaur, bird, and pterosaur traces (Fiorillo and Parrish, 2004; Fiorillo and Adams, 2012; Fiorillo et al., 2007, 2009, 2010, 2011,

2012). It is especially notable that many of the richest bone-bearing formations in Alberta and Montana are nearly bereft of tracks (Lockley and Hunt, 1995; McCrea et al., 2005b), which is likely a symptom of unfavorable preservational environments (Lockley et al., 2004b). In contrast, the Wapiti Formation so far yields roughly equal proportions of footprints and bones. The existence of both well preserved body and trace fossils in the Wapiti Formation within meters of each other suggest a favorable mixture of different environments being represented with different preservational potentials. Such a patchwork mosaic through time of these different environments is perhaps also reflected in the relatively high-diversity assemblage that so far has been recognized from the Wapiti Formation. Of especial note are the low-energy, damp-to-waterlogged ground facies interbedded within the unit 4 sequence, which retain sufficiently fine detail to preserve trace fossils from invertebrates (Bell et al., 2013) and small vertebrates. Late Cretaceous dinosaur track-bearing deposits in Canada are restricted to the Oldman, St. Mary River, Horseshoe Canyon, and Dinosaur Park formations (Therrien et al., 2011). As noted earlier, each of these formations are equivalent to parts of the Wapiti Formation, permitting some comparisons. Currie et al. (1991) noted hadrosaurid (Hadrosauropodus langstoni Lockley et al., 2004b) and less abundant tyrannosaurid tracks from the St Mary River Formation, the latter of which remain undescribed. Hadrosaurid and Ornithomimipus tracks have been described from the Horseshoe Canyon Formation (Sternberg, 1926; Langston, 1960), and rare hadrosaurid tracks have been identified in the Oldman (Therrien et al., 2011) and Dinosaur Park formations (McCrea and Buckley, 2005). Farlow et al. (2009) briefly noted a probable tyrannosaurid track from the Wapiti Formation in British Columbia. The recognition of at least seven track morphotypes (with correspondence to dubious amphibians, as well as mammals, large- and mediumsized theropods, hadrosaurids, and ankylosaurs) makes the Wapiti Formation the richest and most diverse track-bearing formation from the Late Cretaceous of Canada. Hadrosaurid tracks constitute the largest proportion of the Wapiti Formation ichnofauna. Curiously, ceratopsid tracks have not yet been identified in the Wapiti Formation although their bones are abundantly present based on several unusually dense Pachyrhinosaurus bonebeds (Currie et al., 2008). Information from tracks (this study) and microvertebrate remains (Fanti and Miyashita, 2009) may reflect a more ‘typical’ Late Cretaceous terrestrial ecosystem, whereby hadrosaurids are the dominant megaherbivores. At this stage taxonomic resolution in the Wapiti Formation is not detailed enough to accurately identify most potential trackmakers; however, the largest theropod track (UALVP 53475) can be confidently identified to a tyrannosaurid. Diagnostic Edmontosaurus sp. elements (UALVP 53549, UALVP 53722) from the Red Willow Falls area provide circumstantial evidence of the identity of Hadrosauropodus trackmakers. An isolated ankylosaur track provides additional evidence of nodosaurids previously identified from a single tooth (Fanti and Miyashita, 2009) and scute (TMP 2005.66.46). On the contrary, troodontids and dromaeosaurids, known from both shed teeth and skeletal elements (Currie et al., 2008; Fanti and Miyashita, 2009), are not yet represented by tracks. There is evidence for high diversity track assemblages in Cretaceous ecosystems (Zhang et al., 2006), as well as specifically in Late Cretaceous high-latitude continental ecosystems (Fiorillo and Parrish, 2004; Fiorillo et al., 2011; Fiorillo, pers. comm. 2011). Assemblages at higher palaeolatitudes than the Wapiti Formation include theropod and ornithopod traces (Lapparent, 1960; Hurum et al., 2006), indicating a seemingly cosmopolitan distribution of these types of trackmakers during the Cretaceous. The presence of tracksites including ornithopods in the Late Cretacous of Alaska

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(Fiorillo and Parrish, 2004), contemporaneous localities in Mongolia (Currie et al., 2003), and a series of representative sites extending through British Columbia (McCrea, 2003) and Alberta (Currie, 1989; McCrea and Currie, 1998; McCrea et al., 2001; Tanke, 2004; Therrien et al., 2011; this study) indicate the continuous presence of these animals throughout western North America up to its northernmost reaches. In addition, large ornithopod tracks are commonly associated with siliciclastic, plant-rich deposits that accumulated under humid climatic regimes (or water-logged environments) often at mid-to-high latitudes (Lockley, 1991; Matsukawa et al., 1995). Although vertebrate ichnofacies are not always consistent with the skeletal record in terms of inferred faunal composition, such studies support the hypothesis of a large intermittent land bridge between Asia and North America, connecting the dinosaurian fauna of these landmasses during the Cretaceous (Russell, 1993; Fiorillo, 2008; Bell, 2011; Zanno and Makovicky, 2011). In Asia, a review of tracksites revealed an increase in ornithopod-dominated track assemblages in the north relative to more southerly ichnofaunas, in association with humid settings along the continental margins (Matsukawa et al., 1995, 2006). Track proportions dominated by large ornithopods makes the Wapiti Formation assemblage consistent with typical Cretaceous ichnofaunas in floodplain deposits, as noted by Currie et al. (1991) and Lockley and Conrad (1989). This trend carries over to ichnofaunal associations in Mongolia (Currie et al., 2003), despite a skewed body fossil record in that case toward large predatory dinosaurs (Currie, 2009). In Mongolian, the ornithopod-dominated ichnofauna is more consistent with ‘typical’ faunal ratios and may be more representative of the true faunal composition. The notable lack of ceratopsian tracks in the Wapiti Formation despite their high body fossil count is consistent with a general paucity of ceratopsian tracks worldwide, although they have been located elsewhere in Late Cretaceous overbank floodplain deposits (Lockley and Hunt, 1995; Milner et al., 2006). The preponderance of ornithopod tracks to the complete exclusion of ceratopsian tracks in the Wapiti Formation to date is likely reflective of habitat preference, as suggested by other studies (Fricke and Pearson, 2008), although a collection and/or preservational bias cannot be ruled out. 7. Conclusions At least seven morphotypes are recognized and attributed to mammals, amphibians, tyrannosaurids, medium-sized theropods, hadrosaurids, and ankylosaurs. Most of these discoveries are concentrated within unit 4 (latest Campanian) in the exposures along Pipestone Creek, Red Willow River, and the Red Willow Falls area. The Wapiti Formation is unusual in that it yields roughly equal proportions of tracks to bones; however, taxonomic resolution is low, hindering potential identification of most trackmakers. Nevertheless, ichnological evidence supports previous assertions of a diverse high-latitude fauna (Fanti and Miyashita, 2009), which is in agreement with similar polar faunas from the Late Cretaceous of Alaska (Fiorillo et al., 2007, 2009, 2010, 2011, 2012). The ornithopod-dominated ichnofauna of the Wapiti Formation is typical of a Late Cretaceous assemblage, and consistent with other coeval assemblages in lowland floodplains in western North America. Of additional significance is the presence of small-bodied ectotherms (amphibian or lacertilian tracks) within a high-latitude context. The Wapiti Formation tracks provide an important additional data point linking a chain of sites from the Western Interior from Montana to Alaska. Their inclusion aids interpretation of a growing palaeobiogeographical picture of the dinosaur faunas of northwestern North America and eastern Asia during the Late Cretaceous.

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Acknowledgments D. Tanke (TMP) is gratefully acknowledged for his systematic surveys of the Wapiti Formation outcrops that has fueled this and other research in the area. Most of the tracks described here were found by the authors and collected with the help of M. Burns, C. Coy (Univ. of Alberta), R. Hunt and K. Ormay (GPRC) and other volunteers. We are indebted to R. Bickell for his skillful extraction of many of the described specimens and his generous donation of time and equipment. TMP 2004.97.1 was found and collected by D. Tanke with the help of S. Graber, B. Hunt, G. Erickson, and the first author. 3D models were acquired and processed by M. Contessi at the Museo Geologico Giovanni Capellini (Dipartimento di Scienze della Terra,Bologna, Italy). Grande Prairie Regional College and the Dinosaur Research Institute are gratefully acknowledged for funding and logistical support to F.F. We thank B. Strilisky (TMP) and P. Currie (Univ. of Alberta) for access to specimens. Comments from R.T. McCrea greatly improved this manuscritp: helpful reviews of an earlier version of the manuscript by A. Fiorillo and M. Avanzini are greatly appreciated. References Avanzini, M., Garcia-Ramos, J.C., Lires, J., Menegon, M., Pinuela, L., Fernandez, L.A., 2005. Turtle tracks from the Late Jurassic of Asturias, Spain. Acta Palaeontologica Polonica 50, 743e755. Avanzini, M., Pinuela, L., Garcia-Ramos, J.C., 2010. First report of a Late Jurassic lizard-like footprint (Asturias, Spain). Journal of Iberian Geology 36, 175e180. Avanzini, M., Pinuela, L., Garcìa-Ramos, J.C., 2012. Late Jurassic footprints reveal walking kinematics of theropod dinosaurs. Lethaia 45, 238e252. Bell, P.R., 2011. Cranial osteology and ontogeny of Saurolophus angustirostris from the Late Cretaceous of Mongolia with comments on Saurolophus osborni from Canada. Acta Palaeontologica Polonica 56, 703e722. Bell, P.R., 2012. Standardized terminology and potential taxonomic utility of hadrosaurid skin impressions: a case study for Saurolophus from Canada and Mongolia. PLoS One 7 (2), e31295. http://dx.doi.org/10.1371/journal. pone.0031295. Bell, P.R., Fanti, F., Sissons, R.L., Burns, M.E., Currie, P.J. Hadrosaurine material from the Wapiti Formation (CampanianeMaastrichtian), northwestern Alberta, In: Eberth, D.A., Evans, D.C., (Eds.), Hadrosaurs. Indiana University Press, Bloomington, in press. Bell, P.R., Fanti, F., Acorn, J., Sissons, R.L., 2013. Fossil mayfly larvae (Ephemeroptera, cf. Heptageniidae) from the Late Cretaceous Wapiti Formation, Alberta, Canada. Journal of Paleontology 87 (1), 146e149. Brand, L.R., 1979. Field and laboratory studies on the Coconino Sandstone (Permian) vertebrate footprints and their paleoecological implications. Palaeogeography, Palaeoclimatology, Palaeoecology 28, 25e38. Brand, L.R., 1992. Fossil vertebrate footprints in the Coconino Sandstone (Permian) of northern Arizona: evidence for underwater origin. Geology 20, 668e670. Brand, L.R., 1996. Variations in salamander trackways resulting from substrate differences. Journal of Paleontology 70, 1004e1010. Brinkman, D., 2003. A review of nonmarine turtles from the late Cretaceous of Alberta. Canadian Journal of Earth Sciences 40, 557e571. Brown, B., 1916. Corythosaurus casuarius: skeleton, musculature and epidermis. Bulletin of the American Museum of Natural History 35, 709e723. Brown, R.W., Lawrance, M.J., Pope, J., 1995. Animal tracks, trails and signs. Hamylin Guide, London, 320 pp. Buatois, L.A., Mangano, M.G., 1995. The paleoenvironmental and paleoecological significance of the lacustrine Mermia ichnofacies: an archetypical subaqueous nonmarine trace fossil assemblage. Ichnos 4, 151e161. Buatois, L.A., Mangano, M.G., 2004. Animal-substrate interactions in freshwater environments: applications of ichnology in facies and sequence stratigraphic analysis of fluvio-lacustrine successions. In: McIlroy, D. (Ed.), The application of ichnology to palaeoenvironmental and stratigraphic analysis. Geological Society, London, UK, Special Publication 228, pp. 311e333. Buckley, L., McCrea, R.T., 2009. The sodium hypochlorite solution for the removal of lichen from vertebrate track surfaces. Ichnos 16, 230e234. Contessi, M., Fanti, F., 2012. Vertebrate Tracksites in the Middle Jurassic-Upper Cretaceous of South Tunisia. Ichnos 19, 211e227. Currie, P.J., 1981. Bird footprints from the Gething Formation (Aptian, Lower Cretaceous) of Northeastern British Columbia, Canada. Journal of Vertebrate Paleontology 1 (3-4), 257e264. Currie, P. J., 1983. Hadrosaur trackways from the Lower Cretaceous of Canada. Acta Palaeontologica Polonica 28 (1-2), Second Symposium on Mesozoic Terrestrial Ecosystems, Jadwisim 1981, pp. 63e73. Currie, P.J., 1989. Dinosaur footprints of western Canada. In: Gillette, D.D., Lockley, M.G. (Eds.), Dinosaur Tracks and Traces. Cambridge University Press, Cambridge, pp. 293e300.

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