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Xiphactinus Audax Vertebrate Anatomy Morphology Palaeontology 1(1):89-100 89 ISSN 2292-1389 Xiphactinus audax Leidy 1870 from the Puskwaskau Formation (Santonian to Campanian) of north- western Alberta, Canada and the distribution of Xiphactinus in North America Matthew J. Vavrek1, Alison M. Murray2 and Phil R. Bell3 1Royal Ontario Museum, Department of Natural History, 100 Queen’s Park, Toronto, ON M5S 2C6, Canada, [email protected] 2Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada, [email protected] 3Department of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia, [email protected] Abstract: Xiphactinus is the largest teleost fish known from the Late Cretaceous of North America, and has been found across much of the Western Interior Basin. Despite extensive Late Cretaceous marine deposits occurring in Alberta, there has previ- ously been only two possible records of Xiphactinus from the province, neither of which has been diagnosable to the species level. We describe here a portion of the lower jaws, including teeth, of Xiphactinus audax from northeast of Grande Prairie, Alberta. The fossil has large, thecodont teeth that are circular in cross section and lack any carinae, and are highly variable in their overall size. This fossil is the first diagnostic material of X. audax from Alberta, and extends the range of the species by over a thousand kilometres. During the Late Cretaceous, the area the fossil was found in was near the Arctic Circle, and repre- sents an important datapoint within the poorly known, northern portion of the Western Interior Basin. Key Words: Ichthyodectiformes; Late Cretaceous; marine; Teleostei; Western Interior Basin INTRODUCTION from even larger individuals are also known (Bardack 1965; Shimada and Everhart 2004). The ichthyodectid Xiphactinus is the largest teleost fish Despite extensive marine deposits in Alberta, to date known from the Late Cretaceous of North America only two other questionable records of Xiphactinus have (Bardack 1965; Schwimmer et al. 1997; Shimada et al. been reported from the province. The first record is from 2006). Specimens of Xiphactinus have been found from “east of Lesser Slave Lake” noted by Bardack (1965). Cenomanian (Cumbaa et al. 2006) through Campanian However, he listed no referred material and gave no de- (DeMar and Breithaupt 2006) deposits throughout much scription of any specimen, with the record consisting only of the southern Western Interior Basin, from central of a personal communication from Wann Langston. A Saskatchewan (Cumbaa and Tokaryk 1999; Cumbaa et al. search of likely museum collections where any such fossils 2006) south to Texas (Bardack 1965), as well as Campanian would have been accessioned has yielded nothing. The to Maastrichtian beds along the Atlantic coast in New general lack of appropriate-aged fossil bearing deposits Jersey (Grandstaff et al. 1992), North Carolina, Georgia from that area, as well as the lack of referable or figured and Alabama (Schwimmer et al. 1997). Although known specimens, makes this record dubious. A second Albertan from a variety of formations, the most spectacular speci- record consists of two isolated scales from the Kaskapau mens of Xiphactinus come from the Niobrara Formation of Formation near Watino, Alberta (Wilson and Chalifa Kansas, where well-preserved, virtually complete skeletons 1989), although those authors note that the scales do not were being excavated as early as the 1870s (Cope 1872; conform in every aspect with those of Xiphactinus and so Bardack 1965). Some of these nearly complete specimens referred the specimens to “cf. Xiphactinus”. are close to 5 m in total length, although isolated elements The specimen we describe here, TMP 1973.011.3081, was first mentioned in an unpublished PhD thesis by Published 4 February, 2016 © 2016 by the authors Christopher Collom (2001), and later mentioned again by submitted August 23, 2015; revisions received January 28, 2016; Bell et al. (2014). However, the specimen itself was never accepted January 29, 2016. Handling editor: Robert Holmes. Vertebrate Anatomy Morphology Palaeontology is an open access journal http://ejournals.library.ualberta.ca/index.php/VAMP Article copyright by the author(s). This open access work is distributed under a Creative Commons Attribution 4.0 International (CC By 4.0) License, meaning you must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use. No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits. Vertebrate Anatomy Morphology Palaeontology 1(1):89-100 described and was only assigned to the genus Xiphactinus. Although the exact stratigraphic position of the fossil is Further study of the specimen has revealed a number of unknown, the matrix still attached to the fossil is similar in characteristics that allow the assignment of the specimen nature to a number of other marine vertebrate specimens more precisely to Xiphactinus audax, expanding the range found in the area, particularly those discussed by Bell et of this species considerably. The specimen itself is nota- al. (2014). The majority of the specimens discussed in that ble for its relatively northern location within the Western paper were inferred to have come from the upper portions Interior Seaway, and also confirms and fully documents the of the Puskwaskau Formation, likely the Chungo or Nomad presence of Xiphactinus in Alberta. members (Bell et al. 2014). This is further corroborated by Institutional Abbreviations: CMN, Canadian the location where TMP 1973.011.3081 was found, on Museum of Nature, Ottawa, Ontario, Canada; TMP, Royal a relatively small, shallow creek that drains a limited area. Tyrrell Museum of Palaeontology, Drumheller, Alberta, Geologic maps of the region indicate that the creek drains Canada; UALVP, University of Alberta Laboratory for an area that is mainly part of the upper portions of the Vertebrate Palaeontology, Edmonton, Alberta, Canada. Puskwaskau Formation, concordant with the idea that the fossil comes from one of the upper members of the forma- GEOLOGICAL SETTING tion. Assuming TMP 1973.011.3081 is from one of these upper members, it would be early Campanian in age. The Puskwaskau Formation is a marine, mudstone-dom- inated wedge up to 350 m in thickness, that was deposited SYSTEMATIC PALAEONTOLOGY in relatively shallow waters of the Western Interior Seaway (Hu and Plint 2009). The Puskwaskau was deposited during Order ICHTHYODECTIFORMES Bardack and the Niobrara Cycle (Kauffman 1977), and is Santonian to Sprinkle, 1969 early Campanian in age (Hu and Plint 2009; Fig. 1). The Family ICHTHYODECTIDAE Patterson and Rosen 1977 Puskwaskau is divided into five members, which are, in Genus Xiphactinus Leidy 1870 ascending order, Dowling, Thistle, Hanson, Chungo and Xiphactinus audax Leidy 1870 Nomad (Stott 1963, 1967; Hu and Plint 2009). Collom Figure 2 (2001) suggested that the Santonian/Campanian boundary is within the upper part of the Hanson Member, placing the Referred Material: TMP 1973.011.3081, the anterior Chungo and Nomad members within the lower Campanian. portion of articulated left and right dentaries. Figure 1. A) Summary stratigraph- ic chart for the Santonian to early Campanian of northwestern Alberta. B) Maps showing, counter-clockwise from top right: location of Alberta within Canada; location of regional map of Grande Prairie area within Al- berta; location of fossil site along Ka- kut Creek, northeast of Grande Prai- rie. Location of TMP 1973.011.3081 is marked with an arrow. 90 Vavrek et al. — Xiphactinus from Alberta Figure 2. TMP 1973.011.3081, partial jaws of Xiphactinus audax Leidy 1870. A) Right lateral view. B) Left lateral view. C) Posterior view. For all line drawings matrix is shaded white, bone is shaded light grey, teeth are shaded dark grey, and cross-hatching indicates areas of exposed tooth root. Locality and Horizon: The fossil was likely collected Description: TMP 1973.011.3081 preserves approximately sometime in the 1950s or 1960s, based on the personal the anterior one-third of the left and right dentaries, and meas- collection records of George Robinson, the original collector. ures 16 cm long. The dentary symphysis forms a sigmoidal The notes associated with the fossil in the TMP collections curve in lateral view with a tooth positioned on each side right state that the specimen was “from the Bad Heart River near beside the symphysis. The pores for the mandibular canal are bridge.” However, in Robinson’s original collections ledg- not clearly visible as this area of the jaw is somewhat dis- er, he noted that he found the fossil along “Kakut Ck near torted and very worn. The symphysis measures 9.2 cm in a bridge on Wanham Rd” and that it came from the “Bad straight line from the lower edge to the upper, which is close Heart Sst.” Another note he made, beside the entry for sev- to the average length for X. audax [8.7 cm with a range of eral invertebrate specimens collected from the same location, 6.0–13.85 based on measurements of 81 specimens (Bardack states that the bridge had been replaced by a culvert. His 1965)]. The dorsal surfaces of the dentaries undulate, being description, and comparison with historical maps of the area deepest under the largest tooth. and modern maps, shows that the fossil came from exposures There are six right and six left tooth positions preserved, near Kakut Creek where the present day Secondary Highway some of which contain almost complete teeth while others 733 crosses it, at approximately 55.61°N 118.39°W. The are represented only by the tooth base. The two anterior-most exact horizon the fossil came from is unknown, and it was teeth on either side of the symphysis are fairly large, and likely found ex situ, as the unprepared portions of matrix still would have reached an estimated 3 cm above the dentary attached appear to have been water worn, likely from sitting bone.
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