Vertebrate Anatomy Morphology Palaeontology 1(1):23-33 23 ISSN 2292-1389 New information on two Late Cretaceous (Turonian) fishes from Lac des Bois, Northwest Territories, Canada Alison M. Murray*,1 and Stephen L. Cumbaa2 1Department of Biological Sciences, University of Alberta, Edmonton, AB, T6G 2E9, Canada, [email protected] 2Palaeobiology, Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, ON, K1P 6P4, [email protected] Abstract: Fishes from Turonian deposits at Lac des Bois, Northwest Territories, Canada, have previously been described based on material from calcareous mudstone concretions collected in 1969. A more recent collecting trip to the locality in 2010 led to the discovery of additional fossil fishes in a shale layer. These fishes, preserved in a different manner from the earlier collections, provide new information and allow reinterpretations of two previously described fishes, Aquilopiscis wilsoni (Pachyrhizodontidae) and Avitosmerus canadensis (Euteleostei). Although the new material allows a better under- standing of these two fishes, it does not change our ideas about their relationships.Avitosmerus canadensis remains in the Euteleostei with relationships uncertain, and Aquilopiscis wilsoni is confirmed as a member of the Pachyrhizodontidae. Key Words: Crossognathiformes; Euteleostei; North America; Western Interior Seaway INTRODUCTION metres lower, exposing more of the dipping shales. From these shales a small acanthomorph fish,Boreiohydrias dayi, Fossil fishes have been known from Turonian deposits at was described (Murray and Cumbaa 2013), and additional Lac des Bois, Northwest Territories since 1968 when geol- examples of Avitosmerus and Aquilopiscis that form the basis ogists studied the area and found fossil remains. In 1969, of this paper were recovered. David Bardack undertook the first concerted effort to collect The preservation of the fishes in the shales is differ- fossils from these deposits. The fossils collected by Bardack ent from the preservation in the concretions, in that and his team were almost exclusively recovered from calcar- the shales preserve finer details and therefore provide eous concretions, collected in situ and where tumbled down new information about the fishes previously described along the base of a kilometre-long shale outcrop. From this from the concretions. We here present this additional collection, several fishes were named including Avitosmerus information for two of the fishes previously described canadensis Fielitz, 2002, a small euteleost, Aquilopiscis from the nodules, Aquilopiscis wilsoni and Avitosmerus wilsoni Cumbaa and Murray, 2008, a pachyrhizodontid, canadensis. The new specimens preserved in the shales and Ornatipholis sahtu Cumbaa and Murray, 2008, an not only provide information on features not previously enchodontoid. Other fishes reported from the locality are described, but also allow us to significantly change the an unidentified caturid amiiform,Ichthyodectes ctenodon interpretation of some features, such as the caudal fin (Ichthyodectiformes), Osmeroides sp. (Elopiformes) and the skeleton of Avitosmerus canadensis. aulopiforms Enchodus gladiolus, E. petrosus and Cimolichthys sp. (Fielitz 1996; Cumbaa and Murray 2008). The locality was again visited by our field party in 2010. During this trip, GEOLOGY we discovered that vertebrate and invertebrate fossils were The Lac des Bois locality (GSC locality 84342, at about also recoverable in situ from shales along the shore of the 66˚52’N, 125˚22’W), is on the south shore of a small lake, 15 to 20 metres away from the base of the cliff, from peninsula that juts out into Lac des Bois on the western just above water level to the practical limit of our quarrying, side of the lake. The peninsula has greater relief than the about 15 to 20 cm below the water table. Estimating from surrounding area, with a kilometre-long, low shale cliff that field photographs supplied by David Bardack from his 1969 crops out a few metres from the lake shore. The fossilif- expedition, the level of Lac des Bois in 2010 was 1.5 to 2 erous concretions come from about three-quarters of the *corresponding author way up the cliff. The fossiliferous shales, in contrast, were Published February 6 2015 accessed from the lakeshore and even under the lake waters close to shore. Based on our correlation of the dipping © 2015 by the authors submitted October 28 2014; revisions received January 19 2015; sediments, the shales we sampled at the edge of the water accepted January 23 2015. Handling editor: Jordan Mallon. would be 2.07 m below the only layer with visible concre- Copyright by the author(s). This open access work is distributed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License, which permits non- commercial use, distribution, and reproduction provided no modifications are made and the original author and source are credited. For other permissions, contact the author(s). Vertebrate Anatomy Morphology Palaeontology 1(1):xxx-yyy tions in 2010. Examination of Bardack’s field photographs Holotype: CMN 17444. shows a second, lower, concretion-bearing layer on the cliff Paratype: CMN 17443. which was unfortunately covered by severe slumping in New Material: UALVP 55646 complete fish in part 2010. Extrapolating from our measurements of the dip, and counterpart (Fig. 1), UALVP 55647 isolated dentary, this second layer of smaller concretions sample by Bardack UALVP 55648 isolated dentary, and CMN 56501 anterior would have been within a few tens of centimetres strati- half of a fish in part and counterpart (Fig. 2). graphically of our lakeshore quarry shales. The Lac des Bois locality has been dated as early Turonian, based on the invertebrate assemblage (Jeletzky 1969 report DESCRIPTION in Cook and Aitken 1971). The formation itself has not This taxon was erected based mainly on two specimens, been named, but represents an open marine shale facies the holotype CMN 17444, and the paratype CMN 17443, (Yorath and Cook 1981). More precise dating based on both of which were preserved in part and counterpart. An bentonite samples bracketing the fossiliferous layer, and additional very poorly preserved specimen (CMN 17440) examination of the macro-invertebrates and Foraminifera and one in which most details have become obscured collected during the 2010 field season, are in progress. through embedding in bioplastic (CMN 17461), as well as some disarticulated bones (CMN 17428) and an isolated Materials head (CMN 17465), were also referred to this species. The collections from field work in 2010 are housed in the Most of these specimens preserve the elements as natural Canadian Museum of Nature (CMN) and the University of moulds, with some bone still present. Alberta Laboratory for Vertebrate Palaeontology (UALVP). Compared to the original description, there are few Photographs of smaller specimens and close-ups of larger details to add to the skull. The supraoccipital is larger than specimens were taken with a Nikon DCM1200C digital originally determined, and does appear to separate the two camera mounted on a Zeiss Discovery.V8 stereo micro- parietals in the midline, which is more similar to Rhacolepis scope, with the specimens first being coated with ammo- than Notelops (Forey 1977: figs. 1, 12). The mesethmoid nium chloride. Larger specimens were left uncoated and reaches farther posteriorly than previously described, to a photographed with an Olympus FE-370 digital camera. level above the middle of the lateral ethmoid, and this latter Anatomical terminology follows traditional usage. element does not quite reach the parasphenoid. The vomer Anatomical Abbreviations: ach, anterior ceratohyal; is hard to identify, but there are four large tooth sockets in ang, anguloarticular; ao, antorbital; brst, branchiostegal rays; specimen UALVP 55646 that are positioned anteriorly and cl, cleithrum; cor, coracoid; den, dentary; dfin pt, dorsal fin above the area of the premaxilla, which should correspond pterygiophores; ect, ectopterygoid; end, endopterygoid; epi, to the vomer, indicating this bone bore several large teeth. epioccipital; ex, extrascapular; fr, frontal; hy1-6, hypurals We cannot confirm the shape of a nasal, but we confirm 1-6; hyo, hyomandibula; io2-3, infraorbitals 2-3; iop, inter- there is no ornamentation on any of the bones. opercle; lac, lacrimal; le, lateral ethmoid; meth, mesethmoid; Similar to both Rhacolepis and Notelops (Forey 1977), the mx, maxilla; met, metapterygoid; npu1, neural spine of first angular and articular cannot be distinguished, thus appearing preural centrum; op, opercle; pa, parietal; pal, palatine; pch, to be fused together. The retroarticular is a small but robust posterior ceratohyal; pfin, pectoral fin; phy, parhypural; bone at the posteroventral medial corner of the lower jaw. pmx, premaxilla; pop, preopercle; psph, parasphenoid; ptf, Details of the postcranial skeleton are much better pre- posttemporal fossa; pto, pterotic; ptt, posttemporal; pu1- served on the new material than the original specimens. 2, preural centra 1-2; qu, quadrate; ret, retroarticular; sa, The cleithrum is gently curved and quite broad ventrally sesamoid articular; scl, supracleithrum; sm, supramaxilla; sn, but it narrows greatly at its dorsal extremity. There are 17 supraneural bones; so, supraorbital; soc, supraoccipital; sop, pectoral rays in UALVP 55646, as in the holotype. The subopercle; sph, sphenoid; sym, symplectic; u1-2, ural centra dorsal fin preserves 15 rays (UALVP 55646)