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Estonian Journal of Earth Sciences, 2018, 67, 1, 88–95 https://doi.org/10.3176/earth.2018.06 A new species of cyathaspid (Vertebrata: Pteraspidomorphi: Heterostraci) from the Lower Devonian Drake Bay Formation, Prince of Wales Island, Nunavut, Arctic Canada David K. Elliotta, Linda S. Lassiterb and Alain Blieckc a Geology Program, SESES, Northern Arizona University, Flagstaff, Arizona 86011-4099, U.S.A.; [email protected] b Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86011-5640, U.S.A.; [email protected] c Université de Lille – Sciences et technologies, bâtiment SN5 (Sciences de la Terre), UMR 8198 du CNRS “EvoEcoPaléo”, F-59655 Villeneuve d’Ascq Cedex, France; [email protected] Received 31 August 2017, accepted 4 December 2017, available online 31 January 2018 Abstract. A new genus and species of cyathaspid heterostracan, Faberaspis elgae, is described from the Early Devonian (Lochkovian, Pedavis pesavis conodont Zone) Drake Bay Formation of Prince of Wales Island, Nunavut, Arctic Canada, where it is associated with a rich shallow marine invertebrate fauna. Faberaspis is most closely related to Poraspis, but differs in details of the ornament and in possessing a more complete network of lateral line canals. Key words: phylogeny, Cyathaspididae, Agnatha, Heterostraci, Lower Devonian, Drake Bay Formation, Arctic Canada. INTRODUCTION position ranges from far posteriorly to the mid-shield. The ornamentation consists of dentine ridges commonly Vertebrate faunas from the Upper Silurian and Lower arranged in a longitudinal pattern on the shields. However, Devonian of Arctic Canada are well known and have in a few of the geologically oldest members of this taxon, been published in a series of papers since their discovery the ornamentation is dominated by scale-like elements in 1955 (Thorsteinsson 1958). This is particularly true formed by short ridges. The presently known age range for the Heterostraci, a widespread group of armoured of this order is Wenlock to Emsian (Denison 1964; jawless vertebrates in which the head and forepart of the Elliott & Petriello 2011). body are encased in a carapace consisting of a variable In 1975 a palaeontological expedition from Göttingen number of bony plates, and that are associated with and Cologne universities (Germany) visited Arctic possible non-marine and proximal environments of the Canada (Langenstrassen & Schultze 1996) and inter Old Red Sandstone continent (see Elliott et al. 1998 alia collected agnathans and gnathostomes in Lower and references therein; Elliott & Swift 2010; Elliott Devonian localities on the northern part of Prince of 2013, 2016). The Cyathaspididae constitute a family Wales Island (Fig. 1A). At Drake Bay, on the north- within the Heterostraci in which the carapace consists western coast of Prince of Wales Island, the group of a dorsal and ventral shield including branchial and explored exposures along Drake Bay and Smith Bay suborbital plates. The dorsal shield consists of a dorsal further south and collected the cyathaspid described median plate, the surface of which may be divided by here at locality P11 at the northern end of Smith Bay sutures into subdivisions termed epitega that represent (Langenstrassen & Schultze 1996: fig. 11; Elliott et al. areas of independent growth, and the paired branchial 2015; Fig. 1B). This cyathaspid is a member of the sub- and suborbital plates. The ventral shield contains the family Poraspidinae (sensu Denison 1964), members ventral median plate and the plates of the oral cover. of which are already well known from the Arctic The branchial plates are long and narrow, and the (Elliott et al. 1998). The type genus, Poraspis, has a branchial notch on the dorsal margin encloses the wide geographic distribution having been reported from branchial opening ventrally, a corresponding notch in Spitsbergen, eastern and western Europe as well as the lateral margin of the dorsal plate encloses them Canada’s District of Mackenzie and Arctic Archipelago, dorsally. The paired branchial openings commonly occur and the western United States (see Elliott & Petriello along the lateral borders of the dorsal plate where their 2011 and references therein). The genus also has a wide © 2018 Authors. This is an Open Access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International Licence (http://creativecommons.org/licenses/by/4.0). 88 D. K. Elliott et al.: New Devonian cyathaspid Fig. 1. Geologic map of Prince of Wales Island (A) with the location of the fossil locality P11 (B). temporal range from the Pridoli of Arctic Canada, through of the transition of sediments from fresh water to marine the Lochkovian of western Europe, Spitsbergen and Arctic that grades westwards across Prince of Wales Island. Canada, to the early or middle Pragian of Arctic Canada To the east the Peel Sound Formation (Thorsteinsson & and the Emsian of the western United States. Tozer 1963) consists of red sandstones and siltstones grading upwards into oligomict conglomerates and pebbly sandstones, deposited over a large delta system as sub- MATERIAL AND METHODS aerial fans prograding from the rising Boothia Uplift. The formation was divided into lower and upper members The specimen is preserved in a calcareous siltstone and on Prince of Wales Island (Miall 1970); the lower was prepared mechanically using an engraving tool with consisting of interbedded limestone, siltstone, sandstone a tungsten-carbide bit. The measurements and ratios and oligomict conglomerate is exposed only as a narrow employed follow those used by Denison (1964). The band along the flank of the Boothia Uplift. The upper specimen is the property of the Geology–Palaeontology member is characterized by the disappearance of virtually Institute and Museum of the University of Göttingen all but conglomerate in the succession (Miall 1970). and bears its catalogue number (prefixed GZG.V.). Westwards it grades through five distinct facies cropping out as north–south bands; conglomerate in the east is replaced laterally by conglomerate–sandstone, sandstone, STRATIGRAPHY AND AGE sandstone–carbonate and carbonate. To the west the marine carbonate facies has been renamed the Drake The cyathaspid described here was collected from the Bay Formation (Mayr 1978), based on a section from Drake Bay Formation (Mayr 1978), at Smith Bay on the a well on Russell Island, off the north coast of Prince of western coast of Prince of Wales Island, in 1975 Wales Island, and is probably laterally equivalent to the (Langenstrassen & Schultze 1996; Fig. 1). The Drake entire Peel Sound Formation (Mayr 1978). The lower Bay Formation represents the most distal carbonate facies member consists of white to very light brown, crystalline 89 Estonian Journal of Earth Sciences, 2018, 67, 1, 88–95 dolomite, while the upper member consists of grey Etymology. From Latin faber, a smith, after Smith Bay, carbonates interbedded with siltstones (Mayr 1978). The and Greek aspis, a shield. specimen described here comes from the upper member. Remarks. The Poraspidinae are a cyathaspid subfamily A geological section is not available for the locality in which the epitega are indicated faintly or not at all, that yielded the specimen described here (Fig. 1B). The and the dentine ridges are long and mainly longitudinal sediments consist of grey, marly to sandy and dolomitic in orientation, although they may radiate on the anterior limestones. A continuous transition from fine-grained, and diagonally on the lateral parts of the dorsal shield limy sandstone, to limy siltstone, to micritic limestones (Denison 1964). Faberaspis has no epitega and shows a and limy marlstones with dolomitic content changing particularly regular arrangement of longitudinal ridges from horizon to horizon was observed. The sediments that show only a slight radiation anteriorly. are well sorted with thinly bedded layers changing to fissile layers. At more northerly localities at Drake Faberaspis elgae new species Bay (Fig. 1B, P1) 50 cm to 2 m thick sandstones are Figure 2 intercalated in the marly limestones. These can be seen to thin out over short distances and are interpreted as tidal Holotype. One dorsal shield, GZG.V.29511. channels within a shallow coastal sea (Langenstrassen & Schultze 1996). Diagnosis. Large poraspid, length 52.0 mm, width ratio Smith (1976, 1980) and Mayr (1978) noted the 0.49, orbital ratio 0.21. Ridges flat-topped, 7 per mm at presence of brachiopods of possible Early Devonian age midline and 5 per mm at lateral margin; longitudinal on from the lowest part of the upper member and suggested the dorsal shield, fanning slightly over rostrum; starting an age of Ludlow to earliest Devonian for the lower at the level of the branchial opening a band of two or member and Gedinnian to early Siegenian (Lochkovian– three coarse round-topped ridges is present marginally, early Pragian) for the upper member. Sampling for increasing to seven around the orbit and 12 at the conodonts in the upper member (Smith 1976; Mayr anterior margin. Pineal macula present. Epitega not et al. 1980) yielded Ozarkodina remscheidensis in the present. Sensory canal system as in Poraspis but with lower and middle parts, indicating a Pridoli–Lochkovian more complete connection of the transverse commissures. age, and O. remscheidensis remscheidensis and Pedavis Etymology. Named after our colleague Dr Elga Mark- pesavis (Langenstrassen & Schultze 1996) in the upper Kurik in recognition of her many important contributions part, indicating a Lochkovian age (pesavis Zone). Surface to the study of early vertebrates. outcrops near the well on Russell Island yielded a Pragian fauna from strata near the top of the section, so the Occurrence. Twenty-eight kilometres south of the upper member appears to be Lochkovian, extending into Powichthys locality, Smith Bay, western coast of Prince the Pragian at the top. This age determination is supported of Wales Island, Nunavut, Arctic Canada (Fig. 1). Locality by identification of microvertebrates in the upper member P11 of Langenstrassen & Schultze (1996). Drake Bay (Vieth 1980; Märss et al.

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