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Microvertebrates from the Silurian–Devonian Boundary Beds of the Eastport Formation, Maine, Eastern USA Susan Turner and Carole J

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Microvertebrates from the Silurian–Devonian Boundary Beds of the Eastport Formation, Maine, Eastern USA Susan Turner and Carole J Document generated on 09/27/2021 5:08 a.m. Atlantic Geology Journal of the Atlantic Geoscience Society Revue de la Société Géoscientifique de l'Atlantique Microvertebrates from the Silurian–Devonian boundary beds of the Eastport Formation, Maine, eastern USA Susan Turner and Carole J. Burrow Volume 54, 2018 Article abstract Agnathan and gnathostome remains, associated with lingulid brachiopod URI: https://id.erudit.org/iderudit/1055415ar fragments and distinctive ostracods, have been extracted from a small DOI: https://doi.org/10.4138/atlgeol.2018.006 calcareous mudstone sample collected from the type section of the Eastport Formation on the northern shore of Moose Island, Maine. The vertebrate See table of contents assemblage includes osteostracan, anaspid, and thelodont scales, and acanthodian scales, spines and teeth, which support a late Pridoli, or possibly earliest Lochkovian, age for the stratum. The thelodont Paralogania denisoni n. Publisher(s) sp. is described, associated with a single thelodont scale referred tentatively to Talivalia? sp. indet., and acanthodians Nostolepis striata, Gomphonchus Atlantic Geoscience Society sandelensis, and Poracanthodes punctatus in a fauna that shows similarities to late Pridoli assemblages in Britain, parts of Europe, Russia, Greenland, and ISSN arctic Canada. 0843-5561 (print) 1718-7885 (digital) Explore this journal Cite this article Turner, S. & Burrow, C. (2018). Microvertebrates from the Silurian–Devonian boundary beds of the Eastport Formation, Maine, eastern USA. Atlantic Geology, 54, 171–187. https://doi.org/10.4138/atlgeol.2018.006 All Rights Reserved ©, 2018 Atlantic Geology This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ Microvertebrates from the Silurian–Devonian boundary beds of the Eastport Formation, Maine, eastern USA Susan Turner and Carole J. Burrow* Geosciences, Queensland Museum, 122 Gerler Road, Hendra, Queensland 4011, Australia *Corresponding author <[email protected]> Date received: 13 November 2017 ¶ Date accepted: 27 January 2018 ABSTRACT Agnathan and gnathostome remains, associated with lingulid brachiopod fragments and distinctive ostracods, have been extracted from a small calcareous mudstone sample collected from the type section of the Eastport Formation on the northern shore of Moose Island, Maine. The vertebrate assemblage includes osteostracan, anaspid, and thelodont scales, and acanthodian scales, spines and teeth, which support a late Pridoli, or possibly earliest Lochkovian, age for the stratum. The thelodont Paralogania denisoni n. sp. is described, associated with a single thelodont scale referred tentatively to Talivalia? sp. indet., and acanthodians Nostolepis striata, Gomphonchus sandelensis, and Poracanthodes punctatus in a fauna that shows similarities to late Pridoli assemblages in Britain, parts of Europe, Russia, Greenland, and arctic Canada. RÉSUMÉ Les restes d’agnathes et de gnathostomes, associés à des fragments de brachiopodes lingulidés et à des ostracodes distinctifs, ont été extraits d’un petit échantillon de mudstone calcaire prélevé de la section type de la formation d’Eastport sur la côte nord de Moose Island, dans le Maine. L’ ensemble d’animaux vertébrés comprend les ostéostracés, les anaspides, les écailles de thélodontes et les écailles, épines dorsales et dents d’acanthodiens, ce qui laisse penser que la strate date du Pridoli tardif ou du Lochkovien précoce. Le Paralogania denisoni n. sp. de thélodonte est décrit, en lien avec une seule écaille de thélodonte provisoirement appelée Talivalia? sp. indet., de même que les Nostolepis striata, Gomphonchus sandelensis et Poracanthodes punctatus d’acanthodiens, dans une faune qui montre des similarités avec des assemblages du Pridoli tardif de Grande-Bretagne, d’autres parties d’Europe, de Russie, du Groenland et de l’Arctique canadien. [Traduit par la redaction] INTRODUCTION a possible loganiid scale, was also reported from the Pridoli Dekker Formation (K. Denkler, pers. comm. to ST, 1990s, Few Silurian vertebrate sites have been described from unconfirmed record). Turner et al. (1999) discovered older the USA, and even fewer have been studied for vertebrate early Silurian microfossils of the thelodont Zuegelepis pota- microfossils (hereafter microvertebrates) such as thelodont nos from Illinois. Few other microvertebrate occurrences and acanthodian remains. The first record was of fin spines are known from the Silurian of the United States east coast; and heterostracans from Pennsylvania by Claypole (1884, other possible records (e.g., Turner 1999), such as Thelodus 1885); he assigned the fin spines (“small spines apparently sp. from Maryland, are also yet to be verified. of Selachian fish”: Claypole 1885, p. 426) to Onchus clintoni Abundant microvertebrate faunas have been described (Llandovery) and Onchus pennsylvanicus (Pridoli), and the from arctic Canadian localities, particularly of thelodont as- poraspidid heterostracan shields and scales to Palaeaspis semblages (e.g., Märss et al. 2007), with rarer descriptions americana and Palaeaspis bitruncata. Other records from of late Silurian to Early Devonian acanthodians (Spjeldnaes Pennsylvania were published by DeWindt (1974), who de- 1967; Vieth 1980; Burrow et al. 1999; Burrow 2013). From scribed purported acanthodian scales (actually thelodont eastern Canada, tolypelepid and corvaspid heterostracans scales) from upper Silurian beds of the Bloomsburg Forma- have been reported from the middle Silurian Eramosa La- tion, central Pennsylvania, and Giffin (1979), who published gerstätte, Ontario (von Bitter et al. 2007). From the late a full description of the thelodont scales from the same beds; Silurian, Turner (1986) redescribed the only known artic- her material is currently being re-assessed. One thelodont, ulated material of the thelodont type genus Thelodus and ATLANTIC GEOLOGY 54, 171–187 (2018) doi:10.4138/atlgeol.2018.006 Copyright © Atlantic Geology, 2018 0843-5561|18|00171–187$3.55|0 ATLANTIC GEOLOGY · VOLUME 54 · 2018 172 identified a Paralogania, as well as an acanthodian, from that extends from Massachusetts, USA, into New Bruns- the Cunningham Creek Formation of southern New Bruns- wick, Canada (Fig. 2); the type locality is at Moose Island, wick; and Burrow (2011) described the latter as a new acan- Hancock County, Maine (Bastin and Williams 1914). The thodian Nerepisacanthus denisoni from the nodule horizon. formation extends for more than 500 km, and is approxi- Burrow et al. (2013) redescribed a microvertebrate fauna, mately 2440 m thick in Maine according to Bastin and including thelodonts and acanthodians, from the upper Si- Williams (1914). The Eastport Formation is in a complex lurian outcrops at Arisaig, Nova Scotia (first described by stratigraphic setting, with subareal volcanic rocks and shal- Legault 1968), and Burrow and Rudkin (2014) described an low-water sedimentary rocks. Sedimentary rocks include: articulated specimen of Nerepisacanthus denisoni from the red siltstone; fine- to medium-grained sandstone; dark grey Bertie Formation of Ontario. Blaise et al. (1990, 1991) also to green mudstone, siltstone and sandstone some with cal- recorded Thelodus parvidens and undetermined acanthodi- careous content; minor red polymictic conglomerate; and an scales from late Silurian sites in the Meguma terrane of volcaniclastics. This succession represents deposition in a Nova Scotia. low-energy, peritidal environment, with volcanic rocks in- Relatively few middle Paleozoic fish remains are known tercalated throughout the formation, predominating over from Maine (Churchill-Dickson 2004). Bastin and Wil- the sedimentary rocks. liams (1914) mentioned a fish spine in a calcareous nodule The Silurian succession in the coastal volcanic belt of from the Eastport Formation, and the acanthodian Nosto Maine exhibits strong similarities to European Silurian se- lepis sp. was recorded informally by Robert Denison (Chur- quences, a fact that troubled pre-continental-drift workers chill-Dickson 2004, table 1). Churchill-Dickson (2007) (Churchill-Dickson 2004). Previously the age of this suc- reviewed vertebrate records from the Silurian–Devonian cession had been regarded as wholly Early Devonian (Loc- of Maine, noting Silurian records of ‘fish teeth’ (probably hkovian or Pragian), based principally on an undescribed conodonts) from the Edmunds Formation and acanthodian ostracod, which Berdan (1990) considered to belong to a spines from the Ames Knob Formation, as well as Devonian quadrilobate beyrichiacean form allied to Cornikloedenina; placoderm remains (‘Asterolepis’) from the Chapman Sand- but it is more like Carinokloedenia from the Pragian of Pod- stone. To date, other than the Denison material noted below, olia and the Lochkovian of northern France. Subsequently, we have been unable to track down any of the vertebrate careful analysis of the known fossil data led Churchill-Dick- specimens previously reported. son (2004) to conclude that the Eastport Formation is late Here we describe the microvertebrates from a sample Silurian (Pridoli) in age, an interpretation
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