1405 Early stylonurine from Arctic Canada

James C. Lamsdell, Simon J. Braddy, Elizabeth J. Loeffler, and David L. Dineley

Abstract: Two new stylonurine eurypterids are described from the Peel Sound Formation (Early Devonian, Lochkovian) of the northern coast of Prince of Wales Island, Nunavut, Arctic Canada. Associations including pteraspids and ostracodes indicate a fluvial depositional environment. An almost complete stylonurid, Pagea plotnicki sp. nov., is recognized by its large size and lack of vaulting on the carapace, and it provides evidence that Stylonurus and Pagea are sister-taxa. Also, a smaller incomplete rhenopterid assigned to Leiopterella tetliei gen. et sp. nov., is characterized by its broad turbinate cara- pace and lack of cuticular sculpture. This assemblage provides the first Canadian record of Pagea, and the youngest occur- rence of a rhenopterid outside the Rheno-Hercynian Terrane, indicating that these taxa were more geographically widespread than previously supposed. Re´sume´ : Deux nouveaux eurypte´rides stylonuride´s provenant de la Formation de Peel Sound (De´vonien pre´coce, Lochko- vien) de la coˆte nord de l’ıˆle Prince-de-Galles, au Nunavut, dans l’Arctique canadien, sont de´crits. Des associations com- prenant des pte´raspides et des ostracodes indiquent un milieu de de´poˆt fluvial. Un stylonuride quasi complet, Pagea plotnicki sp. nov., se distinguant par sa grande taille et l’absence de structures en vouˆte sur sa carapace, appuie l’hypo- the`se selon laquelle Stylonurus et Pagea seraient des taxons fre`res. En outre, un rhe´nopte´ride incomplet plus petit affecte´ a` Leiopterella tetliei gen. et sp. nov. se distingue par sa large carapace turbine´e et l’absence de sculpture cuticulaire. Cet as- semblage constitue le premier exemple canadien documente´ de Pagea et l’exemple le plus re´cent d’un rhe´nopte´ride a` l’ex- te´rieur du terrane rhe´no-hercynien, ce qui e´largie la distribution ge´ographique de ces taxons.

Introduction Enigmatic raptorial appendages assigned to Angustidon- tus, known from the Late Devonian of Yukon Territory and Eurypterids () are Palaeozoic aquatic predatory the lowermost of Alberta (Copeland and Bol- . Some grew to gigantic proportions, probably ton 1960), were previously suggested to have affinities with driven by environmental stress and competition with other Eurypterida (Briggs 1979; Braddy and Dunlop 2000), (Lamsdell and Braddy 2010). Eurypterids are glob- although more recent work has convincingly shown that An- ally widespread but tend to be restricted to Konservat–La- gustidontus is a eumalacostracan crustacean (Rolfe and Dzik gersta¨tte because of their unmineralized cuticle (Gupta et al. 2006). 2007), the most famous of which are found along the eastern trackways are also known from the of seaboard of the USA (Clarke and Ruedemann 1912). Most Ontario (Braddy and Dunlop 2000), the Early Devonian of eurypterids reported from Canadian localities represent nek- New Brunswick (Greiner 1972), and the Middle Devonian tonic forms with prosomal appendage VI modified into a of Quebec (Braddy and Milner 1998), some of which are at- swimming paddle (Eurypterina). These are known primarily tributed to large stylonurine eurypterids. from the Late (Stott et al. 2005) and Silurian The fossil record of Canadian Stylonurina (eurypterids (Copeland and Bolton 1960, 1985; Rudkin et al. 1998) of with their posterior prosomal appendages adapted for walk- Ontario, with more recent reports from the Late Ordovician ing) is even sparser than that of the Eurypterina. Only four of Manitoba (Young et al. 2007). The Canadian Arctic re- stylonurine species are known: (1) a kokomopterid (Rudkin cord of Eurypterina is very sparse; only , Carci- et al. 1998); (2) an unidentified taxon from the Middle Dev- nosoma, Rhinocarcinosoma, and Erieopterus have so far onian of Quebec (Jeram 1996); (3) a specimen described as been reported, from the Silurian and Early Devonian Stylonurus sp. from the Early Devonian of Cornwallis Island (Braddy and Dunlop 2000, and references therein), based on (Plotnick and Elliott 1995); and, (4) Drepanopterus sp. from fragmentary specimens of isolated carapaces or appendages. the Early Devonian of Anderson River in the Northwest Ter- Received 11 February 2010. Accepted 25 May 2010. Published ritories (Braddy and Dunlop 2000; Lamsdell et al. 2009). on the NRC Research Press Web site at cjes.nrc.ca on In this paper, we report on a new Early Devonian euryp- 27 October 2010. terid fauna from the Peel Sound Formation, 29 km south- west of Bellot Cliff on the north coast of Prince of Wales Paper handled by Associate Editor J. Jin. Island, Nunavut, in the Canadian Arctic (Dineley 1994, J.C. Lamsdell,1,2 S.J. Braddy, E.J. Loeffler, and D.L. Dineley. Fig. 1, locality F). The strata at this locality have been dated Department of Earth Sciences, University of Bristol, Wills as Early Devonian (Lochkovian), based on agnathan and Memorial Building, Queen’s Road, Bristol, BS8 1RJ, UK. gnathostome vertebrate occurrences (Elliott 1984). 1Corresponding author (e-mail: [email protected]). The palaeoenvironment most likely represents an alluvial 2Present address: Paleontological Institute, University of Kansas, fan system (Broad et al. 1968), with the marine Douro For- 1475 Jayhawk Boulevard, Lawrence, KS 66045, USA. mation grading into the nonmarine Peel Sound Formation

Can. J. Earth Sci. 47: 1405–1415 (2010) doi:10.1139/E10-053 Published by NRC Research Press 1406 Can. J. Earth Sci. Vol. 47, 2010

(Dineley 1965). The fossils are found in two lenses of calca- positioned lateral eyes, also indicate affinities with the Laur- reous siltstone and sandstone, which yield enormous quanti- ieipteridae. The two families were, therefore, synonymized ties of well preserved, transported material. One lens is by Lamsdell et al. (2010). characterized by numerous well-preserved cephalaspids, with associated Ctenaspis, and a few pteraspids (Dineley Genus Pagea Waterston, 1962 1966). The other contains abundant large pteraspids, Ctenas- Pagea plotnicki sp. nov pis, arthrodires (Arctolepida), acanthodian spines, possible antiarchs, arthropods, and vascular plant material. These ar- (Figs. 1a,1b;2a,2b) Stylonurus thropods consist of the stylonurines reported here, fragments 1995 sp. Plotnick and Elliott, p. 399, fig. 2. of pterygotid cuticle, an , and ostracodes. Etymology Materials and methods Named after Professor Roy Plotnick, who described a specimen now assigned to this new species with Professor The material described here was collected in 1973 as part David Elliott in 1995. of a joint University of Bristol (Bristol, UK) and University of Ottawa (Ottawa, Ontario, Canada) expedition led by DLD Diagnosis and Brian Jones. The eurypterids are preserved in a dark Large Pagea lacking clear vaulting of the carapace or tri- grey, poorly laminated pale brown marl matrix. Cuticle is lobation of the opisthosoma; spines on appendage IV broad often preserved as a darker brown film. The fossils were and robust; tergites with acicular scales along their posterior photographed using a Nikon D40 with 60 mm micro Nikkor margins. lens, under water to emphasise contrast, and drawn using Adobe Illustrator CS3. All measurements are given in milli- Type material metres. Morphological terminology follows Tollerton (1989) and Selden (1981), while higher systematics follows Lams- CMN 53570 (holotype), single large specimen comprising dell et al. (2010). The phylogenetic analysis was performed carapace, opisthosomal segments 1–12 and prosomal appen- using Phylogenetic Analysis Using Parsimony (PAUP)* dages III, IV, V, and VI; CMN 53571 (paratype) prosomal 4.0b10 (Swofford 2003), using the matrix in Lamsdell et al. appendage; CMN 53572 (paratype) base of the pretelson. (2010) with the addition of the taxa described herein and Pagea symondsii along with several characters that help to Additional material differentiate these taxa. The synziphosurine Weinbergina UA10477 (University of Alberta, Edmonton, Canada), opitzi was retained as outgroup for the reasons outlined by large specimen consisting of carapace and anterior tergites Lamsdell et al. (2010), while Eurypterina is represented by (Plotnick and Elliott 1995). Moselopterus ancylotelson,‘‘Drepanopterus’’ bembycoides, Vinetopterus struvei, Onychopterella augusti, Eurypterus re- Horizon and locality mipes, and socialis. Multiple exemplars of the As described earlier in the text. suborder are included as they more accurately represent the character states and transitions of the group than a single Description exemplar, such as Eurypterus or a composite taxon would Holotype CMN 53570 (Fig. 1a,1b). Almost complete (see Brusatte 2010). The material described herein is depos- specimen lacking telson and majority of anterior prosomal ited in the collections of the Canadian Museum of Nature appendages. Opisthosomal segments dimensions shown in (CMN 53570 – CMN 53573), Ottawa, Canada. Table 1. Carapace has a preserved length of 160 mm and a width of 120 mm. Marginal rim 7 mm wide along the ante- rior edge, narrowing evenly posteriorly to 2 mm. Lateral Systematic palaeontology eyes positioned centrimesially, 50 mm apart with an oval Order Eurypterida Burmeister, 1843 ocular area 30 mm long and 27 mm wide. Median ridge sit- Suborder Stylonurina Diener, 1924 uated between the lateral eyes, 14 mm wide and 91 mm Superfamily Stylonuroidea Diener, 1924 long, terminating at the probable location of the ocelli and Family Stylonuridae Diener, 1924 extending back to the raised posterior of the carapace. = Laurieipteridae Kjellesvig-Waering, 1966 Raised area correlates with the position of the coxae of ap- pendage VI, which were very large. Carapace notches in- wards along the lateral edge, 67 mm from base. Diagnosis Ornamentation appears dimpled with occasional semi-lunate Stylonuroidea with undifferentiated opisthosoma, proso- scales. Two prosomal appendages are articulated on the mal appendages II–IV spiniferous Ctenopterus-type and V– right side of the carapace; appendage V has three podomeres VI non-spiniferous Pagea-type. preserved in full (V-3, V-4, V-5), and appendage VI only two (VI-4, VI-5). Single podomere joint of appendage IV Remarks also preserved, 12 mm wide. V-3 is 18 mm long, 20 mm Kjellesvig-Waering (1966) separated the Laurieipteridae wide, V-4 is 59 mm long, 24 mm wide at base narrowing from the Stylonuridae based on the broad, rectangular shape to 16 mm distally. V-5 preserved length 64 mm, 12 mm of their . The prosomal appendages of Pagea in- wide at base narrowing to 7 mm distally. VI-4 is 45 mm dicate that it belongs within the Laurieipteridae, and several long, 11 mm wide. VI-5 preserved length 50 mm, narrows features in Stylonurus, including its long telson and centrally distally with grooves along each lateral edge. Left side of

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Fig. 1. Pagea plotnicki sp. nov., Prince of Wales Island, Nunavut, Canada. (a) Holotype CMN 53570. Scale bar = 4 cm. (b) Interpretive drawing of CMN 53570. Scale bar = 4 cm. MR, marginal rim; C, carapace; LE, lateral eyes; MRi, median ridge; S, spines; AF, axial fur- rows; TR, transverse ridges. Prosomal appendages are labelled with Roman numerals and individual podomeres with Arabic numerals from proximally to distally.

carapace preserves four appendages; single podomere of ap- grooved along each lateral edge. Second podomere has a pendage III, 50 mm long and 15 mm wide, with four pairs preserved length of 59 mm with a median ridge running of fixed spines, 5 mm wide and 10 mm long, single poorly along its length. preserved podomere of appendage IV, 44 mm long and Paratype CMN 53572 (Fig. 2b). Segments 10 and 11 of 11 mm wide, six podomeres of appendage V and a distal po- metasoma and pretelson. Segment 10 is 72 mm wide, length domere of appendage VI. V-2 and V-3 are poorly preserved, unknown. Segment 11 preserved width 60 mm, length V-4 is 35 mm long and 14 mm wide, V-5 is 76 mm long, 32 mm. Pretelson has a preserved length of 130 mm and is 10 mm wide at its base expanding distally to 11 mm, bow- keeled medially. ing centrally to 9 mm with grooves 2 mm from each lateral edge. V-6 is 36 mm long and 11 mm wide, V-7 is indistinct, Remarks 34 mm long and 11 mm wide. The opisthosoma is raised Although lacking some of the diagnostic ventral struc- centrally with faint axial furrows running along either side. tures, these specimens display several characteristics that Each mesosomal segment has a transverse ridge 7 mm from firmly place them in the genus Pagea:(i) the multiple pairs its anterior margin. Pretelson greatly elongated, bears a me- of fixed spines on appendage III; (ii) the quadrate-shaped dian keel 23 mm wide, 29 mm from the lateral pretelson carapace; (iii) the broad marginal rim of the carapace nar- edge. The mesosomal segments have rounded edges, while rowing posteriorly; (iv) the oval shape, large size, and cen- the metasomal segments bear small epimerae. trimesial position of the lateral eyes; (v) the Pagea-type Paratype CMN 53571 (Fig. 2a). Prosomal appendage con- posterior pairs of prosomal appendages; (vi) the axial fur- sisting of two podomeres of Pagea-type. First podomere rows on the opisthosoma; and (vii), the broad, elongated pre- 85 mm long, 10 mm wide expanding to 15 mm distally, telson with its median keel.

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Fig. 2. Pagea plotnicki, Prince of Wales Island, Nunavut, Canada. 115 cm, suggesting that it is the adult form of CMN 53570. (a) Paratype CMN 53571. Prosomal appendage. Scale bar = 5 cm. (b) Paratype CMN 53572. Opisthosomal segments 10 and 11 and Superfamily Rhenopteroidea Størmer, 1951 (nom. trans. pretelson. Scale bar = 5 cm. Lamsdell et al. 2010) Family Rhenopteridae Størmer, 1951 = Brachyopterellidae Tollerton, 1989 = Alkenopteridae Poschmann and Tetlie, 2004

Diagnosis Rhenopteroidea with single fixed spines on prosomal ap- pendage III and a short telson. Appendages II–IV with short, fixed spines; V–VI non-spiniferous.

Remarks The Rhenopteridae, as currently defined, contains five genera, most of which had previously been placed in mono- typic families, forming a basal clade of relatively primitive stylonurines (Lamsdell et al. 2010). Genus Leiopterella gen. nov

Etymology Leio is from the Greek leios, meaning smooth. pterella is from the Greek pteros for wing, the traditional suffix ap- plied to eurypterid genera.

Diagnosis Rhenopteridae with turbinate carapace lacking cuticular sculpture; ventral sutures of Eurypterus-type; gnathobases large and robust; type-B genital appendage short with bi- lobed termination. Leiopterella tetliei sp. nov (Figs. 3a,3b)

Etymology Named after Dr. O. Erik Tetlie for his many contributions Only two other species of Pagea are known, P. sturrocki to the study of eurypterids. and P. symondsii, both from the Early Devonian (Lochko- vian) of the UK. The type species, P. sturrocki Waterston, Type material 1962, is known only from the holotype. The general mor- phology of P. plotnicki n. sp. corresponds well to P. stur- Holotype CMN 53573, single small specimen consisting rocki, although the axial furrows are not so well developed of prosoma and four opisthosomal segments, detailing coxae, and the opisthosoma of the holotype is much broader, a gen- faintly preserved metastoma, ventral sutures, portions of pro- eral trait of juvenile eurypterids (Andrews et al. 1974). The somal appendages IV–VI and type B genital appendage. adult P. sturrocki has a length of 65 cm, while CMN 53570 has an observed length of 54 cm, with an estimated total Horizon and locality length of 75 cm; P. plotnicki reached a far greater adult size. As described earlier in the text. Plotnick and Elliott (1995) described a stylonurine euryp- terid from Arctic Canada as Stylonurus sp. (UA10477), Description based on similarities in the form of the carapace median Holotype CMN 53573 (Fig. 3a,3b) carapace turbinate, ridge, lateral eye shape, and shortening of the first tergite. 37 mm long and 29 mm wide at its base, lateral angle 758. However, it differs significantly from the type species, Sty- Narrow marginal doublure 1 mm wide. Ventral sutures lonurus powriensis, in lacking trilobation of the opistho- faintly preserved, of Eurypterus-type, with right median soma. The holotype specimen of P. plotnicki corresponds ventral plate absent. Left chelicera faintly preserved, length well with UA10477, showing identical form and positioning 3 mm, width 2 mm. Left coxae well preserved; II-1 length of the lateral eyes and shape of the carapace, and they are 5 mm, width 3 mm; III-1 length 7 mm, width 3 mm; IV-1 herein considered conspecific. The opisthosoma of length 7 mm, width 3 mm, with attached IV-2 (3 mm long, UA10477 is much narrower, in keeping with that of Pagea 3 mm wide); V-1 length 7 mm, width 3 mm. VI-1 length sturrocki, and the specimen has an estimated total length of 23 mm, width 15 mm. Large, robust gnathobases preserved as dark stains on right side. Two disarticulated prosomal ap-

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Table 1. Proportions of the holotype specimen CMN 53570 of Pagea plotnicki.

Proportions (length/width) of opisthosomal segments, in specimen CMN 53570 1 2 3 4 5 6 7 8 9 10 11 12 13/132 21/134 37/149 35/153 33/142 39/142 23/129 24/132 19/122 22/119 25/100* 84*/89* *Preserved dimensions.

Fig. 3. Leiopterella tetliei gen. et sp. nov., Prince of Wales Island, Nunavut, Canada. (a) Holotype CMN 53573. Scale bar = 1 cm. (B) Interpretive drawing of CMN 53573. Scale bar = 1 cm. Abbreviations as in Fig. 1b with the addition of TS, transverse suture; MVP, median ventral plate; MS, median suture; G, gnathobases; Ch, chelicera; S, spines; M, metastoma; AOP, anterior opercular plate; MOP, median opercular plate; POP, posterior opercular plate; GA, genital appendage; B, blattfu¨sse.

pendages preserved to the right of the specimen; first (prob- Remarks ably IV) three podomeres 11 mm, 12 mm, and 10 mm long, The specimen probably represents an exuvium, an inter- each 3 mm wide with small, fixed spines at their distal mar- pretation suggested by the absence of one of the ventral gins, second (probably V) two podomeres 10 mm long plates, which detach during ecdysis (Tetlie et al. 2008). 3 mm wide and 4 mm long, 3 mm wide. Metastoma faintly Although it as been suggested that eurypterids moulted in a preserved between coxae VI; anterior and posterior margins supine position (Tollerton 1997) Tetlie et al. found no evi- visible, while sides are barely distinguishable. Shape oval dence for a preferred dorsal or ventral posture in eurypter- with anterior notch; width 15 mm, length 18 mm. Append- ids, while moults could be reoriented after ecdysis by water age VI partially preserved on right side. VI-1 length currents (Braddy 2001). 23 mm, width 15 mm; VI-2 length 4 mm, width 6 mm; VI- Leiopterella gen. nov. shows several similarities with the ge- 3 length 8 mm, width 6 mm, VI-4 length 11 mm, width nus Brachyopterella,fromtheWenlockofScotlandandNor- 4 mm, VI-5 length 6 mm, width 4 mm, VI-6 length 6 mm, way, particularly the anterior widening of the carapace. width 4 mm. Genital operculum 10 mm long and 32 mm Brachyopterella was transferred to the Rhenopteridae by Lams- wide, preserving anterior, median and posterior plates. Type dell et al. (2010) despite its possession of an epistoma, a charac- B genital appendage length 8 mm, width 3 mm, with bi- ter usually associated with the Laurieipterinae in stylonurines. lobed termination. Three blattfu¨sse preserved: first 9 mm The underside of Leiopterella bears a resemblance to Rhe- long and 32 mm wide; second 10 mm long, 32 mm wide; nopterus, as reconstructed by Størmer (1936), yet differs in third 9 mm long, preserved width 16 mm. No ornamentation the shape of the carapace and the lack of cuticular ornamen- or cuticular sculpture is evident on the specimen. tation. The genital appendage faintly preserves a bilobed ter-

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Fig. 4. Cladogram of the relationships of the Stylonurina, as presented by Lamsdell et al. (2010), with the inclusion of the species discussed herein. The single MPT (most parsimonious tree) was retrieved from analysis of the data set in Appendix A. Tree length = 126, CI (consis- tency index) = 0.571, RI (retention index) = 0.729, RC (re-scaled consistency index) = 0.416. Jackknife support (20% resampling, 1000 repetitions) is shown above the nodes and is often higher than at the corresponding nodes in Lamsdell et al. (2010). The taxa representing Eurypterina resolve as in the analysis of Lamsdell et al. (2010) and are represented in the figure by a single terminal.

mination, which may represent the primitive state within Discussion Eurypterida. The specimen clearly links Brachyopterella with the other basal rhenopterids Brachyopterus and Kiaer- The relationships of the Stylonuridae are poorly resolved, opterus; the widest point of the mesosoma is around the sec- with the family previously including several genera (e.g., ond segment, and Brachyopterus, Brachyopterella, and Hallipterus) now known to belong in other families. The Leiopterella all display a narrow marginal rim to the cara- new material of Pagea supports the relationships of the pace, while Brachyopterus, Kiaeropterus, and Leiopterella Superfamily Stylonuroidea and its two constituent families, share a lack of cuticular sculpture. The dorsal structures of the Parastylonuridae and the Stylonuridae, as proposed by the carapace of Leiopterella are not preserved, but it is Lamsdell et al. (2010). likely that the eyes were large and converging anteriorly as The holotype of Pagea sturrocki does not preserve the in Brachyopterella and Kiaeropterus and that the ocelli were dorsal structures of the carapace, and as such Waterston situated within an ocellar area. (1962) reconstructed the dorsal anatomy based on Stylonurus Leiopterella gen. nov. is clearly separated from Brachyop- powriensis. The new specimens with their dorsal structures terus by the possession of crests rather than broad ridges on preserved reveal just how accurate this assumption was; Sty- its podomeres, a more derived rhenopterid character. It dif- lonurus and Pagea appear to be very closely related. Previ- fers from Brachyopterella in the shape of the carapace and ously, Lamsdell et al. (2010) resolved them within a the absence of an epistoma. paraphyletic grade, from the Parastylonuridae to Ctenopterus

Published by NRC Research Press Lamsdell et al. 1411 and Laurieipterus; however, the analysis herein resolves Acknowledgements them as sister-taxa (Fig. 4). Of the three species assigned to We thank Simon Powell (University of Bristol, Bristol, Pagea, P. sturrocki, and P. symondsii are united by strong UK) for photographing CMN 53570 and 53573, Andrew vaulting of the carapace. Both are known from the Lochko- Ross (National Museums of Scotland, Edinburgh, Scotland, vian of the UK (the former from Scotland, the latter from UK) for access to Stylonurus powriensis and for providing Herefordshire), and may be synonyms. P. symondsii could pictures of Pagea sturrocki for comparative purposes, and be a juvenile of P. sturrocki (length 65 cm), as the smaller Paul Shepherd (British Geological Survey (BGS), Keyworth, but otherwise identical carapace of P. symondsii indicates a Nottingham, UK) for access to Pagea symondsii. Jisuo Jin total length of 35 cm. If this were the case then P. symondsii (The University of Western Ontario, London, Ontario, Can- would have priority, but more specimens of both species ada), David Rudkin (Royal Ontario Museum, Toronto, On- would need to be found before such issues of synonymy tario, Canada) and an anonymous referee provided valuable can be resolved. suggestions and comments during review that greatly im- The Rhenopteridae were previously only known from Eu- proved the manuscript. JCL acknowledges the Palaeonto- rope, and in the Devonian only from the Rheno-Hercynian graphical Society for a grant to investigate early stylonurine terrane of Germany. The discovery of Leiopterella gen. evolution that allowed for museum visits. nov. shows that this basal clade of stylonurines was more geographically widespread than previously suggested (e.g., References Tetlie 2007). Our analysis places Leiopterella as basal to the Rhenopterinae, consisting of Rhenopterus and Alkenop- Andrews, H.E., Brower, J.C., Gould, S.J., and Reyment, R.A. 1974. terus (Fig. 4). The genera Brachyopterella and Kiaeropterus Growth and variation in Eurypterus remipes De Kay. Bulletin of themselves form a more basal clade of Silurian rhenopterids. the Geological Institutions of the University of Uppsala, 4: 81– Brachyopterus is basal to both these clades, as befitting its 114. stratigraphic position in the Ordovician. The morphology of Braddy, S.J. 2001. Eurypterid palaeoecology: palaeobiological, ich- the lateral eyes and postabdomen of Leiopterella are equivo- nological and comparative evidence for a ‘mass-moult-mate’ hy- cal; the lateral eyes may be large and converging anteriorly pothesis. Palaeogeography, Palaeoclimatology, Palaeoecology, as in the Silurian genera, while the postabdomen may be 172(1–2): 115–132. doi:10.1016/S0031-0182(01)00274-7. Braddy, S.J., and Dunlop, J.A. 2000. Early Devonian eurypterids caudal as in the Rhenopterinae. There is a clear progression from the Northwest Territories of Arctic Canada. Canadian Jour- throughout rhenopterid evolution from broad carapaces nar- nal of Earth Sciences, 37(8): 1167–1175. doi:10.1139/cjes-37-8- rowest at their base (Brachyopterus, Brachyopterella, Leiop- 1167. terella) to broad carapaces narrowest at their front Braddy, S.J., and Milner, A.R.C. 1998. A large trackway (Alkenopterus) to narrower carapaces narrow at the front from the Gaspe´ Sandstone Group (Middle Devonian) of eastern (Rhenopterus). Kiaeropterus is in some ways unusual in its Canada. Canadian Journal of Earth Sciences, 35(10): 1116– morphology, although several characters, including lateral 1122. doi:10.1139/cjes-35-10-1116. eye morphology and its probable possession of an epistoma Briggs, D.E.G. 1979. Anomalocaris, the largest known (Størmer 1934) place it as sister-taxon to Brachyopterella, arthropod. Palaeontology, 22: 631–664. and it may represent an offshoot during the Silurian. Broad, D.S., Dineley, D.L., and Miall, A.D. 1968. The Peel Sound The first records of Pagea and a rhenopterid from Canada Formation (Devonian) of Prince of Wales and adjacent islands: offer insights into the palaeobiogeography of these groups. A preliminary report. Journal of the Arctic Institue of North Only one other unequivocal member of the Stylonuridae is America, 21: 84–91. known from North America (Ctenopterus,fromtheSilurianof Brusatte, S.L. 2010. Representing supraspecific taxa in hugher-le- New York (Clarke and Ruedemann 1912)), and so the discov- vel phylogenetic analyses: guidelines for palaeontologists. Pa- ery of a more basal taxon (albeit in younger strata) begins to laeontology, 53(1): 1–9. doi:10.1111/j.1475-4983.2009.00918.x. link the European and American occurrences. The fact that the Burmeister, H. 1843. Die Organisation der Trilobiten, aus ihren le- Canadian records of Pagea are of the same age (Lochkovian) benden Verwandten entwickelt; nebst systematische Uebersicht as those from the UK suggests that some stylonurines may aller Seitherbeschriebenen Arten. G. Reimer, Berlin. have had a more cosmopolitan distribution than previously as- Clarke, J.M., and Ruedemann, R. 1912. The Eurypterida of New sumed. The stratigraphic position of Leiopterella suggests that York. New York State Museum Memoirs. Vol. 14, pp. 1–439. it is part of a radiation from the early European rhenopterids; Copeland, M.J., and Bolton, T.E. 1960. The Eurypterida of Canada. the other basal rhenopterids are known from the Ordovician Geological Survey of Canada, Bulletin 60, pp. 13–48. Copeland, M.J., and Bolton, T.E. 1985. Fossils of Ontario Part 3: and Silurian, and appear to go extinct by the Devonian with The eurypterids and phyllocarids. Royal Ontario Museum, Life only the North American genus and those of the Rheno-Hercy- Sciences Miscellaneous Publications. nian terrane surviving. The Stylonuridae and Rhenopteridae are Diener, C. 1924. Fossilium Catalogus, I; Pars 25, Eurypterida. Ber- the most poorly understood stylonurine families, and any new lin. discoveries linked to these families are extremely important. Dineley, D.L. 1965. Notes of the scientific results of the University Ideally specimens of Leiopterella preserving the dorsal cara- of Ottawa expedition to Somerset Island, 1964. Journal of Arctic pace morphology and postabdomen would be required to fully Institute of North America, 18: 55–57. confirm its position within the Rhenopteridae. Although fur- Dineley, D. 1966. Geological studies in Somerset Island, University ther, more complete specimens of Stylonurus powriensis also of Ottawa expedition, 1965. Journal of Arctic Institute of North need to be described before its affinities can be confirmed, the America, 19: 270–277. identification of Stylonurus-like characters in a species of Dineley, D.L. 1994. Cephalaspids from the Lower Devonian of Pagea firmly links these enigmatic eurypterid taxa. Prince of Wales Island, Canada. Palaeontology, 37: 61–70.

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Elliott, D.K. 1984. Siluro-Devonian fish biostratigraphy of the Ca- mony (*and Other Methods). Ver. 4. Sinauer Associates, Sun- nadian Arctic Islands. Proceedings of the Linnean Society of derland, Mass., USA. New South Wales, 107: 197–209. Tetlie, O.E. 2007. Distribution and dispersal history of Eurypterida Greiner, H. 1972. Arthropod trace fossils in the Lower Devonian (Chelicerata). Palaeogeography, Palaeoclimatology, Palaeoecol- Jacquet River Formation of New Brunswick. Canadian Journal ogy, 252(3–4): 557–574. doi:10.1016/j.palaeo.2007.05.011. of Earth Sciences, 9: 1772–1777. Tetlie, O.E., Brandt, D.S., and Briggs, D.E.G. 2008. Ecdysis in sea Gupta, N.S., Tetlie, O.E., Briggs, D.E.G., and Pancost, R.D. 2007. scorpions (Chelicerata: Eurypterida). Palaeogeography, Palaeo- The fossilization of eurypterids: a result of molecular transfor- climatology, Palaeoecology, 265(3–4): 182–194. doi:10.1016/j. mation. Palaios, 22(4): 439–447. doi:10.2110/palo.2006.p06- palaeo.2008.05.008. 057r. Tollerton, V.P., Jr. 1989. Morphology, taxonomy, and classification Jeram, A.J. 1996. Chelicerata from the Escuminac Formation. In of the order Eurypterida Burmeister, 1843. Journal of Paleontol- Devonian fishes and plants of Miguasha, Quebec, Canada. Edi- ogy, 63: 642–657. ted by H.-P. Schultze and R. Cloutier. Verlag Dr Friedrich Pfeil, Tollerton, V.P., Jr. 1997. Eurypterids and associated fauna at Litch- Munich, pp. 103–111. field, a classic locality in Herkimer County. 69th Annual Meet- Kjellesvig-Waering, E.N. 1966. A revision of the families and gen- ing and Guidebook New York State Geological Association, era of the Stylonuracea (Eurypterida). Fieldiana. Geology, 14(9): pp. 253–264. 169–197. Waterston, C.D. 1962. Pagea sturrocki gen. et sp. nov., a new eur- Lamsdell, J.C., and Braddy, S.J. 2010. Cope’s Rule and Romer’s ypterid from the of Scotland. Palaeontology, theory: patterns of diversity and gigantism in eurypterids and 5: 137–148. Palaeozoic vertebrates. Biology Letters, 6(2): 265–269. doi:10. Young, G.A., Rudkin, D.M., Dobrzanski, E.P., Robson, S.P., and 1098/rsbl.2009.0700. PMID:19828493. Nowlan, G.S. 2007. Exceptionally preserved Late Ordovician Lamsdell, J.C., Braddy, S.J., and Tetlie, O.E. 2009. Redescription biotas from Manitoba, Canada. Geology, 35(10): 883–886. of Drepanopterus abonensis (Chelicerata: Eurypterida: Stylonur- doi:10.1130/G23947A.1. ina) from the Late Devonian of Portishead, UK. Palaeontology, 52(5): 1113–1139. doi:10.1111/j.1475-4983.2009.00902.x. Lamsdell, J.C., Braddy, S.J., and Tetlie, O.E. 2010. The systema- Appendix A tics and phylogeny of the Stylonurina (Arthropoda: Chelicerata: Character list and matrix (Table A1) for the phylogenetic Eurypterida). Journal of Systematic Palaeontology, 8: 49–61. analysis. Thirteen new characters (03–04, 47, 62–71) are in- Plotnick, R.E., and Elliott, D.K. 1995. A Lower Devonian stylo- cluded in the analysis, along with the taxa Pagea plotnicki, nurid eurypterid from Arctic Canada. Journal of Paleontology, Pagea symondsii, and Leiopterella tetliei. 69: 399–402. 01. Antero-median carapace protrusion (0 = absent; 1 = Poschmann, M., and Tetlie, O.E. 2004. On the Emsian (Early De- present). vonian) arthropods of the Rhenish Slate Mountains: 4. The eur- 02. Denticulate anterior margin of carapace (0 = absent; 1 ypterids Alkenopterus and Vinetopterus n. gen. (Arthropoda: = present). Chelicerata). Senckenbergiana lethaea, 84(1-2): 173–196. doi:10.1007/BF03043470. 03. Carapace marginal rim broad (0 = absent; 1 = Rolfe, W.D.I., and Dzik, J. 2006. Angustidontus, a Late Devonian present). pelagic predatory crustacean. Transactions of the Royal Society 04. Row of pustules along inside of marginal rim (0 = ab- of Edinburgh. Earth Sciences, 97(01): 75–96. doi:10.1017/ sent; 1 = present). S0263593300001413. 05. Prosomal posterolateral lobes (0 = absent; 1 = Rudkin, D., Stott, C., Tetreault, D., and Rancourt, C. 1998. Ordovi- present). cian and Silurian rocks and fossils of the southern Georgian Bay 06. Prosoma quadrate (0 = absent; 1 = present). area, Ontario. Canadian Paleontology Conference, Field Trip 07. Median ridge between lateral eyes (0 = absent; 1 = Guidebook No. 7. Geological Association of Canada - Paleontol- present). ogy Division, 37 p. 08. Circular plateau ornamentation anterior to median Selden, P.A. 1981. Functional morphology of the prosoma of Bal- ridge (0 = absent; 1 = present). toeurypterus tetragonophthalmus (Fischer) (Chelicerata: Euryp- 09. Position of median eyes on carapace (0 = median terida). Transactions of the Royal Society of Edinburgh. Earth third; 1 = anterior third). Sciences, 72: 9–48. Størmer, L. 1934. Merostomata from the Downtonian Sandstones 10. Ocellar area. (0 = absent; 1 = present). of Ringerike, Norway. Skrifter utgitt au Det Norske, Viddens- 11. Lateral eye shape (0 = crescentic; 1 = expanded). kaps-Akademie i Oslo, 1933, No. 10. 12. Palpebral lobe circular (0 = absent; 1 = present). Størmer, L. 1936. Eurypteriden aus dem Rheinischen Unterdevon. 13. Lateral eyes converging and placed anteriorly on car- Abhandlungen der Preußischen Geologischen Landesanstalt, apace (0 = absent; 1 = present). Vol. 175, pp. 1–74. 14. Round lens overlying lateral eyes (0 = absent; 1 = Størmer, L. 1951. A new eurypterid from the Ordovician of Mon- present). tgomeryshire, Wales. Geological Magazine, 88(6): 409–422. 15. Orbital ridges (0 = absent; 1 = present). doi:10.1017/S001675680006996X. 16. Transverse suture on ventral plates (0 = absent; 1 = Stott, C.A., Tetlie, O.E., Braddy, S.J., Nowlan, G.S., Glasser, P.L., present). and Devereux, M.G. 2005. A new eurypterid (Chelicerata) from 17. Transverse suture curving back at midline (0 = absent; the Upper Ordovician of Manitoulin Island, Ontario, Canada. Journal of Paleontology, 79(6): 1166–1174. doi:10.1666/0022- 1 = present). 3360(2005)079[1166:ANECFT]2.0.CO;2. 18. Suture on ventral plates (0 = epistoma absent; 1 = Swofford, D.L. 2003. PAUP*. Phylogenetic Analysis Using Parsi- epistoma present).

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19. Rostral field (0 = absent; 1 = present). 45. Posterior margin of metastoma (0 = rounded; 1 = flat- 20. Ventral plates widen anteriorly (0 = absent; 1 = tened or recurved). present). 46. Paired tubercles on opisthosomal tergites 2–5 (0 = ab- 21. Appendage III (0 = spiniferous with paired spines; 1 = sent; 1 = present). spiniferous with single spines). 47. Opisthosoma narrower than carapace (0 = absent; 1 = 22. Pairs of spines per podomere on prosomal appendage present). III (0 = one pair; 1 = two or more pairs). 48. Marginal rim on opisthosoma (0 = absent; 1 = 23. Prosomal appendage IV (0 = spiniferous; 1 = non-spi- present). niferous). 49. Positive opisthosomal differentiation of third order 24. Pairs of spines per podomere on prosomal appendage first segment (0 = absent; 1 = present). IV (0 = one pair; 1 = two or more pairs). 50. Second tergite developed into round macrotergite (0 = 25. Spines on prosomal appendage IV (0 = moveable absent; 1 = present). spines; 1 = both moveable and fixed spines; 2 = fixed 51. Preabdominal epimera (0 = absent; 1 = present). spines). 52. Caudal postabdomen (0 = absent; 1 = present). 26. Blade-like structures on podomeres of anterior ap- 53. Lateral pleurae (0 = absent; 1 = present). pendage (0 = absent; 1 = present). 54. Pretelson elongated (0 = absent; 1 = present). 27. Rachis (0 = absent; 1 = present). 55. Pretelson postlaterally expanded (0 = absent; 1 = 28. Coxal laden (0 = absent; 1 = present). present). 29. Prosomal appendage V (0 = spiniferous; 1 = non-spi- 56. Dorsal pretelson lobes (0 = absent; 1 = present). niferous). 57. Telson shortened (0 = absent; 1 = present). 30. Spines on prosomal appendage V reduced (0 = absent; 58. Telson elongate (0 = absent; 1 = present). 1 = present). 59. Dorsal median keel on telson (0 = absent; 1 = 31. Prosomal appendage VI (0 = walking leg; 1 = swim- present). ming leg). 60. Paired, broad rounded ventral keels on telson (0 = ab- 32. Appendage VI reaching to pretelson (0 = absent; 1 = sent; 1 = present). present). 61. Carapace ornament of large lunate scales surrounding 33. Shape of proximal podomere of appendage VI (0 = and pointing away from the central area and eyes. [0 = ab- narrow (length/width (L/W) > or = 2.0); 1 = expanded (L/ sent; 1 = present). W < 2.0)). 62. Row of large, tongue-shaped scales on posterior mar- 34. Distal podomere margin of VI-6 modified (0 = absent; gin of opisthosomal segments (0 = absent; 1 = present]. 1 = present). 63. Pustular ornamentation (0 = absent; 1 = present). 35. ‘‘Ear’’ on coxa VI (0 = absent; 1 present). 64. Acicular scales on opisthosoma (0 = absent; 1 = 36. Appendage VI showing lateral serrations (0 = absent; present). 1 = present). 65. Podomere VI-5 (0 = half the width of VI-4; 1 = equal 37. Podomere 7a on sixth prosomal appendage (0 = ab- width of VI-4). sent; 1 = present). 66. Lateral carapace margin (0 = continuous; 1 = 38. Width of VI-7a (0 = narrow (<50% of width of VI-7); stepped). 1 = wide (>50%)). 67. Carapace anterior (0 = rounded; 1 = angular). 39. Shape of VI-7a (0 = oval; 1 = triangular). 68. Carapace vaulted (0 = absent; 1 = present). 40. Longitudinal grooves on podomeres (0 = absent; 1 = 69. Metasoma (0 = bulky; 1 = gracile). present). 70. Groove running across doublure (0 = absent; 1 = 41. Podomeres ridged (0 = absent; 1 = present). present). 42. Podomeres thicken distally (0 = absent; 1 = present). 71. Carapace position of greatest width (0 = posterior 43. Cleft metastoma (0 = absent; 1 = present). third; 1 = median third). 44. Anterior margin of metastoma (0 = notch absent; 1 = notch present).

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Table A1. Matrix used in the phylogenetic analysis. Weinbergina opitzi 0000000000 00000000–0 0000000000 0010000--0 00—00000 1000000000 0000100000 0 Alkenopterus brevitelson 0010000000 00000????? ??????0?1- 00?0?00--0 10???00000 0100001000 000010001? 0 Brachyopterella pentagonalis 000000??01 001001111? ??1–?0?1- 0000000--0 10????00?? 0?????0?0? 0?00001010 1 Brachyopterus stubblefieldi 00000000?1 00000????? 1–00000?1- 00?0?00--0 000?000000 0000000000 000000000? 1 Ctenopterus cestrotus 010000001? 01000??11? 0101200?1- 01?0?00--0 00???00000 1?0???010? 0001100000 0 Cyrtoctenus wittebergensis 1000100000 00011????? ??00111??? ?00?00???1 01???00000 0000100001 010010000? 0 Drepanopterus abonensis 0011001000 00010100–1 001–1001- 0000000--1 0111–10000 0000000010 0010100000 0 ‘‘Drepanopterus’’ bembycoides 00000000?0 000??0–10? ?????0001- 00?0?01010 0001000000 0000001000 0000100000 0 Drepanopterus pentlandicus 001?00?0?0 000??????? ??1–???1- 00?0?00--? 0111–10000 0000000010 0010100000 0 Hallipterus excelsior 000100110? 000111011? ?????0?0?? ?????????? ?????????? 0????????? 1?00?010?0 0 Hardieopterus macrophthalmus 00000010?0 00000100–1 ??????0?00 0000?00--0 0101100100 00100100?? 1110100000 0 Hibbertopterus scouleri 0000101000 00010????1 ??0011011- 00?0000--0 0111–00000 0000000001 0100100000 0 Kiaeropterus cyclophthalmus 0000000001 00100????? ??????0?1- 00?0??0--0 10???00000 000??????0 0000?0001? ? Kokomopterus longicaudatus 000000???? 0000?????1 0000000?01 00?0010--0 0101100100 0000000000 0100100000 0 Lamontopterus knoxae 000000???? ?????????? ??????0?01 00?0?00--0 01???00100 0000000000 ??0010000? 0 Laurieipterus elegans 0100000010 0100011111 0101200?1- 0?00000--0 0000100000 0?????01?? 00001100?0 0 Megarachne servinei 1000001000 0001?????? ??1–1011- 0???0????1 01????0011 ?????????? 000??000?? 0 Moselopterus ancylotelson 00000000?0 00000??0–0 000000001- 0010101000 0001000000 00000010?0 0000101001 0 Mycterops mathieui 10??00???? 00010????? ?????????? ?????????? ???????01? ????0?0??? 0?0??010?? 0 Pagea sturrocki 000001???? 01001100–1 0101200?1- 01?0000--0 0000101?00 0001100010 0001111100 1 Parastylonurus ornatus 00000000?0 00000100–1 000000001- 0100000--0 0001100000 0001100010 0000100000 0 Rhenopterus diensti 0000000000 00000100–1 1–1–0001- 0000000--0 1001000000 0100001010 0011100011 0 Stylonurella spinipes 00000100?0 00000100–1 ?11000001- 0100000--0 00???01000 000??????? 0000111000 0 Stylonurus powriensis 00000110?0 01001?????0 ????????1- 01?0?00--0 00???00000 000000011 000110000? 0 Tarsopterella scotica 00000011?0 00001????? ?????????? ?????????? 01???00000 001001000? 1100?0100? 0 Vinetopterus struvei 0000000000 00000????? ??????0??? 0010?0110? 0????00000 00001010?0 0?00100000 0 Woodwardopterus scabrosus 000000???? 000??????? ??1–10?1- 00?0?00--1 01????0011 000??0?0?1 000010000? 0 Eurypterus remipes 0000000000 100000–0-0 000000001- 1011101110 0001000000 0000100000 0000100000 0 Hughmilleria socialis 0000000000 100000–100 0000000000 1011101110 0001000000 0000000000 0000100000 0 Onychopterella augusti 00000000?0 ?0000????0 ??0000001- 1010101010 00???00000 0000?000?0 0000100000 0

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Pagea plotnicki 00000110?0 01001????? 11???00?1- 0??0?0???0 00???01000 0001110??? 000111100? 1 Pagea symondsii 00000110?0 01001??0–1 ?????????? ?????????? ?????????? ?????????? 000?1111?0 1 Leiopterella tetliei 000000???? ?????100–1 ??100??01- 0?0000???0 10010?1000 ?????????? ??0?1000?1 1

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