10 Material. Scale or dermal bone fragments, fewer than ten including PF 16479, 16480.

11 Description. Only fragments of scales, or more probably the outer layer of head shield tesserae, are preserved. The base is thin; the ornament comprises short high narrow ridges with smooth rounded crests. The ridges are 0.5 mm or more long, and closely spaced pores open out on the base between the ridges.

12 Remarks. Cephalaspids (= osteostracans) from the Lochkovian MOTH locality of the Northwest Territories were described by Dineley and Loeffler (1976) and Adrain and Wilson (1994), but none has an ornament that closely resembles the Eastport Formation specimens. Osteostracans with similar ornament are found in the lower Old Red Sandstone facies (Pridoli–Lochkovian) of the Welsh Borderland and the Baltic (e.g., Gross 1961; Turner et al. 2017). The Maine specimens are most similar to Ohesaareaspis (?order Cephalaspidiformes, family indet.), Tahulaspis (order Tremataspidiformes), and Thyestes (family Thyestidae) (Märss et al. 2014, figs. 46F, 37C, 30F, L) from the Silurian (Ludlow–Pridoli) of Saaremaa Island, Estonia.

13 Material. Fewer than ten fragments, including PF 16481 and 16482.

14 Description. These few, incomplete scales have a flat anterior (overlap) margin lacking ornament. The ornament on the free field comprises several oblique rows of low ridges formed of close-set overlapping chevrons. The ridges are closely spaced and oriented subparallel to each other. Vascular canal openings occur between the ridges and on the flat anterior margin. The medial rib on the inner surface is well developed.

15 Remarks. Although the ornament is poorly preserved, it closely resembles the distinctive scale ornament of short, wide triangular or heart-shaped sculptural elements in closely spaced or overlapping regular rows for Schidiosteus mustelensis (the type and only species of Schidiosteus), as illustrated by Blom et al. (2002, fig. 30). The taxon is known from: the middle Ludlow of Saaremaa, Estonia; the late Wenlock to early Ludlow of Gotland, Sweden, and Severnaya Zemlya, Russia; and the Ludlow of the central Urals, Russia.

16 Material. Fewer than ten fragments, including PF 16483, 16484.

17 Description. The scales have a sparse ornament comprising nine to ten subparallel, short and long ridges extending obliquely across the scale, with rare rounded tubercles near the anterior margin. The ridges are smooth, narrow and high, and widely separated. Only a few vascular canals open out on the interridge areas and posterior to the medial visceral ridge, which is robust. The ventral surface (Fig. 3i) has a distinct raised lateral curvature.

18 Remarks. The scale ridges are more sparsely distributed than on previously figured scales of Septentrionia spp. from the Ludlow to Lochkovian of the Welsh Borderland, Arctic Canada, northern Greenland, the Baltic, and the central Urals of Russia (Blom et al. 2002, figs. 43–47). The Eastport Formation scales are most similar to scales of Septentrionia lancifera (Blom et al. 2002, figs. 43X–Y) from Man Brook in the Welsh Borderlands (late Pridoli; see also Turner et al. 2017).

20 Material. About 30 poorly preserved grey-black to chalky scales, some fragile, including PF 16485–16493; nearly all are trunk scales.

21 Holotype. FMNH PF 16486 (Figs. 4c–d, 5a–b).

22 Etymology. In honor of the late Robert (Bob) Denison, who made the first discovery of the fish microfossils in Maine.

23 Diagnosis. Paraloganiid with small to medium-sized scales, ~0.3–1.0 mm. Trunk scales lozenge-shaped, generally flattened and elongate with an anterior basal prong up to third scale length; crown high, relatively narrow and rounded anteriorly with a wide flat neck region; high median section flanked with one or more lateral ridges ending in three to five separated posterior points and at least three postero-ventral ribs below them and anteriad to the posterior basal rim; up to nine lateral lappets with an odd number on each side of scale. Base wider than crown; basal surface flattened with shallow pulp cavity with median groove, ending posteriad in a shallow depression. Dentine canal openings concentrated in the pulp groove.

24 Description. Most of the thelodont scales in the sample are presumed to be trunk scales (Figs. 4a–i, l–m, 5a–b), of which the holotype scale is well preserved, with posterior points from at least five separated posterior lappets (Figs. 4e–f, 5b). There are no definite rounded oral scales (sensu Märss et al. 2007), but some relatively wide scales (Figs. 4j–k, n–o, 5q–r) are possibly cephalo-pectoral or from the leading edges of the pectoral fins. One very small scale, around 0.3 mm, has a short-ribbed crown on a deeper rounded base, with well-preserved lateral lappets (Figs. 4q–r, 5c); it may be a pinnal scale. The separation of the posterior ribs with clear long notches (Figs. 4a–b, d, g–h, 5a) is an unusual feature in this species, and may have been accentuated during preservation. The neck is narrow and trough-like in most trunk scales, being wider in those with a wider base (e.g., Figs. 4j–k, n–p). The base in most specimens is shallow in height and as long as or longer than the crown. Generally the scales are flat on the basal surface; only in the smaller scale (Figs. 4q–r) is the base deeper and shorter than the crown. There is anterior thickening or an elongated extension or rootlet/prong in most scales (e.g., Figs. 4g–i, 5a–b).

25 The lack of a shiny surface to the scale crowns, their chalky appearance, and the transparency of some of the lappets and ribs suggest that the scales have been metamorphosed to some extent and that the dentine and basal aspidin is worn (Turner 1994). The posterior points of the crowns and lateral riblets are mostly broken.

26 Histology. The scales are not well enough preserved to obtain any detailed histological information, but in general the style of base with an elongate pulp cavity or slit is suggestive of a loganiid or paraloganiid scale, the latter now placed within the Sheiliiformes (e.g., Žigaitė et al. 2013a). The number and expression of any basal dentine canals is unclear, but there may be at least three in the posteriad depressed area of the base.

27 Remarks. These spiny scales fall within the Paralogania group, which currently includes taxa from the middle to late Silurian and earliest Lochkovian of Laurentia (Märss et al. 2007; Table 1). The scales from Maine seem closest to Paralogania readbayensis Märss et al. 2002 from poorly constrained lowermost Lochkovian of arctic Canada, and to Paralogania kummerowi (Gross 1967) known from the late Pridoli of Europe, where it is a key zone fossil (e.g., Turner et al. 2017).

29 Material. PF 16494; one scale.

30 Description. Elongate, spine-like, poorly preserved specimen of around 1 mm in length with a smooth upper surface ornamented with four or five pairs of fine double ribs on the crown. These fine raised striae are separated by a narrow trough. Each raised ridge is flanked by smooth areas wider than ridge (Figs. 4s–t). The anterior end is gently rounded. The posterior point is broken, revealing a gently curved cross-section. The neck is so shallow as to be almost non-existent. The base has a relatively thickened anterior rim. The basal surface is unclear but appears to be very shallow with an ovoid, wide-open pulp cavity leading posteriorly into the damaged central pulp canal (Fig. 4u).

31 Histology. The posterior end of the scale is broken, exposing the internal structure of the crown dentine. The general form of the scale suggests a thelodontiform affinity.

32 Remarks. The Maine specimen is comparable to the trunk scale shown by Märss et al. (2006, fig. 56P) from the lower Lochkovian Barlow Inlet Formation of Cornwallis island, and others figured by Dineley and Loeffler (1976, text-fig. 65) from the Delorme Formation, Mackenzie River district, Northwest Territories, Canada, and some Talivalia elongata scales from the basal Lochkovian of Earnstrey Brook and other Brown Clee Hill localites in Shropshire, England (Turner 1973, 1984; Turner et al. 2017). The Maine specimen might be an immature scale based on its wide and shallow pulp opening.

33 Based on the squamations of established Paralogania species (e.g., Märss et al. 2007), this specimen does not fit into the probable scale variation of Paralogania denisoni. Instead, it is tentatively referred to the genus Talivalia based on its overall scale form. It also resembles the trumpet-shaped scales of the older Wenlock Nunavutia (Märss et al. 2006) and of younger Lochkovian to Eifelian Talivalia and Amaltheolepis species (Märss et al. 2007, Žigaitė et al. 2013b). However, it differs in that the striae of the crown are separated by narrow troughs rather than being raised ridges. This might be a taphonomic factor, with the denser dentine surface of the ridges worn away, although such a style of preservation has not been observed before except in the ridges of similarly dated Turinia nachoi trunk scales from Spain (e.g., Märss et al. 2007, figs. 113J, K). The genus Talivalia is not known below the lowest Lochkovian, but this may not preclude the possibility that it or a closely related form might appear earlier, in the late Pridoli.

34 More material is needed to assess details of histology and relationships. Hence for now we leave the generic assignment as tentative and the species as indeterminate. More material is needed to assess details of histology and relationships.

35 Material. Five scales including one body scale PF 16495 and one pinnal scale 16496, plus one spine fragment PF 16497.

36 Description. The body scale (Figs. 6a–b) is about 0.6 mm long and wide, and 0.4 mm deep with seven short ridges leading back from the anterior margin of the scale crown, and two narrow ledges at a lower level along the posterolateral sides of the crown. The crown is slightly inclined anterior to posterior, with a negligible neck between the rounded anterior margin and the scale base. The scale base is convex and shallow. The pinnal scale or tessera (Figs. 6c–d) has a sharply pointed crown/tubercle comparable to a typical crown that has been tilted vertically, on a thin flat subcircular base. The small spine fragment has longitudinal ridges with long smooth nodes.

37 Remarks. The body scale resembles the type scale of Nosto lepis striata (Pander 1856, pl. 6 fig. 7) from the Pridoli Ohesaare Formation, Saaremaa Island, Estonia; the scales and spine fragment also closely resemble elements assigned to Nostolepis striata by Gross (1947, 1971). Although Valiukevičius (e.g., 2003a, b) has since split this taxon into more species, the few body scales from the Eastport Formation match those still regarded as Nostolepis striata s.s. ― i.e., scales with the same morphology as those illustrated by Pander (1856). As these are the only recognizable acanthodian scales in the sample that are not ischnacanthiform, it seems reasonable to allocate the few other elements ― the pinnal scale and noded spine fragment ― that match those known to occur in Nostolepis to the same species. Nostolepis species that have been recorded from the Silurian–Lochkovian of eastern and arctic North America include: Nostolepis striata from the late Silurian Stonehouse Formation, Arisaig, Nova Scotia (see Burrow et al. 2013) and late Silurian–Lochkovian of the Canadian Arctic Archipelago (Vieth 1980; Märss et al. 1998); and Nostolepis arctica, Nostolepis applicata and Nostolepis multicostata from the Lochkovian of the Canadian Arctic Archipelago (Vieth 1980). Nostolepis arctica is characterized by long narrow crowns, Nostolepis applicata has a crown formed of overlapping petal-like growth zones, and Nostolepis multicostata has a large number of close-set, irregularly spaced ridges covering the crown; none of these characters are seen in the resent material. The only Nostolepis striata scale figured by Vieth (1980, pl. 5.18, 19) is a placoderm scale, and Märss et al. (1998) did not figure any material, so it is uncertain whether Nostolepis striata sensu stricto occurs in these assemblages. Nostolepis striata has been reported from upper Silurian to Lower Devonian deposits almost worldwide, but it seems likely that at least some of these records are from one of the other morphologically similar species.

38 Material. Ten scales, including PF 16498, 16499.

39 Description. The scale PF 16498 (Figs. 6 f–g) has a smooth flat crown that is slightly wider than long, a neck that is concave all round, and a convex base that protrudes slightly in front of the crown; the neck and base are of similar height, with the scale being about 0.4 mm long, 0.5 mm wide, and 0.4 mm deep. The other scale (PF 16499) assigned to Gomphonchus sandelensis is more poorly preserved and incomplete, but also has a smooth flat crown.

40 Remarks. The symmetrical body scale(s) compares closely in morphology and size to the type scale (Pander 1856, pl. 6 figs. 15–17) from the Pridoli Ohesaare Formation, Saaremaa Island, Estonia. The species is widespread through the Pridoli–Lochkovian of the circum-Arctic region, being recorded from: the Canadian Arctic; Lithuania, Latvia, Estonia, Sweden and northern Germany; Sweden; Severnaya Zemlya and Timan-Pechora, Russia; Welsh Borderland, U.K.; and possibly Greenland (e.g., Gross 1971; Vieth 1980; Märss et al. 1998; Blom 1999; Vergoossen 2000; Valiukevičius 2003a), as well as from Spain (Mader 1986, fig. 8, pl. 1 figs. 1, 2).

41 Material. Sixty-five scales, including figured scales PF 16500–16507.

42 Description. The scales are less than 1.0 mm long, of almost equal width and length, with a flat horizontal crown lacking ornament ribs or ridges, but penetrated by an extensive coverage of small-caliber canals (Figs. 6h–p). The neck is deep and concave all round, delimited from the shallow, convex base by a marked rim (Figs. 6h–i). The poor preservation of the scales, with hyphal borings extending into canals within the scales, has exposed the details of the distribution of den-tine tubules, and also pore canals aligned with the growth zones in the upper crown (Figs. 6j–p), leading into the larger radial and arcade canals. The borings and erosion of the wider pore canals expose the position of the underlying radial canals in many scales (Figs. 6i–o). The smaller pore-canal openings are slit-like and oriented antero-posteriorly (Figs. 6j–l). Other than the smallest scales which have only two radial canals (Fig. 6h), all larger scales appear to have four radial canals, opening out as wide pores under the posterior overhang of the crown (Fig. 6q). Scale PF 16507 (Figs. 6r–s) differs from the normal body scales in having a flat base and an inclined crown.

43 Remarks. Despite their poor preservation, the scales can be readily assigned to Poracanthodes puncatus by the characteristic distribution of pore openings in lines paralleling the straight growth-zone borders on the crown surface. Vergoossen (1999) proffered a diagnosis for the species in which he noted that the scales have a pore-canal-free zone close to the anterior edge of the crown and a pore-canal system that usually only starts in the fourth or fifth growth zone. Erosion of the crown surface on the Maine scales has exposed dentine canals/tubules as well as pore canals, but it does appear that the evenly spaced, slit-like openings of the pore canals running up from the non-exposed arcade canals are only developed in the outermost growth zones (Figs. 6k, n). Vergoossen (1999) also observed that Devonian forms of Poracanthodes punctatus have only two to four radial canals, whereas Silurian forms have up to ten. However, the Maine scales are in the smaller size range for the species, and the number of canals is probably a result of their size rather than stratigraphic age.

44 Poracanthodes punctatus is widespread through the late Silurian to Early Devonian of the circum-Arctic region, having been described from Lithuania, Latvia, Estonia, Sweden, northern Germany, Welsh Borderland, Greenland, arctic Canada, and Severnaya Zemlya (e.g., Gross 1971; Blom 1999; Burrow et al. 1999; Vergoossen 2000; Valiukevičius 2003c). Despite being originally nominated as a zone fossil for the late Pridoli (Märss et al. 1995), Poracanthodes punctatus has been described from older Ludlow deposits (Valiukevičius 2003c; Vergoossen 1999). Its long stratigraphic range, and variations in morphology and histology, could indicate that the taxon encompasses more than one species.

45 Material. Ten spine fragments, including PF 16508, 16509; one tooth ― PF 16510.

46 Description. The spine fragments (Figs. 6t–u) have rounded, smooth longitudinal ridges about 0.2 mm wide, separated by similar width or narrower grooves. The leading edge ridge on PF 16509 (Fig. 6u) is slightly wider than the lateral ridges. PF 16510 (Fig. 6v) is a tall, smooth tooth on a thin circular base; the base has a ring of tiny denticles around the base of the tooth.

47 Remarks. The spine fragments are too incomplete to be assigned more accurately, but as the scales in the sample are either ischnacanthiform or Nostolepis striata, it is likely that the spines are also ischnacanthiform. As Nostolepis striata has noded ridges on the spines, by default the spine fragments with smooth ridges are considered to be ischnacanthiform. The tooth PF 16510 is the same type of element that Gross (1957, pl. 3.1–3; pl. 4.1–3) described as “Dornzähn of Gomphodus” (= ‘thorn’ teeth; the taxon is now Gomphonchus). At the time that Gross wrote, Poracanthodes was considered a form taxon for sensory line scales of Gomphonchus, but since the description by Valiukevičius (1992) of articulated fish with Poracanthodes-type scales, Poracanthodes is now recognized as a biological taxon. Dornzähn could derive from various ischnacanthiforms, not just Gomphonchus.

48 Material. One tooth whorl PF 16511, one tooth whorl fragment PF 16512.

49 Description. The near complete tooth whorl (Fig. 6w) is poorly preserved, but has a subtriangular base with one smooth conical tooth and two rounded nubs forming the whorl; algal or fungal hyphal borings in the nubs indicate these are penetrated by a network of vascular canals. The fragment (Figs. 6x–y) has a recurved tooth about 0.5 mm high, with weak lateral ridges towards the apex, ankylosed to a broken base about 0.2 mm deep. The fracture surfaces through the base show multiple canals leading up into the tooth.

50 Remarks. The tooth whorls resemble those known from many late Silurian and Early Devonian localities worldwide, and could derive from ischnacanthiforms, or other acanthodians with a dentition comprising multiple tooth whorls (see comments in Burrow et al. 2013).

51 Material. Scale or tessera PF 16513.

52 Description. The scale(?) fragment is 0.25 mm long, 0.15 mm wide, and has a flat base. The crown ornament comprises four stellate tubercles.

53 Remarks. The scale could be part of an acanthodian stellate tessera like those that Gross (1971) assigned to Nostolepis striata. Alternatively, it could be an acanthothoracid placoderm scale (see Burrow and Turner 1999).