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A new look at Pleurotomaria perlata Hall, 1852 () from the of Laurentia

John S. Peel

To cite this article: John S. Peel (2018) A new look at Pleurotomaria￿perlata Hall, 1852 (Gastropoda) from the Silurian of Laurentia, GFF, 140:3, 249-253, DOI: 10.1080/11035897.2018.1482564 To link to this article: https://doi.org/10.1080/11035897.2018.1482564

© 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group

Published online: 27 Jun 2018.

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Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=sgff20 GFF 2018, Vol. 140, No. 3, 249–253 https://doi.org/10.1080/11035897.2018.1482564

OPEN ACCESS A new look at Pleurotomaria perlata Hall, 1852 (Gastropoda) from the Silurian of Laurentia

John S. Peel

Department of Earth Sciences (Palaeobiology), Uppsala University, Uppsala, Sweden

ABSTRACT ARTICLE HISTORY New material from Genoa, Ohio, USA, of the distinctive but poorly known Silurian gastropod Pleurotomaria Received 9 April 2018 perlata Hall, 1852, originally described from the Guelph Formation of Ontario, Canada, demonstrates that Accepted 27 May 2018 it is not a pleurotomariinid vetigastropod. It is a species of Isfarispira Gubanov, Peel & Pianovskaya, 1995, KEYWORDS first described from the Silurian of Kyrgyzstan, central Asia, and now recognised from Laurentia. Isfarispira Gastropoda; Silurian; belongs within a pycnomphaline–omphalotrochid group of euomphaloidean gastropods but this group Laurentia; systematics is too poorly understood to allow firm placement at this time.

Pleurotomaria perlata is one of the most distinctive Silurian Historical background gastropods from Laurentia but its systematic position is not As a preliminary, it should be noted that Pleurotomaria perlata well known. It was proposed by Hall (1852, p. 349, pl. 84, fig. Hall, 1852 is distinct from its homonym Pleurotomaria per- 5) and illustrated on the basis of two internal moulds from the lata Conrad, 1865, described from the Eocene of Shark River, “Limestone at Galt, Canada.” The illustrations show the charac- New Jersey (Conrad 1865). That species is also poorly known, teristic multi-whorled shell, with whorls expanding slowly, and although it was subsequently assigned to Leptomaria (?) perlata the acutely lenticular, discoidal, transverse profile. As was the by Whitfield (1892, p. 232). custom of the day, the species was assigned to Pleurotomaria Following its initial description, Pleurotomaria perlata Hall, Sowerby, 1821, but this is typically a Mesozoic genus and does 1852 was listed without comment by Bigsby (1858, 1868). not occur in the Palaeozoic or in present day seas despite Schmidt (1858) compared Euomphalus undiferus Schmidt, 1858 innumerable records in older literature. Pleurotomaria and from the Silurian of Estonia to Pleurotomaria perlata but Isakar et its relatives are characterised by a deep emargination in the al. (1999) assigned Schmidt’s species to the widely phaneromph- outer lip (Knight et al. 1960) and nowadays are placed as an alous euomphaloidean Kiaeromphalus Peel & Yochelson, 1976. order within the clade (Bouchet et al. 2017). Billings in Logan et al. (1863, fig. 347) illustrated an internal The deep emargination in pleurotomariiform gastropods often mould of Pleurotomaria perlata in apertural and umbilical views culminates in a parallel-sided slit that generates a selenizone, although Whiteaves (1884, p. 22) noted “that by some inadver- usually located at or above the whorl periphery. Evidence of tance this species is figured … asPleurotomaria solaroides” by such a selenizone is frequently lacking in poorly preserved Billings but clearly represents P. perlata. The illustrations and material, so internal moulds of many fossil species have been assignment to P. solaroides made by Billings in Logan et al. (1863) assigned to Pleurotomaria just on the basis of overall morpho- were reproduced by Lesley (1889, p. 715). logical similarity with better preserved material. Pleurotomaria Billings (1865) and Nicholson (1875) described Guelph perlata Hall, 1852 is one such species, with the uncertainty con- gastropods but without reference to Pleurotomaria perlata or cerning its identity resulting from its typical preservation as any similar form. Day (1877, p. 116) extended the geographical internal moulds in dolostone. These moulds lack details of shell distribution of Pleurotomaria perlata to Wisconsin in reporting ornamentation useful for interpretation of the nature of the “A magnificent and perfectPleurotomaria perlata five inches aperture, resulting in doubt concerning the generic placement [12 cm] in diameter found in the Niagara shale, and also in the of the species. This uncertainty can now be resolved on the basis Guelph or Gault.” Chamberlin (1883, fig. 53) confirmed the of material from the Silurian of Genoa, Ohio, USA, described Wisconsin distribution when he reproduced the apertural view herein. Pleurotomaria perlata is assigned to the genus Isfarispira of the specimen of Pleurotomaria perlata figured by Billings Gubanov, Peel & Pianovskaya, 1995, originally described from in Logan et al. (1863) without comment. The occurrence of the Silurian of central Asia, and represents the first record of P. perlata in the Silurian dolostones of the Chicago–Milwaukee the genus from Laurentia. region was also noted by Gubanov et al. (1995, p. 836).

CONTACT John S. Peel [email protected] © 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way.

Published online 27 Jun 2018 25 0 J. S. PEEL

Whiteaves (1895, p. 75) formally transferred the Pleurotomaria extending adumbilically as a continuation of the shallowly con- solaroides (Hall) of Billings in Logan et al. (1863) to P. perlata, vex base. Shell interior with numerous adaperturally concave noting its occurrence as internal moulds from Galt, Hespeler, septa in the early stages. Ornamentation of fine comarginal Elora and Belwood in Ontario. In contrast to Hall (1852), who growth lines. considered the umbilicus to be wide, Whiteaves (1895) described the umbilicus of Pleurotomaria perlata as deep, but rather nar- Discussion.— Gubanov et al. (1995) commented that Isfarispira row. Both authors, however, were describing the nature of the is distinguished from Liospira by its much greater size, greater umbilicus as preserved in internal moulds, with shell dissolved, number of more slowly expanding whorls and absence of a and not its true shape when the original shell is preserved. deep peripheral sinus and slit. Wagner (2002) tentatively placed Clarke & Ruedeman (1903, p. 21) listed Pleurotomaria perlata Isfarispira as a junior synonym of Pycnomphalus Lindström, from Hamilton, Ontario, suggesting that Pleurotomaria clipei- 1884, a reflection of his attempts to eliminate monotypic genera formis Spencer, 1884 was probably its junior synonym. from his phylogenetic classification of anisostrophic Palaeozoic Ulrich & Scofield 1897( ) proposed the genus Liospira in gastropods. He noted, however, that the identity of Isfarispira as a which the emargination characteristic of pleurotomariiform separate genus might be maintained if species other than the type gastropods was combined with a low spired, lenticular, shell; species Isfarispira septata were assigned to the genus. That crite- Pleurotomaria has a higher spired, trochifom, profile. Ulrich rion is now achieved through the assignment of Pleurotomaria & Scofield (1897) made no comment concerning Hall’s (1852) perlata to Isfarispira. species but Whiteaves (1906, p. 332) quoted a letter from E.O. Gubanov et al. (1995) tentatively assigned Isfarispira to Ulrich (20th January 1906) suggesting assignment to Liospira, the euomphaloidean Family Omphalotrochidae Knight, 1945 which advice he followed. Whiteaves (1906) noted, however, that which Knight et al. (1960) recognised from –? the species was still only known from internal moulds. Tentative strata. Wagner (2002) placed Isfarispira (as a tentative synonym reports from Southampton Island in the Canadian Arctic were of Pycnomphalus) within the euomphaloidean Anomphalidae made by Low (1906, p. 331) and Teichert (1937, p. 142). Bassler Wenz, 1938, although Knight et al. (1960) had regarded anom- (1915, p. 747) adopted Whiteaves’ (1906) assignment and listed phalids as a separate trochinid superfamily. However, Wagner published records under Liospira perlata (Hall). Williams (1919, (2002) considered the position of Pycnomphalus relative to pl. 24) illustrated a well-preserved internal mould from Galt, later anomphalids to be tentative, a situation recognised by Peel Ontario, almost 10 cm in diameter which he assigned to Liospira (1984a) when he divided the Anomphalidae sensu Knight et al. perlata (Hall) without comment. Coleman & Parks (1922, fig. (1960) into a Subfamily Anomphalinae Wenz, 1938 (Devonian– 109) illustrated the umbilical surface of an internal mould from ?) and a new Subfamily Pycnomphalinae that apparently Guelph assigned to Liospira perlata. The distribution of Hall’s is restricted to the Silurian. Peel (1984a) placed anomphalids (1852) species was extended to Indiana by Cumings (1930) who as a family within Trochoidea Rafinesque,1815 (as Trochacea), noted Liospira perlata (Hall) in a list of fossils from the new although Bouchet et al. (2005) made no superfamily placing; they Coryldon member at Huntington. considered omphalotrochids to be euomphaloideans which they Mironova (1993) assigned specimens from the Pschemack regarded as uncertainly placed within molluscs (?Gastropoda). Mountains of central Asia to Ophileta? aff. perlata (Hall, 1852) Bouchet et al. (2017), however, regarded anomphalids as tro- and Gubanov et al. (1995) based their new genus Isfarispira on choideans and omphalotrochids as euomphaloidean gastropods. similar material from the same locality and horizon. While dis- Peel (1984a) considered the aperture in pycnomphalines to cussing the possible relationship of Pleurotomaria perlata with be subradial, a feature of many euomphaloideans, including Isfarispira or Liospira, Gubanov et al. (1995) pointed out that omphalotrochids, whereas the anomphaline aperture is tangen- determination of the identity of P. perlata required better pre- tial, or nearly so. In this respect, the affinity of Isfarispira lies with served material. The currently described material from Genoa, the pycnomphaline–omphalotrochid group. Amongst ompha- Ohio, provides that crucial information concerning the orna- lotrochids, Labrocuspis kobayashii Kase & Nishida, 1986 from mentation and circumbilical flange of Pleurotomaria perlata the Middle Devonian of Japan most closely resembles Isfarispira, sought by Gubanov et al. (1995) and permits its assignment to although its low, trochoidal shell has fewer whorls. Its umbilicus Isfarispira. is closed by a callus rather than the thin circumbilical flange seen in Isfarispira septata (Kase 1989; Gubanov et al. 1995, text-fig. Systematic palaeontology 2), and the sub-sutural sinus is much more prominent than that in Isfarispira septata; a sub-sutural sinus is lacking in I. perlata. Genus Isfarispira Gubanov, Peel & Pianovskaya, 1995 Placement of Isfarispira perlata within the pleurotomariidan vetigastropods, enshrined in the previous generic assignments to Type species.— Isfarispira septata Gubanov, Peel & Pianovskaya, Pleurotomaria or Liospira, is not justified. It is likely that it is as 1995, from the Chorkuin Formation, Pschemack Mountains, a member of a Silurian pycnomphaline–omphalotrochid group Kyrgyzstan, central Asia. Silurian (Llandovery–Wenlock of euomphaloidean gastropods, unrelated to the trochoidean boundary). anomphalines, but its position is left unresolved until such a group is better founded. Diagnosis (emended).— Large, lenticular gastropod with up to ten or more slowly expanding whorls and a radial aperture. Isfarispira perlata (Hall, 1852) Umbilicus largely closed by a blade-like circumbilical flange, Fig. 1 GFF 251

Figure 1. Isafarispira perlata (Hall, 1852) from the Silurian of Genoa, Ohio; Orton Museum, Ohio State University, Columbus, Ohio. A, B, D. specimen 7056A. A. apical view, lacking apex, with arrow locating D. B. oblique lateral view showing acute periphery, D. detail of shell patch on upper whorl surface showing shallowly prosocline growth lines, discontinuous circumperipheral striations (arrow) and concentric striations below suture. C, E–H. specimen 7056B. C, G. specimen in apical (C) and lateral (G) view with earliest whorls and almost half of the shell missing, showing the circumbilical flange (f), outer whorl face (owf) and parietal wall (pw) inC . E. central part of specimen in oblique basal view showing umbilical wall (uw) and flange (f).. F.. under surface of whorl fragment showing prosocyrt growth lines. H. upper surface of fragment of whorl showing comarginal growth lines and concentric striations (arrow). Scale bars: 5 mm.

Type material.— Two specimens figured by Hall (1852, p. 349, surface. A blade-like flange (Fig.1 C and E, arrow uw) extends pl. 84, fig. 5a–c) from Galt, Ontario, currrent location unknown. adaxially as a continuation of the basal surface almost completely The specimen figured as Hall (1852, pl. 84, fig. 5a–b) is desig- closing the umbilicus. In apical view, the narrow outer whorl face nated lectotype; it is an internal mould illustrated in apical and (Fig. 1C, owf) is flattened between only slightly incised sutures oblique lateral views, broken around its periphery. The specimen and has a similar width, measured radially, to the parietal wall figured as Hall 1852( , pl. 84, fig. 5c), designated paralectotype, is (Fig. 1C, pw). Thus, in apical view (Fig. 1A and C) the whorls a fragment of two conjoined whorls. appear narrow and expand at a rate of about 1.1, measured along a radius as the ratio of the linear distance between successive Figured material.— Two mainly exfoliated specimens labelled sutures. In cross-section, the height of the whorl varies between “Silurian, Niagara Group, Genoa, O[hio]” preserved in The one third and almost half its maximum width. Orton Museum, Ohio State University, Columbus, Ohio, under The shell aperture is known from the fine growth lines on the catalogue number 7056. Specimen 7056A (Fig. 1A, B and D) has whorl surfaces. It is radial with a shallow emargination at the the flanks broken away on two sides; the apex (not figured) is periphery. Growth lines on the upper whorl surface are shallowly detached from the main part of the specimen. Specimen 7056B prosocline and slightly oblique to the preceding suture (Fig. 1A and (Fig. 1C, E–H) lacks the apex and is broken approximately across D). Growth lines on the basal surface are also prosocline, initially a diameter. The final preserved half whorl (Fig. 1F and H) is perpendicular to the umbilical shoulder before curving backwards detached but fits accurately together with the earlier growth stage. towards the periphery (Fig. 1F and H). A slit and resultant sele- nizone are seemingly not present. Fine discontinuous spiral stria- Description.— A species of Isfarispira with lenticular, discoidal, tions may occur on the upper whorl surface (Fig. 1D and H, arrows). form, height about one third of maximum width, and acutely Shell interior septate; shell wall thin. angular periphery. About eight, possibly ten whorls are pres- ent, with the sides of the spire almost flat; incremental angle Discussion.— Isfarispira perlata is distinguished from the type about 130°. Basal surface shallowly convex, inclined, between the species, I. septata, by its acutely angular periphery. Cross-sections periphery and the umbilicus which is about one quarter of the of weathered specimens of I. septata illustrated by Gubanov et al. shell diameter. Umbilical wall (Fig. 1E, arrow uw) short, flat and (1995, text.fig. 2) show considerable variation in form, but the parallel to the axis of coiling, forming a right angle to the basal shell is usually taller, the base often flatter, and the whorls more 252 J. S. PEEL

rounded at the periphery than in I. perlata. Growth lines on the varies from open to completely closed by a callus plug (Peel 1977, upper whorl surface in I. septata appear to have been shallowly fig. 6), unlike the blade-like flange ofI. perlata. concave towards the periphery (Gubanov et al. 1995) while they Kiaeromphalus kristianiensis Peel & Yochelson, 1976 from are shallowly convex in I. perlata, producing a shallow peripheral the Silurian of Norway and K. undiferus (Schmidt, 1858) from sinus. Internal septae which are so abundant in I. septata have not the Silurian of Estonia have similar rates of whorl expansion to been observed in the material from Genoa, Ohio, or commented Isfarispira perlata which they resemble therefore in apical view upon by earlier authors. However, septa are clearly visible in the (Peel & Yochelson 1976; Isakar et al. 1999). However, the height and earliest whorls in the original illustration of Hall (1852, pl. 84, width of whorls in Kiaeromphalus are almost equal in cross-section fig. 5a) of the designated lectotype. (Isakar et al. 1999, fig. 5), whereas whorls inIsfarispira are at least Pleurotomaria clipeiformis Spencer, 1884 from the Niagaran twice as wide as high. Furthermore, in contrast to Isfarispira per- of Hamilton, Ontario, was considered to be a probable junior lata, a circumbilical flange is not present inKiaeromphalus and its synonym of Hall’s (1852) species by Clarke & Ruedeman (1903, p. comarginal ornamentation is often periodically nodose. Wagner 21, footnote) and this is supported by the illustrations of Spencer (2002) tentatively placed Kiaeromphalus as a junior synonym of (1884, pl. 7, figs. 6, 6a). Bassler 1915( , p. 1010) retained the orig- Poleumita Clarke & Ruedemann, 1903 but description of the sec- inal assignment of Spencer (1884) without comment. ond species by Isakar et al. (1999) justifies its recognition. Mironova (1993, pl. 1, figs. 1a, b) assigned toOphileta ? aff. Gubanov et al. (1995) interpreted the large size and flat base perlata (Hall, 1852) a single specimen from the Pschemack with a prominent circumbilical flange ofIsfarispira as adaptations Mountains, Kyrgyzstan, east of the Isfara River, illustrated in to life on a soft substratum. The slow rate of whorl expansion ena- oblique lateral and apical views (the species authorship is inad- bled the growing gastropod to minimise increase in the volume of vertently given as 1952). In terms of the height of the spire, the its soft parts through a combination of withdrawal from the earli- specimen is morphologically indistinguishable from Hall’s (1852, est whorls, as indicated by the septation, and rapid growth, as indi- fig. 5b) illustration of the lectotype of Pleurotomaria perlata. A cated by the high number of wide but low whorls. This so-called specimen with a similar profile was illustrated by Gubanov et “snow-shoe effect” is seen in several Palaeozoic euomphaloid and al. (1995, text-fig. 2B) in cross-section, showing that the whorl macluritid gastropods, including the frilled Euomphalopterus periphery is more rounded than in Isfarispira perlata (fig. 1B and Roemer, 1876 (Linsley et al. 1978; Peel 1984b). It is often associated G). In apical view (Mironova 1993, pl. 1, fig. 1b), the Kyrgyzstan with loose coiling and the acquisition of a wide umbilicus, either specimen has a greater number of narrower whorls, with barely basally, as in euomphaloids, or apically as in macluritids, but the discernible increase in rate of expansion from one whorl to vulnerability of shells of this type to destruction due to the rise of the next, than Hall’s (1852) lectotype, the specimen figured by durophagous predators during the Palaeozoic ultimately limited Williams (1919, pl. 24) and the specimens illustrated herein from its acquisition (Peel 1984b; Ebbestad & Peel 1997; Lindström & Genoa (Fig. 1A and C). Peel 1997, 2005; Ebbestad et al. 2009). Kase (1989) developed a Mironova (1993, pl. 1, fig. 3a, b) illustrated a second spec- discussion of Grantlandispira by Peel (1984a) in proposing that the imen from the Pschemack Mountains, collected at the village Devonian omphalotrochid Labrocuspis may have been an infau- Samarkandyk, with a higher spire and a trochoidal form. It was nal, or semi-infaunal, sedentary gastropod, but Vermeij (2017) assigned to Pycnotrochus viator, originally described from the suggested that this thick-shelled form was a sedentary epifaunal Silurian of Bohemia by Perner (1903), but shows little relation- gastropod, perhaps living on hard bottoms. Isfarispira perlata, ship to the holotype of that species as described by Knight (1941). however, is thin-shelled and likely preferred softer ground. The shallowly convex base shows a well-developed circumbilical flange and radial growth ornamentation. Gubanov et al. 1995( , Acknowledgements text-fig. 2D, pl. 1, fig. 7) also illustrated this morphotype, con- cluding that Isfarispira septata showed considerable variation in Dale M. Gnidovec (Orton Museum) kindly facilitated the loan of material. the morphology of the spire. Such a range in morphology is not Reviews by Jan Ove Ebbestad (Uppsala) and Jiří Frýda (Prague) are grate- fully acknowledged. documented in Isfarispira perlata where the discoidal form and acutely angular periphery are characteristic. Liospira marklandensis McLearn, 1924 from the upper Silurian Disclosure statement Stonehouse Formation of Arisaig, Nova Scotia, is much smaller The author reports no potential conflict of interest. than Isfarispira perlata (diameter 23 mm contra 100 mm) and less acutely lenticular; its higher rate of whorl expansion results in fewer whorls. While its aperture is radial, the growth lines on References its upper whorl surface are prosocyrt, curving forward (adaper- Bassler, R.S., 1915: Bibliographic index of American and turally) below the suture before sweeping strongly back to a broad Silurian fossils. United States National Museum, Bulletin 92, 1521 pp. selenizone with shallow lunulae, located just above the whorl Bigsby, J.J., 1858: On the Palæozoic basin of the state of New York. Part periphery (Peel 1977, pl. 2, figs. 11–14). In this respect it differs I. A synoptical view of the mineralogical and fossil characters of the from other species assigned to Liospira (e.g. Liospira lenticularis palæozoic strata of the state of New York. Quarterly Journal of the Sowerby in Murchison, 1839 as described from the lower Silurian Geological Society 14, 335–427. Bigsby, J.J., 1868: Thesaurus siluricus: the fauna and flora of the Silurian by Longstaff1924 and Pitcher 1939) where the growth lines are period. J. 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