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Scaphopoda from the Alexander Terrane, Southeast Alaska—The first occurrence of Scaphopoda in the Silurian
Palaeoworld 15 (2006) 211–215
Research paper
Scaphopoda from the Alexander Terrane, Southeast Alaska—The first occurrence of Scaphopoda in the Silurian David M. Rohr a,∗ , Robert B. Blodgett b , James Baichtal c a
Department of Earth and Physical Sciences, 400 N. Harrison Street, Sul Ross State University, Alpine, TX 79832, USA b U.S. Geological Survey-Contractor, 4200 University Drive, Anchorage, AK 99508, USA c U.S. Forest Service, Tongass National Forest, Thorne Bay, AK 99919, USA Received 15 October 2005; received in revised form 23 March 2006; accepted 7 July 2006 Available online 1 September 2006
Abstract The scaphopods Dentalium hecetaensis n. sp. and Rhytiodentalium cf. kentuckyensis Pojeta et Runnegar, 1979, are described from Ludlow-age strata of the Heceta Limestone on Prince of Wales Island, Southeast Alaska. This is the first occurrence of Silurian scaphopods known to date. They are part of a diverse macrobenthic fauna of the Alexander terrane, an accreted southern Alaskan terrane of Siberian or Uralian affinities. © 2006 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved. Keywords: Scaphopoda; Silurian; Alaska; Dentalium; Heceta
1. Introduction Scaphopods are a minor class of marine Mollusca with a tapering, tubular calcareous skeleton. No unequivocal scaphopods have previously been described or illustrated from the Silurian (Ludbrook, 1960; Pojeta, 1987; Yochelson, 2004). Scaphopods form only a minor portion of the diverse, mollusc-rich silicified fauna recovered from acidization of limestone talus blocks from the Heceta Formation. Gastropods are the most abundant part of the fauna, followed by calcareous algae, tabulate corals, minor brachiopods, bivalves, and crinoids. The described specimens are from locality 2002RB32 (Fig. 1), talus blocks derived from a horizon near the top
∗ Corresponding author. Tel.: +1 432 837 8167; fax: +1 432 837 8692. E-mail address: [email protected] (D.M. Rohr).
of the wall face at the northwest corner of a large quarry in the Heceta Limestone situated on the border between sections 20 and 21, T70S, R81E, Craig D-4 quadrangle (Lat. 55◦ 47.26 N, Long. 133◦ 00.74 W, NAD 27), Prince of Wales Island. About 300 kg of silty wackstone to packstone was etched for the silicified fauna. Although the fossil fauna is relatively abundant and diverse within the Heceta Limestone, faunal studies remain few to date. Elements of the fauna described to date from the unit include brachiopods (Kirk, 1922, 1925, 1926; Kirk and Amsden, 1952; Savage, 1989); sphinctozoan sponges (Rigby et al., 1994), corals (Oliver, 1964; Oliver et al., 1975), gastropods (Rohr and Blodgett, in preparation) and calcareous algae (Riding and Soja, 1993; Soja and Riding, 1993). The rocks of Prince of Wales Island belong to the Alexander terrane, an accreted terrane of Siberian or Uralian affinities (Blodgett et al., 2002). Specimen numbers are those of the U.S. National Museum (Natural History), Washington, D.C. (USNM).
1871-174X/$ – see front matter © 2006 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.palwor.2006.07.002
212
D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215
Fig. 1. Locality 2002RB32 is in a large quarry in the Silurian Heceta Limestone, Craig D-4 quadrangle, Prince of Wales Island, Southeast Alaska.
2. Systematic Paleontology 2.1. Class Scaphopoda Bronn, 1862 2.1.1. Discussion Very few Paleozoic scaphopods have been reported. Genera include Dentalium Linnaeus, 1758, Laevidentalium Cossmann, 1888, Plagioglypta Pilsbry et Sharp, 1897–1898, Prodentalium Young, 1942, Rhytiodental-
ium Pojeta et Runnegar, 1979, Calstevenus Yancey, 1973, Paleodentalium Gentile, 1974, and Quasidentalium Shimansky, 1974. Understanding of scaphopod phylogeny is poor because of a limited suite of external shell characters (Reynolds, 2002). Yochelson (2004) concluded that no true scaphopods are older than the Early Carboniferous. However, in our experience there are many occurrences of true scaphopods from the Devonian, and they are
D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215
locally abundant in the Eifelian (early Middle Devonian) of east-central Alaska (Blodgett, 1992), as well as in the Emsian of west-central Alaska (Blodgett, personal observation). According to Yochelson (2004) the features that indicate Paleozoic shells are scaphopods include: a curved, slowly expanding conical shell with bilateral symmetry, tube with openings at both ends, and low population densities. 2.2. Order Dentaloidea Pojeta, 1987 2.2.1. Discussion The order Dentaloidea includes scaphopods with longitudinal ribs or transverse annulations, and is known to range from Middle Ordovician to Holocene (Emerson, 1952, 1962; Pojeta, 1987). Yochelson (2004) reviewed the four reports of Scaphopoda from the Ordovician and rejected them; however, we include Rhytiodentalium Pojeta et Runnegar, 1979 with the scaphopods.
213
2.3.1.1. Etymology. After the Heceta Limestone from which these specimens were collected. 2.3.1.2. Types. Holotype USNM 531341, paratypes 531338–531340. All types are from locality 2002RB32, Hecta Limestone, Ludlow (Silurian). 2.3.1.3. Diagnosis. Slightly curved, slowly expanding, bilaterally symmetrical, circular tubes open at both ends; up to 12 longitudinal, angular ribs along entire length of tube; weak, closely spaced growth lines, slight constrictions due to shell repair. Oral opening straight and perpendicular to axis of tube.
2.3. Genus Dentalium Linnaeus, 1758
2.3.1.4. Description. Slightly curved, slightly tapered cylindrical tubes, up to 4 mm in diameter, with about 12 straight, longitudinal, multiangled ribs; one or two weaker, secondary ribs between primary ribs; fine, closely spaced transverse growth lines indicating oral opening has a straight margin and is perpendicular to axis to axis of tube; shell breakage and renewed growth forms constrictions relatively and is common on specimens.
2.3.1. Dentalium hecetaensis n. sp. See Fig. 2A–G.
2.3.1.5. Discussion. This is the only known occurrence of Dentalium in the Paleozoic, but because the features
Fig. 2. All specimens are from locality 2002RB32, Silurian (Ludlovian) Heceta Limestone on Prince of Wales Island, Southeast Alaska. Scale bars are 5 mm. Specimen numbers are those of the US National Museum (Natural History), Washington, D.C. (USNM). (2A–G), Dentalium hecetaensis n. sp. (A) Longitudinal ribs and repaired breakage, ×5; (B) cross-sectional view of same specimen, ×6, USNM 531338; (C and D) larger specimen with ribs and growth lines, ×3, USNM 531339; (E) ribs and repaired breakage, ×3, USNM 531340; (F and G) ribs and repaired breakage, ×3, holotype, USNM 531341. (2H–J), Rhytiodentalium cf. kentuckyensis Pojeta et Runnegar, 1979. (H) Cross-sectional view of the anterior end, ×6; (I and J) curved tube with shell repair and faint growth lines, ×6, USNM 531342.
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D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215
of the Alaskan specimens appear identical, we assign it to that genus. Dentalium hecetaensis differs from the Middle Ordovician Rhytiodentalium kentuckyensis Pojeta et Runnegar, 1979 in the presence of longitudinal ribs. Paleodentalium has riblets on the posterior end, but the anterior is smooth. Yancey (1973) considered the strongly curved Calstevenus to be a siphonodentaloid. Prodentalium has strong longitudinal ribs only in the juvenile stage and also has oblique growth lines (Yancey, 1973). Laevidentalium is smooth with growth lines only. Growth stoppages possibly due to shell breakage and repair are present on some specimens. These are similar to those illustrated in the Ordovician Rhytiodentalium kentuckyensis (Pojeta and Runnegar, 1979, pl. 1, figs. 11, 14–17) and Recent Dentalium (Pojeta and Runnegar, 1979, pl. 1, figs. 7–10). Several hundred specimens were recovered, but nearly all are broken fragments. 2.3.1.6. Occurrence. Ludlovian Limestone.
(Silurian),
Heceta
2.4. Genus Rhytiodentalium Pojeta et Runnegar, 1979 2.4.1. Discussion Pojeta and Runnegar (1979) established the genus for what they considered to be the oldest scaphopod from the Upper Ordovician (Shermanian) of Kentucky. Yochelson (2004) discussed the genus and concluded that it is not a scaphopod; however, we include it with the scaphopods. 2.5. Rhytiodentalium cf. kentuckyensis Pojeta et Runnegar, 1979 2.5.1. Numbered specimen USNM 531342 2.5.2. Description Relatively thin, slightly curved and tapered cylindrical tubes, up to 4 mm in diameter, smooth exterior with weak growth lines, circular cross-section, complete shell open at both ends; shell breakage and renewed growth present on some specimens. 2.5.3. Discussion Paleodentalium has riblets on the posterior end. Prodentalium has strong longitudinal ribs in the juvenile stage and also has oblique growth lines (Yancey, 1973). This species is less common that Dentalium hecetaensis, but several complete specimens were recovered in addition to many broken specimens. The Alaskan spec-
imens have no external ornament, and demonstrate the difficulty of working with shells that have so few diagnostic features. The few characteristics do seem to match the class. 2.5.4. Occurrence Heceta Limestone Ludlovian (Silurian). Acknowledgments We are grateful to A.J. Boucot (Oregon State University, Corvallis) for helpful comments on the manuscript and the use of acid etching facilities. Field work was supported in part by the U.S. Forest Service and by a grant from the National Geographic Society to Rohr. We thank John Pojeta, Jr. (U.S. Geological Survey, Washington, D.C.) and Jiˇr´ı Fr´yda (Czech Geological Survey, Prague) for their helpful reviews. References Blodgett, R.B., 1992. Taxonomy and paleobiogeographic affinities of an early Middle Devonian (Eifelian) gastropod faunule from the Livengood quadrangle, east-central Alaska. Palaeontographica Abteilung A 221, 125–168. Blodgett, R.B., Rohr, D.M., Boucot, A.J., 2002. Paleozoic links among some Alaskan accreted terranes and Siberia based on megafossils. In: Miller, E.L., Grantz, A., Klemperer, S.L. (Eds.), Tectonic Evolution of the Bering Shelf-Chukchi Sea-Arctic Margin and Adjacent Landmasses. Geological Society of America Special Paper 360, pp. 273–291. Bronn, H.G., 1862. Klassen and Ordnungen der Weilchthiere (Malacozoa) Wisseneschluflich durgstellt in Wort und Bild, vol. 3, sec. 2, Kopftragende Weichthiere (Macacozoa, Cephalopora). Leipzig and Heidelburg. Cossmann, M., 1888. Catalogue illustr´e des coquilles fossiles de ´ ene des environs de Paris. Soci´et´e royale Malacolog Belgique l’Eoc` Annales, fasc. 3, v. 23, 328 pp. Emerson, W.K., 1952. Generic and subgeneric names in the molluscan class Scaphopoda. J. Washington Acad. Sci. 42, 296–303. Emerson, W.K., 1962. A classification of the scaphopod mollusks. J. Paleontol. 36 (2), 76–80. Gentile, R.J., 1974. A new species of Dentalium from the Pennsylvanian of eastern Kansas. J. Paleontol. 48, 1213–1216. Kirk, E., 1922. Brooksina, a new pentameroid genus from the Upper Silurian of southeastern Alaska. In: Proceedings of the United States National Museum, pp. 1–8, v. 60, article 19. Kirk, E., 1925. Harpidium, a new pentameroid brachiopod genus from southeastern Alaska. In: Proceedings of the United States National Museum, pp. 1–7, v. 66, article 32. Kirk, E., 1926. Cymbidium, a new genus of Silurian pentameroid brachiopods from Alaska. In: Proceedings of the United States National Museum, pp. 1–5, v. 69, article 23. Kirk, E., Amsden, T.W., 1952. Upper Silurian brachiopods from Southeastern Alaska. U.S. Geological Survey Professional Paper 233-C, pp. C53–C66. Linnaeus, C., 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis,
D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215 synonymis, locis. Tomus I. Editio decima, Regnum animale, pp. 1–824. Ludbrook, N.H., 1960. Scaphopoda. In: Moore, R.C. (Ed.), Treatise on Invertebrate Paleontology, Part I, Mollusca 1. Geological Society of America and University of Kansas Press, Lawrence, pp. I37–I41. Oliver Jr., W.A., 1964. New Occurrences of the Rugose Coral Rhizophyllum in North America. U.S. Geological Survey Professional Paper 475-D, pp. D149–D158. Oliver Jr., W.A., Merriam, C.W., Churkin Jr., M., 1975. Ordovician, Silurian, and Devonian Corals of Alaska. U.S. Geological Survey Professional Paper 823-B, pp. B13–B44. Pilsbry, H.A., Sharp, B., 1897–1898. Scaphopoda. In: Tyron, G.W. (Ed.), Manual of Conchology, v. 17. Philadelphia, 280 pp. Pojeta J.Jr., 1987. Class Scaphopoda. In: Boardman, R.S., Cheetham, A.H., Rowell, A.J. (Eds.), Fossil Invertebrates. Blackwell Scientific Publications, Palo Alto, California, pp. 380–386. Pojeta J.Jr., Runnegar, B., 1979. Rhytiodentalium kentuckyensis, a new genus and new species of Ordovician scaphopod, and the early history of scaphopod mollusks. J. Paleontol. 53 (3), 530–541. Reynolds, P.D., 2002. The Scaphopoda. Adv. Marine Biol. 42, 139–236.
215
Riding, R., Soja, C.M., 1993. Silurian calcareous algae, cyanobacteria, and microproblematica from the Alexander terrane. J. Paleontol. 67 (5), 710–728. Rigby, J.K., Nitecki, M.H., Soja, C.M., Blodgett, R.B., 1994. Silurian aphrosalpingid sphinctozoans from Alaska and Russia. Acta Palaeontol. Polonica 39, 341–391. Savage, N.M., 1989. The occurrence of the brachiopods Nanukidium and Atrypoidea in the Late Silurian of southeastern Alaska, Alexander terrane. J. Paleontol. 63 (4), 530–533. Shimansky, V.N., 1974. A new scaphopod genus from the Carboniferous of the Donbass. Paleontol. J. 8 (1), 125–127. Soja, C.M., Riding, R., 1993. Silurian microbial associations from the Alexander terrane, Alaska. J. Paleontol. 67 (5), 728–738. Yancey, T.E., 1973. A new genus of Permian siphonodentalid scaphopods, and its bearing on the origin of the Siphonodentaliidae. J. Paleontol. 47 (6), 1062–1064. Yochelson, E.L., 2004. The record the early “Scaphopoda” (?Mollusca) reevaluated. Annalen des Naturhistorischen Museums in Wien 106A, 13–31. Young, J.A., 1942. Pennsylvanian Scaphopoda and Cephalopoda from New Mexico. J. Paleontol. 16 (1), 120–125.
Research paper
Scaphopoda from the Alexander Terrane, Southeast Alaska—The first occurrence of Scaphopoda in the Silurian David M. Rohr a,∗ , Robert B. Blodgett b , James Baichtal c a
Department of Earth and Physical Sciences, 400 N. Harrison Street, Sul Ross State University, Alpine, TX 79832, USA b U.S. Geological Survey-Contractor, 4200 University Drive, Anchorage, AK 99508, USA c U.S. Forest Service, Tongass National Forest, Thorne Bay, AK 99919, USA Received 15 October 2005; received in revised form 23 March 2006; accepted 7 July 2006 Available online 1 September 2006
Abstract The scaphopods Dentalium hecetaensis n. sp. and Rhytiodentalium cf. kentuckyensis Pojeta et Runnegar, 1979, are described from Ludlow-age strata of the Heceta Limestone on Prince of Wales Island, Southeast Alaska. This is the first occurrence of Silurian scaphopods known to date. They are part of a diverse macrobenthic fauna of the Alexander terrane, an accreted southern Alaskan terrane of Siberian or Uralian affinities. © 2006 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved. Keywords: Scaphopoda; Silurian; Alaska; Dentalium; Heceta
1. Introduction Scaphopods are a minor class of marine Mollusca with a tapering, tubular calcareous skeleton. No unequivocal scaphopods have previously been described or illustrated from the Silurian (Ludbrook, 1960; Pojeta, 1987; Yochelson, 2004). Scaphopods form only a minor portion of the diverse, mollusc-rich silicified fauna recovered from acidization of limestone talus blocks from the Heceta Formation. Gastropods are the most abundant part of the fauna, followed by calcareous algae, tabulate corals, minor brachiopods, bivalves, and crinoids. The described specimens are from locality 2002RB32 (Fig. 1), talus blocks derived from a horizon near the top
∗ Corresponding author. Tel.: +1 432 837 8167; fax: +1 432 837 8692. E-mail address: [email protected] (D.M. Rohr).
of the wall face at the northwest corner of a large quarry in the Heceta Limestone situated on the border between sections 20 and 21, T70S, R81E, Craig D-4 quadrangle (Lat. 55◦ 47.26 N, Long. 133◦ 00.74 W, NAD 27), Prince of Wales Island. About 300 kg of silty wackstone to packstone was etched for the silicified fauna. Although the fossil fauna is relatively abundant and diverse within the Heceta Limestone, faunal studies remain few to date. Elements of the fauna described to date from the unit include brachiopods (Kirk, 1922, 1925, 1926; Kirk and Amsden, 1952; Savage, 1989); sphinctozoan sponges (Rigby et al., 1994), corals (Oliver, 1964; Oliver et al., 1975), gastropods (Rohr and Blodgett, in preparation) and calcareous algae (Riding and Soja, 1993; Soja and Riding, 1993). The rocks of Prince of Wales Island belong to the Alexander terrane, an accreted terrane of Siberian or Uralian affinities (Blodgett et al., 2002). Specimen numbers are those of the U.S. National Museum (Natural History), Washington, D.C. (USNM).
1871-174X/$ – see front matter © 2006 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.palwor.2006.07.002
212
D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215
Fig. 1. Locality 2002RB32 is in a large quarry in the Silurian Heceta Limestone, Craig D-4 quadrangle, Prince of Wales Island, Southeast Alaska.
2. Systematic Paleontology 2.1. Class Scaphopoda Bronn, 1862 2.1.1. Discussion Very few Paleozoic scaphopods have been reported. Genera include Dentalium Linnaeus, 1758, Laevidentalium Cossmann, 1888, Plagioglypta Pilsbry et Sharp, 1897–1898, Prodentalium Young, 1942, Rhytiodental-
ium Pojeta et Runnegar, 1979, Calstevenus Yancey, 1973, Paleodentalium Gentile, 1974, and Quasidentalium Shimansky, 1974. Understanding of scaphopod phylogeny is poor because of a limited suite of external shell characters (Reynolds, 2002). Yochelson (2004) concluded that no true scaphopods are older than the Early Carboniferous. However, in our experience there are many occurrences of true scaphopods from the Devonian, and they are
D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215
locally abundant in the Eifelian (early Middle Devonian) of east-central Alaska (Blodgett, 1992), as well as in the Emsian of west-central Alaska (Blodgett, personal observation). According to Yochelson (2004) the features that indicate Paleozoic shells are scaphopods include: a curved, slowly expanding conical shell with bilateral symmetry, tube with openings at both ends, and low population densities. 2.2. Order Dentaloidea Pojeta, 1987 2.2.1. Discussion The order Dentaloidea includes scaphopods with longitudinal ribs or transverse annulations, and is known to range from Middle Ordovician to Holocene (Emerson, 1952, 1962; Pojeta, 1987). Yochelson (2004) reviewed the four reports of Scaphopoda from the Ordovician and rejected them; however, we include Rhytiodentalium Pojeta et Runnegar, 1979 with the scaphopods.
213
2.3.1.1. Etymology. After the Heceta Limestone from which these specimens were collected. 2.3.1.2. Types. Holotype USNM 531341, paratypes 531338–531340. All types are from locality 2002RB32, Hecta Limestone, Ludlow (Silurian). 2.3.1.3. Diagnosis. Slightly curved, slowly expanding, bilaterally symmetrical, circular tubes open at both ends; up to 12 longitudinal, angular ribs along entire length of tube; weak, closely spaced growth lines, slight constrictions due to shell repair. Oral opening straight and perpendicular to axis of tube.
2.3. Genus Dentalium Linnaeus, 1758
2.3.1.4. Description. Slightly curved, slightly tapered cylindrical tubes, up to 4 mm in diameter, with about 12 straight, longitudinal, multiangled ribs; one or two weaker, secondary ribs between primary ribs; fine, closely spaced transverse growth lines indicating oral opening has a straight margin and is perpendicular to axis to axis of tube; shell breakage and renewed growth forms constrictions relatively and is common on specimens.
2.3.1. Dentalium hecetaensis n. sp. See Fig. 2A–G.
2.3.1.5. Discussion. This is the only known occurrence of Dentalium in the Paleozoic, but because the features
Fig. 2. All specimens are from locality 2002RB32, Silurian (Ludlovian) Heceta Limestone on Prince of Wales Island, Southeast Alaska. Scale bars are 5 mm. Specimen numbers are those of the US National Museum (Natural History), Washington, D.C. (USNM). (2A–G), Dentalium hecetaensis n. sp. (A) Longitudinal ribs and repaired breakage, ×5; (B) cross-sectional view of same specimen, ×6, USNM 531338; (C and D) larger specimen with ribs and growth lines, ×3, USNM 531339; (E) ribs and repaired breakage, ×3, USNM 531340; (F and G) ribs and repaired breakage, ×3, holotype, USNM 531341. (2H–J), Rhytiodentalium cf. kentuckyensis Pojeta et Runnegar, 1979. (H) Cross-sectional view of the anterior end, ×6; (I and J) curved tube with shell repair and faint growth lines, ×6, USNM 531342.
214
D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215
of the Alaskan specimens appear identical, we assign it to that genus. Dentalium hecetaensis differs from the Middle Ordovician Rhytiodentalium kentuckyensis Pojeta et Runnegar, 1979 in the presence of longitudinal ribs. Paleodentalium has riblets on the posterior end, but the anterior is smooth. Yancey (1973) considered the strongly curved Calstevenus to be a siphonodentaloid. Prodentalium has strong longitudinal ribs only in the juvenile stage and also has oblique growth lines (Yancey, 1973). Laevidentalium is smooth with growth lines only. Growth stoppages possibly due to shell breakage and repair are present on some specimens. These are similar to those illustrated in the Ordovician Rhytiodentalium kentuckyensis (Pojeta and Runnegar, 1979, pl. 1, figs. 11, 14–17) and Recent Dentalium (Pojeta and Runnegar, 1979, pl. 1, figs. 7–10). Several hundred specimens were recovered, but nearly all are broken fragments. 2.3.1.6. Occurrence. Ludlovian Limestone.
(Silurian),
Heceta
2.4. Genus Rhytiodentalium Pojeta et Runnegar, 1979 2.4.1. Discussion Pojeta and Runnegar (1979) established the genus for what they considered to be the oldest scaphopod from the Upper Ordovician (Shermanian) of Kentucky. Yochelson (2004) discussed the genus and concluded that it is not a scaphopod; however, we include it with the scaphopods. 2.5. Rhytiodentalium cf. kentuckyensis Pojeta et Runnegar, 1979 2.5.1. Numbered specimen USNM 531342 2.5.2. Description Relatively thin, slightly curved and tapered cylindrical tubes, up to 4 mm in diameter, smooth exterior with weak growth lines, circular cross-section, complete shell open at both ends; shell breakage and renewed growth present on some specimens. 2.5.3. Discussion Paleodentalium has riblets on the posterior end. Prodentalium has strong longitudinal ribs in the juvenile stage and also has oblique growth lines (Yancey, 1973). This species is less common that Dentalium hecetaensis, but several complete specimens were recovered in addition to many broken specimens. The Alaskan spec-
imens have no external ornament, and demonstrate the difficulty of working with shells that have so few diagnostic features. The few characteristics do seem to match the class. 2.5.4. Occurrence Heceta Limestone Ludlovian (Silurian). Acknowledgments We are grateful to A.J. Boucot (Oregon State University, Corvallis) for helpful comments on the manuscript and the use of acid etching facilities. Field work was supported in part by the U.S. Forest Service and by a grant from the National Geographic Society to Rohr. We thank John Pojeta, Jr. (U.S. Geological Survey, Washington, D.C.) and Jiˇr´ı Fr´yda (Czech Geological Survey, Prague) for their helpful reviews. References Blodgett, R.B., 1992. Taxonomy and paleobiogeographic affinities of an early Middle Devonian (Eifelian) gastropod faunule from the Livengood quadrangle, east-central Alaska. Palaeontographica Abteilung A 221, 125–168. Blodgett, R.B., Rohr, D.M., Boucot, A.J., 2002. Paleozoic links among some Alaskan accreted terranes and Siberia based on megafossils. In: Miller, E.L., Grantz, A., Klemperer, S.L. (Eds.), Tectonic Evolution of the Bering Shelf-Chukchi Sea-Arctic Margin and Adjacent Landmasses. Geological Society of America Special Paper 360, pp. 273–291. Bronn, H.G., 1862. Klassen and Ordnungen der Weilchthiere (Malacozoa) Wisseneschluflich durgstellt in Wort und Bild, vol. 3, sec. 2, Kopftragende Weichthiere (Macacozoa, Cephalopora). Leipzig and Heidelburg. Cossmann, M., 1888. Catalogue illustr´e des coquilles fossiles de ´ ene des environs de Paris. Soci´et´e royale Malacolog Belgique l’Eoc` Annales, fasc. 3, v. 23, 328 pp. Emerson, W.K., 1952. Generic and subgeneric names in the molluscan class Scaphopoda. J. Washington Acad. Sci. 42, 296–303. Emerson, W.K., 1962. A classification of the scaphopod mollusks. J. Paleontol. 36 (2), 76–80. Gentile, R.J., 1974. A new species of Dentalium from the Pennsylvanian of eastern Kansas. J. Paleontol. 48, 1213–1216. Kirk, E., 1922. Brooksina, a new pentameroid genus from the Upper Silurian of southeastern Alaska. In: Proceedings of the United States National Museum, pp. 1–8, v. 60, article 19. Kirk, E., 1925. Harpidium, a new pentameroid brachiopod genus from southeastern Alaska. In: Proceedings of the United States National Museum, pp. 1–7, v. 66, article 32. Kirk, E., 1926. Cymbidium, a new genus of Silurian pentameroid brachiopods from Alaska. In: Proceedings of the United States National Museum, pp. 1–5, v. 69, article 23. Kirk, E., Amsden, T.W., 1952. Upper Silurian brachiopods from Southeastern Alaska. U.S. Geological Survey Professional Paper 233-C, pp. C53–C66. Linnaeus, C., 1758. Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis,
D.M. Rohr et al. / Palaeoworld 15 (2006) 211–215 synonymis, locis. Tomus I. Editio decima, Regnum animale, pp. 1–824. Ludbrook, N.H., 1960. Scaphopoda. In: Moore, R.C. (Ed.), Treatise on Invertebrate Paleontology, Part I, Mollusca 1. Geological Society of America and University of Kansas Press, Lawrence, pp. I37–I41. Oliver Jr., W.A., 1964. New Occurrences of the Rugose Coral Rhizophyllum in North America. U.S. Geological Survey Professional Paper 475-D, pp. D149–D158. Oliver Jr., W.A., Merriam, C.W., Churkin Jr., M., 1975. Ordovician, Silurian, and Devonian Corals of Alaska. U.S. Geological Survey Professional Paper 823-B, pp. B13–B44. Pilsbry, H.A., Sharp, B., 1897–1898. Scaphopoda. In: Tyron, G.W. (Ed.), Manual of Conchology, v. 17. Philadelphia, 280 pp. Pojeta J.Jr., 1987. Class Scaphopoda. In: Boardman, R.S., Cheetham, A.H., Rowell, A.J. (Eds.), Fossil Invertebrates. Blackwell Scientific Publications, Palo Alto, California, pp. 380–386. Pojeta J.Jr., Runnegar, B., 1979. Rhytiodentalium kentuckyensis, a new genus and new species of Ordovician scaphopod, and the early history of scaphopod mollusks. J. Paleontol. 53 (3), 530–541. Reynolds, P.D., 2002. The Scaphopoda. Adv. Marine Biol. 42, 139–236.
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