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1 December 2011 A New Microconchid Tubeworm from the Artinskian (Lower Permian) of Central Texas, USA
Author Affiliations +
Abstract

Calcareous tubeworms are common in the Artinskian (Lower Permian) shale and limestone rocks of the Wichita-Albany Group in central Texas. In some units they form small reefs of budding tubes spreading outward from a common origin. These tubular fossils have been traditionally referred to as serpulids, but here we identify them as microconchids (Helicoconchus elongatus gen. et sp. nov.) These microconchids are unusual because of their greatly elongated impunctate tubes with centrally pitted diaphragms. They also show two types of budding: lateral with small daughter tubes that begin as small coils, and binary fission that produced two daughter tubes of equal diameters. These microconchids flourished in shallow marine environments with a fauna dominated by mollusks, echinoids, and foraminifera.

Introduction

Calcareous tubeworms are common fossils throughout the Phanerozoic, but only recently have their systematics been addressed in detail (Vinn and Mutvei 2009). Studies of skeletal microstructure were used in the early 1990s to begin sorting out the serpulids, tentaculitids, cornulitids, trypanoporids, and other fossil tubeworms (Weedon 1990, 1991, 1994). The Order Microconchida Weedon, 1991, in particular has emerged as a diverse group found from the Upper Ordovician to the Middle Jurassic around the world (Vinn 2006, 2010a; Vinn and Mutvei 2009; Zatoń and Taylor 2009). Long misidentified as serpulid worms (especially “Spirorbis”) (Taylor and Vinn 2006), the microconchids are now seen as likely lophophorates (Taylor et al. 2010). In addition to normal marine environments, microconchids also colonized freshwater, brackish and hypersaline environments during the Devonian to Triassic (Taylor and Vinn 2006). However, in general, microconchids occupy a similar niche in the Upper Paleozoic to that of the oyster/serpulids association of the Mesozoic and Cenozoic (Burchette and Riding 1977; Wright and Wright 1981; Weedon 1990). This paper describes an unusual microconchid (Helicoconchus elongatus gen. et sp. nov.) from the Lower Permian of Texas that provides significant new information on the morphology and paleoecology of the order.

These microconchids from the Wichita-Albany Group had previously been described as “Serpula” and “serpulid worm colonies” (Walsh 2002). They are locally known as “spaghetti corals” (Peter Holterhoff, personal communication 2010). Late Paleozoic to Triassic microconchids often occur as secondary frame builders in algal/microconchid buildups (Peryt 1974; Burchette and Riding 1977; Toomey and Cys 1977; Wright and Wright 1981). In contrast, Helicoconchus forms relatively large independent buildups (Fig. 1), which is also less common in microconchids than solitary growth, biostromes or small aggregations (a few cm in diameter). Serpulid buildups of similar size (fossil and modern) have commonly been termed “reefs” (e.g., Leeder 1973; Hove and Hurk 1993; Bianchi and Morri 2001; Moore et al. 2009), so we prefer to use this term for the aggregations of Helicoconchus as well because it emphasizes their large size for microconchids and their integrated skeletons. The earliest known microconchid reefs are probably Early Devonian (Vinn 2010a). In contrast to the Carboniferous (Barrois 1904; Leeder 1973; Burchette and Riding 1977; Wright and Wright 1981; Weedon 1990) and Triassic (Brönnimann and Zaninetti 1972; Peryt 1974; Ball 1980; Warth 1982; Weedon 1990) microconchid faunas, little attention has paid to Permian microconchids (Toomey and Cys 1977). Permian microconchids are important for reconstructing the evolutionary history of Microconchida, especially for understanding the survival strategies of microconchids in the end-Permian mass extinction.

Institutional abbreviations.—C/W, The College of Wooster Geology Department, Wooster, USA; NHM, Natural History Museum, London, UK; NPL, Non-vertebrate Paleontology Laboratory, Texas Natural Science Center, The University of Texas at Austin, USA.

Geological setting

Sedimentary deposits containing microconchid tubeworm aggregates of Helicoconchus occur in strata of ArtinskianKungurian (Early Permian) age on the Eastern Shelf of the Midland Basin in central Texas, within an outcrop trend extending north from the Colorado River Valley to the Brazos River Valley. Helicoconchus occurs in strata of the Elm Creek, Valera, Bead Mountain and Leuders Formations of the Wichita-Albany Group, an interval of thick limestone and shale, with some beds of evaporite sediments present near the top of the Valera Formation (Moore 1949). These sediments were deposited on a flat shelf surface, gently tilted to the west and located between highlands to the east and the deep center of the Midland Basin (Brown et al. 1987). Clastic sediments in this area were derived from mountainous highlands of the Ouachita trend, a upland region that was eroding during the Permian and later subsided to great depths during late Triassic rifting and opening of the Gulf of Mexico by detachment of the Yucatan block (Bird et al. 2005). Artinskian sedimentation on the Eastern Shelf is the beginning of dominantly autochthonous carbonate deposition in an area formerly dominated by siliciclastic sediments derived from the eastern uplands.

Strata of the Wichita-Albany Group are characterized by low diversity, mollusk-dominated marine biotas, in contrast to the high diversity marine biotas present in the underlying siliciclastic-dominated Cisco Group. This biotic change is associated with a change to drier climates and occurrence of intermittent evaporite sediment deposition (Moore 1949). In the Colorado River Valley exposures, microconchid tubeworm aggregates are common in the base of the Bead Mountain Formation within an interval at the top of a transition from deposits of bedded gypsum evaporites (top of Valera Formation) to beds of argillaceous-to-silty limestone (base of Bead Mountain Formation) This interval of common Helicoconchus aggregates is traceable to the Brazos River Valley (Peter Holterhoff, personal communication 2010).

The common occurrence of Helicoconchus in the late stages of a transition from evaporite sediment deposition suggests it was tolerant of fluctuating salinities in a shallow marine environment. Strata in this interval have nearly planar bedding, consistent with deposition on a shallow gently sloping surface with minor seafloor relief. Bioclastic strata contain fragmental fossils and indicate episodic higher energy conditions, but these beds also contain substantial amounts of siliciclastic silt and mud and are poorly winnowed.

Material and methods

This material was studied with both light microscopes (dissecting and petrographic) and an environmental scanning electron microscope in the Department of Geology at the University of Akron. A micrometer system was used in the light microscopes for the measurements. All of the figured specimens, holotypes, and paratypes have been registered into the fossil worm collections of NHM. Additional topotype material is deposited in NPL.

Microconchids and polychaete tubeworms

The order Microconchida is distinguished from tubicolous polychaetes by its lamellar skeletal microstructure and bulblike (rather than open) tube origin (Weedon 1991; Taylor and Vinn 2006). It is these features that have been used to classify all pre-Cretaceous specimens of the ubiquitous encruster “Spirorbis” as microconchids and not serpulids like the Cretaceous to Recent Spirorbis (Taylor and Vinn 2006).

Systematic paleontology

Class Tentaculita Bouček, 1964
Order Microconchida Weedon, 1991
Genus Helicoconchus nov.

  • Type species: Helicoconchus elongatus sp. nov.; by monotypy, see below.

  • Etymology: Combination of helico, spiral and conch, tubicolous shell.

  • Diagnosis.—Small calcitic tube with planispiral, dextrallycoiling attachment surface, tube diameter increasing rapidly; after one to two whorls the tube becomes erect, helical, very long and its diameter remains relatively constant. Well-developed umbilicus absent in planispiral portion of juvenile attached tube. Tube wall microlamellar with no punctae or pseudopunctae. Tube interior with diaphragms, many of which have central pits; spacing of diaphragms changes with growth from infrequent to an average of one every two mm in erect portion of tubes; tube interior walls smooth. Tube exterior with very fine growth lines. Tubes show lateral budding and binary fission budding with the interior connections between parent and daughter tubes apparently repaired by secretion of new wall. Gregarious habits, some forming small reefs up to two meters in diameter of radial, tightly packed, branching tubes and others remaining as isolated tubes.

  • Discussion.Helicoconchus, like all microconchids, can be distinguished from serpulid and spirorbid polychaetes by its microlamellar shell structure and the closed proximal end of the tube (Vinn and Mutvei 2009). This new genus differs from Punctaconchus Vinn and Taylor, 2007; Microconchus Murchison, 1839; and Pseudobrachidium Grupe, 1907; by its lack of punctae, budding origin of daughter tubes, and greatly extended late growth erect tube. Species of Microconchus with an erect helical adult tube part, such as M. advena (Salter, 1863) (Late Devonian—Carboniferous) and M. aberrans (Hohenstein, 1913) (Middle Triassic), are normally less extended than the tubes of new genus. Helicoconchus also lacks the annulated shell of Annuliconchus Vinn, 2006, and the pseudopunctae of Palaeoconchus Vinn, 2006. These latter two microconchid genera also do not have the extended, budding helical tube that distinguishes Helicoconchus.

    Helicoconchus aggregations superficially resemble the “serpulid” Serpula helicalis Beus, 1980, found in the Upper Devonian (Frasnian) of Arizona, USA, with their narrow helical tubes and distinct exterior growth lines. S. helicalis, however, appears to have no internal features, no known budding, nor a planispiral attachment surface. The only known specimens are silicified, so its shell microstructure remains unknown. The “tabulate coral” Spirapora Copper, 1981, of the Upper Ordovician (Ashgill) of Ontario, Canada, looks even more like Helicoconchus as a colony of helical, budding tubes of the same general size and shape. Spirapora, though, has no internal structures or a planispiral attachment surface. Serpula helicalis and Spirapora are almost certainly not serpulids or corals, and they deserve further study. They are not apparently related to Helicoconchus.

    Stratigraphic and geographic range.Helicoconchus is thus far known only from the Wichita-Albany Group (Lower Permian, Artinskian-Kungurian, of central Texas), beginning with occurrences through an interval of Artinskian restricted marine strata including the Elm Creek Limestone (Walsh 2002: fig. 5.9), Valera Shale and basal Bead Mountain Formation and at a higher level of Kungurian age restricted marine deposits in the Leuders Limestone and Lytle Limestone of the lower Clear Fork Group (Peter Holterhoff, personal communication 2010). Age assignments of north-central Texas formations are from Wardlaw (2005).

Fig. 1.

Microconchid tubeworm Helicoconchus elongatus gen. et sp. nov. aggregation, NHM PI AN 1183 (holotype) in top (A), basal (B), and side (C) views.

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Fig. 2.

Isolated origin of microconchid tubeworm Helicoconchus elongatus gen. et sp. nov. (scanning electron micrograph), NHM PI AN 1184.

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Helicoconchus elongatus sp. nov.
Figs. 18.

  • Etymology: Refers to the elongated nature of the late growth tube.

  • Holotype: NHM PI AN 1183, aggregation of tubes.

  • Type locality: Roadcut on Farm-to-Market Road 1929 (Ray Stoker Jr. Highway) on the south side of Ivie Reservoir on the Colorado River, Concho County, Texas (coordinates: N 31.48454°, W 99.69368°).

  • Type horizon: Base of the Bead Mountain Formation (Lower Permian, Artinskian), Wichita-Albany Group; 3.9 meters above the top of a massive gypsum unit.

  • Material.—Holotype NHM PI AN 1183. Paratypes NHM PI AN 1184–1189. Topotypes also deposited at The University of Texas, Texas Natural Science Center.

  • Diagnosis.—As for genus, by monotypy.

  • Description.—Tube small, dextrally coiled and attached at its base and then extended as an erect, free helical tube, elongated many times its attachment diameter. Attachment portion consists of one to two slightly overlapping whorls, circular to elliptical in outline. Well-developed umbilicus absent in planispiral portion of juvenile attached tube. Tube origin is closed, bulb-like; tube diameter increases rapidly through whorls to erect portion, where it then maintains a consistent diameter (Figs. 15). Two types of budding present. Erect portion of the tube has frequent lateral budding, producing daughter tubes that grew parallel to the parent tube and at least started as helical (Fig. 6). Tubes also show budding by distal fission that produced daughter tubes of equal diameter (Fig. 7). When tubes become closely packed in mature colonies their helical nature is lost and they are more or less straight.

    Tube interior walls are smooth. Diaphragms are common in the erect portion of the tubes, roughly one every two mm of length, and planar, convex or concave toward the distal end. The diaphragms are microlamellar like the tube walls, with about half their thickness. The diaphragms have small openings in their centers formed by invaginated diaphragm shell structure. The living chamber (portion of the tube from the last diaphragm to its aperture) is between 5 and 7 mm long.

    Tube exteriors have fine growth lines, about 4 per 0.1 mm. They often form incomplete rings and merge on parts of the tube.

    Tube walls are thin (0.03–0.05 mm) and microlamellar with no punctae or pseudopunctae (Fig. 8). There are roughly 4–5 microlamellae in the walls of erect tubes. The junction between a parent tube and a daughter tube shows no internal connection (no pore or other canal).

    Often forming an integrated colony of tubes with a radial growth habit of spreading laterally over substrate and growing upward in closely packed array of tubes. Large colonies have closely packed tubes; loose arrangement of tubes allows helical coiling to develop (Figs. 1, 2).

  • Dimensions.—The planispiral coiled attachment base of H. elongatus ranges from 0.8 to 1.9 mm in outline diameter; the proximal bulb within it is about 0.6 mm at its widest. The erect portion of the tube ranges from 0.9 mm (where it emerges from the coiled attachment) to 1.5 mm in diameter and up to 5.0 cm in length and probably extended much longer. (Individual tube length is difficult to estimate because of the budding and closely packed nature of mature aggregations.) Mature aggregations form small reefs up to 2.0 meter in diameter and at least 0.5 meters high.

  • Stratigraphic and geographic range.—As for the genus.

Fig. 3.

Microconchid tubeworm Helicoconchus elongatus gen. et sp. nov. reef in the lower portion of the E unit of the Bead Mountain Formation (Lellis and Holterhoff, 2010) and more specifically the 3B cycle set of Lellis (2010) at location N latitude 32° 41′ 39.31″, W longitude 99° 22′ 58.37″. Viewed from above. The radiating surficial pattern is due to weathering. The scale is numbered in tenths of meters. Photograph courtesy of Peter Holterhoff.

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Fig. 4.

Thin-section of tube origin in microconchid tubeworm Helicoconchus elongatus gen. et sp. nov., NHM PI AN 1185.

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Discussion

Helicoconchus elongatus extends our knowledge of microconchid morphology and paleoecology, and hence what we can deduce about the evolution of the group. The initially helical and greatly extended erect impunctate tube, centrally pitted diaphragms, and two styles of budding of H. elongatus are distinctive in the order. Its lateral style of budding, shell structure and growth lines show similarities with the hederelloids (Taylor and Wilson 2008), and its centrally pitted diaphragms resemble those of some microconchids and other tentaculitoids (Weedon 1990).

The H. elongatus reefs are in the “loosely coiled helical aggregative tubes” tentaculitoid morphotype of Vinn (2010a: 214), which he interpreted as an adaptation to limited hard substrates and as a protection against burial by sediment. As such, these microconchid reefs are in the same ecological niche space as serpulid reefs and bioherms of the Upper Jurassic and above (Palma and Angeleri 1992; Hove and Hurk 1993; Kiessling et al. 2006).

Reef building.—Because of its asexual reproduction of daughter tubes, Helicoconchus could be the most advanced reef builder among microconchids. Forming a colony by budding is probably energetically cheaper than forming a colony via larvae with gregarious behavior. It could also offer better control of the growth of the “colony”, increasing its mechanical strength and probably offering more effective feeding opportunities for individuals. Helicoconchus aggregations probably evolved from helical gregarious (not budding) reef-building microconchids that first appeared in Early Devonian (Vinn 2010a). Budding could be considered the last innovation in the evolution of microconchids, which otherwise had not changed much since the Early Devonian (Vinn 2010b). Microconchid aggregations and reefs are not known from the earliest Triassic, probably due to the end-Permian ecosystem collapse and extinction of Helicoconchus-like forms. Microconchid aggregations and small reefs evolved in the Middle Triassic, but they did not have asexual reproduction (budding), and were similar to the microconchid buildups of their earliest evolutionary stage (Devonian—Carboniferous).

Phylogenetic affinities.—Asexual reproduction is widespread among many tubicolous members of various invertebrate phyla (i.e., cnidarians, bryozoans, annelids, phoronids) and so does not on its own support any particular suggested biological affinity of microconchids (i.e., tentaculitoid tube-worms). However, this type of asexual reproduction (budding) in order to form an aggregation is alien to mollusks and thus supports the non-molluscan affinities of microconchids. The occurrence of two types of asexual reproduction is a peculiar feature of Helicoconchus, and its adaptational meaning is unclear.

Fig. 5.

Eroded side view of microconchid tubeworm Helicoconchus elongatus gen. et sp. nov. aggregation, NHM PI AN 1186.

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Fig. 6.

Coiled lateral bud on the side of a tube of microconchid tubeworm Helicoconchus elongatus gen. et sp. nov., NHM PI AN 1187.

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Central pits.—Common central pits in the diaphragms of Helicoconchus (Fig. 7) are atypical for microconchids. Usually microconchids have simple slightly concave diaphragms without pits. However, Weedon (1990) has reported domelike central projections in some diaphragms of Devonian to Lower Triassic microconchids. He interpreted the folding of posterior micro-lamellar sheets of the diaphragms as perforations. We believe these unusual structures were not related to real perforations, but are the result of a folding process comparable to that in Helicoconchus. In spite of the different orientation of the central deflections of diaphragms described by Weedon (1990) from those in Helicoconchus, it could indicate that microconchid diaphragms had a certain degree of plasticity during the early phase of their formation. Alternatively, the central pits of Helicoconchus could reflect soft body characteristics, but in this case one would expect to find central pits in all the diaphragms. This probable early plasticity of diaphragms in microconchids is different from the other encrusting members of tentaculitoid tubeworms such as cornulitids and trypanoporids. Similar deflections could be present in some tentaculitids, interpreted as the perforations by Blind (1969). Most likely the diaphragms were not strongly calcified during secretion and were deformed by body movements (causing the pits and the mix of concave, planar and convex cross-sections) before final calcification.

Fig. 7.

Binary fission budding and diaphragms in microconchid tubeworm Helicoconchus elongatus gen. et sp. nov., NHM PI AN 1188.

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Fig. 8.

Scanning electron image of two microlamellar walls of microconchid tubeworm Helicoconchus elongatus gen. et sp. nov. abutting each other in a polished and etched cross-section, NHM PI AN 1189.

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Shell structure.Helicoconchus has no pseudopunctae or pores (Fig. 8), which have been interpreted as shell strengthening structures in microconchids (Vinn and Taylor 2007). However, there is probably not a direct correlation between the presence of pseudopunctae and the erect growth of the tube (a mechanically more demanding growth form than a planispiral shell) in microconchids. The helically coiled microconchid M. aberrans from the Middle Triassic had fewer pseudopunctae (if any at all) than its contemporary the planispiral microconchid species M. valvatus (Vinn 2010b).

Acknowledgements

Lisa Park (University of Akron, Akron, Ohio, USA) assisted with the environmental scanning electron microscopy. Peter Holterhoff (Texas Tech University, Lubbock, Texas, USA) provided several important observations from the field. Phil Lanman (Champion Stone Company, Lueders, Texas, USA) allowed access to the Schkade Mines quarry. Leif Tapanila (Idaho State University, Pocatello, Idaho, USA) and an anonymous reviewer provided helpful suggestions and corrections. This is a contribution to International Geoscience Programme Project 572. MAW is grateful for support from the Faculty Development Fund at The College of Wooster.

References

  1. H.W. Ball 1980. Spirorbis from the Triassic Bromsgrove Sandstone Formation (Sherwood Sandstone Group) of Bromsgrove, Worcestershire. Proceedings of the Geologists' Association 91: 149–154. Google Scholar
  2. C. Barrois 1904. Sur les spirorbes du terrain houiller de Bruay (Pas-de-Calais). Annales de la Société Géologique du Nord 33: 50–63. Google Scholar
  3. S.S. Beus 1980. Devonian serpulid bioherms in Arizona. Journal of Paleontology 54: 1125–1128. Google Scholar
  4. C.N. Bianchi and C. Morri 2001. The battle is not to the strong: serpulid reefs in the lagoon of Orbetello (Tuscany, Italy). Estuarine, Coastal and Shelf Science 53: 215–220. Google Scholar
  5. D.E. Bird , K. Burke , S.A. Hall , and J.F. Casey 2005. Gulf of Mexico tectonic history: hotspot tracks, crustal boundaries, and early salt distribution. American Association of Petroleum Geologists Bulletin 89: 311–328. Google Scholar
  6. W. Blind 1969. Die Systematiche Stellung der Tentaculiten. Paleontographica A 133: 101–145. Google Scholar
  7. B. Bouček 1964. The Tentaculites of Bohemia. 125 pp. Czechoslovakian Academy of Sciences, Prague. Google Scholar
  8. P. Brönnimann and L. Zaninetti 1972. On the occurrence of the serpulid Spirorbis Daudin, 1800 (Annelida, Polychaetia, Sedentarida) in thin sections of Triassic rocks of Europe and Iran. Rivista ltaliana di Paleontologia e Stratigrafia 78: 67–84. Google Scholar
  9. L.F. Brown Jr. , R.F. Solis Iriarte , and D.A. Johns 1987. Regional Stratigraphic Cross Sections, Upper Pennsylvanian and Lower Permian Strata (Virgilian and Wolfcampian Series), North-central Texas. 27 pp. University of Texas at Austin, Bureau of Economic Geology, Austin. Google Scholar
  10. T.P. Burchette and R. Riding 1977. Attached vermiform gastropods in Carboniferous marginal marine stromatolites and biostromes. Lethaia 10: 17–28. Google Scholar
  11. P. Copper 1981. Spirapora: a new Late Ordovician tabulate coral from Manitoulin Island, Ontario, Canada. Journal of Paleontology 55: 1071–1075. Google Scholar
  12. O. Grupe 1907. Der Untere Keuper im südlichen Hannover. In : H. Menzel (ed.), Festschrift Adolf v. Koenen , 65–134. Schweitzerbart, Stuttgart. Google Scholar
  13. V. Hohenstein 1913. Beiträge zur Kenntnis des Mittleren Muschelkalks und des unteren Trochitenkalks am östlichen Schwarzwaldrand. Geologischpaläontologische Abhandlungen, Neue Folge 12: 173–272. Google Scholar
  14. H.A. ten Hove and P. van den Hurk . 1993. A review of recent and fossil serpulid “reefs”: actuopalaeontology and the “Upper Malm” serpulid limestone in NW Germany. Geologie en Mijnbouw 72: 23–67. Google Scholar
  15. W. Kiessling , R. Scasso , M. Aberhan , L. Ruiz , and S. Weidemeyer 2006. A Maastrichtian microbial reef and associated limestones in the Roca Formation of Patagonia (Neuquén Province, Argentina). Fossil RecordMitteilungen aus dem Museum für Naturkunde 9: 183–197. Google Scholar
  16. M.R. Leeder 1973. Lower Carboniferous serpulid patch reefs, bioherms and biostromes. Nature 242: 41–42. Google Scholar
  17. R. Lellis 2010. Sequence Stratigraphy of the Bead Mountain Limestone (Wichita-Albany Group, Permian), North-central Texas: Sea Level and Climate Controls on Lithofacies and Sequence Architecture. 101 pp. Unpublished MSc. thesis, Texas Tech University, Lubbock. Google Scholar
  18. R. Lellis and P. Holterhoff 2010. Stop 1.5-Valera Shale and Bead Mountain Limestone. In : P. Holterhoff (ed.), Sequence Stratigraphy and Depositional Systems of the Eastern Shelf Lower Permian, Central Texas: Examining the Tropical Record of Late Paleozoic Climate Change. Permian Basin Section , 72–82. SEPM Publication 2010-50. Google Scholar
  19. C.G. Moore , C.R. Bates , J.M. Mair , G.R. Saunders , D.B. Harries , and A.R. Lyndon 2009. Mapping serpulid worm reefs (Polychaeta: Serpulidae) for conservation management. Aquatic Conservation: Marine and Freshwater Ecosystems 19: 226–236. Google Scholar
  20. R.C. Moore 1949. Rocks of Permian(?) age in the Colorado River Valley, north-central Texas. U.S. Geological Survey Oil and Gas Investigations Preliminary Map 80: 2 sheets. Google Scholar
  21. R.I. Murchison 1839. The Silurian System. 768 pp. Murray, London. Google Scholar
  22. R.M. Palma and M.P. Angeleri 1992. Early Cretaceous serpulid limestones: Chachao Formation, Neuquen Basin, Argentina. Facies 27: 175–178. Google Scholar
  23. T.M. Peryt 1974. Spirorbid-algal stromatolites. Nature 249: 239–240. Google Scholar
  24. J.W. Salter 1863. On the old red sandstone and Upper Devonian rocks. The Quarterly Journal of the Geological Society 19: 474–496. Google Scholar
  25. P.D. Taylor and O. Vinn 2006. Convergent morphology in small spiral worm tubes (“Spirorbis”) and its palaeoenvironmental implications. Journal of the Geological Society, London 163: 225–228. Google Scholar
  26. P.D. Taylor , O. Vinn , and M.A. Wilson 2010. Evolution of biomineralisation in “lophophorates”. Special Papers in Palaeontology 84: 317–333. Google Scholar
  27. P.D. Taylor and M.A. Wilson 2008. Morphology and affinities of hederelloid “bryozoans”. In : S.J. Hageman , M.M. Key Jr, and J.E. Winston (eds.), Bryozoan Studies 2007: Proceedings of the 14th International Bryozoology Conference, Boone, North Carolina, July 1–8, 2007. Virginia Museum of Natural History Special Publication 15: 301–309. Google Scholar
  28. D.F. Toomey and J.M. Cys 1977. Spirorbid/algal stromatolites, a probable marginal marine occurrence from the Lower Permian of Mexico, U.S.A. Neues Jahrbuch für Geologie und Paläontologie, Monatschefte 1977 (6): 331–342. Google Scholar
  29. O. Vinn 2006. Two new microconchid (Tentaculita Bouček 1964) genera from the Early Palaeozoic of Baltoscandia and England. Neues Jahrbuch für Geologie und Paläontologie, Monatschefte 2006 (2): 89–100. Google Scholar
  30. O. Vinn 2010a. Adaptive strategies in the evolution of encrusting tentaculitoid tubeworms. Palaeogeography, Palaeoclimatology, Palaeoecology 292: 211–221. Google Scholar
  31. O. Vinn 2010b. Shell structure of helically coiled microconchids from the Middle Triassic (Anisian) of Germany. Paläontologische Zeitschrift 84: 495–499. Google Scholar
  32. O. Vinn and H. Mutvei 2009. Calcareous tubeworms of the Phanerozoic. Estonian Journal of Earth Sciences 58: 286–296. Google Scholar
  33. O. Vinn and P.D. Taylor 2007. Microconchid tubeworms from the Jurassic of England and France. Acta Palaeontologica Polonica 52: 391–399. Google Scholar
  34. T.R. Walsh 2002. Permian Foramol carbonates from a Variable Salinity Shelf Environment: the Elm Creek Limestone (Artinskian) of North-central Texas. 239 pages. Unpublished M.Sc. thesis, Texas Tech University, Lubbock. Google Scholar
  35. B.R. Wardlaw 2005. Age assignment of the Pennsylvanian—Early Permian succession of North Central Texas. Permophiles 46: 21–22. Google Scholar
  36. M. Warth 1982. Vorkommen von Spirorbis (Annelida, Polychaeta) im Lettenkeuper (Unterkeuper, Obere Trias) von Nordwürttemberg. Jahreshefte der Gesellschaft für Naturkunde in Württemberg 137: 87–98. Google Scholar
  37. M.J. Weedon 1990. Shell structure and affinity of vermiform “gastropods”. Lethaia 23: 297–309. Google Scholar
  38. M.J. Weedon 1991. Microstructure and affinity of the enigmatic Devonian tubular fossil Trypanopora. Lethaia 24: 227–23. Google Scholar
  39. M.J. Weedon 1994. Tube microstructure of Recent and Jurassic serpulid polychaetes and the question of the Palaeozoic “spirorbids”. Acta Palaeontologica Polonica 39: 1–15. Google Scholar
  40. V.P. Wright and E.V.G Wright 1981. The palaeoecology of some algalgastropod bioherms in the Lower Carboniferous of South Wales. Neues Jahrbuch für Geologie und Paläontologie, Monatschefte 1981 (9): 546–558. Google Scholar
  41. M. Zatoń and P.D. Taylor 2009. Microconchids (Tentaculita) from the Middle Jurassic of Poland. Bulletin of Geosciences 84: 653–660. Google Scholar
Mark A. Wilson, Olev Vinn and Thomas E. Yancey "A New Microconchid Tubeworm from the Artinskian (Lower Permian) of Central Texas, USA," Acta Palaeontologica Polonica 56(4), (1 December 2011). https://doi.org/10.4202/app.2010.0086
Received: 22 August 2010; Accepted: 1 November 2010; Published: 1 December 2011
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