The earliest Osprioneides kampto borings were found in bryozoan colonies of Sandbian age from northern Estonia (Baltica). The Ordovician was a time of great increase in the quantities of hard substrate removed by single trace makers. Increased predation pressure was most likely the driving force behind the infaunalization of larger invertebrates such as the Osprioneides trace makers in the Ordovician. It is possible that the Osprioneides borer originated in Baltica or in other paleocontinents outside of North America.
Citation: Vinn O, Wilson MA, Mõtus M-A (2014) The Earliest Giant Osprioneides Borings from the Sandbian (Late Ordovician) of Estonia. PLoS ONE 9(6): e99455. https://doi.org/10.1371/journal.pone.0099455
Editor: Andrew A. Farke, Raymond M. Alf Museum of Paleontology, United States of America
Received: March 18, 2014; Accepted: May 14, 2014; Published: June 5, 2014
Copyright: © 2014 Vinn et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All data are included within the manuscript.
Funding: O.V. is indebted to the Sepkoski Grant program (Paleontological Society), Estonian Science Foundation grant ETF9064, Estonian Research Council grant IUT20-34 and a target-financed project from the Estonian Ministry of Education and Science (SF0180051s08; Ordovician and Silurian climate changes, as documented from the biotic changes and depositional environments in the Baltoscandian Palaeobasin) for financial support. M-A.M was also supported by a target-financed project from the Estonian Ministry of Education and Science (SF0140020s08). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
The oldest macroborings in the world are the small simple holes of Trypanites reported in Early Cambrian archaeocyathid reefs in Labrador , . The next oldest macroborings are found in carbonate hardgrounds of Early Ordovician age , , , . There was a great increase in bioerosion intensity and diversity in the Ordovician, now termed the Ordovician Bioerosion Revolution . In the Middle and Late Ordovician, shells and hardgrounds are often thoroughly riddled with holes, most of them attributable to Trypanites and Palaeosabella . In addition, Ordovician bioerosion trace fossils include bivalve borings (Petroxestes), bryozoan etchings (Ropalonaria), sponge borings (Cicatricula), Sanctum (a cavernous domichnium excavated in bryozoan zoaria by an unknown borer) and Gastrochaenolites , . Bioerosion was very common in the Middle Paleozoic, especially in the Devonian . Later in the Mesozoic bioerosion intensity and diversity further increased , , , , and deep, large borings became especially common .
The bioerosion trace fossils of Ordovician of North America are relatively well studied , , . In contrast, there is a limited number of works devoted to the study of bioerosional trace fossils in the Ordovician of Baltica. The earliest large boring occurs in the Early to Middle Ordovician hardgrounds and could belong to Gastrochaenolites , . Abundant Trypanites borings are known from brachiopods of the Arenigian  and Sandbian . Wyse Jackson and Key  published a study on borings in trepostome bryozoans from the Ordovician of Estonia. They identified two ichnogenera, Trypanites and Sanctum, in bryozoans of Middle and Upper Ordovician strata of northern Estonia.
The aims of this paper are to: 1) determine whether the shafts in large Sandbian bryozoans belong to previously known or a new bioerosional ichnotaxon for the Ordovician; 2) determine the systematic affinity of the trace fossil; 3) discuss the ecology of the trace makers; 4) discuss the paleobiogeographic distribution of the trace fossil; and 4) discuss the occurrence of large borings during the Ordovician Bioerosion Revolution.
Geological Background and Locality
During the Ordovician, the Baltica paleocontinent migrated from the temperate to the subtropical realm , . The climatic change resulted in an increase of carbonate production and sedimentation rate on the shelf during the Middle and Late Ordovician. In the Upper Ordovician the first carbonate buildups are recorded, emphasizing a striking change in the overall character of the paleobasin .
The total thickness of the Ordovician in Estonia varies from 70 to 180 m . The Ordovician limestones of Estonia form a wide belt from the Narva River in the northeast to Hiiumaa Island in the northwest . In the Middle Ordovician and early Late Ordovician, the slowly subsiding western part of the East-European Platform was covered by a shallow, epicontinental sea with little bathymetric differentiation and an extremely low sedimentation rate. Along the extent of the ramp a series of grey calcareous - argillaceous sediments accumulated (argillaceous limestones and marls), with a trend of increasing clay and decreasing bioclasts in the offshore direction .
The material studied here was collected from the Hirmuse Creek (Fig. 1) and Alliku Ditches (Fig. 1) of Sandbian age (Haljala Stage) (Fig. 2). Hirmuse Creek is located in Maidla parish of Ida-Viru County. Clayey and skeletal limestones with interlayers of marls are exposed on the creek bed and in its banks. The fossil assemblage includes algae (Mastopora), brachiopods (Clinambon, Leptaena, Platystrophia, Apartorthis, Porambonites, Pseudolingula), conulariids, gastropods (Lesueurilla, Holopea, Bucanella, Pachydictya, Megalomphala, Cymbularia), ichnofossils (Amphorichnus, Arachnostega), sponges, receptaculitids (Tettragonis), rugosans (Lambelasma), bryozoans, and asaphid trilobites. The Alliku Ditches are located in Harju County near the village of Alliku. Clayey limestones with interlayers of marls are exposed here. The fauna includes algae, brachiopods, bryozoans (Aluverina, Annunziopora, Batostoma, Ceramoporella, Coeloclema, Constellaria, Corynotrypa, Crepipora, Dekayella, Diazipora, Diplotrypa, Enallopora, Esthoniophora, Graptodictya, Hallopora, Hemiphragma, Homotrypa, Homotrypella, Kukersella, Lioclemella, Mesotrypa, Monotrypa, Nematopora, Nematotrypa, Oanduella, Moyerella, Pachydictya, Phylloporina, Prasopora, Proavella, Pseudohornera, Rhinidictya, Stictoporella), echinoderms, gastropods, ostracods, rugosans, receptaculitids and trilobites according to Rõõmusoks .
Location of Hirmuse Creek and Alliku Ditches in North Estonia.
The Middle and Upper Ordovician in Estonia. Location of Osprioneides kampto borings. Modified after Hints et al. (2008).
No permits were required for the described study, which complied with all relevant Estonian regulations, as our study did not involve collecting protected fossil species. Three described bryozoan specimens with the Osprioneides borings are deposited at the Institute of Geology, Tallinn University of Technology (GIT), Ehitajate tee 5, Tallinn, Estonia, with specimen numbers GIT-398-729, GIT 665-18 and GIT 665-19.
Numerous unbranched, single-entrance, large deep borings with oval cross sections were found in three large trepostome bryozoan colonies (Figs. 3, 4, 5, 6). The borings are vertical to subparallel to the bryozoan surfaces and have a tapered to rounded terminus. Several borings have lost their roofs due to erosion. The boring apertures’ minor axis is 2.7 to 7.0 mm (M = 5.05, sd = 1.34, N = 12) and major axis is 7.0 to 15.0 mm (M = 10.37, sd = 2.60, N = 12) long. The axial ratio (major axis/minor axis) of the borings ranges from 1.60 to 2.59 (M = 2.08, sd = 0.29, N = 12). Three completely preserved borings are 25 mm (aperture 12×6 mm), 28 mm (aperture 9×4.5 mm), and 32 mm (aperture 13×6 mm) deep. Two unroofed borings have depths of 35 mm and 50 mm. The borings are abundant in the studied samples (Figs. 3, 4, 5, 6). They occasionally truncate each other, which somewhat resembles a branching pattern. There are no linings or septa inside the borings. The growth lamellae of the bryozoans show no reactions around the borings. Small Trypanites borings occur inside the large boring with oval cross section. The apertures of the large borings occur on both the upper and lower surfaces of the bryozoans (the upper and lower surface of bryozoans was determined by looking at skeletal growth).
Schematic line drawing showing a straight boring.
A bryozoan from Hirmuse Creek, Sandbian, Upper Ordovician, Estonia. Tr – Trypanites borings. GIT 398–729.
A bryozoan from Hirmuse Creek, Sandbian, Upper Ordovician, Estonia. Tr – Trypanites borings. GIT 665-18.
Taxonomic Affinity of the Borings and the Possible Trace Maker
The borings in these bryozoans resemble somewhat Petroxestes known from Late Ordovician bryozoans and hardgrounds of North America . Both are of unusually large size for Ordovician borings, and both have oval-shaped apertures. However, in Petroxestes the aperture width is much greater than the boring’s depth. In contrast, the depth of the borings in bryozoans is much greater than their apertural width. Unlike Petroxestes, the Sandbian borings examined here have a tapering terminus and somewhat sinuous course. The axial ratio of Petroxestes borings aperture (major axis/minor axis) is also much greater than observed in these borings.
The other similar large Palaeozoic boring is Osprioneides, which is known from the Silurian of Baltica, Britain and North America . We assign borings in the bryozoans studied here to Osprioneides kampto because of their similar general morphology. They have a single entrance, an oval cross section, and significant depth similar to Osprioneides kampto. Their straight, curved to somewhat sinuous shape also resembles that of Osprioneides. Both Osprioneides and these borings in bryozoans have a tapered to rounded terminus.
Most likely the Osprioneides trace maker was a soft-bodied animal similar to polychaete worms that used chemical means of boring as suggested by Beuck et al. . This is supported by the slightly curved to sinuous course of several borings and their variable length. The presence of a tapered terminus in Osprioneides means bivalves were very unlikely to have been the trace makers.
Paleoecology and Taphonomy
Osprioneides borings were made post mortem because the growth lamellae of the bryozoan do not deflect around the borings. There are also no signs of skeletal repair by the bryozoans. Several Osprioneides borings truncate other Osprioneides borings that were likely abandoned by the trace maker by that time. Similarly, empty Osprioneides borings were colonized by Trypanites trace makers. This indicates that the Osprioneides borings may have appeared relatively early in the ecological succession. Overturning of the bryozoan zoaria can explain the occurrence of Osprioneides borings apertures on both upper and lower surfaces. There is no sign of encrustation on the walls of the studied Osprioneides borings, suggesting relatively rapid burial of the host bryozoans shortly after the Osprioneides colonization.
It is likely that Osprioneides trace makers were suspension feeders similar to the Trypanites animals due to their stationary life mode . Bryozoan skeletons may have offered them protection against predators and a higher tier for suspension feeding. Previously known host substrates of Osprioneides comprise stromatoporoids and tabulate corals. This new occurrence of Osprioneides borings in large bryozoans shows that the trace maker possibly selected its substrate only by size of skeleton because the traces are not found in smaller fossils. However, they are not found in any Ordovician hardgrounds that provide more area than do the bryozoan colonies. Wyse Jackson and Key  suggest that large bryozoan colonies were exploited by borers because they would have been easy to bore into.
Ordovician Bioerosion Revolution
Morphological diversification was not the only result of the Ordovician Bioerosion Revolution. Most of the large bioerosional traces of the Paleozoic had their earliest appearances in the Ordovician , . The earliest known large borings are those of Gastrochaenolites from the Early Ordovician of Baltica , . Later, during the Late Ordovician, large Petroxestes borings appeared in North America. At the same time the Osprioneides borings described here appeared in Baltica. Thus the Ordovician was also the time of great increase in quantities of hard substrate removed by single trace makers. The biological affinities of Ordovician Gastrochaenolites are not known , but it may have been a soft-bodied animal. The Late Ordovician Petroxestes was almost certainly produced by the facultatively boring bivalve Corallidomus scobina . Boring polychaetes were the likely Osprioneides trace makers, which is suggested by the somewhat sinuous shape of some borings. This indicates that more than one group of animal was involved in the appearance of large bioerosional traces during the Ordovician Bioerosion Revolution. Increased predation pressure  was most likely the driving force behind the infaunalization of larger invertebrates such as the Osprioneides trace makers in the Ordovician. On the other hand in echinoids, for example, infaunalization was presumably the result of colonization of unoccupied niche space .
Osprioneides is a relatively rare fossil compared to the abundance of Trypanites in the Silurian of Baltica . In the Silurian, Osprioneides borings also occur outside of Baltica. They are known from the Llandovery of North America and Ludlow of the Welsh Borderlands . Osprioneides is presumably absent in the Ordovician of North America because Ordovician bioerosional trace fossils of North America are relatively well studied , . Thus, it is possible that the Osprioneides trace maker originated in Baltica or elsewhere and migrated to North America in the Silurian. This may well be connected to the decreased distance between Baltica and Laurentia (the closing of the Iapetus Ocean) and the loss of provinciality of faunas in the Silurian.
We are grateful to Ursula Toom for finding the specimens among the old collections of the Institute of Geology, Tallinn University of Technology. Ursula Toom, Prof. Dimitri Kaljo, Dr. Linda Hints, Dr. Helje Pärnaste from the Institute of Geology, Tallinn University of Technology and Dr. Mare Isakar from the Geological Museum of the University of Tartu Natural History Museum are thanked for identifications of the associated fossils. We are grateful to G. Baranov from Institute of Geology at TUT for technical help with images. We are grateful to Dr. Harry Mutvei and an anonymous reviewer for the constructive reviews.
Conceived and designed the experiments: OV MAW MAM. Performed the experiments: OV MAW MAM. Analyzed the data: OV MAW MAM. Contributed reagents/materials/analysis tools: OV MAW MAM. Contributed to the writing of the manuscript: OV MAW MAM.
- 1. James NP, Kobluk DR, Pemberton SG (1977) The oldest macroborers: Lower Cambrian of Labrador. Science 197: 980–983.
- 2. Kobluk DR, James NP, Pemberton SG (1978) Initial diversification of macroboring ichnofossils and exploitation of the macroboring niche in the lower Paleozoic. Paleobiology 4: 163–170.
- 3. Palmer TJ, Plewes CR (1993) Borings and bioerosion in the fossil record: Geology Today. 9: 138–142.
- 4. Ekdale AA, Bromley RG (2001) Bioerosional innovation for living in carbonate hardgrounds in the Early Ordovician of Sweden. Lethaia 34: 1–12.
- 5. Dronov AV, Mikuláš R, Logvinova M (2002) Trace fossils and ichnofabrics across the Volkhov depositional sequence (Ordovician, Arenigian of St. Petersburg Region, Russia). J Czech Geol Soc 47: 133–146.
- 6. Taylor PD, Wilson MA (2003) Palaeoecology and evolution of marine hard substrate communities. Earth Sci Rev 62: 1–103.
- 7. Wilson MA, Palmer TJ (2006) Patterns and processes in the Ordovician Bioerosion Revolution. Ichnos 13: 109–112.
- 8. Wilson MA (2007) Macroborings and the evolution of bioerosion. In Miller III, W (ed.). Trace fossils: concepts, problems, prospects. Amsterdam: Elsevier. 356–367.
- 9. Bromley RG (2004) A stratigraphy of marine bioerosion, p.455–481. In McIlroy, D. (ed.) The application of ichnology to palaeoenvironmental and stratigraphical analysis. Geological Society of London Special Publications, 228p.
- 10. Zatoń M, Zhuravlev AV, Rakociński M, Filipiak P, Borszcz T, et al. (2014) Microconchid-dominated cobbles from the Upper Devonian of Russia: Opportunism and dominance in a restricted environment following the Frasnian–Famennian biotic crisis. Palaeogeogr Palaeoclimat Palaeoecol 401: 142–153.
- 11. Zatoń M, Machocka S, Wilson MA, Marynowski L, Taylor PD (2011) Origin and paleoecology of Middle Jurassic hiatus concretions from Poland. Facies 57: 275–300.
- 12. Zatoń M, Wilson MA, Zavar E (2011) Diverse sclerozoan assemblages encrusting large bivalve shells from the Callovian (Middle Jurassic) of southern Poland. Palaeogeogr Palaeoclimat Palaeoecol 307: 232–244.
- 13. Beuck L, Wisshak M, Munnecke A, Freiwald A (2008) A giant boring in a Silurian stromatoporoid analysed by computer tomography. Acta Palaeont Pol 53: 149–160.
- 14. Wilson MA, Palmer TJ (1988) Nomenclature of a bivalve boring from the Upper Ordovician of the Midwestern United States. J Paleont 62: 306–308.
- 15. Erickson JM, Bouchard TD (2003) Description and interpretation of Sanctum laurentiensis, new ichnogenus and ichnospecies, a domichnium mined into Late Ordovician (Cincinnatian) ramose bryozoan colonies. J Paleont 77: 1002–1010.
- 16. Tapanila L, Copper P (2002) Endolithic trace fossils in the Ordovician-Silurian corals and stromatoporoids, Anticosti Island, eastern Canada. Acta Geol Hisp 37: 15–20.
- 17. Vinn O, Wilson MA (2010a) Early large borings from a hardground of Floian-Dapingian age (Early and Middle Ordovician) in northeastern Estonia (Baltica). Carnets Géol CG2010_L04.
- 18. Vinn O (2004) The earliest known Trypanites borings in the shells of articulate brachiopods from the Arenig (Ordovician) of Baltica. Proc Est Acad Sci Geol 53: 257–266.
- 19. Vinn O (2005) The distribution of worm borings in brachiopod shells from the Caradoc Oil Shale of Estonia. Carnets Géol CG2005_A03.
- 20. Wyse Jackson PN, Key MM Jr (2007) Borings in trepostome bryozoans from the Ordovician of Estonia: two ichnogenera produced by a single maker, a case of host morphology control. Lethaia 40: 237–252.
- 21. Torsvik TH, Smethurst MA, van der Voo R, Trench A, Abrahamsen N, et al. (1992) Baltica. A synopsis of Vendian–Permian palaeomagnetic data and their palaeotectonic implications. Earth Sci Rev 33: 133–152.
- 22. Nestor H, Einasto R (1997) Ordovician and Silurian carbonate sedimentation basin. 192–204. In A. Raukas and A. Teedumäe (eds.), Geology and mineral resources of Estonia. Estonian Academy Publishers, Tallinn, 436 pp.
- 23. Mõtus MA, Hints O (2007) Excursion Guidebook. In 10th International Symposium on Fossil Cnidaria and Porifera. Excursion B2: Lower Paleozoic geology and corals of Estonia. August 18–22, 2007. Institute of Geology at Tallinn University of Technology, 66 p.
- 24. Rõõmusoks A (1970) Stratigraphy of the Viruan series (Middle Ordovician) in northern Estonia. University of Tartu, Tallinn, 346 pp.
- 25. Nield EW (1984) The boring of Silurian stromatoporoids – towards an understanding of larval behaviour in the Trypanites organism. Palaeogeogr Palaeoclimat Palaeoecol 48: 229–243.
- 26. Pojeta J Jr, Palmer J (1976) The origin of rock boring in mytilacean pelecypods. Alcheringa 1: 167–179.
- 27. Huntley JW, Kowalewski M (2007) Strong coupling of predation intensity and diversity in the Phanerozoic fossil record. PNAS 38: 15006–15010.
- 28. Borszcz T, Zatoń M (2013) The oldest record of predation on echinoids: evidence from the Middle Jurassic of Poland. Lethaia 46: 141–145.
- 29. Vinn O, Wilson MA (2010) Occurrence of giant borings of Osprioneides kampto in the lower Silurian (Sheinwoodian) stromatoporoids of Saaremaa, Estonia. Ichnos 17: 166–171.
- 30. Newall G (1970) A symbiotic relationship between Lingula and the coral Heliolites in the Silurian. Geol J Spec Issue 3: 335–344.