Oncodella

Oncodella is an extinct genus of conodont. The genus was given the type species Oncodella idiodentica by Mosher (1968), on the basis of fossils from the Late Triassic of Austria.[1] However, Mosher (1969) later revised the species name to Oncodella paucidentata, since identical fossils from the same area were previously given the name Hindeodella paucidentata by Mostler (1967).[2][3]

Occurrence

Tethyan region

Oncodella is most common in European outcrops corresponding to the western Tethys Ocean. It was first reported from the Someraukogel and Steinbergkogel sites near Hallstatt in Austria.[1] At outcrops B and C of Steinbergkogel, Oncodella first occurs alongside Misikella hernsteini and morphotype A of Epigondolella mosheri. These conodonts first appear near the end of the Sevatian (late Norian), only a short time before the base of the Rhaetian. This indicates that Oncodella first evolved in the latest Norian as well.[4][5][6][7] Oncodella is also known from other outcrops in the Northern Calcareous Alps. These include Dachstein reef facies at Gosausee in Austria,[8] and the Donnerkogel Formation at Mount Hohes Brett in Germany.[9]

In Sicily, Oncodella is a common early Rhaetian conodont which co-occurs alongside Misikella posthernsteini. It has been found in the Portella Gebia limestone of the Pizzo Mondello section,[10] as well as the Calcari con Selce ("cherty limestone") formation at Monte Triona.[11] Calcari con Selce outcrops of the Italian mainland, such as the Pignola, Vietri di Potenza, and Pezza la Quagliara sections, have also produced Oncodella fossils. Despite being characteristic of the early Rhaetian (as defined by the appearance of M. posthernsteini), Oncodella actually first appears in the Norian, slightly before M. posthernsteini.[12]

Reworked Oncodella fossils have been found in the Western Carpathians. Oncodella is one of several conodonts used to determine the age of limestone pebbles within Jurassic and Cretaceous-age conglomerate. Conglomerate in Slovakia is known to preserve Oncodella within Rhaetian limestone pebbles transitional between Hallstatt and Zlambach facies.[13] Turonian-age conglomerate from the Sromowce Formation of Poland preserves late Norian pebbles, as indicated by the presence of Oncodella and absence of Misikella posthernsteini.[14] Oncodella fossils have been found in non-reworked limestone in the area as well.[15] The Carnian-Rhaetian Silická Brezová sequence of Slovakia is one of the most well-studied examples of these types of sites.[16] Further south in Hungary, the Csővár Formation has produced not only the typical Norian-Rhaetian Oncodella paucidentata species,[17][18] but also a new early Norian species, Oncodella mostleri.[18]

Oncodella is a component of Norian-Rhaetian conodont faunas in the Julian Alps of Slovenia. In the Triassic, this area was a deep basin (the Slovenian Basin) nowadays represented by the limestone-dominated Slatnik Formation,[19] as well as the Bača Dolomite.[20] At the Mount Kobla section of the Slatnik Formation, Oncodella first appears in the upper part of the Sevatian-age Parvigondolella andrusovi-Misikella hernsteini conodont zone.[21][22] However, it only occupies a relatively short interval of time which bridges the Norian-Rhaetian Boundary.[19] Albania[23][24] and Serbia[25] are other Balkan states known to produce Oncodella fossils. It has also been found along the Mediterranean in Turkey[26] and Cyprus.[27]

Although Oncodella has been reported from Asia, these reports are dubious. Claims of Oncodella being found in Kashmir originated from a fraudulent conodont researcher.[28] "Oncodella obuti" was named from Olenekian-age material in southern Primorye of southeast Russia,[29] but it may actually represent an S element of Neostrachanognathus.[30]

Panthalassan region

Oncodella is typically not found in areas corresponding to Panthalassa, the giant proto-Pacific Ocean. It also persists for a shorter period of time, with no late Norian record and a reduced Rhaetian record.[6] However, it is a notable part of the early Rhaetian conodont fauna of the San Hipolito Formation in Baja California Sur, Mexico. The oldest Oncodella fossils in this area are found at the INB section, a sampled section of the formation's sandstone member. At INB, it first appears in the Proparvicingla moniliformis 2a radiolarian assemblage zone. At least in the San Hipolito Formation, Oncodella has a similar stratigraphic range to Epigondolella mosheri sensu lato, a conodont often used to establish the early Rhaetian in North America. Oncodella also occurs at the COB section, although it first appears in the slightly younger moniliformis 2b zone. Oncodella goes extinct at the end of the moniliformis 2c zone in Baja California Sur.[17]

A single Oncodella specimen has been found alongside moniliformis 2a-zone radiolarians in the Sandilands Formation of Kunga Island in British Columbia, Canada. Other Tethyan-type conodonts are also extremely rare or absent from Canada. The more notable presence of Tethyan-type conodonts in Mexico may be indicative of biogeographical pressures on conodonts. Oncodella could be considered a low-latitude conodont, since it is practically absent in northern Panthalassa (now accreted onto Canada) and more common in low-latitude areas of the Panthalassa and Tethys oceans (now accreted onto Mexico and Europe, respectively).[31][17]

References

1. Mosher, L. Cameron (July 1968). "Triassic Conodonts from Western North America and Europe and Their Correlation". Journal of Paleontology. 42 (4): 895–946 – via JSTOR.
2. Mostler, Von H. (1967). "Conodonten und Holothuriensklerite aus den norischen Hallstätter-Kalken von Hernstein (Niederösterreich)" (PDF). Verhandlugen der Geologische Bundesanstalt. 1–2: 177–188.
3. Mosher, L. Cameron (November 1969). "Nomenclatural Revisions for Triassic Conodonts in Mosher, 1968". Journal of Paleontology. 43 (6): 1441.
4. Krystyn, L.; Richoz, S.; Gallet, Y.; Bouquerel, H.; Kürschner, W.M.; Spötl, C. (2007). "Updated bio- and magnetostratigraphy from steinbergkogel (Austria), candidate GSSP for the base of the Rhaetian stage". Albertiana. 36: 164–173.
5. Krystyn, L.; Bouquerel, H.; Kuerschner, W.; Richoz, S.; Gallet, Y. (2007). "Proposal for a candidate GSSP for the base of the Rhaetian Stage". New Mexico Museum of Natural History and Science. 41: 189–199.
6. Orchard, Michael J. (2010-01-01). "Triassic conodonts and their role in stage boundary definition". Geological Society, London, Special Publications. 334 (1): 139–161. doi:10.1144/SP334.7. ISSN 0305-8719.
7. Hüsing, Silja K.; Deenen, Martijn H. L.; Koopmans, Jort G.; Krijgsman, Wout (2011-02-01). "Magnetostratigraphic dating of the proposed Rhaetian GSSP at Steinbergkogel (Upper Triassic, Austria): Implications for the Late Triassic time scale". Earth and Planetary Science Letters. 302 (1): 203–216. doi:10.1016/j.epsl.2010.12.012. ISSN 0012-821X.
8. Richoz, Sylvain; Krystyn, Leopold (2015). "The Upper Triassic events recorded in platform and basin of the Austrian Alps. The Triassic/Jurassic GSSP and Norian/Rhaetian GSSP candidate" (PDF). Berichte der Geologischen Bundesanstalt. 111: 75–136.
9. Missoni, Sigrid; Gawlick, Hans-Jürgen (2011-01-01). "Jurassic mountain building and Mesozoic-Cenozoic geodynamic evolution of the Northern Calcareous Alps as proven in the Berchtesgaden Alps (Germany)". Facies. 57 (1): 137–186. doi:10.1007/s10347-010-0225-1. ISSN 1612-4820.
10. Gullo, M. (1996-12-06). "Conodont biostratigraphy of uppermost Triassic deep-water calcilutites from Pizzo Mondello (Sicani Mountains): Evidence for Rhaetian pelagites in Sicily". Palaeogeography, Palaeoclimatology, Palaeoecology. 126 (3): 309–323. doi:10.1016/S0031-0182(96)00043-0. ISSN 0031-0182.
11. Di Stefano, Pietro; Alessi, Aldo; Gullo, Maria (1996-12-01). "Mesozoic and Paleogene megabreccias in Southern Sicily: New data on the Triassic Paleomargin of the Siculo-Tunisian platform". Facies. 34 (1): 101–122. doi:10.1007/BF02546159. ISSN 1612-4820.
12. Amodeo, Filomena; Molisso, Flavia; Kozur, Heinz; Marsella, Ennio; D'Argenio, Bruno (1993). "Age of Transitional Beds from «Cherty Limestones» (calcari con selce) to «Radiolarites» (scisti silicei) in the Lagonegro Domain (Southern Italy). First evidence of Rhaetian conodonts in peninsular Italy". Bolletino del Servizio Geologico d'Italia. 110: 3–22.
13. Sýkora, Milan; Siblík, Miloš; Soták, Ján (April 1998). "An Upper Triassic limestone pebble with "Spirigera" deslongchampsi Suess from the southern part of the Western Carpathians, Southern Slovakia". Geologica Carpathica. 49 (2): 99–108.
14. Birkenmajer, Krzysztof; Kozur, Heinz; Mock, Rudolf (1990). "Exotic Triassic pelagic limestone pebbles from the Pieniny Klippen Belt of Poland: a further evidence for early Mesozoic rifting in West Carpathians". Annates Societatis Geologorum Poloniae. 60 (1–4): 3–44.
15. Gaździcki, Andrzej; Kozur, Heinz; Mock, Rudolf (1979). "The Norian-Rhaetian boundary in the light of micropaleontological data" (PDF). Geologija. 22 (1): 71–112.
16. Channell, J. E. T.; Kozur, H. W.; Sievers, T.; Mock, R.; Aubrecht, R.; Sykora, M. (2003-02-15). "Carnian–Norian biomagnetostratigraphy at Silická Brezová (Slovakia): correlation to other Tethyan sections and to the Newark Basin". Palaeogeography, Palaeoclimatology, Palaeoecology. 191 (2): 65–109. doi:10.1016/S0031-0182(02)006545. ISSN 0031-0182.
17. Orchard, Michael J.; Whalen, Patricia A.; Carter, Elizabeth S.; Taylor, Hillary J. (2007). "Latest Triassic conodonts and radiolarian-bearing successions in Baja California Sur". New Mexico Museum of Natural History and Science Bulletin. 41: 355–365.
18. Karádi, Victor; Kozur, Heinz W.; Görög, Ágnes (2013). "Stratigraphically important Lower Norian conodonts from the Csővár borehole (CSV-1), Hungary - comparison with the conodont succession of the Norian GSSP candidate Pizzo Mondello (Sicily, Italy)". New Mexico Museum of Natural History and Science Bulletin. 61: 284–295.
19. Rožič, Boštjan; Kolar-Jurkovšek, Tea; Šmuc, Andrej (2008-11-07). "Late Triassic sedimentary evolution of Slovenian Basin (eastern Southern Alps): description and correlation of the Slatnik Formation". Facies. 55 (1): 137. doi:10.1007/s10347-008-0164-2. ISSN 1612-4820.
20. Rožič, Boštjan; Jurkovšek, Tea Kolar; Rožič, Petra Žvab; Gale, Luka (2017-08-01). "Sedimentary record of subsidence pulse at the Triassic/Jurassic boundary interval in the Slovenian Basin (eastern Southern Alps)". Geologica Carpathica. 68 (6): 543–561. doi:10.1515/geoca-2017-0036. ISSN 1336-8052.
21. Kolar-Jurkovšek, Tea (2011). "Latest Triassic conodonts of the Slovenian Basin and some remarks on their evolution" (PDF). Geologija. 54 (1): 81–90. doi:10.5474/geologija.2011.006.
22. Gale, Luka; Kolar-Jurkovšek, Tea; Šmuc, Andrej; Rožič, Boštjan (2012-10-01). "Integrated Rhaetian foraminiferal and conodont biostratigraphy from the Slovenian Basin, eastern Southern Alps". Swiss Journal of Geosciences. 105 (3): 435–462. doi:10.1007/s00015-012-0117-1. ISSN 1661-8734.
23. Meço, Selam (2010-03-04). "Litho-biostratigraphy and the conodonts of Palaeozoic/Triassic deposits in Albania". Palaeontographica Abteilung A. 290 (4–6): 131–197. doi:10.1127/pala/290/2010/131.
24. Gawlick, Hans-Jürgen; Frisch, Wolfgang; Hoxha, Lirim; Dumitrica, Paulian; Krystyn, Leopold; Lein, Richard; Missoni, Sigrid; Schlagintweit, Felix (2007-06-15). "Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin". International Journal of Earth Sciences. 97 (4): 865. doi:10.1007/s00531-007-0193-z. ISSN 1437-3262.
25. Gawlick, Hans-Jürgen; Missoni, Sigrid; Sudar, Milan N.; Suzuki, Hisashi; Méres, Štefan; Lein, Richard; Jovanović, Divna (April 2018). "The Jurassic Hallstatt Mélange of the Inner Dinarides (SW Serbia): implications for Triassic-Jurassic geodynamic and palaeogeographic reconstructions of the Western Tethyan realm". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen: 1–47. doi:10.1127/njgpa/2018/0721.
26. Gallet, Yves; Krystyn, Leopold; Marcoux, Jean; Besse, Jean (2007-03-30). "New constraints on the End-Triassic (Upper Norian–Rhaetian) magnetostratigraphy". Earth and Planetary Science Letters. 255 (3): 458–470. doi:10.1016/j.epsl.2007.01.004. ISSN 0012-821X.
27. Christopher, Charles (1987). Multielement taxonomy, biostratigraphy, and paleoecology of late Triassic conodonts from the Mamonia Complex, southwestern Cyprus (PDF). Memorial University of Newfoundland. pp. 1–191.
28. Webster, Gary D.; Rexroad, Carl B.; Talent, John A. (May 1993). "An evaluation of the V. J. Gupta conodont papers". Journal of Paleontology. 67 (3): 486–493. doi:10.1017/S0022336000036933. ISSN 0022-3360.
29. Buryi, G. (1979). "Lower Triassic conodonts of the South Primory'e" (PDF). Instituta Geologii i Geofiziki, Sibirskoe Otdelenie: 1–142.
30. Orchard, Michael J. (2007-08-20). "Conodont diversity and evolution through the latest Permian and Early Triassic upheavals". Palaeogeography, Palaeoclimatology, Palaeoecology. The Permian-Triassic Boundary Crisis and Early Triassic Biotic Recovery. 252 (1): 93–117. doi:10.1016/j.palaeo.2006.11.037. ISSN 0031-0182.
31. Carter, Elizabeth S.; Orchard, Michael J. (2007). "Radiolarian - conodont – ammonoid intercalibration around the Norian-Rhaetian Boundary and implications for trans-Panthalassan correlation". Albertiana. 36: 139–163.