Late Cretaceous dinosaur remains and other tetrapod fauna from...
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99 Late Cretaceous dinosaur remains and other tetrapod fauna from the vicinity of Tran town (Western Srednogorie) Къснокредни останки от динозаври и други тетраподи от района на гр. Трън (Западно Средногорие) Vladimir Nikolov 1 , Polina Pavlishina 2 , Marlena Yaneva 3 , Docho Dochev 2 , Ralitsa Konyovska 4 , Latinka Hristova 4 Владимир Николов 1 , Полина Павлишина 2 , Марлена Янева 3 , Дочо Дочев 2 , Ралица Коньовска 4 , Латинка Христова 4 1 Independent researcher; E-mail: [email protected] 2 Sofia University “St. Kliment Ohridski”, Department of Geology, Paleontology and Fossil Fuels, 15 Tsar Osvoboditel Blvd., 1504 Sofia; E-mails: [email protected]; [email protected] 3 Geological Institute, Bulg. Acad. Sci., Department Earthquake Geology, Acad. G. Bonchev str., bl. 24, 1113 Sofia; E-mail: [email protected] 4 National Museum of Natural History, 1 Tzar Osvoboditel Blvd., 1000 Sofia; E-mails: [email protected]; [email protected] Keywords: Late Cretaceous, Bulgaria, dinosaurs, tetrapods. Until recently, the fossil record of terrestrial Mesozoic tetrapods in Bulgaria was scarce, restricted to frag- mentary remains of non-avian dinosaurs from the Maastrichtian limestones of the Kajlâka Formation (Mateus et al., 2010; Godefroit, Motchurova-Dekova, 2010). Herein were present preliminary data on a new Late Cretaceous fossil site near the town of Tran (Western Srednogorie, Western Bulgaria), which yields a diverse terrestrial tetrapod fauna. Despite ear- lier finds of amber close to the fossil site (Minchev, 1958) suggesting the existence of terrestrial environ- ments at the time, no tetrapod fossils were known from the area – this is the first record of Mesozoic tetrapods from the Western Srednogorie. In 2006, Mr. Andrey Tzonkov found a fossil- ized bone fragment in the area, which was brought for identification to the paleontologists at the Sofia University in 2012 (Fig. 1a, b). The fossil is partial diaphysis of an undetermined long bone with no ap- parent osteological hallmarks to allow for a reliable taxonomical identification. Histological study of the specimen, however, showed that it belongs to a non- avian dinosaur. After unsuccessful attempt at localiz- ing the sediments sourcing the bone fragment, a team from the National Museum of Natural History, Sofia, found new fossils and located the fossil site in 2017. Further analysis of the original specimen and a second partial bone revealed a suite of informative osteohisto- logical characters, which allow for a tentative interpre- tation of these fossils as pertaining to a titanosaurian sauropod (Nikolov et al., in review). The fossil remains come from the westernmost part of the Western Srednogorie Zone (sensu Ivanov, 2017) of Western Bulgaria. During the Late Cretaceous this zone formed an arc/backarc basin system within the Alpine orogenic belt composed of a chain of strike-slip and pull-apart basins, in which sedimentary and volca- no-sedimentary sequences were deposited. The stud- ied locality, part of the recently introduced Rezhantsi Formation (Sinnyovsky et al., 2013), is a cliff about 20 m in width. It reveals relatively soft and cracked sedimentary rocks exposed on a small slumped block, with unclear relationship with underlying and overly- ing rocks due to soil and vegetation covering. The vis- ible part of the sedimentary section, yielding the fossil bones, has thickness of about 8 m and is composed of limy clays of various shades of gray, silicified limy clays, and coal and coaly shales, most likely formed in continental lacustrine environments. Earlier this year, an expedition to the fossil site recovered fossilized remains from a diverse ter- restrial tetrapod fauna and amber (Fig. 1c–e). Two fossiliferous layers were recognized at the locality – from the upper layer have been excavated isolated dinosaur bone fragments, while from the lower one were excavated dinosaur bone fragments as well as fossils from crocodylomorphs and testudines (turtles and tortoises). The latter represent the first occur- rence of Mesozoic crocodylomorphs and testudines in Bulgaria. Collected material indicates the presence of at least two groups of non-avian dinosaurs – fea- tures of one of the bones suggest that it may belong СПИСАНИЕ НА БЪЛГАРСКОТО ГЕОЛОГИЧЕСКО ДРУЖЕСТВО, год. 79, кн. 3, 2018, с. 99–100 REVIEW OF THE BULGARIAN GEOLOGICAL SOCIETY, vol. 79, part 3, 2018, p. 99–100 National Conference with international participation “GEOSCIENCES 2018”
Transcript of Late Cretaceous dinosaur remains and other tetrapod fauna from...
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Late Cretaceous dinosaur remains and other tetrapod fauna from the vicinity of Tran town (Western Srednogorie)Къснокредни останки от динозаври и други тетраподи от района на гр. Трън (Западно Средногорие)Vladimir Nikolov1, Polina Pavlishina2, Marlena Yaneva3, Docho Dochev2, Ralitsa Konyovska4, Latinka Hristova4
Владимир Николов1, Полина Павлишина2, Марлена Янева3, Дочо Дочев2, Ралица Коньовска4, Латинка Христова4
1 Independent researcher; E-mail: [email protected] 2 Sofia University “St. Kliment Ohridski”, Department of Geology, Paleontology and Fossil Fuels, 15 Tsar Osvoboditel Blvd., 1504 Sofia; E-mails: [email protected]; [email protected] 3 Geological Institute, Bulg. Acad. Sci., Department Earthquake Geology, Acad. G. Bonchev str., bl. 24, 1113 Sofia; E-mail: [email protected] 4 National Museum of Natural History, 1 Tzar Osvoboditel Blvd., 1000 Sofia; E-mails: [email protected]; [email protected]
Keywords: Late Cretaceous, Bulgaria, dinosaurs, tetrapods.
Until recently, the fossil record of terrestrial Mesozoic tetrapods in Bulgaria was scarce, restricted to frag-mentary remains of non-avian dinosaurs from the Maastrichtian limestones of the Kajlâka Formation (Mateus et al., 2010; Godefroit, Motchurova-Dekova, 2010). Herein were present preliminary data on a new Late Cretaceous fossil site near the town of Tran (Western Srednogorie, Western Bulgaria), which yields a diverse terrestrial tetrapod fauna. Despite ear-lier finds of amber close to the fossil site (Minchev, 1958) suggesting the existence of terrestrial environ-ments at the time, no tetrapod fossils were known from the area – this is the first record of Mesozoic tetrapods from the Western Srednogorie.
In 2006, Mr. Andrey Tzonkov found a fossil-ized bone fragment in the area, which was brought for identification to the paleontologists at the Sofia University in 2012 (Fig. 1a, b). The fossil is partial diaphysis of an undetermined long bone with no ap-parent osteological hallmarks to allow for a reliable taxonomical identification. Histological study of the specimen, however, showed that it belongs to a non-avian dinosaur. After unsuccessful attempt at localiz-ing the sediments sourcing the bone fragment, a team from the National Museum of Natural History, Sofia, found new fossils and located the fossil site in 2017. Further analysis of the original specimen and a second partial bone revealed a suite of informative osteohisto-logical characters, which allow for a tentative interpre-tation of these fossils as pertaining to a titanosaurian sauropod (Nikolov et al., in review).
The fossil remains come from the westernmost part of the Western Srednogorie Zone (sensu Ivanov, 2017) of Western Bulgaria. During the Late Cretaceous this zone formed an arc/backarc basin system within the Alpine orogenic belt composed of a chain of strike-slip and pull-apart basins, in which sedimentary and volca-no-sedimentary sequences were deposited. The stud-ied locality, part of the recently introduced Rezhantsi Formation (Sinnyovsky et al., 2013), is a cliff about 20 m in width. It reveals relatively soft and cracked sedimentary rocks exposed on a small slumped block, with unclear relationship with underlying and overly-ing rocks due to soil and vegetation covering. The vis-ible part of the sedimentary section, yielding the fossil bones, has thickness of about 8 m and is composed of limy clays of various shades of gray, silicified limy clays, and coal and coaly shales, most likely formed in continental lacustrine environments.
Earlier this year, an expedition to the fossil site recovered fossilized remains from a diverse ter-restrial tetrapod fauna and amber (Fig. 1c–e). Two fossiliferous layers were recognized at the locality – from the upper layer have been excavated isolated dinosaur bone fragments, while from the lower one were excavated dinosaur bone fragments as well as fossils from crocodylomorphs and testudines (turtles and tortoises). The latter represent the first occur-rence of Mesozoic crocodylomorphs and testudines in Bulgaria. Collected material indicates the presence of at least two groups of non-avian dinosaurs – fea-tures of one of the bones suggest that it may belong
СПИСАНИЕ НА БЪЛГАРСКОТО ГЕОЛОГИЧЕСКО ДРУЖЕСТВО, год. 79, кн. 3, 2018, с. 99–100REVIEW OF THE BULGARIAN GEOLOGICAL SOCIETY, vol. 79, part 3, 2018, p. 99–100National Conference with international participation “GEOSCIENCES 2018”
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to a large theropod dinosaur (theropods are group of bipedal, mostly meat-eating dinosaurs, to which modern birds also belong).
During the field trip in 2017 three samples for pa-lynological analyses were collected. The palynologi-cal study provides novel data concerning the age as-sessment of the dinosaur-bearing succession, as well as for understanding the paleoenvironment during the studied time interval. Palynological analysis of these samples reveals a well-preserved and consider-ably rich palynoflora dominated by angiosperm pol-len (which slightly dominates the assemblages over the pterydophyte spores and is represented mainly by the morphologically characteristic pollen from the Normapolles group) and perydophite spores, but sparse gymnosperms. Collectively, the palynologi-cal assemblages from the dinosaur bearing strata and the adjacent sediments are similar in their taxonomic composition indicating that the local flora is reflected without reworking from the surrounding sediments. The encountered key angiosperm Normapolles taxa suggest Late Santonian–Early Campanian age both for the dinosaur host strata and the succession below them. The palynofacies analysis carried out of the samples reveals an organic content dominated by continental particles with abundant translucent plant debris. The group of land derived sporomorphs (angiosperm pol-len, spores and exceptionally gymnosperms) reaches up to 25%. The sedimentary succession shows no evi-dence of marine elements and a very low proportion of AOM that attests to deposition within a continental to very proximal environment, with high continental input and short transportation of the phytoclasts.
The paleontological discoveries made near the town of Tran are of importance, because according to their suggested age, they come from a time interval in which the fossil tetrapod record in Europe is some-what patchy and not known well enough (Csiki-Sava et al., 2015). Future excavations and further analyses of the collected material will help evaluating the taxo-nomic diversity of this fossil site and will improve our understanding of the tetrapod faunas which inhabited the islands of the European archipelago during the Late Cretaceous.
ReferencesCsiki-Sava, Z., E. Buffetaut, A. Ősi, X. Pereda-Suberbiola, S.
L. Brusatte. 2015. Island life in the Cretaceous – faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. – ZooKeys, 469, 1–161.
Godefroit, P., N. Motchurova-Dekova. 2010. Latest Cretaceous hadrosauriod (Dinosauria: Ornithopoda) remains from Bulgaria. – C. R. Palevol., 9, 163–169.
Ivanov, Zh. 2017. Tectonics of Bulgaria. Sofia, “St. Kl. Ohridski” University Press, 332 p. (in Bulgarian).
Mateus, O., G. J. Dyke, N. Motchurova-Dekova, G. D. Ka-menov, P. Ivanov. 2010. The first record of a dinosaur from Bulgaria. – Lethaia, 43, 88–94.
Minchev, D. 1958. A find of a fossil resin in the Turonian coals at v. Vrabcha, Tran. – Ann. Univ. de Sofia, Fac. Biol., géol. et géogr., 51, 2–géol. 101–105 (in Bulgarian).
Nikolov, V., D. Dochev, M. Yaneva, R. Konyovska, L. Hristova. Bone histology reveals the first record of titanosaur (Dinosauria; Sauropoda) from Bulgaria. – Palaeontologia Electronic (in review).
Sinnyovsky, D., R. Marinova, V. Jelev. 2013. Upper Cretaceous lithostratigraphy in the West Srednogorie. Part 2. – Rev. Bulg. Geol. Soc., 74, 1–3, 65–79.
Fig. 1. a, putative titanosaurian bone fragment (specimen U. S., K21586), scale bar: 3 cm; b, histology of U. S., K21586 in cross-polarized light, scale bar: 200 µm; c, unidentified partial dinosaur bone, scale bar: 4 cm; d, putative theropod (?) long bone in cross-section, scale bar: 4 cm; e, Testudines, partial hyoplastron, scale bar: 1 cm
