FERNANDEZ Diana Elizabeth
congresos y reuniones científicas
Bolonia lata Meunier in Lower Cretaceous shallow marine facies from Patagonia: ichnotaxonomic implications
Congreso; 5th International Paleontological Congress; 2018
In this work, Bolonia Meunier specimens are thoroughly described from wave dominated deposits in the Cretaceous of the Neuquen Basin (northern Patagonia). According to the latest amendment of the diagnosis, this monotypic ichnogenus includes horizontal to subhorizontal, epichnial, non-branching, straight, occasionally tapering at the ends, bilobed structures. The outline in cross-section is trapezoidal to heart-shaped. Bolonia lata Meunier has been described from shallow marine paleoenvironments with storm influence. The specimenspresented herein are found in sandstone beds with symmetrical ripple lamination covered by massive or horizontally laminated mudstones. These beds are within intervals interpreted as shoreface deposits, probably upper shoreface given the presence of primary current lineation indicating high-energy flow conditions. Even when in the diagnosis of Bolonia these trace fossils are described as having a straight pattern, B. lata was also described as "straight to slightly winding" by the same author. Some of the material now included in Bolonia and previously assigned to Scolicia was also originally described as straight to slightly. The Bolonia specimens reported in the present work bear all the diagnostic characteristics but are straight to curved. Hence, to our understanding the diagnosis of Bolonia should be emended: B. lata should not be restricted to straight structures, since curved patterns are very common inthe material presented here and were also described as such by previous authors. Paleozoic records of Bolonia have been found in the Devonian of Spain, the Carboniferous of USA and Ireland, and the Permian of Australia. Post-Paleozoic records of B. lata are restricted to the Jurassic of France, Great Britain, Greenland and India, and the Eocene of Spain. Most of these records were originally named dierently and later reassigned to Bolonia in the latestrevision of the ichnogenus. To our knowledge, the specimens described herein are the only Cretaceous record of this ichnotaxon and its only post-Paleozoic example for the Southern Hemisphere. They also show a greater morphological variety in bedding-plane view than previously reported for Bolonia, and might therefore have future ethological implications for this ichnotaxon whose tracemakers remain uncertain.