Mid-Cretaceous fish assemblages in north-eastern Mexico: A case-study for the actinopterygian diversification and global palaeobiogeography
Final Report Abstract
Within the project eight Plattenkalk quarry fields in north-eastern Mexico were mapped, which yield exceptionally well preserved fossils, with fishes being the most abundant vertebrates in the fossil assemblages. The wide regional occurrence of these Plattenkalk deposits of about 15000 square km and their geological age range within the early Late Cretaceous, from the Cenomanian to the Santonian, allows for a detailed reconstruction of the development and evolution of fish assemblages in the Mesozoic Gulf of Mexico. We differentiated 24 species of osteichthyans belonging to 23 genera. Seven genera were hitherto unknown. Five genera were previously only known outside the western hemisphere, four genera were described for Mexico for the first time. Four genera were revised. Altogether there are ten new species within the NE-Mexico assemblages discovered and described during the course of the project. A compilation of the Cretaceous actinopterygian record of Mexico integrates 65 genera from ten localities, distributed within six time slices from the Albian to the Middle Santonian. A significant faunal turnover is evidenced by taxonomical changes during the Albian and Cenomanian, followed by an interval of taxonomic stability during the Latest Cenomanian up to the Santonian. This evolutionary pattern parallels a similar pattern of environmental factors such as sea surface temperature and sea level. The Mexican fish assemblages are palaeobiogeographically related with western Gondwana localities during the Albian, but these similarities decline during the Cenomanian. A Central and Eastern Tethyan influence on Mexican fish assemblages increases during this stage and culminates during the early Turonian in similar species on both sides of the early Proto Atlantic and Tethys. The Coniacian and Santonian localities of Mexico share the majority of genera with the Western Interior Seaway forming a distinct actinopterygian “Southern Interior-Northern Gulfian” paleobiogeographical sub-province which developed in the Early Turonian. These faunal changes coincide with an almost constant tectonic framework, which identifies oceanic dispersal as a driving mechanism for the changes of Mexican actinopterygian assemblages. Vicariance events in the Cenomanian were followed by regional extinction and subsequent strong westbound oceanic dispersal during the Early Turonian. Postulated dispersal routes coincide with ocean current models for this period of time. The composition of Mexican “Mid” Cretaceous actinopterygian assemblages was therefore affected by a mixture of dispersal, subsequent vicariance and extinction events, followed by faunal replacement due to subsequent dispersal. The velocity of the faunal turnover is correlated to the frequency of environmental changes. The exceptionally well preserved fossils and scientific results of this research were integrated in three temporal and one permanent exhibition. The exhibition “Fosiles del Noreste de México” was presented in the Museo de Historia Mexicana of the Foro Monterrey, a major show of world cultures and arts, and in the international airport at Monterrey, Mexico. Furthermore, actinopterygian fossils of this project formed part of the temporary fossil show “Huellas de la vida” on the main square of Mexico City, with a total of 14 million visitors in three months. New and well equipped museums in Nuevo Laredo (Tamaulipas) and Las Delicias (Chihuahua) contain major permanent exhibitions of fossil fishes from Vallecillo and Múzquiz. Fishes from the laminated limestone of north-eastern Mexico were also exhibited at the Facultad de Ciencias de la Tierra in Linares, and, finally, in the Museo del Desierto, at Saltillo, in the context of international geoscientific meetings. The scientific contents of all these exhibitions were supervised by us, always with reference to the DFG. The project therefore has a definite impact in public education in Mexico and a wide echo in print media and TV.
Publications
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(2008): Comment on „The oldest stratigraphic record of the Late Cretaceous shark Ptychodus mortoni Agassiz, from Vallecillo, Nuevo León, northeastern Mexico. – Revista de Ciencias Geologias 25/2: 365-366
Stinnesbeck, W., López-Oliva, J. G., Frey, E., Ifrim, C. & Giersch, S.
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(2008): Upper Cretaceous (Cenomanian – Turonian and Turonian – Coniacian) open marine Plattenkalk-deposits in NE Mexico. – Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, vol. 245/1, S. 71-81
Ifrim, C., Stinnesbeck, W. & Frey, E.
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(2010): Glyphiteuthis rhinophora n. sp., a trachyteuthidid (Coleoidea, Cephalopoda) from the Cenomanian (Late Cretaceous) of Mexico. – Paläontologische Zeitschrift 84/4: 523-532
Fuchs, D., Stinnesbeck, W., Ifrim, C., Giersch, S., Padilla Gutierrez, J. M. & Frey, E.
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(2010): Pachyrhizodus caninus Cope, 1872 (Teleostei, Crossognathiformes) from the early Turonian of Vallecillo (Mexico). – Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 258/2: 219-228
Giersch, S., Frey, E., Stinnesbeck, W. & Gonzalez-Gonzalez, A. H.
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2010. Palaeoctopus pelagicus from the Turonian of Mexico reinterpreted as a coelacanth (Sarcopterygian) gular plate. Palaeontology 53, 689-694
Schultze, H. P., Fuchs, D., Giersch, S., Ifrim, C., Stinnesbeck, W.
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(2011): Fluctuations of the oxygen minimum zone at the end of OAE 2 reflected by benthic and planktic fossils. Geology 39, 1043-1046
Ifrim, C., Götz, S., Stinnesbeck, W.
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(2011): Scombroclupea occidentalis sp. nov. (Clupeiformes, Teleostei) from the Late Cretaceous (Cenomanian) Plattenkalk deposits of Coahuila (NE Mexico). – Swiss Journal of Geosciences 104 (Suppl.1): 73-84
Giersch, S., Frey, E., Ifrim, C. & Stinnesbeck, W. & Padilla Gutierrez, J. M.
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(2012): A new specimen of nyctosaurid pterosaur, cf. Muzquizopteryx sp. from the Late Cretaceous of northeast Mexico. – Revista Mexicana de Ciencias Geológicas, 29/1: 131-139
Frey, E., Elgin, R. A., Stinnesbeck, W., Padilla Gutierrez, J. M., Ifrim, C., Giersch, S. & Gonzalez-Gonzalez, A. H.
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(2012): Osteology of Eubiodectes libanicus (Pictet & Humbert, 1866) and some other ichthyodectiformes (Teleostei): phylogenetic implications. – Journal of systematic paleontology, iFirst 2012: 1-63
Cavin, L., Forey, P. L. & Giersch, S.
