The result of seven years of research on Late Cretaceous Osteichthyan fishes from the northeastern Mexican states Coahuila and Nuevo León is presented here. The fossil record of the area yielded single species of Coelacanthiforms, Pycnodontiforms, Aspidorhynchids, Elopiforms, Crossognathids, Clupeiforms and Beryciforms. Additionally two tselfatiiform species and two aulopiform species were recognized. Furthermore three Pachyrhizodontids and four Ichthyodectiforms were described. Nine species were recognized for the first time in the area. Seven of them were hitherto unknown in the Western hemisphere. Four species were erected. The combined assemblage consisting of 18 taxa came from six localities and is distributed into four different stratigraphic stages ranging from the middle Cenomanian to the middle Santonian. A compilation of the “mid”-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. During the Albian the Mexican fish assemblages are palaeobiogeographically related with western Gondwana localities, 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 Turonian. These faunal changes coincide with an unchanging 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 probably due to subsequent dispersal. The velocity of faunal turnover is correlated to the frequency of environmental changes.
|Supervisor:||Stinnesbeck, Prof. Dr. Wolfgang|
|Date of thesis defense:||17 July 2014|
|Date Deposited:||29 Jul 2014 07:48|
|Faculties / Institutes:||Fakultät für Chemie und Geowissenschaften > Institut für Geowissenschaften|
|Subjects:||550 Earth sciences
560 Paleontology Paleozoology