Phylogenetic analysis, paleoenvironmental and paleobiogeographic interpretation of theropod dinosaurs from the Upper Jurassic of the Lusitanian Basin

Malafaia, Elisabete

http://hdl.handle.net/10451/35031

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Authors

Malafaia, Elisabete

Advisor(s)

Cachão, Mário A. P., 1961-

Coloma, Francisco Javier Ortega

Abstract(s)

The currently known record of Upper Jurassic theropod dinosaurs from the Lusitanian Basin is relatively abundant and diverse. It includes mainly medium to large-sized forms belonging to primitive theropod clades, such as Ceratosauria, or Tetanurae, including Megalosauridae and Allosauroidea. Small-sized and more derived theropods have also been identified based mainly on isolated elements. This study provides new information about the Portuguese Upper Jurassic record of theropod dinosaurs. The main objective of this research is to improve the knowledge about the evolutionary history of these dinosaur faunas. Several unpublished specimens collected in different sites of the Consolação, Turcifal and Bombarral-Alcobaça sub-basins indicate the presence of previously unidentified clades, including non-megalosaurid megalosauroids and a form of derived allosauroid closely related with Carcharodontosauria. These new specimens suggest a greater diversity among the Late Jurassic theropod faunas from the Lusitanian Basin than previously known. The Late Jurassic theropod fauna of the Lusitanian Basin have been traditionally interpreted as being closely related to those of correlative sedimentary sequences from the North American Morrison Formation and from the African Tendaguru Formation. Most of the genera currently known in the Portuguese record have a closely related taxon at the North American record and most of them were previously interpreted as belonging to species shared by both landmasses. However, more recently the Portuguese forms have been reinterpreted as separate species exclusive for the Lusitanian Basin. This faunal composition seems to indicate an incipient vicariant evolution of the dinosaur faunas from the Late Jurassic of the Lusitanian Basin suggesting that the seaway(s) between North America and Iberia represented barriers to the dispersion of these faunas. However, these barriers may have had different effects on different species, which would explain the stronger affinities of the fauna of theropods between the Lusitanian Basin and Morrison Formation than those of other dinosaur faunas such as the sauropods. Despite this similarity, it has been identified in the Portuguese record some dinosaur groups that apparently are absent in correlative North American strata and that are more closely related with Gondwanan faunas. These differences may indicate differential patterns of regional extinction and ecological constraints such as environmental preferences.