Vertebrados marinos del neógeno del suroeste de la península Ibérica

Abstract

This PHD thesis studies the marine vertebrates present in the Miocene and Pliocene formations of Southwestern Guadalquivir Basin in the province of Huelva, its evolutionary aspects and paleoecological implications. The results obtained allow to define with higher resolution the development of coastal and marine ecosystems in the Southwest of the Iberian Peninsula during the late Neogene. During this time, the two main pathways between the Atlantic Ocean and the Mediterranean Sea were Norbético Strait and the Strait Rif. The studied area for their paleogeographic situation between Atlantic and Mediterranean is in a prime location for the study of the fossil record of these groups. The Neogene studied materials belong to the following formations: Fm. Niebla (Tortoniense sup.) Fm. Arcillas de Gibraleón (Tortoniense sup.-Messinian), and Fm. Arenas de Huelva (Pliocene inf.). Representative sites were selected and was made systematic sampling (350 kg.), and surface searches. Also, a facies mapping and geological sections ware made. The samples were sieved in the laboratory in order to separate the remains of small vertebrates, and microfossils to detail the paleoecological conditions and their dating. They also cleaned and consolidated large vertebrate fossils. The remains were cataloged, labeled and photographed. In all, it has obtained more than 3,000 teeth, 230 otoliths and 2000 skeletal remains, along with 8 skeletons of cetaceans. We have identified 116 taxa of marine vertebrate of the Neogene of Huelva. Of these, there are 50 species of seláceos (sharks and rays), 5 holocephalans (chimeras), 48 Osteichthyes (bony fish), 1 Bird, 2 sea turtles and 10 marine mammals (2 seals, 4 cetacean baleen and 4 toothed whales). In total 43 taxa are species mentioned for the first time in the area, 16 of which are also for the first time in Spain. All this is a great contribution to paleocommunities vertebrate and its implications in the knowledge of the food chains of the past. The data have allowed to establish a paleoecological, biochronological paleobiogeographic and environmental approach. Thus, Niebla Fm. is characteristic of a shallow coastal environment of warm subtropical waters; Arcillas de Gibraleón Fm. indicates a deep and far from shore environment, with open sea fauna of the area above the continental slope, between 150 and 400 m deep. Arenas de Huelva Fm. would be a shallower area of something deeper at the base and lesser on its roof continental shelf, from about 100 to about 30 m deep. It considerably increases the wildlife both in number and diversity. The shallowing by the silting of the Guadalquivir basin is well recorded in vertebrates associations. Fossils indicate a mixture of species of temperate and warm waters, with a predominance of the latter. This would indicate a subtropical climate somewhat warmer than it currently has in the area. In addition, communities of vertebrates other upper Neogene of Portugal, Greece Messinian, Pliocene of Catalonia, C. Valenciana, Murcia and Baleares, Italian Pliocene and Pliocene in Southeastern France were compared. All this is an improvement in the understanding of the marine ecosystem and paleoenvironmental evolution Southwest of the Iberian Peninsula during the late Tertiary or Cenozoic era.