Os carcharhiniformes (cCondrichthyes, Neoselachii) da Bacia de Alvalade (Portugal)
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[1] Universitat de València
Universitat de València
Valencia, España
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- Localización: Spanish journal of palaeontology, ISSN 2255-0550, Vol. 19, Nº. 1, 2004 (Ejemplar dedicado a: REVISTA ESPAÑOLA DE PALEONTOLOGÍA), págs. 73-92
- Idioma: español
- Enlaces
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Resumen
The uppermost Miocene, Esbarrondadoiro Formation (Alvalade basin, Portugal) yielded more than 10 thousandSelachian teeth at Santa Margarida, Esbarrondadoiro and Vale de Zebro outcrops. Forty-five taxa were identifiedbelonging to the orders Hexanchiformes, Squaliformes, Lamniformes, Carcharhiniformes, Torpediniformes and Myliobatiformes. The Carcharhiniformes make up about 40% of the selachian fauna that has been identified in the studiedarea. The different distribution of the Carcharhiniformes (as well as that of the other orders) by the three sitespoints out to distinct environments in the corresponding areas: Esbarrondadoiro indicates relatively deeper, ratherstill waters; Santa Margarida represents a very littoral area and rough waters; while Vale de Zebro was a (probablyinner) part of a gulf with muddy bottoms. At the Alvalade Basin localities there are several “temperate” elements that still are present in Portuguese waters. However the high frequence of Carcharhinus, a genus that is scarce at present off Portugal, indicates waters somewhatwarmer than today’s but less warm than during Tortonian times. This is corroborated by the large number of Dasyatisspecies and the rarity of Raja. We may conclude that moderately warm (less warm than during Tortonian, but warmerthan today’s) waters predominated in the Alvalade Basin close by the end of Miocene. The scarcity of pelagic forms and especially of the larger pelagic predators points out to a quite narrow gulf and not to an open Atlantic front. The faunal differences between the Tortonian near Lisbon and the Messinian of the Alvalade Basin also indicate a rather confined gulf.
