Aalenian Tmetoceras (Ammonoidea) from Iberia: taphonomy and palaeobiogeography



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Fernández López, Sixto Rafael and Henriques, María Helena Paiva and Linares Rodríguez, Asunción (1996) Aalenian Tmetoceras (Ammonoidea) from Iberia: taphonomy and palaeobiogeography. In Advancing Research on Living and Fossil Cephalopods: Proceedings of the IVth International Symposium on Cephalopods: Present and Past, held in Granada, Spain, July 14-18, 1996. Kluwer, New York, pp. 395-417. ISBN 978-1-4613-7193-9

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From different areas of the Iberian Peninsula more than 600 specimens of Aalenian Tmetoceras
have been found. This taxonomic group represents less than 20% of the whole ammonoids
recorded in Opalinum, Murchisonae, Bradfordensis and Concavum biozones.
Tmetoceras representatives, as well as Phylloceratina and Lytoceratina, were more frequent
in shelfal basins than in epicontinental platforms. Taphonomic data suggest a
eudemic character of the representatives of T. scissum in shelfal basins or oceanic areas.
Exceptional immigrants and drifted shells of this species arrived in shallow environments
of neighbouring platforms. In contrast, representatives of T. regleyi inhabited preferentially
shallow environments of epicontinental platforms.
T. scissum was a pandemic species, inhabiting oceanic or shelfal environments in the
early Aalenian. However, some species of Tmetoceras, such as T. regleyi and T. flexicostatum,
were geographically restricted in very distant areas. T. regleyi has been found only in European areas of the West Tethyan Subrealm. A pattern of adaptive radiation may have taken
place in the Western Tethys during the Opalinum-Murchisonae biochrons, giving rise to T.
regleyi from T. scissum. Specialized forms of Tmetoceras (k-strategists such as the individuals
of the species T. regleyi) are widespread in the epicontinental platforms around the Western
Tethys during the Murchisonae and Bradfordensis biochrons. Epicontinental, specialized
forms of T. regleyi suffered extinction in the latest Bradfordensis Biochron. Shelfal or oceanic,
generalist forms of T. scissum disappeared in the Western Tethys or the Mediterranean
Province in the latest Bradfordensis Biochron, but they survived in the East-Pacific Subrealm.

Item Type:Book Section
Uncontrolled Keywords:Aalenian; Tmetoceras (Ammonoidea), Iberia
Subjects:Sciences > Geology > Paleontology
ID Code:21822
Deposited On:13 Jun 2013 10:23
Last Modified:11 Dec 2018 08:42

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