Publication: Aalenian Tmetoceras (Ammonoidea) from Iberia: taxonomy, habitats and evolution.
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Publication Date
1999
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Kluwer
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Abstract
Several hundred Aalenian Tmetoceras from the Iberian Peninsula (N Lusitanian Basin, Asturias,
Basque-Cantabrian Basin, NE Cameros, NW Iberian Basin, Aragonese Platform,
Tortosa Platform, Castilian Platform, Majorca and Betic Basin) have been reviewed. Two
species of Aalenian Tmetoceras have been identified on the basis of morphological, biochronological
and palaeobiogeographical data: T. scissum and T. regleyi.
T. scissum was dominant among the Tmetoceras populations developed in the Betic
and Lusitanian basins during Opalinum, Murchisonae and Bradfordensis biochrons. Populations
composed by evolute individuals of T. scissum inhabited shelfal or oceanic environments.
A chronocline, from rectiradiate and primitive forms to flexicostate and derived
forms, can be recognized in these populations of T. scissum. In contrast, shallow epicontinental
platforms were inhabited by involute individuals of T. regleyi. This second species
was phyletically derived from T. scissum, representing an adaptive radiation from populations
of shelfal or oceanic basins to populations of epicontinental platforms.