Publication: Aalenian Tmetoceras (Ammonoidea) from Iberia: taphonomy and palaeobiogeography
Loading...
Official URL
Full text at PDC
Publication Date
1996
Authors
Advisors (or tutors)
Journal Title
Journal ISSN
Volume Title
Publisher
Kluwer
Abstract
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.