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EARLY–MIDDLE JURASSIC LYTOCERATID AMMONITES WITH CONSTRICTIONS FROM MOROCCO: PALAEOBIOGEOGRAPHICAL AND EVOLUTIONARY IMPLICATIONS
Author(s) -
BOURILLOT RAPHAEL,
NEIGE PASCAL,
PIERRE AURELIEN,
DURLET CHRISTOPHE
Publication year - 2008
Publication title -
palaeontology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.69
H-Index - 63
eISSN - 1475-4983
pISSN - 0031-0239
DOI - 10.1111/j.1475-4983.2008.00766.x
Subject(s) - ammonite , paleontology , biozone , ammonoidea , geology , ecological succession , fauna , genus , outcrop , biostratigraphy , structural basin , ecology , biology , mesozoic , cretaceous
The ammonite genus Alocolytoceras Hyatt, 1900 is an uncommon lytoceratid with distinctive shell ornament. A set of 58 specimens, recently collected at Amellago in the central High Atlas (Morocco), has enabled us to trace a succession of three species over eight biozones from the Toarcian to the Aalenian. Two specimens from the Lusitanian Basin are added for comparison. Following a review of the genus, based on original specimens and data from the literature, seven species are considered valid. A palaeobiogeographical synthesis of 13 regions demonstrates irregular distribution patterns over time, with a constant presence in the south‐west Tethys and an instance of rapid diversification of an endemic fauna in north‐west Europe. Our data challenge the conventional view that lytoceratid ammonite evolution was ‘conservative’.