Sandoval Gabarrón, José and Henriques, María Helena Paiva and Chandler, Robert B. and Ureta Gil, María Soledad (2012) Latest Toarcian-earliest Bajocian (Jurassic) Grammoceratinae (Hildoceratidae, Ammonitina) of the western Tethys: Their palaeobiogeographic and phylogenetic significance. Geobios, 45 . pp. 109-119. ISSN 0016-6995
Grammoceratinae (Hildoceratidae, Ammonitina) abound in the Toarcian strata of many western Tethyan
localities, especially the Subbetic and Lusitanian basins (of southern Spain and central western Portugal,
respectively). They decline through the Aalenian and disappear by the lowermost Bajocian. The genera
Asthenoceras, Vacekia (subgenera Vacekia and Nadorites) and Fontannesia are traditionally considered as
the last Grammoceratinae, with species of Osperleioceras occurring in the uppermost Toarcian.
Grammoceratinae are common in the eastern Pacific, especially Oregon and Alaska where Asthenoceras is
abundant. They also occur in the eastern Tethys (Thailand). Although studies of Toarcian to early
Bajocian Subbetic and Lusitanian grammoceratins already exist, new material from these and other
palaeogeographic areas (England, Portugal and Spain) is revised here. A new genus, Linaresites nov. gen.
(for Fontannesia montillanensis Linares and Sandoval) and two new species (Vacekia striata Henriques,
and Asthenoceras taverai Sandoval) are described. Another form, ‘‘Asthenoceras’’ sp. A is described and let
in open nomenclature. Temporal analysis of Aalenian to early Bajocian Grammoceratinae demonstrates
a progressively more evolute morphology through time, sometimes coupled with size reduction.
Palaeogeographic evidence suggests that during the early Middle Jurassic, western Tethys and eastern
Pacific were temporarily well connected, possibly through the Hispanic Corridor, as demonstrated by the
similarity between Tethyan and eastern Pacific Grammoceratinae.
|Uncontrolled Keywords:||Grammoceratinae; Ammonitina; Jurassic; Western Tethys; Taxonomy; Palaeobiogeography|
|Subjects:||Sciences > Geology > Paleontology|
|Deposited On:||03 Oct 2012 09:37|
|Last Modified:||03 Oct 2012 09:37|
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