The Sarganidae (Pyrifusoidea, Latrogastropoda), their taxonomy and paleobiogeography
The family Sarganidae Stephenson, 1923, represents an extinct group of gastropods of Cretaceous age that contains species with rather characteristic low-spired, subpyriform shells, with anteriorly constricted whorls, large pseudumbilicus and posteriorly notched aperture that anteriorly extends in a narrow siphonal canal. While the teleoconch resembles that of modern Neogastropoda, the almost planispirally-coiled protoconch is like that found among modern Neomesogastropoda. These two represent the Latrogastropoda, as subunit of the gastropod subclass Caenogastropoda which has its origin in the Cretaceous. Two new species, Sargana chapelvillei and S. mississippiensis, from the Late Campanian Coffee Sand of Mississippi in the USA are described. They closely resemble Sargana geversi and two new species, S. xsosanensis and S. kieli, from the Santonian Umzamba locality in the Eastern Cape Province of South Africa. Sargana exima from the Santonian/Campanian of Tamil Nadu in southern India differs from the Gulf-Coast and South African species, but resembles Praesargana confraga from the Turonian of California. Also the relation to Pseudecphora gen. nov. of the Pseudecphorinae n. subfam., Morea of the Moreinae, Hippocampoides of the Thalassocynidae, Schizobasis, Hillites and Xsosaites of the Schizobasinae n. subfam., Weeksia and Lowenstamia of the Weeksiidae is discussed, all of which resemble Sargana. The Sarganidae are seen among the Pyrifusoidea n. superfam, which can neither be considered to belong to the Neomesogastropoda nor the Neogastropoda.
The evolutionary history of the Sarganidae occurred in two geographically very distant regions. Earliest known representatives are from the Turonian of California. They have migrated across the Tethys Ocean to the Gondwanian shelf of the evolving Indian Ocean to develop further species during Santonian time. These migrated to the southern shores of the North American Inland Sea, evolving new species here during Late Campanian/Maastrichtian time. Migration pathway probably was the Southern Atlantic Ocean that provided fitting surface currents as well as cool water stop-over shelf regions, since Sarganidae lived in subtropical environments but not in the tropical water of the Tethys Ocean.
SNIP (Scopus, 2015): 0.700
IF (ISI, 2015): 1.326
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