blodgett fryda (3 risultati)

New taxon: Semitubina yukonensis n. sp. 5 pp., 8 figs, 4.

Twelve new Devonian gastropod genera are established in this paper which we deem important in better delineating Devonian biogeographic units. New genera include: Semilukispira, Teutonophon, Goldfussoceras, Manitobiella, Ibergia, Humboldtiella, Paragnesia, Winterbergiella, Spiniplatyceras, Roemeriella, Devononerita, and Dahmeria. In addition, one new Silurian genus, Ornatosinuitina, is established. 16 pp., 11 figs, 4.

Two new cirroidean gastropod genera, Alaskiella (family Porcelliidae) and Alaskacirrus (family Cirridae), from the Emsian (late Early Devonian) of west-central Alaska (Medfra B-4 quadrangle) are described. The shell of Alaskiella medfraensis new genus and species exhibits inclined heterostrophic coiling. This shell character is known among other members of the subclass Archaeogastropoda, but is recorded for the first time within members of the superfamily Cirroidea. Inclined heterostrophic coiling of the shell was probably developed independently in several different groups of the subclass Archaeogastropoda. The new genus Alaskacirrus, represented by Alaskacirrus bandeli new species, is the oldest and only known Paleozoic member of the family Cirridae. This suggests that the family Cirridae was separated from the family Porcelliidae since at least Early Devonian time and that it most probably developed from the subfamily Agnesiinae of the family Porcelliidae. Thus, the stratigraphic range of the family Cirridae is at least from Lower Devonian to Cretaceous, an interval of about 350 million years. New taxa: Alaskiella n. gen., Alaskiella medfraensis n. sp., Alaskacirrus n. gen., Alaskacirrus bandeli n. sp. 7 pp., 3 figs, 4.