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Blodgett, R.B., 1987

Taxonomy and paleobiogeographic affinities of an early Middle Devonian (Eifelian) gastropod faunule from the Livengood Quadrangle, east-central Alaska

Bibliographic Reference

Blodgett, R.B., 1987, Taxonomy and paleobiogeographic affinities of an early Middle Devonian (Eifelian) gastropod faunule from the Livengood Quadrangle, east-central Alaska: Corvallis, Oregon, Oregon State University, Ph.D. dissertation, 132 p., illust., map.


Thirty-five species of gastropods are described from a gastropod-dominated faunule (USNM locality 38755) in an unnamed Middle Devonian clastic unit in the Livengood Quadrangle, east-central Alaska. Three new genera are described, each represented by a single new species: Pseudomphalotrochus dutroi, Clathronema cloughi, and Alaskozygopleura crassicostata. In addition, 11 new species belonging to extant genera are described: Bucanopsis sullivani, Bellerophon (Bellerophon) chapmani, B. (B.) livengoodensis, Straparollus (Euomphalus) bundtzeni, Buechelia nodosa, Peruvispira churkini, Gyronema ormistoni, Naticopsis (Naticopsis) bowsheri, Naticopsis (Jedria) deckeri, and 'Goniasma' plumleyi. Conodonts recovered from limestone beds 24.7 m above the gastropod horizon indicate an australis Zone (mid-Eifelian) age. A middle Eifelian age for the gastropod fauna of USNM locality 38755 is accordant with the high number of the same or similar species shared with undescribed early-middle Eifelian faunas from west-central Alaska (Nixon Fork terrane). A single, new gastropod-based community, the Buechelia nodosa - Naticopsis (Jedria) deckeri - Alaskozygopleura crassiocostata Community, is defined on the three most abundant species present in the faunule, each representing respectively 21.8%, 14.4%, and 13.0% of the gastropod specimens collected. Two new Eifelian paleobiogeographic subprovinces are defined for gastropod faunas of the Cordilleran Region of the Old World Realm: the Alaska-Yukon and Nevada Subprovinces. The Alaska-Yukon Subprovince includes faunas from west-central Alaska (Nixon Fork terrane) and east-central Alaska (Livengood terrane). It is characterized by a rich calcareous green algal flora (absent in Nevada), greater diversity and more highly ornamented shells than that of the Nevada Subprovince in central Nevada. These differences are thought to indicate that these areas were located in the equatorial and warm, subtropical regions, respectively. The faunal unity of interior Alaska Paleozoic rocks in the Eifelian, and throughout much of Ordovician-Devonian time, as well as lithofacies continuity with rocks of the Yukon Territory, suggests that this region represents a western extension of the Cordilleran geosyncline, albeit tectonically slivered, and not a collage of disparate, accreted terranes.

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