New records of early Jurassic gladius-bearing coleoids (Prototeuthidina and Loligosepiina) from Alberta, Canada

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2016-05

Authors

Marroquin, Selva Mariana

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Abstract

The Ya Ha Tinda Lagerstätte from Alberta, Canada, preserves organic-rich black shales that capture the carbon isotope excursion (CIE) characteristic of the Toarcian Oceanic Anoxic Event (183 Ma). Excavations at Ya Ha Tinda uncovered fifteen Vampyropoda fossils from Pliensbachian and Toarcian strata. Vampyropoda are a group of cephalopods with eight arms and an internalized chitinous shell called a gladius. Ya Ha Tinda represents the largest record of Vampyropoda gladii found outside of Europe for the Early Jurassic, and provides the unique opportunity to place Vampyropoda in a chemostratigraphic context. The goals of this thesis were threefold: (1) to taxonomically identify the Vampyropoda found at Ya Ha Tinda, including two specimens that were collected by Russell Hall from the same formation in the 1980s, (2) to compare the distribution and paleoecology of Vampyropoda to coeval European Lagerstätten, and (3) to conduct a detailed analysis of how Vampyropoda taxa were influenced by the Toarcian Oceanic Anoxic Event. In total, only fourteen specimens have sufficient morphological details preserved for taxonomic descriptions. Twelve specimens are identified to the genus level; six Paraplesioteuthis cf. sagittata, three Loligosepia cf. aalensis, one Geopeltis cf. simplex, one Parabelopeltis cf. flexuosa, and one Jeletzkyteuthis sp. The remaining two specimens belong to the suborder Loligosepiina, one to the family Geopeltididae. With the exception of Paraplesioteuthis, this is the first time all of these taxa have been found outside of Europe. The discovery of L. cf. aalensis within Pliensbachian strata pushes back the earliest occurrences of these taxa from the Early Toarcian to the Late Pliensbachian. Vampyropoda discovered at Ya Ha Tinda are nearly identical to those found in German deposits of the coeval Posidonia Shale, but, unlike European Lagerstätten, the fauna from Alberta has a relatively even proportion of Prototeuthidina and Loligosepiina. There are no taxa found within the CIE interval. The absence of taxa from this interval may be a result of taphonomy, sampling bias, or water chemistry. My results highlight several challenges associated with Vampyropoda taxonomy and provide paleoecological data of Early Jurassic specimens that are vital for understanding the taphonomic controls influencing the fragmentary Vampyropoda fossil record.

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