A new genus and new species of freshwater mussel from the mid Late Triassic rift lakes of eastern North Carolina (Bivalvia: Unionida: of. Unionidae)

作者：Began Arthur E^*; Weaver Patricia G

来源：Nautilus, 2012, 126(3): 105-112.

• Unionida
• Uniomorphi
• Newark Supergroup

In eastern North America, surface exposures of Triassic basins extend from Nova Scotia southwestward to South Carolina. This interrupted series of half-grabens resulted from early Mesozoic rifting of the supercontinent Pangaea. In south central North Carolina, the Deep River basin is comprised of the Durham subbasin, the Colon cross-structure, the Sandford subbasin, the Pekin cross structure, and the Wadesboro subbasin. Deposits within the Durham subbasin are recognized as the Chatham Group, part of the Newark Supergroup and form part of a series informally designated as Lithofacies Association II. These strata are considered to be alternating fluvial and lacustrine sediments. Though research on the vertebrate fauna from this lithofacies has been ongoing for over a century, considerably less research, particularly in North Carolina, has been done on the lacustrine invertebrate fauna.
Ongoing field work at a brick-clay quarry in the village of Genlee, Durham County, North Carolina, has yielded three distinct forms of Triassic freshwater bivalves, one is considered here to he of the order Unionoida and the others tentatively a mytiloid in shell outline and a sphaeriid in shell outline. The unionoid specimens are assigned to Triaslacus new germs and Triaslacus carolinesis new species and are tentatively assigned the Unionidae. These new specimens are compared with specimens described as belonging to the unionoid families Unionidae, Hyriidae, and Mulleriidae [+Mycetopodidae] from Massachusetts and Pennsylvania. However, none of the North Carolina specimens exhibit the umbonal sculpture exhibited by the northeastern specimens. The North Carolina unionoid specimens lack any evidence of hinge development or umbonal sculpture.
Non-unionoid bivalves are quite rare in these deposits. The bivalve fauna is found in association with ostracods of the genus Darwinula; clam shrimp, Euestheria, represented by carbonized impressions of the shells; and fish and plant remains. This freshwater environment is preserved in a mud-stone or clayey siltstone sediments.

• 出版日期2012-10-25