A Late Triassic Nuculanoid Clam (Bivalvia: Nuculanoidea) and Associated Mollusks: Implications for Luning Formation (Nevada, USA) Paleobathymetry

A silicified, thick-shelled, smooth-surfaced nuculanoid bivalve has been recovered using acid maceration of the Late Triassic (Carnian–Norian) strata of the Luning Formation, Nevada. Comparable modern nuculanoid clams inhabit water depths from 525 to 2562 m, and the living clam (an undescribed speci...

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Bibliographic Details
Published inGeosciences (Basel) Vol. 13; no. 3; p. 80
Main Author McMenamin, Mark A. S.
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 01.03.2023
Subjects
abyssochrysoid gastropods
Abyssochrysoidae
Bivalvia
Clams
Earth science
Fossils
Hypotheses
Limestone
Maceration
Marine molluscs
Mollusks
Morphology
Nevada
Nuculanoidea
Paleontology
Parks & recreation areas
protobranch bivalves
Shellfish
Storms
Strata
Triassic
Water depth
United States > US
Nevada
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Summary:A silicified, thick-shelled, smooth-surfaced nuculanoid bivalve has been recovered using acid maceration of the Late Triassic (Carnian–Norian) strata of the Luning Formation, Nevada. Comparable modern nuculanoid clams inhabit water depths from 525 to 2562 m, and the living clam (an undescribed species of Pseudoneilonella from Caleta Sierra, Coquimbo, Chile) most similar to the fossil lives at 878–933 m. The Triassic nuculanoid clam (possibly a neilonellid) is inferred here to have inhabited marine waters at approximately 1000 m deep during the deposition of the Shaly Limestone Member of the Luning Formation. The acid maceration sample also produced a silicified specimen of an abyssochrysoid gastropod. The most similar living species to the fossil snail is Abyssochrysos brasilianus, an abyssochrysoid known to occur in water depths from 1540 to 620 m. This depth range also suggests an approximate 1000 m depositional depth for the silicified fossil-producing acid maceration sample from the Luning Formation. These new fossil discoveries falsify hypotheses that the ichthyosaurs (Shonisaurus popularis) of Berlin-Ichthyosaur State Park, Nevada, USA, were deposited, respectively, in either shoreline deposits or in strata that accumulated above the storm wave base. Evidence is also presented here for the existence of a giant Triassic cephalopod that, by comparison with the modern Mesonychoteuthis, preferred water depths of approximately 1000 m.
ISSN:2076-3263
2076-3263
DOI:10.3390/geosciences13030080