Unanswered Questions in Palaeontology

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The Life and Death of Jamoytius kerwoodi White; A Silurian Jawless Nektonic Herbivore?

by Michael E. Brookfield

Foss. Stud. 2024, 2(2), 77-91; https://doi.org/10.3390/fossils2020003 - 09 Apr 2024

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Jamoytius kerwoodi, is a primitive, eel-like jawless vertebrate found uniquely in an Early Silurian (Llandovery epoch; 444–433 Ma) horizon near Lesmahagow, Scotland. This species is a rare component of a low-diversity dominantly nektonic detritus-feeding and herbivorous fauna living over an anoxic bottom and is found at the transition from a marine-influenced, probably brackish-water, deep-water basin to a shallower-water, less saline and likely freshwater basin. In the absence of true teeth, Jamoytius was probably a detritivore or herbivore feeding on Dictyocaris. Jamoytius may have a common ancestor with living lampreys, especially as their ectoparasitic mode of life might have evolved from ancestral detritivores or herbivores. Full article

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

by Mark A. S. McMenamin

Geosciences 2023, 13(3), 80; https://doi.org/10.3390/geosciences13030080 - 10 Mar 2023

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Abstract

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. Full article

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Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Diversity diversity	2.4	3.1	2009	17.8 Days	CHF 2600
Geosciences geosciences	2.7	5.2	2011	23.6 Days	CHF 1800
Life life	3.2	2.7	2011	17.5 Days	CHF 2600
Quaternary quaternary	2.3	3.6	2018	29.2 Days	CHF 1600
Animals animals	3.0	4.2	2011	18.1 Days	CHF 2400
Fishes fishes	2.3	1.9	2016	15.7 Days	CHF 2600
Minerals minerals	2.5	3.9	2011	18.7 Days	CHF 2400
Fossil Studies fossstud	-	-	2023	15.0 days *	CHF 1000

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