First discovery of Early PalaeozoicBathysiphon(Foraminifera) – test structure and habitat of a ‘living fossil’

Abstract

The giant, agglutinated foraminiferan Bathysiphon Sars, previously Triassic–Recent, occurs in much older sedimentary rock (Early Ordovician, late early Tremadocian) of Avalonia. The genus extends back to c. 485 Ma based on its discovery in platform mudstone of the Chesley Drive Group in Cape Breton Island, Nova Scotia. Elongate (up to 60 mm), epibenthic Bathysiphon tubes occur in wave-rippled, green-grey mudstone with a low diversity, probably dysoxic fauna. The mudstone is coeval with and lithologically similar to the Shineton Formation in Shropshire and the Welsh Borderlands. Scanning microscopy of the Bathysiphon walls shows imbricated mica grains that parallel the long axis of the tests. The lumen has a mélange of packed sediment grains, some of which are spherical structures of siliciclastic mud studded with tetrahedral pyrite crystals. A felt-like, agglutinated test, a lumen packed with spherical structures (probable stercomata) and the domal ends of some specimens are consistent with modern Bathysiphon. This report is the first time that cytoplasmic activity and stercomata formation have been used to refer fossil protists to a modern group. Bathysiphon differs from the Cambrian foraminiferan Platysolenites Pander, which has an open lumen without stercomata, but support a comparable, sediment deposit-feeding niche. Bathysiphon is truly a ‘living fossil’, with a mode of test construction, cytoplasmic activity that formed stercomata and a niche unchanged for almost 500 million years. Foraminiferans have not been found prior to the Cambrian Period, and the Early Cambrian appearance of agglutinated foraminiferans is part of the radiation of Phanerozoic communities.

First evaluation of foraminiferal metabarcoding for monitoring environmental impact from an offshore oil drilling site

“…Without further taxonomic information on OTUs 73,145,226,234,297 and 313, comparison with known ecological information on these taxa is not possible. Bathysiphon species are well-known for occupying deposit-feeding niches (Landing et al, 2012). Because they mainly feed on detritus and bacteria (Duffield et al, 2014) this may give them the ability to thrive in low organic content conditions such as those observed near the WHs.…”

Late Cambrian (middle Furongian) shallow-marine dysoxic mudstone with calcrete and brachiopod–olenid–Lotagnostusfaunas in Avalonian Cape Breton Island, Nova Scotia

“…Although exposed in heavily overgrown, tectonized short sections and spot localities, the Chesley Drive Group in Cape Breton Island yields rich Furongian–Tremadocian faunas dominated by trilobites (e.g. Hutchinson, 1952; Landing & Fortey, 2011; Landing et al 2012). The fossils are primarily from dark-grey, thin and nodular to bedded limestones.…”