Rheotropic Epifaunal Growth, Not Felling by Density Currents, Is Responsible for Many Ediacaran Fossil Orientations at Mistaken Point

McIlroy, Duncan; Pérez-Pinedo, Daniel; Pasinetti, Giovanni; McKean, Christopher; Taylor, Rod S.; Hiscott, Richard N.

doi:10.3389/feart.2022.849194

Cited by 6 publications

(29 citation statements)

References 27 publications

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“… 15 One other possibility is chemoautotrophy—an idea recently championed by McIlroy et al. 31 , 69 —which proposes that rangeomorph tissues possessed sulfur-oxidizing ectosymbionts, that in turn took advantage of sulfidic porewaters generated in the sediment underneath organisms. Although many of the reconstructions favored by these authors apparently require frondose rangeomorphs to be reclining on the seafloor—something at odds with the majority of fossil evidence 12 , 13 , 32 , 51 , 70 —our study does suggest that chemoautotrophy requires more detailed testing.…”

Section: Discussionmentioning

confidence: 99%

The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life

Darroch¹,

Gutarra²,

Masaki³

et al. 2023

iScience

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Section: Discussionmentioning

confidence: 99%

The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life

Darroch¹,

Gutarra²,

Masaki³

et al. 2023

iScience

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“…2015; Mitchell et al . 2015), which contrasts with the possibly rheotropically orientated Charniodiscus procerus of ‘Seilacher’s Corner’ (McIlroy et al ., 2022; Fig. 8).…”

Section: Discussionmentioning

confidence: 94%

Morphological variation in the rangeomorph organism Fractofusus misrai from the Ediacaran of Newfoundland, Canada

Taylor

Nicholls²,

Neville³

et al. 2022

Geol. Mag.

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The Ediacaran rangeomorph Fractofusus misrai is the most common and best-preserved of the E Surface fossil assemblage in the Mistaken Point Ecological Reserve of southeastern Newfoundland, Canada. Fractofusus has been interpreted as a fusiform epifaunal soft-sediment recliner, and like other rangeomorphs it has a self-similar, fractal-like branching morphology. The rangeomorph branching of Fractofusus has been considered to be identical on the upper and lower surfaces; however, study of specimens with complex biostratinomic histories suggests clear differences between the upper and lower surfaces. The first-order branches grew downwards into the sediment from a high point near the midline but grew above the sediment–water interface at their lateral and distal margins. Our new three-dimensional appreciation of rangeomorph branching in Fractofusus explains many of the taphomorphs of Fractofusus including straight, curved, kinked and tousled forms. The three-dimensional morphology, mode of life, taphonomy and palaeoenvironmental interactions of F. misrai are discussed along with a new three-dimensional reconstruction.

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“…These orientations make the felling precept unlikely, even if an orthogonal bottom current to the one observed was inferred, as they would have been felled into and against the current (Fig. 11) (see McIlroy et al 2022).…”

Section: Bradgatia Spmentioning

confidence: 96%

“…The Ediacaran biota has been much explored in recent years, with research debating aspects of their phylogenetic affinity (Seilacher 1989(Seilacher , 1992Budd and Jensen 2017;Dunn and Donoghue 2018), ecology (Clapham et al 2003;Darroch et al 2018;Mitchell et al 2020), mode of life (Glaessner 1985;Laflamme et al 2009;Dufour and McIlroy 2017;McIlroy et al 2021), and taphonomy (Gehling 1999;Narbonne 2005;Liu et al 2011;Bobrovskiy et al 2019). Inferences that most of the Ediacaran biota-particularly the fractal-branching frondose Rangeomorpha-lived erect within the water column during life (i.e., Glaessner 1985;Laflamme et al 2007) have recently been contested (McIlroy et al 2020(McIlroy et al , 2021(McIlroy et al , 2022Pérez-Pinedo et al 2022). The high fidelity of preservation of originally soft tissues such as fractal-like fronds (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…McIlroy et al 2021McIlroy et al , 2022. The tightly organized branching hierarchy coupled with the basal down-current inflation suggests a functional morphology that simultaneously maximizes the surface area in contact with the seafloor and exchange with the water column.Similar lifestyles have been suggested for the rangeomorphs Beothukis mistakensis (McIlroy et al 2020) and Fractofusus misrai (Dufour and McIlroy 2017).…”

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confidence: 99%

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Frond orientations with independent current indicators demonstrate the reclining rheotropic mode of life of several Ediacaran rangeomorph taxa

Pérez-Pinedo

Neville²,

Pasinetti³

et al. 2023

Paleobiology

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Fossils from the deep-sea Ediacaran biotas of Newfoundland are among the oldest architecturally complex soft-bodied macroorganisms on Earth. Most organisms in the Mistaken Point–type biotas of Avalonia—particularly the fractal-branching frondose Rangeomorpha— have been traditionally interpreted as living erect within the water column during life. However, due to the scarcity of documented physical sedimentological proxies associated with fossiliferous beds, Ediacaran paleocurrents have been inferred in some instances from the preferential orientation of fronds. This calls into question the relationship between frond orientation and paleocurrents. In this study, we present an integrated approach from a newly described fossiliferous surface (the “Melrose Surface” in the Fermeuse Formation at Melrose, on the southern portion of the Catalina Dome in the Discovery UNESCO Global Geopark) combining: (1) physical sedimentological evidence for paleocurrent direction in the form of climbing ripple cross-lamination and (2) a series of statistical analyses based on modified polythetic and monothetic clustering techniques reflecting the circular nature of the recorded orientation of Fractofusus misrai specimens. This study demonstrates the reclining rheotropic mode of life of the Ediacaran rangeomorph taxon Fractofusus misrai and presents preliminary inferences suggesting a similar mode of life for Bradgatia sp. and Pectinifrons abyssalis based on qualitative evidence. These results advocate for the consideration of an alternative conceptual hypothesis for position of life of Ediacaran organisms in which they are interpreted as having lived reclined on the seafloor, in the position that they are preserved.

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Rheotropic Epifaunal Growth, Not Felling by Density Currents, Is Responsible for Many Ediacaran Fossil Orientations at Mistaken Point

Cited by 6 publications

References 27 publications

The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life

The rangeomorph Pectinifrons abyssalis: Hydrodynamic function at the dawn of animal life

Morphological variation in the rangeomorph organism Fractofusus misrai from the Ediacaran of Newfoundland, Canada

Frond orientations with independent current indicators demonstrate the reclining rheotropic mode of life of several Ediacaran rangeomorph taxa

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