Ediacaran macrofossils prior to the ~580 Ma Gaskiers glaciation in Newfoundland, Canada

Macrofossils of the inferred protist‐grade organism Palaeopascichnus linearis occur stratigraphically beneath glacial diamictites of the ~580 Ma, Gaskiers‐equivalent, Trinity ‘facies’ of the Rocky Harbour Formation on the Bonavista Peninsula of Newfoundland, Canada. These fossils significantly pre‐date previously reported macrofossils from Avalonia and extend the taphonomic window for moldic preservation of macroscopic organisms beyond the Gaskiers glacial event into the middle Ediacaran Period. This finding confirms the long stratigraphical range of palaeopascichnid fossils worldwide and informs discussions surrounding both the age of poorly time‐constrained stratigraphical units in Norway and Australia, and formal sub‐division of the Ediacaran System. □ Bonavista Peninsula, Ediacara biota, Palaeopascichnus, protist, stratigraphy.

The island of Newfoundland in eastern Canada hosts several globally significant localities for late Ediacaran age fossils of the Ediacaran Macrobiota. Such localities record benthic palaeocommunities of diverse soft-bodied organisms and include Mistaken Point Ecological Reserve UNESCO World Heritage Site and Spaniard's Bay on the Avalon Peninsula, and the Catalina Dome (within the Discovery Global Geopark) on the Bonavista Peninsula (Fig. 1B;Narbonne 2004;Narbonne in Fedonkin et al. 2007;Hofmann et al. 2008;Liu & Matthews 2017). These fossil assemblages are dated to between~574 and 562 Ma (Canfield et al. 2020;Matthews et al. 2020) and lie within siliciclastic strata deposited in deep-marine to marine-slope settings (Wood et al. 2003). Over 30 distinct taxa have been described to date , and in addition to non-metazoan and problematic taxa, the assemblages include some of the oldest reported body (e.g. Liu et al. 2014;Dunn et al. 2018) and trace (Liu et al. 2010;Menon et al. 2013) fossil evidence for total group metazoans. Fossils of the Ediacaran Macrobiota from Newfoundland represent some of the oldest known examples of the classic Ediacara-type biota anywhere in the world (alongside Charnwood Forest, England, and the Wernecke and Mackenzie Mountains of Canada; Noble et al. 2015;Rooney et al. 2020).
All previously documented Ediacaran macrofossils in Newfoundland stratigraphically and radiometrically post-date glacigenic diamictites of the Gaskiers Formation (Eyles & Eyles 1989), or its northern equivalent on the Bonavista Peninsula, the Trinity 'facies' of the Rocky Harbour Formation (Normore 2011). Both of these units have been dated to~580-579 million years (Bowring et al. 2003;Pu et al. 2016), and along with other glacial deposits of this age (e.g. the Mortensnes Formation of Finnmark, Norway; Rice et al. 2011) are considered to record an important regional glacial event: the Gaskiers glaciation (e.g. Halverson et al. 2005;Fairchild & Kennedy 2007). Iron speciation data from Newfoundland indicate at least local oxygenation of the deep ocean following the Gaskiers glaciation (Canfield et al. 2007), encouraging proposed links between the Gaskiers event and the evolution of diverse macroscopic complexity and large body size (as represented by the rise and diversification of the classic Ediacara-type biota; e.g. . However, such physiological links remain unproven at present (Sperling et al. 2015;Pu et al. 2016).
Globally, the Lantian Formation of South China provides the most compelling evidence for complex macroscopic Ediacaran life prior to 580 Ma (Yuan et al. 2011;Wan et al. 2016), but its precise age is yet to be ascertained, and the vast majority of its taxa are not observed in later Ediacaran fossil assemblages. Older reports of complex macroscopic eukaryotes remain contentious (e.g. El Albani et al. 2010), reflect problematic taxa (Fedonkin & Yochelson 2002) or comprise simple algal-like (Ye et al. 2015;Zhu et al. 2016) or discoidal impressions (e.g. Burzynski et al. 2020).
This study presents specimens of the probable protozoan Palaeopascichnus linearis from marine strata within the Rocky Harbour Formation of Newfoundland. These specimens demonstrably pre-date ~580 Ma diamictites of the Trinity 'facies' and therefore represent the oldest documented macrofossils from the Ediacaran successions of Newfoundland.

Materials and methods
Fossil-bearing horizons are situated on the western shoreline of an inlet known locally as Freshwater Trestle, just a few hundred metres to the west of the town of Trinity East on the Bonavista Peninsula, Newfoundland ( Fig. 1). Continuous exposure through the middle of the Rocky Harbour Formation (Musgravetown Group) is observed along a disused railway cutting that runs parallel to the shoreline. Fossil-bearing surfaces from two discrete horizons were sampled (Fig. 2), yielding 32 distinct fossil specimens, which were studied in the laboratory. Studied specimens are accessioned in the collections of the Sedgwick Museum, University of Cambridge under specimen numbers CAMSM X 50348.1 to CAMSM X 50348.7 in Appendix S1. The sedimentary section along the western side of Freshwater Trestle was logged at a 10-cm resolution as part of an ongoing study into Ediacaran glacial sedimentology in Newfoundland. The stratigraphical and sedimentological discussions below draw upon observations made during that regional study, and are additionally informed by the findings of a team of six undergraduates from the University of Cambridge who mapped the wider region around the town of Trinity at 1:10,000 scale in the summer of 2018.

Geological context
Two distinct Ediacaran age stratigraphical successions on the Bonavista Peninsula are separated by the Spillars Cove-English Harbour fault (O'Brien & King 2002, 2004Normore 2011). To the east of the fault lies the St. John's Basin, with a succession comprising shallowing-upwards deep-marine to fluvial units of the Conception, St. John's and Signal Hill Groups. The Conception and St. John's Groups host almost all previous reports of fossils of the Ediacaran Macrobiota in Newfoundland (e.g. Hofmann et al. 2008;Mason et al. 2013;. To the west,  the Bonavista Basin hosts sedimentary rocks of the Musgravetown Group, which reflect sedimentation in shallow marine depositional environments, beneath non-marine sedimentary rocks of the Crown Hill Formation (O'Brien & King 2002;Normore 2011). This western basin has not previously yielded reports of Ediacaran age macrofossils.
The Rocky Harbour Formation lies within the Musgravetown Group and comprises siliciclastic and volcanogenic lithologies that have been divided into seven mappable 'facies' by Normore (2011, following O'Brien & King 2002, 2004 during regional mapping for the Geological Survey of Newfoundland and Labrador. These mapped 'facies' commonly contain several distinct sedimentary lithologies and facies (sensu stricto), and they could therefore be better described as facies assemblages. The Rocky Harbour Formation 'facies' are interpreted to reflect marginal marine and glacially influenced depositional environments (Normore 2010(Normore , 2011. The Trinity 'facies' lies towards the middle of the Rocky Harbour Formation and is composed of matrix-supported diamictite with dropstones, faceted and striated clasts (Normore 2011). Local relationships between the Trinity 'facies' and other lithologies within the Rocky Harbour Formation are not straightforward, with considerable lateral facies variation (Normore 2011). However, diamictite deposits across the Bonavista Peninsula have been considered broadly coeval (Normore 2011), and dates obtained from above and below this 'facies' at Old Bonaventure (Fig. 1C) indicate a short duration for deposition of the diamictite, contemporaneous within error with deposition of the Gaskiers Formation on the Avalon Peninsula (Pu et al. 2016, see discussion below).

Freshwater Trestle fossil locality
The studied section in Freshwater Trestle comprises approximately 200 m of largely continuous stratigraphy. Beds dip at 80-90°to the northeast. With the possible exception of the base of the diamictite, the observed succession appears to be conformable (Fig. 2).
The section begins with massive, polymictic, fineto very coarse-grained grey sandstones that match previous descriptions of the Cape Bonavista 'facies', and pink to grey sandstones with occasional purplebrown mudstone drapes assigned to the King's Cove Lighthouse 'facies'. These two 'facies' are recognized to be laterally transitional elsewhere on the Bonavista Peninsula (Normore 2011, fig. 2). Thin-to mediumbeds comprising packages of laminated purplebrown mudrock, dark brown siltstone and discontinuous grey-brown sandstone within the King's Cove Lighthouse 'facies' exhibit rare symmetrical ripples, synaeresis cracks and pebbles (Fig. 3). The mudrock laminae host Palaeopascichnus specimens as hypoand epirelief surface impressions (Fig. 4). The symmetrical ripples indicate oscillatory flow, which we attribute to wave action in a nearshore marine depositional environment. The polymictic nature of the sands, grits and rare pebbles in the sandstone, combined with their sub-rounded to rounded aspect and wide size range, may result from fluvial or marine reworking of nearby volcanogenic and glacial material.
A pink, highly silicified siltstone at 56-59 m (Fig. 2) is interpreted to be tuffaceous. This lithology separates the sandstones below from 18 m of mostly massive, silty, unstructured polymictic diamictites attributed to the Trinity 'facies' of the Rocky Harbour Formation (Normore 2011). The uppermost 3.6 m of this diamictite is stratified and contains dropstones that suggest deposition of material from floating ice (Fig. 3D), favouring a glaciomarine/ glaciolacustrine environment for this unit during glacial retreat, as opposed to a terrestrial till (following Eyles et al. 1983). The dropstones also provide way up indicators, which in addition to ripples in the underlying King's Cove Lighthouse 'facies', and cross-lamination in the Cape Bonavista 'facies', have enabled us to orientate the stratigraphical succession.
The diamictite is overlain by 40 m of laminated green-grey siltstones, previously mapped within the Herring Cove 'facies' of the Rocky Harbour Formation (Normore 2011). Elsewhere in the region, Normore described the Herring Cove 'facies' as a volcano-sedimentary unit with sills, peperites, tuffs, mudstones and laminated siltstones, but we observed only limited evidence for volcanogenic material in our measured section. We interpret the Herring Cove 'facies' siltstones to reflect predominantly quiescent marine conditions following ice retreat.
No fossils were found above the diamictite in the Freshwater Trestle section, but we did observe several Palaeopascichnus specimens in a section previously mapped as the Herring Cove 'facies' (Normore 2011) at Herring Cove, between Port Rexton and Champney's West (~3km to the east of our measured section; Figs 1C, 5D). Those specimens occur as positive epirelief impressions on the top of a green siltstone and are found 70 cm above a prominent pink bed previously described as a volcanic tuff with tepee-like Fig. 4. Palaeopascichnus linearis fossils from Freshwater Trestle, Trinity East. A, branching specimens (arrowed) of P. linearis, CAMSM X 50348.1.2c-e. B, two specimens (arrowed) with chambers that gently expand along the length of the chain, CAMSM X 50348.1.2a-b. C, straight palaeopascichnid specimen (arrowed), with globular chambers. This specimen could potentially be referred to Orbisiana (following Kolesnikov et al. 2018b, see discussion in the main text), CAMSM X 50348.2a. D, dense P. linearis assemblage, CAMSM X 50348.3c-e, i. E, several discrete but irregular specimens of Palaeopascichnus, some of which (arrowed) could reflect aggregations of chambers that could be more correctly assigned to Orbisiana, CAMSM X 50348.4c-e. Scale bars all = 5 mm.
structures (Normore 2011, pl. 9E), but which we interpret as a possible peperite. The Trinity 'facies' is not observed to crop out at Herring Cove, preventing direct confirmation of the relative stratigraphical position of the specimens with respect to the diamictite at this location.
Taken together, the Freshwater Trestle section appears to document a transition from a proximal, shallow marine environment, through glacigenic diamictite deposition, to quiescent marine conditions, punctuated by influxes of volcanogenic material (which may be primary, or secondarily reworked). This general history is consistent with our observations elsewhere in the area. There is considerable variation in the thickness of the Trinity 'facies' at sites across the Trinity Bay region (ranging from 15 to >100 m; Normore 2011; Supplementary Information of Pu et al. 2016), but we interpret the diamictite to be a single marker horizon in the region.

Fossil assemblage
Fossils were identified at two levels within the Freshwater Trestle section, at~7 and 35 m below the base of the Trinity 'facies' diamictite (Fig. 2). The upper level yielded fossils on a single bedding surface of purple-brown mudstone, <1 mm thick, overlying a sandstone. The lower level consisted of several fossiliferous horizons, with fossils all found on purplebrown mudstone surfaces, within a thin-bedded fineto-coarse grey sandstone succession (Fig. 3A).
The most common macrofossils are surface impressions of linear chains of rounded, hollow chambers that can be assigned to P. linearis (Fedonkin, 1976) Kolesnikov et al. 2018b, following the synonymizations suggested by those authors. P. linearis specimens are between 0.34 and 2.60 cm in length (n = 32). The chambers either maintain constant width along the length of a chain (maximum chamber widths within individual specimens range between 1.29 and 3.41 mm), or exhibit gentle widening and/or branching into multiple chains (Fig. 4A,  B). Some specimens appear to comprise globular rather than elongate chambers (Fig. 4C) and could potentially be assigned to Orbisiana, another palaeopascichnid taxon (see Kolesnikov et al. 2018a). Both Palaeopascichnus and Orbisiana are known to be preserved as moldic impressions elsewhere, for example in the Fermeuse Formation of Newfoundland (Hawco et al. 2020, fig . 5), and the Verkhovka Formation of the White Sea, Russia (Kolesnikov et al. 2018a , fig. 4).
Recent revision of palaeopascichnid taxonomy has seen multiple taxa assigned to this group, while other morphologically similar taxa have been distanced from it (e.g. Ivantsov 2017; Kolesnikov et al. 2018aKolesnikov et al. , 2018b. Comparison of material from different global localities has aided recognition of distinct morphotypes (e.g. Kolesnikov et al. 2018aKolesnikov et al. , 2018b, but detailed morphometric work on populations of specimens has revealed considerable morphological variation in chamber shape, size and ability to branch within individual populations, questioning the utility of such characters for differentiating taxa at a species level (Hawco et al. 2020). Furthermore, several examples of apparently transitional forms between taxa at both generic and species level exist within individual populations (discussed in Jensen et al. 2018), and our material appears consistent with this phenomenon.
At present, Orbisiana and Palaeopascichnus are distinguished by Orbisiana typically having consistently sized, globular/circular chambers arranged in biserial or multiserial chains or aggregated clusters, whereas Palaeopascichnus specimens comprise only uniserial chains of relatively elongate chambers (commonly ellipsoidal to globular), which can change in width along the length of the organism (e.g. Jensen 2003;Jensen et al. 2018;Kolesnikov et al. 2018a). Specimens of both genera are capable of branching distally, but in Palaeopascichnus the chambers on subsequent branches are smaller in width than their predecessors, whereas in Orbisiana there is no change in width (Kolesnikov et al. 2018a). The majority of our specimens comprise uniserial chains possessing chambers with an elongate morphology (Fig. 4A,B,D), and an ability for chambers to sequentially expand, but some specimens exhibit chains of chambers that are more circular in shape and which show no change in width (e.g. Fig. 4C). We assume that the observed variation in shape in our studied population is original, but note that we do not possess independent strain indicators for the outcrop. Our material is morphologically most similar to described and figured specimens from the late Ediacaran Stáhpogieddi Formation of Arctic Norway, referred to Palaeopascichnus delicatus (Jensen et al. 2018, fig. 3). Our material differs from P. delicatus Palij, 1976 in having relatively low expansion rates within individual chains of chambers, and reasonably consistent chamber size throughout individual chains (sensu Kolesnikov et al. 2018b). We therefore attribute the majority of our specimens to P. linearis.

Microbially induced sedimentary structures
The mudstone horizons in the King's Cove Lighthouse 'facies' also record several sedimentary surface textures (sensu Davies et al. 2016; Fig. 5A-C), some of which closely resemble impressions that have been interpreted as biotic in origin in other late Neoproterozoic successions. These include very fine, seemingly paired wavy ridges of <0.1 mm width, which are similar to fabrics originally referred to as Arenicola didyma from the Long Mynd of Shropshire (Salter 1856). Irregularly spaced positive hyporelief circular bumps, ≤1-3 mm in diameter, are interpreted as likely bubble or gas escape impressions (Fig. 5B,C). Surface fabrics present on many of the Palaeopascichnus-bearing surfaces are finely undulating (e.g. Fig. 4A-C), and may or may not be biogenic in origin.

Discussion
Constraining the age of the fossil assemblage Radiometric dating of volcanogenic deposits associated with the Trinity 'facies' near Old Bonaventure (Fig. 1C) constrains the age of diamictite deposition to between 579.63 ± 0.15 and 579.24 ± 0.17 Ma (Pu et al. 2016 , fig. DR2A). These dates imply that the Trinity diamictite was deposited broadly synchronously with glacigenic diamictites of the Gaskiers Formation on the Avalon Peninsula (which were deposited between 580.90 ± 0.40 and 579.88 ± 0.44 Ma; all dates U-Pb CA-ID-TIMS analyses on volcanogenic zircons; Pu et al. 2016). The age of the fossil-bearing King's Cove Lighthouse 'facies' at Freshwater Trestle is therefore most likely ≥579.63 ± 0.15 Ma (Fig. 1D). Due to structural deformation, lateral facies variation and poor regional exposure, it is not possible to conclusively demonstrate synchronicity in the onset and termination of glacial sedimentation across the 12-km area separating the Freshwater Trestle fossil locality and the dated Old Bonaventure sections without further radiometric dating. Previously proposed stratigraphical relationships for the Trinity 'facies' within the Rocky Harbour Formation (Normore 2011, fig . 4) raise the possibility that some sections may contain two diamictite horizons, but we did not observe any evidence for this scenario within the study area. We follow Pu et al. (2016) in interpreting the Trinity 'facies' of the Rocky Harbour Formation as a singular regional event equivalent to the Gaskiers Formation. This interpretation requires that the Freshwater Trestle fossils pre-date the Gaskiers glaciation. The global age range of palaeopascichnids Taxa assigned to the Palaeopascichnida (Grazhdankin 2014) are commonly found in shallow marine settings in the terminal Ediacaran, including just below the Ediacaran-Cambrian boundary Global Standard Stratotype section and Point on the Burin Peninsula of Newfoundland (Gehling et al. 2001), and stratigraphically close to horizons bearing Cambrian-type trace fossils in the Urals and Arctic Norway (Kolesnikov et al. 2015;Jensen et al. 2018). The genus Palaeopascichnus has also been reported from several sites on the East European Platform in Ukraine (Palij 1976), Poland (Paczesna 1986) and Russia (Fedonkin 1981;Kolesnikov et al. 2015;Golubkova et al. 2018), the Yudoma Group of Siberia (Ivantsov 2017), the Itajaí Basin of Brazil (Becker-Kerber et al. 2020) and South Australia (Glaessner 1969;Haines 2000). In Newfoundland, it also frequently occurs in marine slope deposits of the (~560 Ma) Fermeuse Formation at Ferryland (Gehling et al. 2000;Liu & McIlroy 2015;Hawco et al. 2020). Notably, material originally referred to Orbisiana linearis by Wan et al. (2014) from the Lantian Formation of South China has recently been synonymized within P. linearis (Kolesnikov et al. 2018b), on the basis of its morphological attributes (Kolesnikov et al. 2018a).
Orbisiana has previously been interpreted as a possible alga (e.g. Sokolov 1976), but its close similarities in form and probable wall structure to Palaeopascichnus require consideration of a protistan phylogenetic placement (Kolesnikov et al. 2018a).
Our discovery of P. linearis in pre-Gaskiers (i.e. >580 Ma) sedimentary successions follows suggestions that the Lantian Formation palaeopascichnids are early-middle Ediacaran in age (considered perhaps as old as 600 Ma on the basis of litho-and chemostratigraphical correlation with Member II of the Doushantuo Formation; Yuan et al. 2011;Wan et al. 2016 and references therein). Fossil material from the Kimberley region of Australia that likely pre-dates the Gaskiers (Lan & Chen 2012) might be better described as Curviacus following the more recent description of that genus (Shen et al. 2017), but reflects an additional example of a pre-Gaskiers palaeopascichnid.
Palaeopascichnids therefore appear to have been globally distributed prior to the Gaskiers glaciation, seemingly providing a prelude to the larger and more complex organisms of the late Ediacaran Macrobiota.
In the absence of radiometric dates, specimens from the upper Wonoka Formation in the Flinders Ranges of South Australia (Haines 2000) have typically been assumed to be of late Ediacaran age, on the basis of their stratigraphical occurrence above a negative carbon isotope excursion (CIE) within the Wonoka Fm. (correlated to the Shuram event; e.g. Bowring et al. 2007) and the suggestion that lonestones, granule clusters and pellets associated with the Acraman impact ejecta layer in the underlying Bunyeroo Formation correlate to the Gaskiers event (Gostin et al. 2010). That correlation with the Gaskiers is tenuous (Gostin et al. 2011). Recent dating of the Shuram CIE to between~574 and 567 Ma in NW Canada and Oman (Rooney et al. 2020; see also Canfield et al. 2020) would appear to confirm that, if the Wonoka-Shuram correlation is reliable, the taxonomically depauperate Palaeopascichnus assemblage in the Wonoka Fm. is of late Ediacaran age (i.e. 567-539 Ma). Confirmation of the Wonoka-Shuram CIE correlation is necessary to rule out alternative interpretations for the age of the Wonoka Formation, some of which (e.g. a Wonoka-Gaskiers correlation, Halverson et al. 2005) find support from the recognition of pre-Gaskiers palaeopascichnids in Newfoundland.
The oldest occurrences of Palaeopascichnus on the Digermulen Peninsula of Norway closely overlie the glacigenic Mortensnes Formation, which has been correlated with the Gaskiers glaciation (Halverson et al. 2005;Rice et al. 2011). Palaeopascichnus at the base of the Indreelva Member have been used to constrain the age of that unit to <565 Ma, therefore supporting a Gaskiers age for the underlying tillites of the Mortensnes Formation (Jensen et al. 2018).
Although close association of those specimens with discoidal fossils just a few metres up section would appear to support a late Ediacaran (post-Gaskiers) age for that unit, recognition of palaeopascichnids in Avalonian pre-Gaskiers strata herein relaxes the age constraints provided by the presence of Palaeopascichnus alone, such that the base of the Indreelva Member could lie anywhere within the late Ediacaran.
Palaeopascichnus has long been recognized as a frequent component of Ediacaran macrofossil assemblages, with some authors even considering palaeopascichnids to be members of the Vendobionta (Seilacher et al. 2003;Grazhdankin 2014). However, recognition that the Ediacaran Macrobiota comprises a range of diverse, unrelated organisms, alongside questioning of the Vendobiont hypothesis (e.g. Runnegar 1995;Dunn & Liu 2019) means that consideration of the entire biota as a single entity is no longer appropriate. This is particularly pertinent when discussing palaeopascichnids, which uniquely amongst the original Ediacara biota are increasingly considered to be protists with agglutinated chamber walls. Our discovery of pre-Gaskiers examples of an iconic late Ediacaran macrofossil taxon is thus tempered by the fact that Palaeopascichnus is not particularly representative of the soft-bodied Ediacaran Macrobiota of younger localities. Not only was it probably unrelated to most other late Ediacaran macrofossil taxa, but it is also possible that its preservation requires different taphonomic conditions. Seilacher et al. (2003) suggested that palaeopascichnids lived embedded within microbial mats, which may explain their high preservation potential, and the close association of the Trinity East palaeopascichnids with putative biogenic surface textures is consistent with that scenario. Further investigation is required to determine whether the presence of Palaeopascichnus prior to~580 Ma, and the apparent absence of other soft-bodied Ediacaran taxa (though see Wan et al. 2016), reflects a true evolutionary signal. Our own preliminary investigations in the Mall Bay Formation on the Avalon Peninsula, and within the lower units of the Rocky Harbour Formation, have so far yielded only abiogenic tool marks on the soles of beds.

Conclusions
Pre-Gaskiers (i.e. >580 Ma, middle Ediacaran) lithologies of the Rocky Harbour Formation of the Bonavista Peninsula, Newfoundland, contain impressions of the long-ranging candidate protistan taxon P. linearis, considerably extending the stratigraphical range of this taxon in Avalonia, and confirming a long stratigraphical range for palaeopascichnids throughout the entire late Ediacaran (see Grazhdankin 2014, anddiscussion in Jensen et al. 2018). Since Palaeopascichnus is not considered to be a metazoan (e.g. Antcliffe et al. 2011;Kolesnikov et al. 2018b;Hawco et al. 2020), this discovery does not change our current understanding of the timing of early animal diversification. However, in conjunction with examples from the Lantian Formation of China, it does expand the record of pre-Gaskiers protistan diversity (see also Porter et al. 2003;Bosak et al. 2011Bosak et al. , 2012Riedman et al. 2014) and demonstrates that a variant of the mouldic taphonomic window extends prior to the Gaskiers glaciation in some environmental settings. A stratigraphical range spanning the Lantian Fm. to the Ediacaran-Cambrian boundary, coupled with morphological variation within populations, suggests that palaeopascichnids are not suitable candidates as index fossils for sub-division of the Ediacaran System.