Data From: Spatial Analyses of Ediacaran Communities at Mistaken Point

Supplmentary information for Spatial Analyses of Ediacaran Communities at Mistaken Point

Abstract.— Bedding plane assemblages of Ediacaran fossils from Mistaken Point, Newfoundland, are among the oldest known records of complex multicellular life on Earth (~565 Ma). The in-situ preservation of these sessile, but otherwise deeply enigmatic organisms means that statistical analyses of specimen positions can be used to illuminate their underlying ecological dynamics, including the interactions between taxa.

Fossil assemblages on Mistaken Point D and E surfaces were mapped to millimetre accuracy using differentiated GPS. Spatial correlations between ten well defined taxa (Bradgatia, Charniid, Charniodiscus, Fractofusus, Ivesheadiomorphs, Lobate Discs, Pectinifrons, Plumeropriscum, Hiemalora and Thectardis), were identified using Bayesian Network Inference (BNI), and then described and analysed using Spatial Point Process Analysis. BNI found that the E surface community had a complex web of interactions and associations between taxa, with all but one taxon (Thectardis) interacting with at least one other. The unique spatial distribution of Thectardis supports previous, morphology-based arguments for its fundamentally distinct nature. BNI revealed that the D surface community showed no inter-specific interactions or associations, a pattern consistent with a homogeneous environment.

On the E surface, all six of the abundant taxonomic groups (Fractofusus, Bradgatia, Charniid, Charniodiscus, Thectardis and Plumeropriscum) were each found to have an unique set of interactions with other taxa, reflecting a broad range of underlying responses. Four instances of habitat associations were detected between taxa, of which two (Charniodiscus - Plumeropriscum, and Plumeropriscum - Fractofusus) led to weak competition for resources. One case of pre-emptive competition between Charniid and Lobate discs was detected. There were no instances of inter-specific facilitation. Ivesheadiomorphs interactions mirror those of Fractofusus and Charniodiscus, identifying them as a form-taxonomic grouping of degradationally homogenized taphomorphs. The absence of increased fossil abundance in proximity to these taphomorphs argues against scavenging/saprophytic behaviours dominating the E surface community.