TY - JOUR
T1 - Substrate growth dynamics and biomineralization of an ediacaran encrusting poriferan
AU - Wood, Rachel
AU - Penny, Amelia
N1 - Funding Information:
R.W. and A.P. acknowledge support from the International Centre for Carbonate Reservoirs, and A.P. from the University of Edinburgh and the Daniel Pidgeon fund of the Geological Society of London.
Publisher Copyright:
© 2018 The Author(s) Published by the Royal Society. All rights reserved.
PY - 2018/1/10
Y1 - 2018/1/10
N2 - The ability to encrust in order to secure and maintain growth on a substrate is a key competitive innovation in benthic metazoans. Here we describe the substrate growth dynamics, mode of biomineralization and possible affinity of Namapoikia rietoogensis, a large (up to 1 m), robustly skeletal, and modular Ediacaran metazoan which encrusted thewalls of synsedimentary fissures within microbial–metazoan reefs. Namapoikia formed laminar or domal morphologies with an internal structure of open tubules and transverse elements, and had a very plastic, non-deterministic growth form which could encrust both fully lithified surfaces as well as living microbial substrates, the latter via modified skeletal holdfasts. Namapoikia shows complex growth interactions and substrate competition with contemporary living microbialites and thrombolites, including the production of plate-like dissepiments in response to microbial overgrowth which served to elevate soft tissue above the microbial surface. Namapoikia could also recover from partial mortality due to microbial fouling. We infer initial skeletal growth to have propagated via the rapid formation of an organic scaffold via a basal pinacoderm prior to calcification. This is likely an ancient mode of biomineralization with similarities to the living calcified demosponge Vaceletia. Namapoikia also shows inferred skeletal growth banding which, combined with its large size, implies notable individual longevity. In sum, Namapoikia was a large, relatively long-lived Ediacaran clonal skeletal metazoan that propagated via an organic scaffold prior to calcification, enabling rapid, effective and dynamic substrate occupation and competition in cryptic reef settings. The open tubular internal structure, highly flexible, non-deterministic skeletal organization, and inferred style of biomineralization of Namapoikia places probable affinity within total-group poriferans.
AB - The ability to encrust in order to secure and maintain growth on a substrate is a key competitive innovation in benthic metazoans. Here we describe the substrate growth dynamics, mode of biomineralization and possible affinity of Namapoikia rietoogensis, a large (up to 1 m), robustly skeletal, and modular Ediacaran metazoan which encrusted thewalls of synsedimentary fissures within microbial–metazoan reefs. Namapoikia formed laminar or domal morphologies with an internal structure of open tubules and transverse elements, and had a very plastic, non-deterministic growth form which could encrust both fully lithified surfaces as well as living microbial substrates, the latter via modified skeletal holdfasts. Namapoikia shows complex growth interactions and substrate competition with contemporary living microbialites and thrombolites, including the production of plate-like dissepiments in response to microbial overgrowth which served to elevate soft tissue above the microbial surface. Namapoikia could also recover from partial mortality due to microbial fouling. We infer initial skeletal growth to have propagated via the rapid formation of an organic scaffold via a basal pinacoderm prior to calcification. This is likely an ancient mode of biomineralization with similarities to the living calcified demosponge Vaceletia. Namapoikia also shows inferred skeletal growth banding which, combined with its large size, implies notable individual longevity. In sum, Namapoikia was a large, relatively long-lived Ediacaran clonal skeletal metazoan that propagated via an organic scaffold prior to calcification, enabling rapid, effective and dynamic substrate occupation and competition in cryptic reef settings. The open tubular internal structure, highly flexible, non-deterministic skeletal organization, and inferred style of biomineralization of Namapoikia places probable affinity within total-group poriferans.
KW - Biomineralization
KW - Ediacaran
KW - Namapoikia
KW - Poriferan
KW - Substrate dynamics
UR - http://www.scopus.com/inward/record.url?scp=85040740211&partnerID=8YFLogxK
U2 - 10.1098/rspb.2017.1938
DO - 10.1098/rspb.2017.1938
M3 - Article
C2 - 29321296
AN - SCOPUS:85040740211
SN - 0962-8452
VL - 285
JO - Proceedings of the Royal Society B: Biological Sciences
JF - Proceedings of the Royal Society B: Biological Sciences
IS - 1870
M1 - 20171938
ER -