A well-preserved respiratory system in a Silurian ostracod.

David J Siveter,Derek E G Briggs,Derek J Siveter,Mark D Sutton

doi:10.1098/rsbl.2018.0464

David J Siveter, Derek E G Briggs + Show 2 more

Open Access

https://doi.org/10.1098/rsbl.2018.0464

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Abstract

Ostracod crustaceans are diverse and ubiquitous in aqueous environments today but relatively few known species have gills. Ostracods are the most abundant fossil arthropods but examples of soft-part preservation, especially of gills, are exceptionally rare. A new ostracod, Spiricopia aurita (Myodocopa), from the marine Silurian Herefordshire Lagerstätte (430 Mya), UK, preserves appendages, lateral eyes and gills. The respiratory system includes five pairs of gill lamellae with hypobranchial and epibranchial canals that conveyed haemolymph. A heart and associated vessels had likely evolved in ostracods by the Mid-Silurian.

Highlights

Ostracod crustaceans, originated about 500 Mya [1], are abundant as fossil shells from the Ordovician to the Holocene and have colonized all aquatic environments
Eight ostracod species with soft parts preserved are known from the Palaeozoic, most documented from single specimens ([7] and references therein)
Material and methods Herefordshire Lagerstatte fossils occur as three-dimensional calcitic in fills in calcareous concretions within volcaniclastics [9]

Summary

Introduction

Ostracod crustaceans, originated about 500 Mya [1], are abundant as fossil shells from the Ordovician to the Holocene and have colonized all aquatic environments. Most are benthic/nektobenthic, with pelagic species (exclusively Myodocopa) known from the Silurian onwards ([2] and references therein). Of the respiratory strategies [3,4,5,6] in living species only one involves respiration by gills. Eight ostracod species (six Myodocopa) with soft parts preserved are known from the Palaeozoic, most documented from single specimens ([7] and references therein). 430 Mya), UK, has yielded unparalleled evidence of the palaeobiology and evolutionary significance of diverse Silurian invertebrates, including four ostracod species ([8] and references therein). We report a new Herefordshire ostracod that reveals the ancestry of the respiratory/circulatory system within the group

Material and methods

Systematic palaeontology

Discussion