Proc Biol Sci. 2012 Dec 12;280(1752):20122664. doi: 10.1098/rspb.2012.2664. Print 2013 Feb 7.

A Silurian myodocope with preserved soft-parts: cautioning the interpretation of the shell-based ostracod record.

Siveter DJ¹, Briggs DE, Siveter DJ, Sutton MD, Joomun SC.

Author information

1: Department of Geology, University of Leicester, Leicester LE1 7RH, UK. djs@leicester.ac.uk

Abstract

Ostracod crustaceans are the most abundant fossil arthropods. The Silurian Pauline avibella gen. et sp. nov., from the Herefordshire Lagerstätte, UK, is an extremely rare Palaeozoic example with soft-part preservation. Based on its soft-part morphology, especially the exceptionally preserved limbs and presence of lateral eyes, it is assigned to the myodocopid myodocopes. The ostracod is very large, with an epipod on the fifth limb pair, as well as gills implying the presence of a heart and an integrated respiratory-circulatory system as in living cylindroleberidid myodocopids. Features of its shell morphology, however, recall halocyprid myodocopes and palaeocopes, encouraging caution in classifying ostracods based on the carapace alone and querying the interpretation of their shell-based fossil record, especially for the Palaeozoic, where some 500 genera are presently assigned to the Palaeocopida.

PMID:: 23235709
PMCID:: PMC3574317
DOI:: 10.1098/rspb.2012.2664

[Indexed for MEDLINE]

Free PMC Article

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Figure 1.

(a–l,n–t) Holotype of Pauline avibella, carapace with soft-parts (OUMNH C.29614): (a–k, n–t) ‘virtual’ reconstructions; (l) specimen in rock. The exact boundary between structures such as body and limbs, as indicated by colour changes, is somewhat arbitrary. (a) External right lateral view (stereo-pair). (b) Right lateral view (stereo-pair), valves omitted. (c) Anterior view. (d) Right lateral view (stereo-pair) of gut system. (e) Oblique ventral view of labrum and atrium oris. (f) Anterior view (stereo-pair), valves omitted. (g) Ventral view. (h) Dorsal view. (i) Ventral view (stereo-pair), valves omitted. (j) Dorsal view (stereo-pair), valves omitted. (k) Posterior view. (l) Lateral oblique section. (n–t) Oblique posterior approximately medial view of left limbs: (n) first antenna, (o) second antenna, (p) mandible, (q) first maxilla. (r) second maxilla. (s) sixth limb. (t) seventh limb. (m) Halocyprid myodocope Discoconchoecia pseudodiscophora (Rudjakov []), carapace, right lateral view (OUMNH RY.37); Recent, Sea of Japan, depth 320 m. All scale bars 1 mm. a1, first antenna; a2ba, a2en, a2ex, basipod, endopod and exopod of second antenna; a6, sixth limb; a7, seventh limb; alo, anterior lobe; an, anus; ao, atrium oris; as, adductorial sulcus; co, costa(e); cm?, contact margin structure?; ec?, epibranchial canal?; fs, finger-like structure; fu, furca; gi, gills; hl, hinge line; is, isthmus; la, labrum; le, lateral eye; lv, left valve; maba, maen, maex, basipod, endopod and exopod of mandible; mr, marginal ridge; mx1, first maxilla; mx1ba, mx1en, basipod and endopod of first maxilla; mx2, second maxilla; mx2ba, mx2ep, mx2r, basipod, epipod and ramus of second maxilla; no, node; oe, oesophagus; pg, posterior gape; ri, rostral incisure; ro, rostrum; rv, right valve; s-s, line of section through specimen (h,l); st, stomach.

A Silurian myodocope with preserved soft-parts: cautioning the interpretation of the shell-based ostracod record

Proc Biol Sci. 2013 Feb 7;280(1752):20122664.