Proc Biol Sci. 2010 May 22;277(1687):1539-44. doi: 10.1098/rspb.2009.2122. Epub 2010 Jan 27.

An exceptionally preserved myodocopid ostracod from the Silurian of Herefordshire, UK.

Siveter DJ, Briggs DE, Siveter DJ, Sutton MD.

Source

Department of Geology, University of Leicester, Leicester, UK. djs@leicester.ac.uk

Abstract

An exceptionally preserved new ostracod crustacean from the Silurian of Herefordshire, UK, represents only the third fully documented Palaeozoic ostracod with soft-part preservation. Appendages, gills, gut system, lateral compound eyes and even a medial eye with a Bellonci organ are preserved, allowing assignment of the fossil to a new genus and species of cylindroleberidid myodocope (Myodocopida, Cylindroleberididae). The Bellonci organ is recorded for the first time in fossil ostracods. The find also represents a rare occurrence of gills in fossil ostracods and confirms the earliest direct evidence of a respiratory-cum-circulatory system in the group. The species demonstrates remarkably conserved morphology within myodocopes over a period of 425 Myr. Its shell morphology more closely resembles several families of myodocopes other than the Cylindroleberididae, especially the Cypridinidae and Sarsiellidae, thus questioning the utility of the carapace alone in establishing the affinity of fossil ostracods.

PMID:: 20106847; [PubMed - indexed for MEDLINE]
PMCID:: PMC2871837

Free PMC Article

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Figure 1.

(a–k, m–r) Holotype of Nasunaris flata, carapace with soft parts: (a–c, e–k, m–r) ‘virtual’ reconstructions (a slight diagonal break across the left valve and gaps in the first antenna left exopod and right endopod represent missing data; and the exact boundary between structures such as body and appendages, as indicated by colour changes, is arbitrary); (d) specimen in rock. (a) External right lateral view, ×11. (b) Anterior view (stereo-pair) showing the eyes and first and second antennae, with valves and other features omitted, ×9.9. (c) Ventral view (stereo-pair), with right valve omitted, ×10.9. (d) Oblique posterior section, ×9.9. (e) Right lateral view (stereo-pair) of gut system, ×7. (f) Internal right lateral view (stereo-pair), with right valve omitted, ×11. (g) Anterior view (shadow-casting of valves turned off for clarity), ×9.9. (h) Anterior oblique view (stereo-pair) of eyes, ×15. (i) Dorsal view (stereo-pair), with left valve omitted, ×10.9. (j) Posterior view, ×10.9. (k) Gut contents, ×7. (m–r) Oblique posterior medial view of right limbs, ×11.5: (m) first antenna; (n) second antenna; (o) mandible; (p) first maxilla; (q) second maxilla; (r) seventh appendage. (l) Cylindroleberidid myodocopid, type-species Cylindroleberis mariae (Baird, 1850), male (Department of Zoology, Natural History Museum, London, no. 1973.159), external right lateral view; Recent, Isles of Scilly, ×30. All scale bars, 1 mm. Abbreviations: a1, first antenna; a1cb, c-bristle of first antenna; a1fb, f-bristle of first antenna; a2ba, basipod of second antenna; a2en, endopod of second antenna; a2ex, exopod of second antenna; a7, seventh appendage; am, adductor muscle area; ao, atrium oris; as, adductorial sulcus; bo, Bellonci organ; bu, bulb; cs, caudal siphon; fu, furca; gc, gut content; gi, gill; hi, position of hinge line; hp, hemipenis; is, isthmus; le, lateral eye; lv, left valve; maba, basipod of mandible; maen, endopod of mandible; maex, exopod of mandible; me, medial eye; mx1, first maxilla; mx2, second maxilla; mx2ep, epipod of second maxilla; oe, oesophagus; ri, rostral incisure; ro, rostrum; rv, right valve; st, stomach.

An exceptionally preserved myodocopid ostracod from the Silurian of Herefordshire, UK

Proc Biol Sci. 2010 May 22;277(1687):1539-1544.