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The fossil wonders of the Silurian Eramosa Lagerstätte of Canada : the jawed polychaete faunas

Härling, Jesper LU (2012) In Dissertations in Geology at Lund University GEOX01 20111
Department of Geology
Abstract
The Silurian Eramosa Lagerstätte in Ontario, Canada, is represented by three distinguished biotas (1 to 3) with exceptionally well preserved fossils. In this study, the jawed polychaete fauna is described and discussed for the first time, on the basis of scolecodonts and jaw apparatuses, recovered from Biota 1 and 3. One new paulinitid species, Kettnerites sp. a, is described from a wealthy collection of specimens recovered through acid digestion of rocks from the locality Park Head (comprising Biota 1), the strata of which were probably formed in very shallow, possibly lagoonal environments. The abundant and monospecific material allowed confident reconstruction of the full dorsal maxillary apparatus and the new taxon is compared to... (More)
The Silurian Eramosa Lagerstätte in Ontario, Canada, is represented by three distinguished biotas (1 to 3) with exceptionally well preserved fossils. In this study, the jawed polychaete fauna is described and discussed for the first time, on the basis of scolecodonts and jaw apparatuses, recovered from Biota 1 and 3. One new paulinitid species, Kettnerites sp. a, is described from a wealthy collection of specimens recovered through acid digestion of rocks from the locality Park Head (comprising Biota 1), the strata of which were probably formed in very shallow, possibly lagoonal environments. The abundant and monospecific material allowed confident reconstruction of the full dorsal maxillary apparatus and the new taxon is compared to previously known, approximately coeval ones from other regions. Attempts at finding evidence of jaw moulting for Kettnerites sp. a were inconclusive; similar to a previous study from the Silurian of Gotland, Sweden, no unambiguous evidence for distinct size frequency classes was revealed. In addition to the Park Head collection, bedding plane material from the locality Wiarton (comprising Biota 3) revealed two other taxa; Kettnerites sp. b and Oenonites cf. curvidens. The strata at Wiarton have been interpreted as representing environments with good water circulation and open marine conditions. Based on their relative abundance, jaw bearing polychaetes apparently played a significant role in the Silurian marine biotas that are currently preserved in the Eramosa Lagerstätte and this study provides a fuller picture of this lagerstätte. Moreover, the results reinforce the fact that different polychaete species had variable environmental preferences during the Silurian and that Oenonites and Kettnerites formed two of the most common and widely distributed genera. (Less)
Abstract (Swedish)
I södra Kanada finns ett område med mängder av unikt välbevarade fossil från silurperioden (444-416 miljoner år sedan). I berglager från det så kallade Eramosaområdet har nu omkring 425 miljoner år gamla fossila rester efter havsborstmaskar hittats. Eftersom dessa djur består av mjuka vävnader som snabbt bryts ner efter döden så är det framför allt deras käkar, eller scolecodonter, som bevaras som fossil. Till skillnad från maskkroppen består dessa nämligen av ett motståndskraftigt material som inte bryts ner så lätt. Berglagren i Eramosaområdet, där detta material har hittats, har bildats i tre olika miljöer.

Det här examensarbetet baseras på material som har lösts ut från prov av kalksten insamlade på lokalen Park Head, samt fossil... (More)
I södra Kanada finns ett område med mängder av unikt välbevarade fossil från silurperioden (444-416 miljoner år sedan). I berglager från det så kallade Eramosaområdet har nu omkring 425 miljoner år gamla fossila rester efter havsborstmaskar hittats. Eftersom dessa djur består av mjuka vävnader som snabbt bryts ner efter döden så är det framför allt deras käkar, eller scolecodonter, som bevaras som fossil. Till skillnad från maskkroppen består dessa nämligen av ett motståndskraftigt material som inte bryts ner så lätt. Berglagren i Eramosaområdet, där detta material har hittats, har bildats i tre olika miljöer.

Det här examensarbetet baseras på material som har lösts ut från prov av kalksten insamlade på lokalen Park Head, samt fossil som identifierats direkt på skifferytor från Wiarton. Detta material har sedan undersökts och beskrivits för att förstå vilka arter som en gång fanns i området. Det är första gången som faunan av havsborstmaskar har undersökts i närmare detalj och specifikt baserat på scolecodonter och mer eller mindre kompletta käkapparater.

Bland materialet från Park Head har en ny art hittats, beskrivits och namngivits till Kettnerites sp. a. Tack vare den stora mängd fossil som hittats i Park Head så har det varit möjligt att återskapa hur hela käkapparaten såg ut, under tiden arten levde. Eftersom inga andra arter hittats på denna lokal så var det möjligt att även studera variationer inom arten. Det har även undersökts om käkarna byttes ut, eller ömsades, ut under djurets tillväxt.

Resultaten visar inga entydiga bevis för att käkarna ömsades , snarare tyder det mesta på att samma käkar växte kontinuerligt under djurets levnadstid. Förutom den nya arten så har även två andra arter hittas, Kettnerites sp. b och Oenonites cf. curvidens, bland materialet från Wiarton. Fyndet av Kettnerites och Oenonites, stärker uppfattningen att dessa släkten var två av de vanligaste och mest utbredda under silurtiden. (Less)
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author
Härling, Jesper LU
supervisor
organization
alternative title
Fossila underverk från den siluriska Eramosa Lagerstätte i Kanada : de käkbärande polychaeterna
course
GEOX01 20111
year
type
M2 - Bachelor Degree
subject
keywords
scolecodonter, polychaeter, silur, palaeobiogeography, palaeoecology, Silurian, Eramosa Lagerstätte, scolecodonts, polychaete faunas, paleoekologi, paleobiogeografi.
publication/series
Dissertations in Geology at Lund University
report number
325
language
English
id
3351068
date added to LUP
2013-01-08 11:51:13
date last changed
2015-01-08 03:56:45
@misc{3351068,
  abstract     = {The Silurian Eramosa Lagerstätte in Ontario, Canada, is represented by three distinguished biotas (1 to 3) with exceptionally well preserved fossils. In this study, the jawed polychaete fauna is described and discussed for the first time, on the basis of scolecodonts and jaw apparatuses, recovered from Biota 1 and 3. One new paulinitid species, Kettnerites sp. a, is described from a wealthy collection of specimens recovered through acid digestion of rocks from the locality Park Head (comprising Biota 1), the strata of which were probably formed in very shallow, possibly lagoonal environments. The abundant and monospecific material allowed confident reconstruction of the full dorsal maxillary apparatus and the new taxon is compared to previously known, approximately coeval ones from other regions. Attempts at finding evidence of jaw moulting for Kettnerites sp. a were inconclusive; similar to a previous study from the Silurian of Gotland, Sweden, no unambiguous evidence for distinct size frequency classes was revealed. In addition to the Park Head collection, bedding plane material from the locality Wiarton (comprising Biota 3) revealed two other taxa; Kettnerites sp. b and Oenonites cf. curvidens. The strata at Wiarton have been interpreted as representing environments with good water circulation and open marine conditions. Based on their relative abundance, jaw bearing polychaetes apparently played a significant role in the Silurian marine biotas that are currently preserved in the Eramosa Lagerstätte and this study provides a fuller picture of this lagerstätte. Moreover, the results reinforce the fact that different polychaete species had variable environmental preferences during the Silurian and that Oenonites and Kettnerites formed two of the most common and widely distributed genera.},
  author       = {Härling, Jesper},
  keyword      = {scolecodonter,polychaeter,silur,palaeobiogeography,palaeoecology,Silurian,Eramosa Lagerstätte,scolecodonts,polychaete faunas,paleoekologi,paleobiogeografi.},
  language     = {eng},
  note         = {Student Paper},
  series       = {Dissertations in Geology at Lund University},
  title        = {The fossil wonders of the Silurian Eramosa Lagerstätte of Canada : the jawed polychaete faunas},
  year         = {2012},
}