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A Phylogenetic Appraisal of Pachycormus bollensis: Implications for Pachycormiform Evolution
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
2012 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

The Pachycormiformes were a successful group of stem-teleosts. Although they persisted for more than 100 million years in the Mesozoic seas and occupied a significant space of the ecosystem, little is known about this most diverse group. One of the earliest pachycormiformes is the lower Jurassic Pachycormus bollensis.

A reconstruction of the phylogeny with the early P. bollensis together with more derived and earlier studied species has yielded important information about the relationships within the group. Both a parsimony analysis and a Bayesian analysis were performed. Three exceptionally complete specimens of P. bollensis from the Holzmaden-locality were used for the study. The resulting trees strongly supported pachycormiform monophyly. Three major ecomorphological clades were returned from the analyses: the filter-feeders, hyper carnivores and a more generalist predator radiation that included P. bollensis. Despite, node support within the pachycormiformes are generally weak. The tooth-structure and the phylogenetic position of P. bollensis might indicate an intermediate grade between the filter-feeders and the hyper carnivores.

Abstract [sv]

Pachycormiformer var en mycket framgångsrik ordning utav stam-teleoster. Trots att de överlevde i mer än 100 miljoner år i de Mesosoiska haven och erövrat ett flertal olika platser i ekosystemet, är denna mågfacetterade grupp som helhet tämligen okänd. Pachycormus bollensis från yngre jura är en av de tidigste arterna i denna grupp.

En fylogenetiskt rekonstruktion av den tidiga P. bollensis tillsammans med yngre, mer utvecklade arter kan ge viktig information om släktskapen inom gruppen. En parsimonisk analys och en Bayesian analys utfördes. Tre exceptionellt bevarade exemplar av Pachycormus bollensis från Holzmaden användes i studien. Resultatet visar på ett stark monofyletiskt sammanband inom pachycormiformerna. Båda analyserna visade robusta resultat för tre övergripande grupper; filtrerare, karnivorer och en mer generell predator linje som inkluderar P.  bollensis. Dock hade de interna släktskapen inom varje större grupp svagt stöd. Tand-stukturen tillsammans med den fylogenetiska placeringen av P. bollensis kan tyda på en intermediär grupp mellan filterarna och karnivorerna.

Place, publisher, year, edition, pages
2012. , 42 p.
, Självständigt arbete i geovetenskap, 31
Keyword [en]
Pachycormus bollensis, pachycormiformes, parsimony analysis, Bayesian analysis, Holzmaden
National Category
Other Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-177374OAI: diva2:540806
Educational program
Bachelor Programme in Earth Science
2011-06-01, Hörsalen, Sveriges Geologiska Undersökning (SGU), Uppsala, Villavägen 18, Uppsala, 11:00 (English)
Life Earth Science
Available from: 2012-07-12 Created: 2012-07-11 Last updated: 2012-07-12Bibliographically approved

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