Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes
2016 (English)In: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 36, no 5, e1206022Article in journal (Refereed) Published
The Early Jurassic (Toarcian) actinopterygian Pachycormus is a basal taxon within Pachycormiformes, a Mesozoic marine neopterygian radiation that evolved an extreme ecomorph divergence between hyperspecialized billfish-like' macrocarnivores and gigantic suspension feeders, including the largest fish of all time. Current phylogenies place Pachycormus as an early member of the suspension-feeding lineage; however, species disparity renders character states uncertain and potential exists for considerable intraspecific variability. Given its importance for resolution of pachycormiform phylogenetic topology, we comprehensively reassessed Pachycormus fossils housed in collections across Europe and found that the proportional traits traditionally used to discriminate between species are actually consistent with an ontogenetic size morphocline. Our cladistic analyses further show that the monotypic senior synonym, Pachycormus macropterus, is a wildcard that manifests a mosaic of transitional states. This has significant implications for hypothesized Toarcian marine vertebrate provincialism because P. macropterus had a ubiquitous Boreal Tethyan distribution. Moreover, our tree-based palaeobiogeographical optimizations infer that the western Tethyan region was a pachycormiform dissemination center, with global dispersals occurring through transoceanic migration and invasion of epeiric basins.Citation for this article: Wretman, L., H. Blom, and B. P. Kear. 2016. Resolution of the Early Jurassic actinopterygian fish Pachycormus and a dispersal hypothesis for Pachycormiformes. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1206022.
Place, publisher, year, edition, pages
2016. Vol. 36, no 5, e1206022
IdentifiersURN: urn:nbn:se:uu:diva-305928DOI: 10.1080/02724634.2016.1206022ISI: 000384029300020OAI: oai:DiVA.org:uu-305928DiVA: diva2:1046332