Phylogenetic relationships and evolutionary history of the Paleogene genus Igorina through parsimony analysis

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doi: 10.2113/gsjfr.41.3.260
Author(s): Soldan, Dario M.; Petrizzo, Maria Rose; Premoli Silva, Isabella; Cau, Andrea
Author Affiliation(s): Primary:
Universita di Milano, Dipartimento di Scienze della Terra Ardito Desio, Milan, Italy
Museo Geologico Giovanni Capellini, Italy
Volume Title: Journal of Foraminiferal Research
Source: Journal of Foraminiferal Research, 41(3), p.260-284. Publisher: Cushman Foundation for Foraminiferal Research, Ithaca, NY, United States. ISSN: 0096-1191 CODEN: JFARAH
Note: In English. Supplemental information/data is available in the online version of this article. 67 refs.; illus., incl. 4 tables, sketch map
Summary: The evolution of planktic foraminifera in the Paleocene-Eocene time interval is characterized by a high rate of diversification after the major extinction event observed at the Cretaceous/Paleogene boundary. An accelerated speciation rate resulted in the appearance of several new genera. Phylogenetic relationships among many of genera are still poorly understood. This study investigates the origin and phylogeny of the genus Igorina, which is characterized by a thick, nonspinose and incrusted wall. Igorina appears in Subzone P3a (early late Paleocene) and disappears in Zone P11 (middle Eocene). To date, nine species have been assigned to the genus Igorina (I. pusilla, I. trichotrocha, I. tadjikistanensis, I. convexa, I. albeari, I. laevigata, I. lodoensis, I. broedermanni, and I. anapetes) based on both wall texture and morphologic similarities. However, the taxonomic identification at species level is affected by several problems, mainly those resulting from poor descriptions and illustrations of the primary type specimens of several species. This study reconstructs the phylogeny and evolution of the igorinids through cladistic analysis by applying the method of parsimony. Phylogenetic relationships of the species assigned to Igorina are determined through stratocladistic analysis by using a data matrix of 23 taxa (including key species of Acarinina), 31 morphological characters (unordered), and a stratigraphic character (ordered) mapping the first occurrence of the taxa under investigation. The matrix (Appendix 1) was processed with PAUP* 4.0b10 software by using the heuristic search option to discover the most parsimonious trees. Results suggest that I. pusilla is the first representative of the Igorina lineage, and it is followed by I. laevigata, I. convexa, and I. albeari. Morphotypes of uncertain taxonomic identification have been coded and analyzed separately as morphotypes A-F to determine their ancestor-descendant relationships and to evaluate their validity as discrete species. As the result of our analysis, two new species are formally described as I. praecarinata (=morphotype A) and I. paraspiralis (=morphotypes C, E, and F). Finally, our analysis provides evidence that I. lodoensis, I. broedermanni, and I. anapetes are more closely related to Acarinina than to Igorina and clearly belong to a different lineage.
Year of Publication: 2011
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 10 Paleontology, Invertebrate; Atlantic Ocean; Biologic evolution; Biometry; Caribbean Sea; Cenozoic; Cladistics; DSDP Site 151; DSDP Site 152; Deep Sea Drilling Project; East Pacific; Eocene; Foraminifera; Igorina; Invertebrata; Leg 143; Leg 15; Leg 198; Microfossils; Mid-Pacific Mountains; Morphology; Nicaragua Rise; North Atlantic; North Pacific; Northeast Pacific; Northwest Pacific; ODP Site 1209; ODP Site 865; Ocean Drilling Program; Pacific Ocean; Paleocene; Paleogene; Parsimony; Phylogeny; Planktonic taxa; Protista; SEM data; Shatsky Rise; Taxonomy; Tertiary; West Pacific
Coordinates: N323900 N324000 E1583100 E1583000
N182624 N182626 W1793320 W1793321
N150101 N155243 W0732435 W0743628
Record ID: 2011064946
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Abstract, Copyright, Cushman Foundation for Foraminiferal Research, Reference includes data from GeoScienceWorld, Alexandria, VA, United States