Comparing phylogenetics and linear morphometrics to solve the generic assignment ofParabolinella?triarthroidesHarrington (Trilobita, Olenidae)

Abstract

Abstract.-The use of different methodological approaches together with an exhaustive qualitative study has helped to recognize important morphological traits to distinguish species in a systematic and phylogenetic framework. Parabolinella triarthroides Harrington, 1938 was described based on two cranidia from the Quebrada de Coquena, Purmamarca, Jujuy province. The generic assignment of P. triarthroides has been questioned by a phylogenetic analysis, which resolves this species as the sister group of Bienvillia Clark, 1924. To explore the generic assignment of this species, a revision of the type material, plus a morphometric analysis including specimens of Parabolinella Brøgger, 1882 and Bienvillia were performed. In addition, the original matrix used in the published phylogeny was reviewed and enlarged, including more species of Bienvillia. Continuous characters were coded in different ways in order to compare how they could affect the ordering of specimens and their phylogenetic relationships. Finally, both methodologies were compared, especially in regard to the behavior of the quantitative characters included in the analyses. From the combined analyses, it is shown that similarities between the cranidium of P. triarthroides and all other Parabolinella species are true homologies instead of a by-product of evolutionary convergence. Therefore, P. triarthroides should be considered a member of this genus. Finally, this study demonstrates that the best strategy for solving systematic problems in groups where the morphological variation is the only source of information (i.e., fossil taxa without living representatives) is the implementation of an integrative approach, combining different methodological techniques and a good description of specimens.

First cladistic analysis of the trilobite family Olenidae from the Furongian and Ordovician

“…Prevosti ; Hopkins ; Mannion et al . ; Monti & Confalonieri ). Different strategies were used to code these quantitative partitions: (1) as discrete and (2) as continuous variables (Supinfo S1).…”

“…Goloboff et al 2006;Hornung-Leoni & Sosa 2008;Pereyra & Mound 2009;de Bivort et al 2010;Escapa & Catalano 2013;Mongiardino Koch et al 2015a) especially in fossil taxa, in which morphological variation is the only source of information (e.g. Prevosti 2010;Hopkins 2011;Mannion et al 2013;Monti & Confalonieri 2017). Different strategies were used to code these quantitative partitions: (1) as discrete and (2) as continuous variables (Supinfo S1).…”

“…Moreover, they have proved to be useful in fossil taxa, in which morphological variation is the only source of information (e.g. Prevosti 2010; Abe & Lieberman 2012;Escapa & Catalano 2013;Mannion et al 2013;Monti & Confalonieri 2017).…”

A phylogenetic approach to the study of the evolution of Hypermecaspididae (Olenida, Trilobita)

“…Hopkins 2011; Mannion et al . 2013; Monti & Confalonieri 2017, 2019). The continuous characters were coded as medians because they are less affected by the extreme values in the distribution frequencies.…”

“…2001; Sundberg 2004; Paterson & Edgecombe 2006; Karim 2008; Lee et al . 2008; Hopkins 2011, 2019; Monti & Confalonieri 2013, 2017, 2019; Bignon & Crônier 2014; Oudot et al . 2019).…”