Journal of Systematic Palaeontology, Vol. 10, Issue 3, September 2012, 401–422 Application of numerical cladistic analyses to the Carnian–Norian conodonts: a new approach for phylogenetic interpretations Michele Mazzaa∗, Andrea Caub and Manuel Rigoc aDipartimento di Scienze della Terra “Ardito Desio”, Universita` degli Studi di Milano, Via Mangiagalli 34, 20133 Milano, Italy; bMuseo Geologico “Giovanni Capellini”, Alma Mater Studiorum, Universita` di Bologna, Via Zamboni 63, 40126 Bologna, Italy; cDepartment of Geosciences, University of Padova, Via Giotto 1, 35137 Padova, Italy (Received 1 June 2010; accepted 1 February 2011; printed 6 August 2012) The high intraspecific variability of conodont platform elements in the upper Carnian–lower Norian interval and the prolifer- ation of numerous species in this relatively short time have generated many problems for the understanding of Late Triassic conodont phylogeny, systematics and taxonomy. Since Late Triassic natural assemblages are still unknown, we have applied cladistic methodologies to investigate the evolution of Carnian–Norian conodont platforms and to infer more precise phylo- genetic relationships among taxa. Numerical cladistic analysis was undertaken of species belonging to the five Late Triassic genera Paragondolella, Carnepigondolella, Metapolygnathus, Epigondolella and Norigondolella. A taxon–character data matrix describing the distribution of 64 characters amongst two outgroups and 31 ingroup taxa was compiled and processed using PAUP∗ 4.1. Our analyses show the evolutionary and systematic value of certain morphological characters, and lead to a reinterpretation of the phylogenetic position of the genera considered: Metapolygnathus, Epigondolella and Norigon- dolella are monphyletic taxa, Paragondolella represents a polyphyletic assemblage of basal members of the ingroup, and Carnepigondolella a paraphyletic group including primitive forms of the Metapolygnathus and Epigondolella lineages. Our analyses also clarify the systematic position of ‘Metapolygnathus communisti B’ and confirm the existence of four new species: Carnepigondolella angulata sp. nov., Epigondolella heinzi sp. nov., Epigondolella miettoi sp. nov.and Norigondolella trinacriae sp. nov. Keywords: conodonts; cladistics; phylogeny; platforms; Carnian–Norian; Late Triassic Introduction et al. 2010 and references therein). The lower Carnian (Julian) conodont fauna is mainly characterized by relict The taxonomy and phylogeny of upper Carnian to lower Ladinian forms (e.g. Budurovignathus spp., Gladigondo- Norian conodont platform elements is rather problematic lella spp., Paragondolella spp.), together with some new due to the large number of different forms occurring in taxa belonging to the Auriformis group (Rigo 2006; Rigo this relatively short time interval. The high intraspecific et al. 2007). At the Julian/Tuvalian boundary (early/late variability that affects many conodont taxa, together with Carnian), a marked conodont mass extinction occurred the abundance of synonymous species, has prevented the (Rigo et al. 2007; Rigo & Joachimski 2010): all the relict Downloaded by [Universita di Padova] at 08:58 02 August 2012 establishment of a phylogenetic scheme for Carnian–Norian Ladinian forms disappeared and only a few species belong- conodonts. ing to the Auriformis group and to the genus Paragon- The wide proliferation of different conodont morpho- dolella persisted. After the end of this climatic pertur- types in the Tethys is most likely the consequence of bation, when arid conditions were restored in the early sudden climatic variations that took place during the late Carnian, conodonts recovered and the genus Paragondo- Carnian. The Carnian was in fact a time of biological lella rapidly radiated to give rise to several new genera: crisis for marine organisms, such as ammonoids, crinoids Carnepigondolella, Epigondolella, Metapolygnathus and and bryozoans (Simms & Ruffell 1989; Simms et al. Norigondolella. This is the last significant conodont radi- 1995), affecting carbonate platforms and their productiv- ation before the final extinction of the class Conodonta in ity. Conodonts were also affected by a strong episode of the earliest Jurassic (Palfy´ et al. 2007), and it seemingly crisis around the Julian (lower Carnian)/Tuvalian (upper produced a proliferation of a large number of morpho- Carnian) boundary when a humid climate pulse, known types and transitional forms within a relative short time as the Carnian Pluvial Event, occurred in all Triassic interval, deeply complicating the taxonomy of Late Trias- oceans (Rigo et al. 2007; Rigo & Joachimski 2010; Preto sic conodonts. ∗Corresponding author. Email: mazza [email protected] ISSN 1477-2019 print / 1478-0941 online Copyright C 2012 The Natural History Museum http://dx.doi.org/10.1080/14772019.2011.573584 http://www.tandfonline.com 402 M. Mazza et al. A traditional phenetic approach has not been able to Carnepigondolella baloghi, C. nodosa s.s., Cornudina sp. provide a complete solution to the taxonomic issues asso- nov.A of Orchard (1991a) and the genus Neocavitella.After ciated with this rapid conodont radiation, or to produce a this event the last evolutionary conodont radiation occurred complete phylogenetic model including all Carnian–Norian (Rigo et al. 2007; Rigo & Joachimski 2010). taxa. The objective of this paper is thus to use cladistic Previous studies on changes in platform morphology methods as an alternative approach to understand better during the late Carnian (Tuvalian) (Orchard 1983, 1991a, the morphological evolution of Carnian–Norian conodont b, 2007; Mazza & Rigo 2008) have revealed a series of platform elements. We believe that the application of a non- evolutionary patterns that are common to all Late Trias- parametric statistical method to investigate morphological sic conodonts (see also Kozur 1989, 2003). These trends, relationships of these taxa may provide a sounder basis for emerging cyclically in the superfamily Gondolelloidea from wider phylogenetic interpretations and allow the reinterpre- the Late Carboniferous to the Late Triassic after a biologi- tation of the systematic position of some problematic taxa. cal crisis, comprise: (a) progressive forward shifting of the The application of numerical cladistic analysis represents pit; (b) gradual shortening of the platform; (c) develop- an innovative approach to the study of conodonts evolu- ment of nodes on the platform margins and the evolution tion, since use of cladistic methodology has been almost of nodes into denticles; and (d) gradual prolongation of the neglected in this fossil group. keel behind the pit. Following these evolutionary patterns, Paragondolella polygnathiformis and P. praelindae are the The cladistic approach only two gondolelloids surviving the Julian/Tuvalian crisis, Numerical methods of cladistic analysis have been used followed by further conodont evolution in the Tuvalian only very recently to study conodont relationships and have (see also Rigo et al. 2007). These two species may be been applied only to the entire apparatus of the conodont thus considered as the most probable common ances- animal (Donoghue 2001; Zhang & Barnes 2004; Wickstrom¨ tors of the new taxa that proliferated during the late & Donoghue 2005; Donoghue et al. 2008). Carnian–early Norian. Newly arising taxa belong mainly to Unfortunately, the original structure of the Late Triassic four genera: Carnepigondolella, Metapolygnathus, Epigon- conodont apparatuses is still unknown as natural clusters dolella and Norigondolella. Following the important taxo- of Carnian–Norian conodonts have never been recovered. nomic revision of upper Triassic conodonts by Orchard Some reconstructions of the apparatuses of Late Trias- (1991a,b), studies on Carnian–Norian conodonts have sic genera have been proposed (Orchard 2005), but these increased considerably only during the last 10 years, when interpretations are debated amongst specialists since they much more interest has focused on the definition of Late are modelled on a Middle Triassic Neogondolella natural Triassic (e.g. Norian) GSSPs (Global Boundary Stratotype assemblage (Rieber 1980; Orchard & Rieber 1999). Given Section and Point). These works have improved biostrati- the uncertainty of these reconstructions we focus here on graphical knowledge of this interval by establishing several the results of a cladistic analysis of conodont P1 elements new species and investigating their possible phylogenetic (sensu Purnell et al. 2000). This alternative approach to the relationships. Here we summarize the phylogenetic hypoth- study of the phylogenetic relationships among Upper Trias- esis proposed for Tethyan conodonts: sic conodonts may be tested when better data on apparatus reconstructions become available. 1. Metapolygnathus is considered the direct descen- The application of cladistic methods to conodont plat- dant of Paragondolella (Kozur 2003). This relation- Downloaded by [Universita di Padova] at 08:58 02 August 2012 forms may help in the study of the complex palaeon- ship is suggested by Metapolygnathus praecommu- tology and biostratigraphy of conodonts since, as argued nisti, which represents a transitional form between the by Farris (1977, 1979a, b, 1980, 1982, 1983), parsimo- two genera, showing intermediate features between P. niously grouping by synapomorphy (i.e. shared derived noah, the last representative of genus Paragondolella, character states) provides a more informative classification and M. communisti (Mazza