Data from: Taxonomic and evolutionary pattern revisions resulting from geometric morphometric analysis of Pennsylvanian Neognathodus conodonts, Illinois Basin
Zimmerman, Alex N.
Johnson, Claudia C.
Polly, P. David
Published Jul 03, 2018 on Dryad.
Cite this dataset
Zimmerman, Alex N.; Johnson, Claudia C.; Polly, P. David (2018). Data from: Taxonomic and evolutionary pattern revisions resulting from geometric morphometric analysis of Pennsylvanian Neognathodus conodonts, Illinois Basin [Dataset]. Dryad. https://doi.org/10.5061/dryad.1fm52vv
Conodont fossils are highly valuable for Paleozoic biostratigraphy and for interpreting evolutionary change, but identifying and describing conodont morphologies, and characterizing gradual shape variation remain challenging. We used geometric morphometrics (GM) to conduct the first landmark-based morphometric analysis of the biostratigraphically useful conodont genus Neognathodus. Our objective is to assess whether previously defined morphotype groups are reliably distinct from one another. As such, we reevaluate patterns of morphologic change in Neognathodus P1elements, perform maximum likelihood tests of evolutionary modes, and construct novel, GM-based biozonations through a Desmoinesian (Middle Pennsylvanian) section in the Illinois Basin. Our GM results record the entire spectrum of shape variability among Neognathodus morphotypes thus alleviating the problem of documenting and classifying gradual morphologic transitions between morphotypes. Statistically distinct GM groups support previously established classifications of N. bassleri, N. bothrops, and N. roundyi. Statistically indistinct pairs of GM groups do not support literature designations of N. medadultimus and N. medexultimus, and N. dilatus and N. metanodosus, and we synonymize each pair. Maximum likelihood tests of evolutionary modes provide the first statistical assessment of Neognathodus evolutionary models in the Desmoinesian. The most likely evolutionary models are an unbiased random walk or a general random walk. We name four distinct biozones through the Desmoinesian using GM results and these align with previous biozonation structure based on the Neognathodus Index (NI) illustrating that Neognathodus-based biostratigraphic correlations would not change between GM or NI methods. The structural similarity between both biozonations showcases that determining GM-based biozones is not redundant, as this comparison validates using landmark-based GM work to construct viable biozonations for subsequent stratigraphic correlations. Although this study is limited to the Illinois Basin, our quantitative methodology can be broadly applied to additional genera to test taxonomic designations, interpret statistically-robust evolutionary patterns, and construct valid biozones for this significant chordate group.
Supplementary Figure 1 (Neognathodus plate)
Figure 1. Images of type specimens for synonymized Neognathodus species N. medadultimus/N. medexultimus and N. dilatus/N. metanodosus. Pairs are synonymized here to N. medadultimus and N. dilatus, respectively. All images are re-illustrated from previous studies. Scale bar represents one mm. Conodont element identification is fol¬lowed by repository number (if available) and photo reference, stratigraphic unit and the county and state location. See README file for more specific details.
Supplementary Table 1. Table showing the stratigraphic distribution of Neognathodus specimens selected to test morphotype group affinities. Specimens were chosen between multiple stratigraphic boundaries. For example, to select the 30-specimen sample of N. bassleri, 27 N. bassleri specimens were chosen from the Perth Limestone Member, two were chosen from the Mecca Quarry Shale and Velpen Limestone members, and one was chosen from the Alum Cave Limestone Member. LS = limestone, SH = shale and Mbr = member. The number of specimens chosen from each unit is proportional to the total number of morphotype group occurrences in that unit.
Supplementary Table 2 (Total occurrences of Neognathodus)
Supplementary Table 2. Summary table showing the number of occurrences of each Neognathodus morphotype group in all examined stratigraphic intervals. Data are compiled for six previous studies (Brown et al. 1991; Rexroad et al. 1996; Rexroad et al. 1998; Rexroad et al. 2001; Brown and Rexroad 2009; Brown et al. 2016).
Systematic Paleontology section that official synonymizes Neognathodus the species pairs of N. medadultimus and N. medexultimus to N. medadultimus, and and N. dilatus and N.metanodosus to N. dilatus. This synonymy is based on our geometric morphometric results that show there is no statistically significant shape difference between the species pairs of N. medadultimus/N. medexultimus and between N. dilatus/N. metanodosus.
Additional References for Systematic Paleontology
This document provides full references that are exclusively cited in the Systematic Paleontology section of this paper. These references were not cited in the main paper text, and therefore are not a part of the main reference list.