101-15 Phylogeny and Systematics of Calymenina (Trilobita)

Session: Paleontology, Biogeography/Biostratigraphy & Phylogenetic/Morphological Patterns

Presenting Author:

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Abstract:

Calymenina Swinnerton, 1915, is a suborder of trilobites with generally cosmopolitan distribution, ranging from the earliest Tremadocian to the middle Givetian. Traditionally composed of five families, the phylogenetic structure of the suborder has never properly been explored. Here, we present an extensive phylogenetic analysis to resolve relationships between families, test the monophyly of the different groups, and to explore topology within each clade. Four distinct cladistic analyses, performed under both equal and implied weighting were carried out, including 239 species distributed among 56 genera. One analysis focuses on the basal families Bavarillidae Sdzuy, 1957, “Pharostomatidae" Hupé, 1953, and Bathycheilidae Přibyl, 1953, and the relationships between Calymenina families, while separate analyses were carried out to explore the ingroup structure of Calymenidae Burmeister, 1843, Homalonotidae Chapman, 1890, and Reedocalymenidae Hupé, 1955. Following previous work, the alokistocarid Elrathia Walcott, 1924, and the eulomids Euloma Angelin, 1854 & Proteuloma Sdzuy, 1958, were used as outgroups. The stem of Calymenina is formed of several small opisthoparian clades. Bavarillidae and Bathycheilidae have been retrieved as monophyletic, while the traditional family “Pharostomatidae” appears to be paraphyletic. The group including Prionocheilus Rouault, 1847 & Thulincola Tripp, 1962 is reclassified as Prionocheilidae fam. nov., while that gathering Eulomina Růžička, 1931 and Holoubkocheilus Mergl, 1994 is assigned to Eulominidae Vaněk 1965. All proparian taxa —Homalonotidae, Calymenidae and Reedocalymenidae — form a clade. The monophyly of Homalonotidae, investigated for the first time, is confirmed. Similarly, all three of its traditional subfamilies — Eohomalonotinae Hupé, 1955, Kerfornellinae Henry, 1980, and Homalonotinae Chapman, 1890 — are recovered as monophyletic. The stem of the family consists of the previously ambiguous genus Platycoryphe Foerste, 1919, now formally assigned to Homalonotidae. Traditionally interpreted as the paraphyletic stem of Calymenidae, Reedocalymenidae, elevated to familial rank, was retrieved as a clade. Three monophyletic subfamilies are recognized: Colpocoryphinae Hupé, 1955, Pradoellinae subfam. nov., and Reedocalymeninae Hupé, 1955. Colpocoryphe Novák in Perner, 1918, and Calymenella Bergeron, 1890, genera of disputed affinity, are interpreted as derived Reedocalymenidae. Subjected for the first time to a cladistic analysis, Calymenidae is recovered as monophyletic and sister to Reedocalymenidae. A basal new subfamily is recognized, Metacalymeninae subfam. nov. As suspected in previous studies, Flexicalymeninae Siveter, 1977, is paraphyletic and forms the stem of a clade including derived Calymeninae genera.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10986

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