70-7 Phylogeny and Systematics of the Ordovician Reedocalymenid Trilobites

Session: Paleontology, Biogeography/Biostratigraphy & Phylogenetic/Morphological Patterns (Posters)

Presenting Author:

Authors:

Abstract:

Among trilobites, Reedocalymenidae Hupé, 1955, contains emblematic Ordovician Gondwanan genera such as Neseuretus Hicks, 1873, Colpocoryphe Novák in Perner, 1918, Pradoella Hammann, 1977, and Vietnamia Kobayashi, 1960. The group has traditionally been interpreted as a basal, possibly paraphyletic, subfamily of Calymenidae Milne Edwards, 1840. Despite its paleogeographical importance, reedocalymenid phylogenetic structure has rarely been explored, and none of the previous works tested its monophyly. Here, we present an extensive phylogenetic analysis to resolve relationships between genera, test the monophyly of the group, and to explore relationships with other calymenoidean taxa. Cladistic analyses, performed under both equal and implied weighting, include 11 genera and 63 species of Reedocalymenidae, and 14 genera and 44 species with non-reedocalymenid calymenoidean affinities, selected from Bavarillidae Sdzuy, 1957, Pharostomatidae Hupé, 1953, Bathycheilidae Přibyl, 1953, Homalonotidae Chapman, 1890 and Calymenidae. Following previous works exploring the origin of Calymenina Swinnerton, 1915, the alokistocarid Elrathia Walcott, 1924, and the eulomids Euloma Angelin, 1854, and Proteuloma Sdzuy, 1958, were used as outgroups. Reedocalymenidae, elevated to familial rank, is recovered as the monophyletic sister taxon of Calymenidae. Reedocalymenidae can be subdivided into three monophyletic subfamilies: Colpocoryphinae Hupé, 1955, Pradoellinae subfam. nov., and Reedocalymeninae Hupé, 1955. The results clarify the phylogenetic position of several genera of previously uncertain affinity. Colpocoryphe, Calymenella Bergeron, 1890, Pradoella and Neseuretus are confirmed as members of Reedocalymenidae. Most genera in the family are recovered as monophyletic. The monophyly of Aristocalymene Turvey, 2005, remains ambiguous, and the traditional species of Neseuretus form a paraphyletic grade at the base of the family, with species resolved on the stem of each subfamily. Finally, a group of taxa from Ibero-Armorica that have in the past been assigned to Neseuretus form a clade that is recognized as Synhomalonotus Pompeckj, 1898. The resulting topology reflects strong paleogeographic patterns, with Pradoellinae and Colpocoryphinae characteristic of the north-western gondwanan margin, and Reedocalymeninae distributed on South China and related terranes near the eastern margin of the continent.

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

doi: 10.1130/abs/2025AM-10914

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