70-8 Cladistic Reevaluation of Ordovician Cybelinae (Trilobita)

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

Presenting Author:

Authors:

Abstract:

Encrinuridae is a widely distributed, diverse family of trilobites known from the Ordovician through earliest Devonian, comprising four generally recognized subfamilies. One of these, Cybelinae, is known from 12 genera (Atractocybeloides, Atractopyge, Bevanopsis, Cybele, Cybellela, Cybeloides, Cybelurus, Deacybele, Lyrapyge, Paracybeloides, Sinocybele, and Stiktocybele) and 95 valid species, with a cosmopolitan Ordovician (Floian through Katian) distribution. Evolutionary relationships both within Cybelinae and with the other encrinurid subfamilies remain largely unstudied. Existing taxonomic work is mostly outdated and limited in scope, underscoring the necessity for a modern, exhaustive reevaluation of the subfamily. Fortunately, many cybelines exhibit a wide variety of complex, derived morphological features, such as complex, ordered tuberculation patterns and elaborate anterior border forms. The morphological complexity and variation found within the subfamily lend themselves to a detailed cladistic analysis, where relationships within Cybelinae are clarified. An initial stage of analysis features a 25 taxon, 43 character matrix including all well documented species of Cybeloides, Paracybeloides, and Bevanopsis, and separate, preliminary, character codings for select taxa belonging to all other genera. Initial results challenge the traditional classification of Paracybeloides as a subgenus of Cybeloides as each genus is retrieved as a separate clade. This is supported by multiple unambiguous synapomorphies, including several differences in sculpture (e.g., a decrease in the number of anterior border tubercles in species of Paracybeloides) and general morphology (e.g., the lack of inflated maculae in Cybeloides). Analyses are supported by new silicified material from the Table Cove Formation (mid-Darriwilian) of western Newfoundland. Material includes Cybelurus mirus, the type species of Cybelurus, and three new species of cybeline attributable to Lyrapyge and Atractopyge. Well preserved silicified material provides a rich source of new data on life history and morphological detail.

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

doi: 10.1130/abs/2025AM-7093

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