Abstract
Among the famous Middle Pennsylvanian tetrapod fauna from Linton, Ohio, embolomeres are extremely rare and known only from three snout fragments which are referred to as the eogyrinid Leptophractus obsoletus. We describe herein a skull roof fragment from Linton that consists of the left orbital and cheek region and parts of the palate preserved in dorsal view, which belonged to a skull of approximately 100 mm length. Although diagnostic parts such as the tabular horn and the otic region are not preserved, it can be assigned to embolomeres by its attenuated, irregular dermal bone sculpture. The specimen can be interpreted most plausibly as an eogyrinid because of (1) the distinct, mostly continuous lateral lines that appear like a string of beads due to the subdued ridges on their bottom, and (2) the kinetic line between skull table and cheek in combination with the firm suture between the postorbital and intertemporal. The participation of the lacrimal in the anterior orbital margin is unusual for eogyrinids but might represent a juvenile character. Because the eogyrinid skull roof is derived from the same locality and strata as the eogyrinid L. obsoletus, we tentatively assign it to that genus and species.
Kurzfassung
Innerhalb der berühmten oberkarbonischen Tetrapodenfauna von Linton, Ohio, sind Embolomeren außerordentlich selten und bisher nur durch drei Schnauzenfragmente belegt, die dem Eogyriniden Leptophractus obsoletus zugerechnet werden. In dieser Arbeit beschreiben wir ein teilweise erhaltenes Schädeldach aus Linton, das aus der linken Orbita- und Wangenregion sowie Teilen des Gaumens in dorsaler Erhaltung besteht und zu einem Schädel von etwa 100 mm Länge gehörte. Obwohl diagnostische Bereiche wie das Tabularhorn und die Region der Ohrkapsel nicht erhalten sind, kann das Exemplar aufgrund seiner abgeschwächten, unregelmäßigen Knochenskulptur zu den Embolomeren gerechnet werden. Sehr wahrscheinlich gehört das Exemplar zu einem Eogyriniden, da es (1) deutlich ausgeprägte, zumeist kontinuierliche Furchen für die Seitenlinien aufweist, die aufgrund der niedrigen Leisten auf ihrem Boden einer Perlenschnur ähneln, und (2) eine bewegliche Verbindung zwischen Schädeldach und Wange in Kombination mit einer festen Sutur zwischen Postorbitale und Intertemporale aufweist. Die Beteiligung des Lacrimale am vorderen Rand der Orbita ist ungewöhnlich für Eogyriniden, kann aber als juveniles Merkmal gedeutet werden. Weil das hier beschriebene Eogyriniden-Schädeldach aus der gleichen Lokalität und derselben Schicht wie der Eogyrinide L. obsoletus stammt, wird es provisorisch zur gleichen Gattung und Art gestellt.
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Acknowledgements
We are indebted to the two reviewers, Jenny Clack and Marcello Ruta, and the editors Mike Reich and Jörg Fröbisch, whose comments greatly improved the manuscript. We also thank Markus Brinkmann for producing the silicone cast and Carola Radke for taking the photographs.
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Handling editor: Jörg Fröbisch.
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Witzmann, F., Werneburg, R. & Milner, A.R. A partial skull roof of an embolomere from Linton, Ohio (Middle Pennsylvanian) and its phylogenetic affinities. PalZ 91, 399–408 (2017). https://doi.org/10.1007/s12542-017-0374-4
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DOI: https://doi.org/10.1007/s12542-017-0374-4