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| Paleocanna tentaculum Ramirez-Guerrero, Alghaled, Bateman, Cournoyer & Cameron, 2026 |
Abstract
The fossil record of medusozoan cnidarians is relatively sparse and, in some cases, contentious. Here, we describe a new genus and species of a well-preserved, soft-bodied, tubicolous polyp, Paleocanna tentaculum n. gen. n. sp., from the Upper Ordovician (Katian) Neuville Formation in Québec. These fossils, preserved as carbonaceous compressions, were found in association with typical shelly assemblages. Fifteen slabs of shaly limestone containing ~ 135 specimens of Paleocanna tentaculum n. gen. n. sp. were examined. Individual polyps occupied upright tubes, which occur either solitarily or in clusters. Some tubes exhibit a striated periderm near their base. The polyp is elongated, with a rounded aboral end and a consistent ring of tentacles protruding distally from the tube. A phylogenetic analysis of 69 taxa and 236 discrete morphological characters indicated that the species is more closely related to the extant crown group than it is to the other stem-group medusozoans, e.g., conulariids and carinachitids. The uniform orientation of specimens on single slabs suggests rapid burial. Paleocanna tentaculum n. gen. n. sp. represents an exceptionally preserved member of an Ordovician deposit exhibiting Burgess Shale-type soft-tissue preservation.
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| Paleocanna tentaculum n. gen. n. sp., holotype, MPEP713.4. (1) General view of the organism taken under cross-polarized light; accompanying line drawing illustrates the outline of the tube and tentacles. (2) Detail of the left set of tentacles. (3) Detail of the basal part of the tube. (4) Detail of the tube. Scale bars = 1 cm (1, 3), 0.5 cm (2, 4). |
Systematic paleontology
Phylum Cnidaria Verrill, Reference Verrill1865
Subphylum Anthozoa Ehrenberg, Reference Ehrenberg1834
Genus Paleocanna new genus
Etymology: Paleocanna: palaios, meaning old or ancient, plus canna, meaning flute or pipe.
Paleocanna tentaculum new species
Diagnosis: Cylindrical tubicolous periderm with fine, parallel, transverse annulations; polyp with anterior tentacle crown extending from aperture.
Occurrence: Upper Neuville Formation of the Saint Lawrence Lowlands of Québec, Canada (Clark, Reference Clark1959).
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| Interpretive drawings of Paleocanna tentaculum n. gen. n. sp. as living organisms. (1) Oral view showing a circle of tentacles. (2) Lateral perspective of the tube, highlighting the tube aperture and annular striations. (3) Depiction of individuals living in single tubes, as well as clusters of two or three tubes attached together. |
Greta Ramirez-Guerrero, Huda Alghaled, Louis-Philippe Bateman, Mario Cournoyer and Christopher B. Cameron. 2026. Thecate stem medusozoan polyp from the Upper Ordovician of Québec. Journal of Paleontology. First View. DOI: doi.org/10.1017/jpa.2025.10211 [13 February 2026]
