Wywaonymis

Wywaonymis is a genus of extinct freshwater bivalve mollusks that lived during the Carboniferous period. These marine animals were characterized by their elongated, equally bilaterally symmetrical shells, which were attached to the substrate by a short hinge. The shell morphology showed elongated oval shape, with the anterior end narrower than the posterior.

Fossil evidence suggests that Wywaonymis lived in shallow waters, likely in littoral and sublittoral zones, based on sedimentary facies and the presence of associated trace fossils. Wywaonymis shells are typically moderately to strongly inflated, indicating their position as soft-bottom dwellers.

Wywaonymis was described from the Early Carboniferous Hannington Coal Measures in western Scotland. This genus has affinities with Amelidae, also of Carboniferous origin, but is thought to belong to the subfamily Upperameleninae due to specific characters such as the ligament and the presence of cardinal and lateral teeth. The relationship among Wywaonymis and other Carboniferous categories of Vicarian bivalves is not well established.

Carboniferous sediments containing Wywaonymis are often reported from tidal flats and lower shoreface environments, indicating that the animals were likely adapted to the particular water conditions found in these areas. The stratigraphic position of Wywaonymis within the global Carboniferous fossil record suggests that these animals likely persisted from the Early Carboniferous to the Early or Middle Carboniferous, possibly crossing the global Givetian-Frasnian boundary.