A late Eocene rhinochimaeroid egg capsule from marine coastal strata of British Columbia, Canada

A new fossil chimaeroid egg capsule of the ichnogenus Vaillantoonia (previously designated as Chimaerotheca), V. jonasoni, is described from marine lower Carmanah Group strata at Botanical Beach, along the West Coast of Vancouver Island, British Columbia, Canada. According to foraminifera biostratigraphy and strontium isotope dating it is late Eocene (latest Priabonian) in age. The three dimensionally preserved fossil is about 220 mm long and 80 mm wide. The elongated capsule shows a spindle-shaped central body with a constriction at the anterior end that tapers into a spatula-shaped beak. At the posterior end is a long and slender tail that broadens basally. The wing-like lateral membrane has numerous pronounced and narrow ribs (costae) that split in a V-shape.

The producer fish of V. jonasoni is unknown, since no associated skeletal or dental remains have been found. However, the elongated capsule shape and the number and shape of the membrane ribs are most similar to egg capsules of extant longnose chimaeras (Rhinochimaeridae) suggesting a rhinochimaerid-like fish with a “long” nose, in comparison to other modern chimaeroid capsules and their beak shapes.

Following earlier discoveries of V. alaskana (middle Oligocene, Alaska), V. sp. (Oligocene, Washington), and V. sp. (late Eocene, Oregon), which all show rhinochimaerid egg capsule features, this is the fourth Paleogene chimaeroid egg capsule discovered from the Pacific Northwest. All four fossils have in common that they were fossilized in tectonic foreland basins in bathyal water depths, which perfectly correlate with the known bathyal habitats and nesting sites of extant rhinochimaerids.