EXCEPTIONAL 3D PRESERVATION IN A TARPON-LIKE FISH FROM THE CRETACEOUS OF THE CHATHAM ISLANDS, NEW ZEALAND

We report on a large tarpon-like fish [Elopomorpha] from the Cretaceous of Pitt Island, Chatham Islands, New Zealand. The 3D-preserved specimen is the most complete and informative fossil elopomorph reported to date from the Southern Hemisphere. Features supporting elopomorph affinities include the lack of a separate retroarticular ossification on the lower jaw, and a primitively retained median gular. Affinity with the Family Megalopidae (tarpons) is indicated by the superior mouth position, large posttemporal fossae, and laterally compressed body covered in large and extensively overlapping cycloid scales. The specimen’s elongate body, high and strongly developed coronoid process on the mandible, enlarged median gular, and relatively low-profile head indicate that the Pitt Island fish represents a distinctive new taxon within megalopids. The specimen also possesses two distinctive and unusual features: a cluster of thin scale-like anamestic bones in the cheek region between the infraorbitals and preoperculum, and a continuation of the lateral line scales on a tapering lobe that extends posterior to the caudal peduncle and onto the base of the caudal fin. The nature of the exceptional 3D preservation of the specimen suggests that the carcass was subaerially exposed and ‘mummified’ prior to burial in the tuffaceous matrix. The overall morphology of the specimen indicates a fish similar in many respects to the extant tarpons Megalops atlanticus and M. cyprinoides but with a lower, more shallow head profile and a more attenuated body, along with several unique skeletal features not previously reported on megalopid fishes.