The leptolepid fish Cavenderichthys talbragarensis (Woodward, 1895) from the Talbragar Fish Bed (Late Jurassic) near Gulgong, New South Wales

Leptolepis" talbragarensisWoodward, 1895, is the most common fish species in the Talbragar Fish Bed near Gulgong, New South Wales. The genus Cavenderichthys Arratia, 1997, has this species as its type. The three species originally proposed by Woodward (1895) for "Leptolepis" are a single species. A detailed comparison of Cavenderichthys talbragarensiswith members of the genus Leptolepis, and also with the Late Jurassic forms Tharsis dubius and Leptolepides sprattiformis, indicates that Cavenderichthys talbragarensis is most closely related to Late Jurassic members of the Family Leptolepididae. Analysis of zircons for geochronology showed that the sediment just below the richest fish layer has a youngest component of 151.55 ± 4.27 Ma, corresponding to the Kimmeridgian Stage of the Late Jurassic. Thin sections of the upper prolific fish layer show preservation in tuffaceous sediments, indicating that the fish population was killed by ash falls of felsic tuff that filled the pond they inhabited. INTRODUCTION Fossil fishes were first discovered at Talbragar about 30 km northeast of Gulgong by Arthur Lowe of Wilbertree, NSW in 1889 (Woodward 1895). Later, many specimens were collected by Charles Cullen, the collector of fossils for the NSW Mines Department. This material is now in the Australian Museum, Sydney, and the NSW Department of Mineral Resources. Associated with the fishes is abundant plant material, first described by Walkom (1921), then re-examined and classified by White (1981). Some undescribed insect remains are also housed in the Australian Museum, Sydney. Woodward (1895) described a representative selection of different fossil fishes that had been sent to London in 1890. He considered that the assemblage was of Jurassic age, despite an original field assessment of the age as Triassic, made by W. Anderson of the Geological Survey of NSW. The vast majority of the fishes in the material belong to Leptolepis talbragarensisWoodward, 1895, which was cited by Long (1991) as "the first appearance of the teleosteans in the Australian fossil record". Other fishes include one species of palaeoniscid, Coccolepis australis (Woodward, 1895), and the holosteans Archaeomaene tenui Woodward, 1895, Madariscus robustus Wade, 1941, Aphnelepis australis Woodward, 1895, Aetheolepis mirabilisWoodward, 1895, and Uarbryichthys latusWade, 1941. Interest in Leptolepis talbragarensis is due largely to its early teleostean features. Nybelin (1974) suggested that L. talbragarensis should be excluded from the family Leptolepididae Agassiz, 1833-44. This was based partly on his own observations, but also on the work of Cavender (1970) who compared coregonines and other salmonids with some of the earliest known teleosts, including L. talbragarensis. Arratia (1997) erected a new genus, Cavenderichthys, with talbragarensis as the type species, on the basis of material from the Natural History Museum, London, the Field Museum of Natural History, Chicago, and the Swedish Museum of Natural History, but she did not have access to the vast amount of material available in Australia. The Talbragar site has revealed the best-preserved Jurassic fish in Australia. The outcrop now is very poor, as so much material has been removed in the past and it is now in a paddock used for grazing. The age has been difficult to confirm because there is no control of stratigraphy as the relationship to surrounding rocks is unclear. Previously, no volcanic rocks had been identified to be dated, and palynology is impossible because of the highly oxidised nature of the rocks. The assemblage of fossil fishes has been thought to indicate an Upper Jurassic age (Long 1991), but early workers suggested a Middle Jurassic age, for example Hind and Helby (1969) who suggested Early to Middle Jurassic based on palynology of the Purlawaugh Formation, within which the Fossil Fish Bed occurs. The site is interpreted as a mass kill site with a longitudinal extent of possibly 200 metres. The upper layer contains a high concentration of extremely well preserved fossil fish, while the layer below, probably less that one metre thick, has scattered fish throughout, DOI: 10.18195/issn.0312-3162.23(1). 2006.043-076