Plesiosaur remains from Cretaceous high-latitude non-marine deposits in southeastern Australia

Abstract

Australian plesiosaur remains are common although currently poorly documented. At present, most of the described material is derived from extensive Early Cretaceous epicontinental marine rocks in central and northeastern Australia (Kear, 2003). In recent years, however, a number of fragmentary specimens have been recovered from Lower Cretaceous non-marine sequences in the southeastern part of the continent (Fig. 1). The fossil-producing strata are included within the middle Valanginian– early Albian Wonthaggi (Gippsland Basin) and Eumeralla (Otway Basin) formations, southern Victoria, and early–middle Albian Griman Creek Formation (Surat Basin), Lightning Ridge, New South Wales/ Surat region, Queensland. Interestingly, these units were deposited in an Early Cretaceous high-latitude zone (60–80º S), subject to highly seasonal, cool to cold conditions and months of winter darkness near the southern pole. Fossils recorded include a diverse range of freshwater/ terrestrial vertebrates, non-marine invertebrates, and plants (see Dettmann et al., 1992 for summary). Although several previous reports have mentioned plesiosaur material from southeastern Australia (e.g. Rich et al., 1988; Rich and Rich, 1989; Vickers-Rich, 1996; Smith, 1999; Rich and Vickers-Rich, 2000; Kear, 2003), none of the remains have yet been described. It is therefore, the purpose of this paper to present an up-to-date summary of the existing specimens (Table 1) and assess their taxonomic and paleoecological implications.