Devonian fish remains from the Dulcie Sandstone and Cravens Peak Beds, Georgina Basin, central Australia

WA Museum Records and Supplements | Updated 7 years ago

ABSTRACT – Fossil fish remains belonging to the Wuttagoonaspis assemblage are described from the Devonian rocks of the Georgina Basin, central Australia. The study is based on some 450 samples from 30 localities in the lower Dulcie Sandstone of the Dulcie Syncline (Northern Territory), and Cravens Peak Beds of the Toko Syncline (western Queensland). First recorded from the Darling Basin of western New South Wales, the diverse Wuttagoonaspis assemblage was probably the first vertebrate fauna to become established in rivers and lakes of the Australian continent. It occurs over an area of about one million km2, but up to now only one species has been described from the type area. The Georgina Basin assemblage is highly endemic, with some 20 genera representing about 13 taxa of family or higher rank. It includes three of the four major groups of jawed vertebrates (placoderrns, acanthodians, osteichthyans), and at least two agnathan groups: pituriaspids (previously described), and thelodontids (unstudied). Amongst placoderms, the order Arthrodira is represented by at least six families, one of which is new (family Bulbocanthidae). Seven new arthrodire species are assigned to the following new genera: Lurapulllaspis, Toombalepis, Tnoralaspis, Ethabukaspis, Tokolepis, Cravenaspis, and Mithakaspis. A new species, Wuttagoonaspis milligani sp. nov., is erected within the genus Wuttagoonaspis Ritchie, 1973 (endemic family Wuttagoonaspidae), the only named taxon from the Darling Basin assemblage. Huginaspis australis sp. nov. is assigned to the genus Huginaspis Heintz, 1929 (family Phlyctaeniidae), previously known from the Early-Middle Devonian of Spitsbergen. Tnoralaspis petercooki gen. et sp. nov. has its type locality at Gosses Bluff in the Amadeus Basin (Pertnjara Group). The new actinolepidoid family Bulbocanthidae (Lurapullaspis johannseni gen. et sp. nov.) is also known from the Early Devonian of western USA, Spitsbergen, and Severnaya Zemlya. Toombalepis tuberculata gen. et sp. nov. is placed in the actinolepidoid family Antarctaspidae, also known from the Devonian of Antarctica (Antarctaspis White, 1968) and South China (Yujiangolepis Wang et aI., 1998). Cravenaspis trematosus gen. et sp. nov. is provisionally placed in the phlyctaenioid family Arctaspididae, also known from Spitsbergen. Mithakaspis lyentye gen. et sp. nov. is referred to the cosmopolitan family Groenlandaspidae, together with another new genus (unnamed), and two indeterminate species cf. Groenlandaspis Heintz, 1932. The placoderm order Petalichthyida is represented by an indeterminate genus and species, and the class Acanthodii by indeterminate fin spines. Osteichthyan remains apparently include three orders of sarcopterygians (?rhizodontids, ?porolepiforms, onychodontids), but the material is insufficient to erect new taxa.

Many of the studied localities have yielded remains of large fishes up to one metre long, indicating deposition in substantial water bodies, although previous interpretations have suggested aeolian deposition for part of the sandstone succession. The distribution of taxa and/or morphotypes across the studied localities is analysed. Differences in diversity seem to be related to sample size, and remains referred to Wuttagoonaspis sp. from most localities indicate a broad correlation between the lower Dulcie Sandstone and the Cravens Peak Beds. Faunal affinities with fossil assemblages in the Northern Hemisphere suggest that the Wuttagoonaspis fauna from the Cravens Peak Beds and lower Dulcie Sandstone is probably no older than Pragian, and no younger than early Eifelian. The different species of Wuttagoonaspis, and predominance of high-spined groenlandaspids in the new fauna, suggests a slight difference in age to the Wuttagoonaspis assemblage from the Darling Basin.