Asia–Gondwana connections indicated by Devonian fishes from Australia: palaeogeographic considerations

Abstract

Middle Palaeozoic vertebrate fossil occurrences are summarised for Australia, with reference to faunal connections between Asia and East Gondwana, as first indicated by fish distributions of Lower Devonian fossil sites. Major endemic groups discussed are pituriaspid (Australian) and galeaspid (Asian) agnathans, wuttagoonaspids (Australian) and antarctaspid (Antarctic, Australian, Asian) arthrodires, yunnanolepid and sinolepid antiarchs (South China, Indochina terrane, Australia), and early tetrapodomorphs (South China, Australia). More widespread groups that lived in shallow marine environments (lungfishes, buchanosteid arthrodires, antiarch Bothriolepis) also show species groups shared between South China and East Gondwana. Exchange of continental facies fishes (e.g. tristichopterid tetrapodomorphs) may have been interrupted by marine transgression in the Frasnian, but were restored in the late Famennian with the appearance of Grenfellaspis in eastern Australia, the only sinolepid antiarch known from outside Asia. The hypothesis of Gondwana dispersion and Asian accretion, to explain the collage of geological terranes forming modern east and southeast Asia, implies increasing dissimilarity with increasing age, but the Siluro-Devonian early vertebrate evidence is inconsistent with this. Previous cladistic analysis of Asian terranes predicted galeaspid agnathans on the Indochina terrane, and their subsequent discovery at Ly Hoa, Vietnam, confirms that Indochina and South China had come together across the Song Ma suture by Middle Devonian time.

Evolution of median fin patterning and modularity in living and fossil osteichthyans

“…Janvier (2007; [54]) suggested that the ‘horizontal caudal lobe’ of osteostracans might be a modified anal fin. Galeaspids and pituriaspids appear to lack an anal fin [60, 61] but uncertainty is due to the poor preservation of their postcranial skeleton. In gnathostomes, the anal fin is not preserved usually in ‘placoderms’, probably due to its reduced size and the cartilaginous nature of the radials, but has been illustrated in some cases (e.g., arthrodires like Africanaspis and Dunkleosteus ) [62, 63]).…”

A novel specimen-based mid-Paleozoic dataset of antiarch placoderms (the most basal jawed vertebrates)

“…Weems (2004) questioned the validity of B. virginiensis. Since there is no consensus on the species level of Bothriolepis and Asterolepis, the former researchers only used the evidence of Antiarcha on the genus level to discuss the biostratigraphic significance (Lelievre and Goujet, 1986;Pan, 1981;Young et al, 2010;Young and Lu, 2020). To keep accuracy and consistency, here we choose the genus of Antiarcha to perform data visualization.…”

The Bothriolepis (Placodermi, Antiarcha) material from the Valentia Slate Formation of the Iveragh Peninsula (middle Givetian, Ireland): Morphology, evolutionary and systematic considerations, phylogenetic and palaeogeographic implications

“…The genus then occurs later in Gondwana and Kazakhstan between the Givetian and Famennian (e.g. [62,71]). Until now, the occurrence of Bothriolepis in Euramerica was confined to the Upper Devonian, but has now been lowered to the middle Givetian with B. dairbhrensis sp.…”