A new species ofProegerniafrom the Namba Formation in South Australia and the early evolution and environment of Australian egerniine skinks

Abstract

The diverse living Australian lizard fauna contrasts greatly with their limited Oligo-Miocene fossil record. New Oligo-Miocene fossil vertebrates from the Namba Formation (south of Lake Frome, South Australia) were uncovered from multiple expeditions from 2007 to 2018. Abundant disarticulated material of small vertebrates was concentrated in shallow lenses along the palaeolake edges, now exposed on the western of Lake Pinpa also known from Billeroo Creek 2 km northeast. The fossiliferous lens within the Namba Formation hosting the abundant aquatic (such as fish, platypus Obdurodon and waterfowl) and diverse terrestrial (such as possums, dasyuromorphs and scincids) vertebrates and is hereafter recognized as the Fish Lens. The stratigraphic provenance of these deposits in relation to prior finds in the area is also established. A new egerniine scincid taxon Proegernia mikebulli sp. nov. described herein, is based on a near-complete reconstructed mandible, maxilla, premaxilla and pterygoid. Postcranial scincid elements were also recovered with this material, but could not yet be confidently associated with P. mikebulli . This new taxon is recovered as the sister species to P. palankarinnensis , in a tip-dated total-evidence phylogenetic analysis, where both are recovered as stem Australian egerniines. These taxa also help pinpoint the timing of the arrival of scincids to Australia, with egerniines the first radiation to reach the continent.

First record of a tomistomine crocodylian from Australia

“…By the middle Miocene (Langhian–Serravallian; 15.97–11.63 Ma), the distance between the northwestern margin of Australia and the southern margin of Southeast Asia began to approach its modern span, and dispersal for crocodylians with the capacity to cross relatively short marine barriers through the Sundaic region would have become much easier. Several other reptile groups that inhabit Australia have origins from Southeast Asia, and could have been present in Australia by the late Paleogene 117 . Based on these observations, it is plausible that tomistomines arrived in Australia from Southeast Asia from the middle Miocene onwards.…”

An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia

“…The age of this formation is correlated with that of the Etadunna Formation, in the Tirari Sub-basin of the Lake Eyre Basin (Alley 1998). The Namba Formation contains three primary Local Faunas (LFs): the Pinpa LF, the Ericmas LF, and the Tarkarooloo LF (Callen and Tedford 1976;Rich and Archer 1979;Rich et al 1991;Thorn et al 2021). The Pinpa LF derives from beds of olive and orange mottled clay and white dolomitic mudstone stained with manganese at the top of the lower member of the Namba Formation, which crops out at Lake Pinpa and Billeroo Creek (Tedford et al 1977;Rich et al 1991;Thorn et al 2021).…”

“…The Namba Formation contains three primary Local Faunas (LFs): the Pinpa LF, the Ericmas LF, and the Tarkarooloo LF (Callen and Tedford 1976;Rich and Archer 1979;Rich et al 1991;Thorn et al 2021). The Pinpa LF derives from beds of olive and orange mottled clay and white dolomitic mudstone stained with manganese at the top of the lower member of the Namba Formation, which crops out at Lake Pinpa and Billeroo Creek (Tedford et al 1977;Rich et al 1991;Thorn et al 2021). The Ericmas LF derives from fluvial sands deposited in channels cut into the lacustrine units of the Namba Formation, so is younger than the Pinpa LF, and derives from Ericmas Quarry and South Prospect Quarries at Lake Namba a few kilometres south of Lake Pinpa (Tedford et al 1977;Rich et al 1991).…”

“…There is much overlap of species composition between Pinpa and Ericmas LFs suggesting broad similarity in age. While Rich et al (1991) recognised the Ericmas LF to occur at Lake Pinpa, recent work by THW and ABC recognises only one local fauna from Lake Pinpa and restricts the Ericmas LF to that derived from Ericmas and South Prospect quarries at nearby Lake Namba (Thorn et al 2021). The Tarkarooloo LF derives from fluvial sands in Tom O's Quarry by Lake Tarkarooloo about 10 kilometres west of Lake Pinpa, but the temporal relationship to the Ericmas LF is unknown, though co-occurrence of some species suggests a broadly similar age (Rich et al 1991).…”

“…The Pinpa LF, found at Lake Pinpa and Wells Bog Site at Billeroo Creek (Rich et al 1991;Thorn et al 2021) (Figure 1), is extremely diverse, comprising fish and both aquatic and terrestrial reptiles, mammals, and birds (Rich et al 1991). Reptiles are represented by an indeterminate species of chelid turtle (Emydura sp.…”