A Gigantic Sarcopterygian (Tetrapodomorph Lobe-Finned Fish) from the Upper Devonian of Gondwana (Eden, New South Wales, Australia)

Abstract

Edenopteron keithcrooki gen. et sp. nov. is described from the Famennian Worange Point Formation; the holotype is amongst the largest tristichopterids and sarcopterygians documented by semi-articulated remains from the Devonian Period. The new taxon has dentary fangs and premaxillary tusks, features assumed to be derived for large Northern Hemisphere tristichopterids (Eusthenodon, Hyneria, Langlieria). It resembles Eusthenodon in ornament, but is distinguished by longer proportions of the parietal compared to the post-parietal shield, and numerous differences in shape and proportions of other bones. Several characters (accessory vomers in the palate, submandibulars overlapping ventral jaw margin, scales ornamented with widely-spaced deep grooves) are recorded only in tristichopterids from East Gondwana (Australia-Antarctica). On this evidence Edenopteron gen. nov. is placed in an endemic Gondwanan subfamily Mandageriinae within the Tristichopteridae; it differs from the nominal genotype Mandageria in its larger size, less pointed skull, shape of the orbits and other skull characters. The hypothesis that tristichopterids evolved in Laurussia and later dispersed into Gondwana, and a derived subgroup of large Late Devonian genera dispersed from Gondwana, is inconsistent with the evidence of the new taxon. Using oldest fossil and most primitive clade criteria the most recent phylogeny resolves South China and Gondwana as areas of origin for all tetrapodomorphs. The immediate outgroup to tristichopterids remains unresolved – either Spodichthys from Greenland as recently proposed, or Marsdenichthys from Gondwana, earlier suggested to be the sister group to all tristichopterids. Both taxa combine two characters that do not co-occur in other tetrapodomorphs (extratemporal bone in the skull; non-cosmoid round scales with an internal boss). Recently both ‘primitive’ and ‘derived’ tristichopterids have been discovered in the late Middle Devonian of both hemispheres, implying extensive ghost lineages within the group. Resolving their phylogeny and biogeography will depend on a comprehensive new phylogenetic analysis.

Tristichopterids (Sarcopterygii, Tetrapodomorpha) from the Upper Devonian tetrapod-bearing locality of Strud (Belgium, upper Famennian), with phylogenetic and paleobiogeographic considerations

“…2D-F). Among tristichopterids, a marginal dentary tooth row that appears only distal to the fangs is additionally observed in Cabonnichthys burnsi (Johanson and Ahlberg, 1997), Edenopteron keithcrooki (Young et al, 2013), and Eusthenodon wangsjoi (Jarvik, 1952;Johanson, 2004).…”

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

“…However, alternative interpretations, of endemic tetrapodomorph subgroups (e.g. Canowindridae, Mandageriinae) in Australia-Antarctica (Young 2008;Young et al 1992Young et al , 2013Young et al , 2019 are consistent with the placement of the only Australian taxon (Marsdenichthys) in the analysis of Lu et al (2012, fig. 6), resolved as the sister-group to all other tristichopterids.…”

Long-bone development and life-history traits of the Devonian tristichopterid Hyneria lindae

“…Although the fossil remnants of H. lindae are too fragmentary to allow a reconstruction of the body morphology, and it has not yet been included in a published phylogenetic analysis, its character complement strongly suggests that it belongs in a clade of large derived tristichopterids with Eusthenodon and the Australian genera Mandageria and Edenopteron (Thomson 1976; Johanson & Ahlberg 1997; Young et al . 2013; Daeschler & Downs 2018). Mandageria is known from articulated whole-body specimens, which show a fish with an elongated body and relatively small median fins of low aspect ratio clustered at the posterior end (Ahlberg & Johanson 1997), comparable to the morphology of an ambush predator such as a pike (Webb 1984).…”