Mythunga

Mythunga is known from a partial skull, holotype QM F18896 found in April 1991 by Philip Gilmore in marine rocks of the late Albian-age Toolebuc Formation at Dunluce Station west of Hughenden, Queensland. Only the middle snout and corresponding parts of the lower jaws are known, including the rear of a left premaxilla, the lower parts of both maxillae, the rear dentaries and a right splenial. They were three-dimensionally preserved, associated in a chalk nodule. It represents a subadult individual.[1] The fossil was prepared by Angela Hatch of the Queensland Museum, both by mechanical means and by an acid bath.[2]

The type species Mythunga camara was named and described by Ralph Molnar and R. A. Thulborn in 2007/2008. The generic name is that of the constellation Orion in the local aboriginal language. The specific name, from Latin camera, "room", refers to the camerate air spaces in the bone.[1]

Mythunga was redescribed by Adele Pentland and Stephen Poropat in 2018, benefiting from further preparation of the specimen. At that time it was still the most completely known pterosaur of Australia. No more than twenty pterosaur fossils were known from that continent, most of them teeth and bone fragments.[2]

The wingspan of Mythunga was in 2007 estimated at fifteen feet or 4.7 metres.[1] However, that was done under the assumption that the first preserved teeth were located on the left premaxilla which would imply that Mythunga was a relatively short-snouted form with a skull length of fifty to eighty centimetres. In 2018, it was concluded that they had been confused with a maxillary tooth and replacement tooth and that the skull length was likely between eighty centimetres and one metre, with a corresponding wingspan of between four and six metres.[2]

In 2007, two autapomorphies were suggested, unique derived traits. Firstly, the teeth in the rear dentary of the lower jaw were relatively tall (half the depth of the supporting bone at that point). Secondly, the three hindmost maxillary teeth were widely spaced.[1] In 2018 however, the first trait was rejected, as it could not be reliably established where the dentary ended. Another autapomorphy was now proposed: the outer sides of the jaws are undulating because of the bulging tooth sockets.[2]

The entire piece has a preserved length of 263 millimetres. As with most pterosaurs, the snout was hollow, with a supporting internal boxwork of bone, as could be observed at breaks. The jugal bone apparently extended to a point below the front of the large skull opening, the nasoantorbital fenestra. There are at least eight teeth in each maxilla. That is also the minimal number in the dentary. The teeth are relatively short, conical and moderately recurved. Their cross-section is oval. They are widely spaced at equal distances.[2]

In 2007, Mythunga was provisionally thought to belong to a group of plesiomorphic, and thus possibly basal, pterodactyloids: the Archaeopterodactyloidea.[1] In 2010, Alexander Kellner e.a. placed it in the Anhangueridae.[3] In 2018, it was recovered by a cladistic analysis in the Anhangueria.[2]

Below is a cladogram showing the results of a phylogenetic analysis by Pentland et al. (2019). In the analysis, they recovered Mythunga as a member of the family Ornithocheiridae, more precisely within the subfamily Ornithocheirinae as the sister taxon of Ferrodraco.[4]

• List of pterosaur genera
• Timeline of pterosaur research