Revision of Dugaldia emmilta (Teleostei, Ichthyodectiformes) from the Toolebuc Formation, Albian of Australia, with comments on the jaw mechanics

ABSTRACT

Dugaldia emmilta is a teleostean fish found in the late Albian Toolebuc Formation in Queensland, Australia. In the original description, D. emmilta was attributed to the Neoteleostei because of the presence of a tripartite occipital condyle, and the species was postulated to have a basal position among neoteleosteans because of the presence of several plesiomorphic characters. A reexamination of the holotype, together with the description of two new specimens, indicates that D. emmilta is an ichthyodectiform fish. A phylogenetic analysis resolves this species as the sister to Ogunichthys + Ichthyodectoidei. This species shows unusual features for an ichthyodectiform, in particular the shape of the mandible and the arrangement of the teeth on the lower jaw. Jaw mechanics in ichthyodectiforms are peculiar because they allow a significant lateral enlargement. In Dugaldia, a similar disposition is present but is exaggerated by specific features of the maxilla and the mandible. Comparisons with the sarcastic fringehead (Neoclinus blanchardi), a living blenny that shows a ‘gaping display,’ reveal that Dugaldia was likely able to exhibit extreme lateral mouth enlargement.

ACKNOWLEDGMENTS

We thank T. Holland, P. Smith, M. Johnston, and B. and G. Flewelling (KK, Richmond) and A. Bartholomai, A. Rozefelds, and K. Spring (Queensland Museum Hendra, Brisbane) for allowing us to access the material under their care. We are grateful to A. Kemp (Brisbane) for her help during in the field and for her valued advice. We thank both reviewers, Katia González-Rodríguez (Hidalgo) and Adriana López-Arbarello (Munich), for their thorough and constructive comments. This work is dedicated to the late A. Bartholomai, who was the first modern contributor to our knowledge of the Cretaceous Australian bony fishes. He welcomed us very kindly during our visit and willingly shared his knowledge. Finally, R.W.B. acknowledges a fee offset scholarship from the Australian Government Research Training Program.

ORCID

Lionel Cavin http://orcid.org/0000-0001-9666-5864

Rodney W. Berrell http://orcid.org/0000-0001-5683-4272