Dharragarra

Dharragarra (meaning "platypus" in the Gamilaraay language) is an extinct genus of monotreme mammal from the Late Cretaceous (Cenomanian) Griman Creek Formation of Australia. The genus contains a single species, D. aurora, known from a partial left mandibular ramus. Dharragarra was likely more closely related to the living platypus than many other monotremes of the Cretaceous.

Dharragarra Temporal range: Late Cretaceous (Cenomanian), 100.2–96.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Monotremata
Family:	Ornithorhynchidae (?)
Genus:	†Dharragarra Flannery, 2024
Species:	†D. aurora
Binomial name
†Dharragarra aurora Flannery et al., 2024

Discovery and naming

Dharragarra type locality near Lightning Ridge, Australia

The Dharragarra holotype specimen, AM F97262, was discovered in 2002 in sediments of the Griman Creek Formation (Wallangulla Sandstone Member) near Lightning Ridge, New South Wales, Australia. The specimen consists of a partial left horizontal mandibular ramus.^[1] This bone was first mentioned by Anne Musser in part of a 2013 publication, where it was identified as a steropodontid.^[2] In a 2022 monotreme evolution review, Flannery et al. alluded to it as an unnamed new genus of stem-ornithorhynchid.^[3]

In 2024, Flannery et al. described Dharragarra aurora as a new genus and species of early monotreme based on these fossil remains. The generic name, Dharragarra, is a word that means "platypus" in the Gamilaraay, Yuwaalaraay and Yuwaalayaay languages, referencing this taxon's resemblance to the extant lineage. The specific name, aurora, is a Latin word meaning "dawn", considering the taxon's position at the beginning of monotreme evolution.^[1]

Several other monotremes are known from the Griman Creek Formation, including Opalios and Parvopalus—which were described in the same publication as Dharragarra—as well as Kollikodon, Steropodon, and Stirtodon.^[1][4]

Classification

Dharragarra is one of the oldest members of the platypus and echidna lineage, being closer to them than the coeval ornithorhynchoid Opalios. Due to the close resemblance of its jaw to that of a platypus, Dharragarra is considered one of the oldest members of the platypus stem lineage, although it likely predates the divergence of platypuses and echidnas.^[1]

References

1. Flannery, Timothy F.; McCurry, Matthew R.; Rich, Thomas H.; Vickers-Rich, Patricia; Smith, Elizabeth T.; Helgen, Kristofer M. (2024-05-26). "A diverse assemblage of monotremes (Monotremata) from the Cenomanian Lightning Ridge fauna of New South Wales, Australia". Alcheringa: An Australasian Journal of Palaeontology: 1–19. doi:10.1080/03115518.2024.2348753. ISSN 0311-5518.
2. Musser, A. M. (2013). "Classification and evolution of the monotremes". In Ashwell, K. (ed.). Neurobiology of Monotremes: Brain Evolution in Our Distant Mammalian Cousins. Melbourne: CSIRO Publishing. p. 8. ISBN 9780643103153.
3. Flannery, Timothy F.; Rich, Thomas H.; Vickers-Rich, Patricia; Ziegler, Tim; Veatch, E. Grace; Helgen, Kristofer M. (2022-01-02). "A review of monotreme (Monotremata) evolution". Alcheringa: An Australasian Journal of Palaeontology. 46 (1): 3–20. doi:10.1080/03115518.2022.2025900. ISSN 0311-5518.
4. de Kruijff, Peter (2024-05-26). "'Echidnapus' fossil of potential echidna and platypus ancestor may point to Australian 'age of monotremes'". ABC News. Archived from the original on 2024-05-27. Retrieved 2024-05-27.