Ornithorhynchoidea

Ornithorhynchoidea is a superfamily of mammals containing the only living monotremes, the platypus and the echidnas, as well as their closest fossil relatives, to the exclusion of more primitive fossil monotremes of uncertain affinity.^[1]

Ornithorhynchoids Temporal range: Late Cretaceous (Cenomanian)–present PreꞒ Ꞓ O S D C P T J K Pg N
Two extant ornithorhynchoids: the short-beaked echidna (above) and platypus (below)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Monotremata
Superfamily:	Ornithorhynchoidea Flannery et al., 2024
Families
†Opalionidae Ornithorhynchidae Tachyglossidae
Range of extant ornithorhynchoids

The clade was defined in 2024 following the discovery of some fossil monotremes from the Late Cretaceous (Cenomanian)-aged Griman Creek Formation of Lightning Ridge Australia, which appeared to be more closely related to extant monotremes than to co-occurring early monotremes such as Steropodon and Kollikodon.^[1][2]

Taxonomy

Opalios, the only described member of the extinct family Opalionidae, is considered the most basal ornithorhynchoid due to its unique combination of ancestral and derived traits.^[1]

The presence of the probable stem-ornithorhynchids Dharragarra and Patagorhynchus in the Late Cretaceous implies that the divergence between the platypus and echidnas may have occurred during this time.^[1] However, genetic estimates tend to prefer a Cenozoic divergence between these two extant groups.^[3][4]

Although most members of this group—extinct and extant—are known from Australia, at least two ornithorhynchid-like forms reached southern South America during the Maastrichtian (Patagorhynchus) and early Paleocene (Monotrematum).^[5][6]

The following genera are known:

• Superfamily Ornithorhynchoidea Flannery et al., 2024
  • Family †Opalionidae Flannery et al., 2024
    • Genus †Opalios Flannery et al., 2024
  • Family Ornithorhynchidae Gray, 1825
    • Genus ?†Dharragarra Flannery et al., 2024
    • Genus ?†Monotrematum Pascual et al., 1992
    • Genus †Obdurodon Woodburne & Tedford, 1975
    • Genus ?†Patagorhynchus Chimento et al., 2023
    • Genus Ornithorhynchus Blumenbach, 1800
  • Family Tachyglossidae Gill, 1872
    • Genus †Megalibgwilia Griffiths, Wells & Barrie, 1991
    • Genus †Murrayglossus Flannery et al., 2022
    • Genus Tachyglossus Illiger, 1811
    • Genus Zaglossus Gill, 1877

They can be distinguished from other fossil monotremes by their twisted-shaped dentaries, with the lingual surfaces being dorsoventrally flattened (aside from in 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. 48 (2): 319–337. Bibcode:2024Alch...48..319F. doi:10.1080/03115518.2024.2348753. ISSN 0311-5518.
2. 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.
3. Phillips MJ, Bennett TH, Lee MS (October 2009). "Molecules, morphology, and ecology indicate a recent, amphibious ancestry for echidnas". Proceedings of the National Academy of Sciences of the United States of America. 106 (40): 17089–94. Bibcode:2009PNAS..10617089P. doi:10.1073/pnas.0904649106. PMC 2761324. PMID 19805098.
4. Zhou, Yang; Shearwin-Whyatt, Linda; Li, Jing; Song, Zhenzhen; Hayakawa, Takashi; Stevens, David; Fenelon, Jane C.; Peel, Emma; Cheng, Yuanyuan; Pajpach, Filip; Bradley, Natasha; Suzuki, Hikoyu; Nikaido, Masato; Damas, Joana; Daish, Tasman (2021-04-06). "Platypus and echidna genomes reveal mammalian biology and evolution". Nature. 592 (7856): 756–762. Bibcode:2021Natur.592..756Z. doi:10.1038/s41586-020-03039-0. hdl:2440/130050. ISSN 1476-4687. PMID 33408411.
5. 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. Bibcode:2022Alch...46....3F. doi:10.1080/03115518.2022.2025900. ISSN 0311-5518.
6. Chimento, Nicolás R.; Agnolín, Federico L.; Manabe, Makoto; Tsuihiji, Takanobu; Rich, Thomas H.; Vickers-Rich, Patricia; Novas, Fernando E. (2023-02-16). "First monotreme from the Late Cretaceous of South America". Communications Biology. 6 (1): 146. doi:10.1038/s42003-023-04498-7. ISSN 2399-3642. PMC 9935847. PMID 36797304.