Temporal range: Early Cretaceous, 100Ma
|Species:||† N. eos|
Nanantius eos is the name of an Early Cretaceous (Albian, c. 100-112 mya) species of bird. It is the only described member of the genus Nanantius at present; the supposed second species Nanantius valifanovi has turned out to be a synonym of Gobipteryx minuta. N. eos is known from two incomplete tibiotarsi from the Toolebuc Formation stratum, the first (Queensland Museum F12992) found at Warra Station near Boulia, in Queensland (Australia). Other remains from Australia have also been placed into the genus Nanantius but not assigned to a species. Furthermore, there are some bones from the Late Cretaceous, found in the Bissekty Formation of the Kyzyl Kum desert, Uzbekistan, which belong either into Nanantius or a closely related genus; however, due to the date difference, they are almost certainly not N. eos in any case.
Initially, Nanantius eos was classified as an enanthiornithine, a Cretaceous group of primitive birds that did not survive the Cretaceous–Paleogene mass extinction. However, it is now known that the characters of the tibiotarsus are not sufficiently diagnostic to place a bird into the Enantiornithes. For example, the more modern genus Apsaravis also possessed an "enantiornithine" tibiotarsus (Clarke & Norell, 2002). Thus, although an enantiornithine affinity of Nanantius is likely - these birds were the dominant avian group in the Early Cretaceous, and the tibiotarsus is very similar to the doubtlessly enantiornithine Gobipteryx -, this placement is not certain until more diagnostic material, such as the characteristic tarsometatarsi, have been found.
N. eos was a small species, about the size of a Blackbird; it probably looked like a miniature gull with clawed wings and a neck and head more similar to a feathered theropod dinosaur, but with a beak. It is assumed to have fed on marine invertebrates and small fish; certainly, it lived on the coast of what was then the Eromanga Sea, a shallow subtropical arm of the Tethys Seaway. That Nanantius were seabirds is evidenced by the fact that another tibiotarsus referrable to this genus, and quite possibly to N. eos itself, was found in the gut of an ichthyosaur (Kear et al., 2003).
- Clarke, Julia A. & Norrel, Mark A. (2002): The morphology and phylogenetic position of Apsaravis ukhaana from the late Cretaceous of Mongolia. American Museum Novitates 3387: 1-46. PDF fulltext
- Kear, Benjamin P.; Boles, Walter E. & Smith, Elizabeth T. (2003): Unusual gut contents in a Cretaceous ichthyosaur. Proceedings of the Royal Society B (Supplement) 270: S206–S208. doi:10.1098/rsbl.2003.0050 PDF fulltext Electronic Appendix
- Molnar, Ralph E. (1986): An enantiornithine bird from the Lower Cretaceous of Queensland, Australia. Nature 322: 736-738. doi:10.1038/322736a0 (HTML abstract)