The St Bathans diving duck was described from many bones, recovered from 19-16 million-year-old (Early Miocene) lake-bed deposits on Dunstanburn and Home Hills stations, near St Bathans, central Otago, New Zealand. The type locality is beside Mata Creek.

The holotype (CM 2013.18.1181, right humerus) and six paratype humeri are held at Canterbury Museum, Christchurch. Numerous other bones, including cranial, wing and leg bones, are referred to this species and are held in the Museum of New Zealand Te Papa Tongarewa and Canterbury Museum collections. The name primadividua acknowledges that this species provides the first evidence of a division in the St Bathans Fauna.

The St Bathans diving duck is the fourth species described in the genus Manuherikia. It is the second smallest, after the minute Manuherikia duck, but is smaller than the Manuherikia duck and Douglas’ duck. Many features of the skeleton show that this species was a foot-propelled diving duck and perhaps was the most specialised diver in the genus.

It was small, about the size of grey teal, and was related to other relatively basal anatids such as stiff-tailed ducks in the genus Oxyura.

This species is especially significant as it revealed the first stratigraphic separation of fossil birds in the various sites and fossil horizons that have produced the St Bathans Fauna. The Manuherikia River geological section that spans the basal Bannockburn Formation contains multiple fossil beds that have produced fossils in the lower 40 m of the lacustrine sediments. The St Bathans diving duck has only been found in beds above 34.5 m from the base of the Bannockburn Formation. Importantly, the most common duck in the lower 34 m of the Bannockburn beds, Manuherikia lacustrina (Manuherikia duck), is not found with The St Bathans diving duck. This observation has allowed fossil faunas from isolated sites where the geological stratigraphy is incompletely exposed to be assigned to either, the primadividua zone, or the older lacustrina zone, depending on which species is present. 

References

Worthy, T.H.; Scofield, R.P.; Salisbury, S.W.; Hand, S.J.; De Pietri, V.L.; Blokland, J.C.; Archer, M. 2022. A new species of Manuherikia (Aves: Anatidae) provides evidence of faunal turnover in the St Bathans Fauna, New Zealand. Geobios 70: 87-107.

Recommended citation

Worthy, T.H. 2022. Manuherikia primadividua. In Miskelly, C.M. (ed.) New Zealand Birds Online. www.nzbirdsonline.org.nz