| Nihoroa | |
|---|---|
 | |
| Holotype skull (OU 22162) | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | †Waipatiidae |
| Genus: | †Nihoroa Coste, Fordyce, and Loch2023 |
| Type species | |
| †Nihoroa reimaea Ambre Coste, Robert Ewan Fordyce, and Carolina Loch, 2023 | |
Nihoroa (Māori pronunciation:[ˌnihɔˈɾɔa]) (meaning "long teeth") is an extinct genus ofwaipatiidodontocetecetacean from theglauconiticOtekaike Limestone inNorth Otago;New Zealand. The type species isN.reimaea, known from only the holotype which comprises various skull elements.[1]
Theholotype ofNihoroa (OU 22126) was collected byR. E. Fordyce, A. Grebneff, C. Samson and G. Ferguson in late January 1992 from the top of a cliff overlooking the north-western bank of theAwamoko stream inTokarahi. The specimen was retrieved fromglauconiticOtekaike Limestone, with the sediment being a calcarenite, fine light yellow-white sand, bioclastic limestone. Nihoroa reimaea was retrieved from a stratigraphically higher location thanAwamokoa tokarahi,[1][2] which was retrieved from the transitionallithology between theKokoamu Greensand andOtekaike Limestone. The suggested age forAwamokoa tokarahi was 25.0–25.4 Ma.Foraminifera from thematrix of OU 22126 include specimens of the planktonicGloboquadrina dehiscens with a first appearance datum at the start of theWaitakian stage, indicating that OU 22126 is no older than 25.2 Ma,[3] and likely closer to 24–23 Ma.[1]
The generic name,Nihoroa (Māori pronunciation:[ˌnihɔˈɾɔa]), is derived from theMaori words 'niho' and 'roa'. 'Niho' translates to tooth or tusk, and 'roa' translates to long. The specific name,reimaea ([ˌɾɛiˈmaea]), is derived from the Maori words 'rei' and maea'. 'Rei' translates to ivory, and 'Maea' refers to emerging in reference to incompletely emerged tusk-like first incisors.[1]
Nihoroa is known only from the holotype,OU 22162, which was described in 2023 by Coste, Fordyce, and Loch, (2023). The holotype measures at around 50 cm (19.7 in) in length. It consists of a near-complete skull missing its leftnasal, bothlacrimojugals andpterygoids. Bothtympanoperiotics andossicles are present other than the rightstapes; the right earbones are in place in the skull, the left was removed to allow further description. Six tusk-like teeth are in place in therostrum and a further 16 teeth are loose. The right nasal is loose and detached from the skull. However nomandibles orpostcrania were recovered.[1]
In theirphylogenetic analysis, Coste, Fordyce, and Loch, (2023) recoveredNihoroa amongst thewaipatiids grade ofbasalodontocetes and most closely related toNihohae, OU 22262 andEdiscetus. The followingcladogram represents thephylogenetic results of a consensus tree which was obtained using the 50% majority rule in Tree analysis using New Technology (TNT). The original tree used several basal cetaceans asoutgroups, however for simplicity only members ofOdontoceti are shown below.[1]
