Oligosoma is a genus comprising the New Zealand skinks and a closely related species the Lord Howe Island skink (Oligosoma lichenigera).
The North Island skink fauna is notable for the ex-Cyclodina species - a diverse group of largely nocturnal skinks which prefer areas of higher humidity, are now largely restricted to islands, and includes both NZ's largest species - the robust skink (Oligosoma alani) shown above, and our smallest - the slight skink (Oligosoma levidensum). The North Island is also home to New Zealand's only oviparous lizard, the aptly named egg-laying skink (Oligosoma suteri).
In addition to this, the North Island is home to New Zealand's three largest skink species, the aforementioned robust skink (Oligosoma alani), chevron skink (Oligosoma homalonotum), and Falla's skink (Oligosoma fallai). These three, along with many other large-bodied species are now entirely restricted to islands where the numbers of introduced predators are reduced (or absent).