Early Miocene gull-like birds (Charadriiformes: Laridae) from New Zealand

The shorebird family Laridae encompasses gulls, terns, skimmers, and noddies, which today primarily inhabit near-shore marine environments worldwide. Several species of larids of uncertain phylogenetic position within the group have been described from the late Oligocene-Early Miocene of Saint-Gérand-le-Puy, France, but despite this diversity, their global pre-Pliocene fossil record remains poor, especially in the Southern Hemisphere. Here we describe two new species of Laridae from the lacustrine deposits of St Bathans in Central Otago, New Zealand: Australarus bakeri nov. gen., nov. sp., one of the smallest larids known to date, and the medium-sized Miolarus rectirostrum nov. gen., nov. sp. The new species are very distinct from the Oligo-Miocene European taxa, and, at least for A. bakeri, the presence of immature bones indicates local breeding. Australarus bakeri's distinctiveness and presence of seemingly plesiomorphic features, especially of the humerus and some referred elements may support a phylogenetic position outside crown-group Laridae. The intra-familial relationships of M. rectirostrum remain unclear due to the fragmentary nature of the specimens, despite a resemblance of the maxillary rostrum to some species of gulls. Both new species underscore the diversity and importance of the shorebirds so far described from the Early Miocene St Bathans Fauna.