2019-10-01 17:09:56
Between 16 and 19 million years ago, in the late Lower Miocene, much of the Maniototo Plain in the central Otago region of south-eastern New Zealand’s South Island was covered by a shallow lake. of about 5,600 square kilometers, twice the size of Luxembourg, which has been given the name of one of the rivers in the region, the Manuherikia, which in Maori means “cry of a tied bird”. There are two different explanations for the origin of this strange name. According to the first, when a group of Maori moved, the explorers, who went ahead reconnoitering the path, tied a bird to a stake to mark the ford of the river with its song. The second says that, in times of flood, at the confluence of the Manuherikia with the much larger Clutha River, the clear waters of the former are held back, like a tethered bird, by the dark, muddy waters of the latter. Lake Manuherikia was surrounded by a wetland, which was grassy in some areas and more wooded and swampy in others, with species typical of the southern hemisphere, such as casuarinas, eucalyptus, palms, mañíos, araucarias, and southern beeches. The climate was warm and subtropical.
The fauna that inhabited the region is known as the “Saint Bathans fauna”, because the first fossils came to light in the vicinity of the historic gold mines of that name. Most of the fossils are freshwater fish, such as Prototroctes oxyrhynchus, an endemic to New Zealand that survived until 1927. There are also mussels and crabs in the lake.
Among the amphibians that live on the shores of the lake there are leiopelmatid frogs, a primitive group that still exists, and that has only been found in New Zealand, except for a species that inhabited the Jurassic in Argentina, Vieraella herbsti, which is the true frog. oldest known. These frogs are characterized by their clumsy jumps: they do not land on their legs, but rather on the trunk.
There are reptiles related to those that currently inhabit New Zealand, such as geckos, skinks and a tuatara-like sphenodontid, and others that no longer exist on the islands: crocodiles up to three meters long, snake-necked turtles and tortoises. armored of the family of the meiolanidos.
The bird life is very varied. There are a large number of waterfowl, and parrots and, to a much lesser extent, doves live in the trees. We also find the ancestors of the current kiwis and the recently extinct moas. Some bones and eggshells of a large flightless moa have been identified, and the kiwis are represented by Proapteryx, a small bird weighing between 250 and 350 grams, less than half that of the smallest living kiwi. It is very likely that Proapteryx could fly, which would support the hypothesis, supported by anatomical and genetic data, that the ancestors of kiwis and moas arrived in New Zealand separately. Moas are thought to be related to tinamous, and kiwis to emus and cassowaries, or to the elephant birds of Madagascar.
Similar to the moas were the aptornitids, of the genus Aptornis, although they were related to the sarothurids, a group of African rails and chicks, or with the trumpeters of the Amazon, or with the kago of New Caledonia and the tigana of the Amazon. Aptornitids, called adzebill in English, were less than one meter tall and weighed less than twenty kilos. They are characterized by their enormous beak, curved downwards and ending in a point, by their stunted wings and by their strong legs. They were omnivorous birds adapted to dry environments, which could hunt large invertebrates, lizards, and birds. The Saint Bathans species, Aptornis proasciarostratus, is the oldest known, and also the smallest.
Among the aquatic birds there are herons, bitterns and two species of flightless purple swine; of these, the most abundant is the size of a sparrow. There is also a representative of the extinct group of the palaelodidae, intermediate between the flamingos and the loons. But the most abundant are the anseriformes: fossils of two species of geese, five of ducks, one of duck and one of jar have been found.
Pigeons and, above all, parrots flutter in the trees. There are four species of nestorid parrots in the genus Nelepsittacus, related to the living kea and kaka parrots, in the genus Nestor. The genus Nelepsittacus takes its name from the Greek demigod Neleus, father of King Nestor, to emphasize its relationship to the genus of that name. These parrots were quite large; the largest species was the size of the kea parrot, about half a meter long. But there was an even bigger parrot. In fact, it is the largest known parrot. So big that, when its remains were discovered in 2008, they were confused with those of an eagle. It was not until 2019 that the description of this new species of parrot was published, which received the name of Heracles, the Greek hero who, outraged by Neleus, killed him and all his children, except Nestor. The Heracles parrot was one meter long and weighed about seven kilos, almost twice as much as the kakapo, the heaviest living parrot. Like him, Heracles could not fly, but he could use his strong beak to climb trees.
Two species of pigeon have been described from Saint Bathans. Rupephaps taketake is a large fruit-eating pigeon; perhaps it is related to the Maori pigeon. The other species, Deliaphaps zealandiensis, however, is related to the Nicobar pigeon, the closest living relative of the extinct dodo.
St Bathans’ birdlife is rounded out by a small hawk, an eagle the size of an imperial eagle, and the Kuiornis indicator, a bird related to the greenish acanthusite, New Zealand’s smallest bird.
In Saint Bathans there are also bats; among them, a giant bat, related to the New Zealand short-tailed bat, which reached eight inches in length. These bats spend much of their time on the ground, feeding on invertebrates, fruit, pollen, nectar, and carrion, and dig their burrows in rotting logs or use crevices in rocks or seabird burrows. Today, New Zealand’s only native land mammals are bats. But the remains of a primitive flightless mammal have been found in Saint Bathans, disproving the theory that flightless mammals never colonized New Zealand. This small animal, of which we only know a femur and a fragment of the jaw, would be located in the evolutionary tree of mammals between the monotremes, the order to which the platypus belongs, and the marsupials, without belonging to either of the two groups.
What happened to this mammal, and to all this fauna in Saint Bathans? Throughout the Miocene, the climate became colder and drier, and species that were unable to adapt to the new conditions disappeared.
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