The earliest Bird fossils appear in the Late Jurassic of Eurasia, with well articulated Bird fossils becoming numerous in Eurasia in the Early Cretaceous (about 120 million years ago) and Gondwana slightly later (about 115 million years ago). However Birds appear to have reached North America somewhat later, with the oldest known fragmentary Bird remains appearing in the Ashville Formation of Saskatchewan about 95 million years ago and the earliest articulated Birds dating to about 83 million years ago.
In a paper published in the journal Scientific Reports on 19 December 2016, Richard Bono of the Department of Earth &Environmental Sciences at the University of Rochester, Julia Clarke of the Department of Geological Sciences at The University of Texas at Austin, John Tarduno, also of the Department of Earth & Environmental Sciences, and of the Department of Physics & Astronomy at the University of Rochester, and Donald Brinkman of the Royal Tyrrell Museum of Paleontology, describe a new species of Bird from the early Late Cretaceous of Axel Heiberg Island in the High Canadian Arctic.
The new species is named Tingmiatornis arctica, where ‘Tingmiat’ means ‘those that fly’ in Inuktitut, ‘-ornis’ implies a Bird, and ‘arctica’ refers to the location where it was found. The species is described from a complete left humerus, a portion of a second humerus and a portion of an ulna. These bones come from a layer of shale and siltstone between the Fiord Formation Flood Basalts and the Kanguk Shale; this layer has previously produced a variety of freshwater Fish and Turtle bones as well as rare juvenile Elasmosaur teeth. Based upon the structure of the humerus, Tingmiatornis arctica is thought to be an Ornithurine, i.e. a member of the same group as all modern Birds, rather than the more common (in the Cretaceous) Enantiornithines.
Specimen of Tingmiatornis arctica, a complete left humerus. Photograph (left) and x-ray computed tomography images (right) of the element in caudal, proximal, cranial, and ventral views. Bono et al. (2016).
Ornithurine Birds have been discovered at a number of high latitude locations in both the Arctic and Antarctic, whereas Enantiornithines are generally absent from such locations, which has led to speculation that the Ornithurines had biological adaptations to such environments the Enantiornithines lacked, and that these adaptations may also have helped then survive the End Cretaceous Extinction event. Bono et al. speculate that this may have been connected to the different reproductive strategies of the two groups. Modern Birds have a very short childhood, with physical maturity always reached within a year of the egg being laid. This enables Birds to breed in climates with very strong seasonality, such as the High Arctic, by raising their brood and flying away before the weather turns bad. The Cretaceous had a much warmer climate, and even the Arctic is thought to have been warm, with a mean annual temperature of 14 °C, and little or no ice at any time of year. However the High Arctic would still have experienced periods of total darkness lasting several months each year, which would have given a distinct advantage to animals which were able to mature rapidly.
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