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.
See also...
