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Skull of Ichthyornis reveals unforeseen mosaicism (1 Viewer)

Fred Ruhe

Well-known member
Netherlands
Daniel Field, Michael Hanson, Bhart-Anjan Bhullar, 2017

Newly discovered complete skull of Ichthyornis reveals unforeseen mosaicism late in the dinosaur-bird transition

The abstracts book for the 2017 Palaeontological Society meeting at Imperial College in London.

All abstracts:
https://www.palass.org/sites/defaul...s_annual_meeting_2017_programme_abstracts.pdf

Abstract:
The Late Cretaceous toothed avialan Ichthyornis dispar represents one of the closest Mesozoic relatives to crown-group birds, and since its initial description in 1872 has provided critical information on the biology of birds preceding the evolutionary radiation of crown clade Aves. Despite continued work affirming its evolutionary importance, no substantial new cranial material of I. dispar has been reported since the 19th Century. Furthermore, Jurassic and Cretaceous lagerstätten that have yielded the most evolutionarily informative Mesozoic bird fossils typically preserve crushed and distorted skulls, severely limiting our understanding of non-avian ornithuromorph cranial morphology. Here we report four new specimens of I. dispar bearing cranial remains, including a new, extraordinarily complete skull and two previously unrecognized elements from the holotype. We found that I. dispar exhibited a transitional beak – small, lacking a palatal shelf, and restricted to the tip of the jaws – coupled with a crown-like kinetic system. The brain was relatively modern but the temporal region, poorly known in most non-avian avialans, was surprisingly archaic and deinonychosaur-like, bearing a large adductor chamber bounded dorsally by substantial bony remnants of the upper temporal fenestra. The far-crownward persistence of this temporal configuration demonstrates unforeseen complexity during the modernization of the avian skull.

Enjoy,

Fred
 
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