Skull of modern day birds depicts dinosaurs times: Ornithology

New Delhi : A new development in the field of ornithology details about the transition of beaks from dinosaurs age to modern times, today. Researchers have segmented together the three-dimensional skull of an iconic, toothed bird that represents a pivotal moment in the transition from archaic period to recent birds.

Ichthyornis dispar, a genus of toothed seabird is best known for evolutionary trail that leads from dinosaurian species to avians of modern times. It lived nearly 100 million years ago in North America and looked like a toothy seabird. It is the species which drew the attention of such famous naturalists as Yale's O.C. Marsh and Charles Darwin.

Despite the existence of partial specimens of Ichthyornis dispar, there has been no major new skull material beyond the scrappy remains first found in the 1870s. Now, a Yale based team mentions on new specimens with three-dimensional cranial remains, including one example of a complete skull and two previously ignored cranial elements that were part of the original specimen at Yale, that reveal new details about one of the most striking transformations in evolutionary history.

"Right under our noses this whole time was an amazing, transitional bird," said Yale paleontologist Bhart-Anjan Bhullar, principal investigator of a study published in the journal Nature. "It has a modern-looking brain along with a remarkably dinosaurian jaw muscle configuration."

Bhullar added that Ichthyornis dispar explains about the physical appearance of bird beak as it first appeared in nature.

"The first beak was a horn-covered pincer tip at the end of the jaw," said Bhullar, who is an assistant professor and assistant curator in geology and geophysics. "The remainder of the jaw was filled with teeth. At its origin, the beak was a precision grasping mechanism that served as a surrogate hand as the hands transformed into wings."

The research team used CT-scan technology, combined with specimens from the Yale Peabody Museum of Natural History; the Sternberg Museum of Natural History in Fort Hays, Kan.; the Alabama Museum of Natural History; the University of Kansas Biodiversity Institute; and the Black Hills Institute of Geological Research.

Co-lead authors of the new study are Daniel Field of the Milner Centre for Evolution at the University of Bath and Michael Hanson of Yale. Co-authors are David Burnham of the University of Kansas, Laura Wilson and Kristopher Super of Fort Hays State University, Dana Ehret of the Alabama Museum of Natural History, and Jun Ebersole of the McWane Science Center.

"The fossil record provides our only direct evidence of the evolutionary transformations that have given rise to modern forms," said Field. "This extraordinary new specimen reveals the surprisingly late retention of dinosaur-like features in the skull of Ichthyornis -- one of the closest-known relatives of modern birds from the Age of Reptiles."

The researchers claim that their findings offer new insight into how modern birds' skulls eventually formed. Along with its transitional beak, Ichthyornis dispar had a brain mostly similar to modern birds but a temporal region of the skull was noticeably like a dinosaur, indicating that during the evolution of birds, the brain transformed first while the parts of the skull remained more ancient and dinosaur-like.

"Ichthyornis would have looked very similar to today's seabirds, probably very much like a gull or tern," said Hanson. "The teeth probably would not have been visible unless the mouth was open but covered with some sort of lip-like, extra-oral tissue."

 Bhullar's lab has produced a large body of research on various aspects of vertebrate skulls, often focusing on the origins of the avian beak. "Each new discovery has reinforced our previous conclusions. The skull of Ichthyornis even substantiates our molecular finding that the beak and palate are patterned by the same genes," Bhullar said. "The story of the evolution of birds, the most species-rich group of vertebrates on land, is one of the most important in all of history. It is, after all, still the age of dinosaurs."