Money quote from the Times science article:
In a new study of a fossil fish that lived 375 million years ago, scientists are finding striking evidence of the intermediate steps by which some marine vertebrates evolved into animals that walked on land.
There was much more to the complex transition than fins evolving into sturdy limbs. The head and braincase were changing, a mobile neck was emerging and a bone associated with underwater feeding and gill respiration was diminishing in size, a beginning of the bone’s adaptation for an eventual role in hearing for land animals.
The anatomy of this early transformation in life from water to land had never before been observed with such clarity, paleontologists and biologists said Wednesday in announcing the research.
The scientists said in a report being published Thursday in the journal Nature that the research exposed delicate details of the creature’s head and neck, confirming and elaborating on its evolutionary position as “an important stage in the origin of terrestrial vertebrates.”
In that case, the fish, a predator up to nine feet long, was a predecessor of amphibians, reptiles and dinosaurs, mammals and eventually humans. The fossil species was named Tiktaalik roseae, nicknamed “fishapod” for its fishlike features combined with limbs similar to those of tetrapods, four-legged land animals.
“The braincase, palate and gill arch skeleton of Tiktaalik have been revealed in great detail,” said Jason Downs, a research fellow at the academy and lead author of the report. “By revealing new details of the pattern of change in this part of the skeleton, we see that cranial features once associated with land-living animals were first adaptations for life in shallow water.”