The tough little egg made it all the way through the digestive system of a coscoroba swan like this one. TonyBaggett / iStock. Killifish eggs are known for their resilience: They’ve been found ...

In contrast, exceptionally preserved fossils reveal that derived avian features were present in the digestive systems of some non-enantiornithine birds with ages exceeding 125 million years.

Researchers have found that light modulates digestive system function in sea urchin larvae, even in the absence of food stimuli. Opsin cells, which are involved in light-dependent systems ...