Vertebrates would look very different were it not for the evolution of the head and trunk into separate structures, and this differentiation is a subject of great interest in zoology.
Benjamin Naumann at Friedrich Schiller University in Jena, Germany, and his colleagues investigated the development of a muscle called the cucullaris, which spans the interface between the head and trunk in all vertebrates. They looked at its development in the longnose gar (Lepisosteus osseus). In fish phylogeny, gars sit near the base of the group of bony fish called ray-finned fishes. The team found that muscles previously identified as the cucullaris in these fish had been misidentified, and that the actual cucullaris develops later than the other muscles at the head–trunk interface. This is similar to how it develops in some tetrapods, and suggests that the muscle might have a common origin in all bony fish and tetrapod vertebrates, a subject of debate in the past.