Led by the nose

Abstract

Hagfish embryos show developmental features that contradict the idea that these jawless fish are the most primitive living vertebrates. The findings also help to trace the evolution of vertebrate cranial structure. See Article p.175 The hagfish is the most primitive extant vertebrate. Its anatomy and development hold clues to understanding the evolution of that most enigmatic of structures, the vertebrate head. Hagfish embryos are notoriously hard to obtain, but a few years ago Shigeru Kuratani and colleagues managed to prepare some, and — for the first time since 1899 — significant work on hagfish embryology began. This paper presents the first detailed report on the craniofacial development of a hagfish species, Eptatretus burgeri. The authors identify an embryonic development pattern shared only by the jawless lampreys and hagfish that may have been primitive for all vertebrates.