The discovery of an exceptionally preserved primitive fish from the Ludlow of Yunnan, China, that represents the oldest near-complete gnathostome (jawed vertebrate) offers insights into the origin and early divergence of osteichthyans, and indicates that the minimum date for the actinopterygian–sarcoperygian split was no later than 419 million years ago.
A three-dimensionally preserved 419-million-year-old placoderm fish from the Silurian of China is described that represents the first stem gnathostome with dermal marginal jaw bones (premaxilla, maxilla and dentary), features previously restricted to Osteichthyes.
This first tentative reconstruction of a 400-million-year-old fossil fish from China is presented, which changes the polarity of many characters used at present in reconstructing osteichthyan inter-relationships and offers new insights into the origin and evolution of osteichthyans.
This 405-million-year-old fish from the Lower Devonian of Yunnan (China) demonstrates that cosmine in many fossil sarcopterygians arose step by step through the acquisition of a pore–canal network followed by the subsequently developed ability to resorb previous generations of odontodes and enamel.
Galeaspids, a 435-million-year-old ‘ostracoderm’ group from China and Vietnam, is described, which indicates that the reorganization of vertebrate cranial anatomy was not driven deterministically by the evolutionary origin of jaws but occurred stepwise, ultimately allowing the rostral growth of ectomesenchyme that now characterizes gnathostome head development.
It is shown that Psarolepis romeri, a bony fish from the the Early Devonian period, combines enamel-covered dermal odontodes on scales and skull bones with teeth of naked dentine, and that Lepisosteus oculatus (the spotted gar) has enam and ambn genes that are expressed in the skin, probably associated with ganoine formation.
A basal sarcopterygian fish is described that fills the morphological gap between Psarolepis and higher sarcoptergyians and the presence of eyestalk attachments is reported, showing that this supposedly non-osteichthyan feature occurs in basal sarcoperygians as well as the actinoptergyian-like Australian braincase.
Styloichthys from the Lower Devonian of China bridges the morphological gap between stem-group sarcopterygians (Psarolepis and Achoania) and basal tetrapodomorphs/basal dipnomorphs and provides information that will help in the study of the relationship of early sarcoperygians, and which will also help to resolve the tetrapods–lungfish divergence into a documented sequence of character acquisition.
The discovery of the first Devonian tetrapod from Asia is reported, a finding that substantially extends the geographical range of these animals and raises new questions about their dispersal.
New material of Kenichthys, a 395-million-year-old fossil fish from China, is presented that provides direct evidence for the origin of the choana and establishes its homology: it is indeed a displaced posterior external nostril that, during a brief transitional stage illustrated by KenichThys, separated the maxilla from the premaxilla.