Fig. 5

a Global biostratigraphic summary for placoderms discussed in the text, showing disparate stratigraphic ranges between China, Gondwana and Laurussia, and five postulated biotic dispersal/range enlargement episodes (A-D, square boxes) to explain them. Left column shows international subdivisions for the Silurian and Devonian, with macrovertebrate assemblages MAV1–15 for East Gondwana (from Young and Turner 2000), and I-XI for China (from Zhu et al. 2000). Calibration points (Ma) from ICS International Stratigraphic Chart. Range enlargement events are: S-D, Siluro-Devonian global expansion for various gnathostome groups; A₁, Pragian-Emsian E’Em or mid-Emsian M’Em bio-events (Zhu 2000) for faunal exchange from Asia to East Gondwana, with possible later (Eifelian) extension of asterolepid antiarchs into Laurussia [A₂]; B₁, range enlargement into East Gondwana of Bothriolepis, from its earliest occurrence (Emsian, South China), with extension [B₂] into Laurussia possibly related to the Givetian Taghanic transgressive event; C, expansion of phyllolepids into the Famennian of Laurussia, possibly associated with Kellwasser and Condroz Event sea level changes; other groups with similar patterns consistent with a biotic dispersal event (‘Great Devonian Interchange’) are groenlandaspids, rhizodontids, gyracanthids, and tetrapods; D, range enlargement of sinolepid antiarchs from South and North China into East Gondwana, possibly associated with Hangenberg Event sea level changes; b Summary of placoderm distributions and dispersal episodes in a on a Devonian palaeomagnetic reconstruction (Li and Powell 2001). For placoderm locality details see Young (2003, fig. 1). Abbreviations: KAZ= Kazakhstan, NC= North China, SC= South China. Updated from Young (2010a)