Early Devonian Chitinozoans from Central Guangxi, South China: New Biostratigraphic and Palaeobiogeographic Insights

The latest Silurian to Early Devonian characterises a critical interval in the macroevolution of chitinozoans, marked by a significantly low diversity and the extinction of the entire family Conochitinidae. The South China Block represents one of the classic areas for Devonian research, hosting well-exposed and continuous Pragian successions. However, the Pragian chitinozoans have been poorly investigated, with their biostratigraphical significance remaining to be clarified. This study presents new chitinozoan data from several sections in central Guangxi, South China, where a conodont biostratigraphical framework has been established. A total of 17 species belonging to 4 genera of Early Devonian chitinozoans were recovered and systematically described. Four successive chitinozoan biozones are recognised in ascending order: the Angochitina comosaInterval Zone, the A. caeciliae Interval Zone, Unnamed Zone 1, and Unnamed Zone 2. Integration of these new biostratigraphic data with published global records facilitates intercontinental correlation. Results confirm that the A. comosa and A. caeciliae zones from the South China Block are highly correlative with equivalent units in eastern Australia and North Gondwana. In contrast, Unnamed Zones 1 and 2 (upper Pragian to lower Emsian), characterised by low diversity, present significant challenges for high-resolution global correlation. Integrating global occurrence data, we conducted quantitative palaeobiogeographic analyses (cluster analysis, non-metric multidimensional scaling, network analysis) across 13 regions, identifying three major faunal units: eastern Australia; North Gondwana–South China (southeastern Palaeotethys); and eastern Laurussia–South America (northwestern Palaeotethys). Ocean currents are the primary control on chitinozoan distribution, while genus-level distributional drivers remain unclear due to limited low-latitude data.