Phosphatic stromatoporoid sponges formed reefs ~480 Mya

Area of Science:

• Paleontology
• Marine Biology
• Biomineralization Studies

Background:

• Stromatoporoid sponges were key Paleozoic reef builders, but their early evolution and ecological roles are unclear.
• Understanding early reef ecosystems is crucial for deciphering major evolutionary events like the Great Ordovician Biodiversification Event.

Purpose of the Study:

• To report the oldest known stromatoporoid fossil, Lophiostroma leizunia, from South China.
• To investigate the biomineralization strategies and reef-building capabilities of early stromatoporoids.
• To refine the timeline of reef evolution and the Great Ordovician Biodiversification Event.

Main Methods:

• Stratigraphic analysis of ~480-million-year-old rock strata in South China.
• Detailed morphological and skeletal analysis of the fossil Lophiostroma leizunia.
• Biomineralogical analysis to determine skeletal composition.

Main Results:

• Discovery of Lophiostroma leizunia, the oldest known stromatoporoid, dating to the upper Tremadocian-lower Floian (~480 Ma).
• L. leizunia formed complex reef structures, binding diverse organisms and contributing significantly to framework construction.
• The fossil uniquely exhibits a fluorapatite skeleton, previously unknown in sponges, establishing Porifera's use of silica, calcium carbonate, and calcium phosphate.

Conclusions:

• This discovery advances the fossil record of stromatoporoids and reef evolution by ~20 million years, impacting the understanding of the Great Ordovician Biodiversification Event.
• The phosphatic skeleton of L. leizunia reveals novel biomineralization capabilities in early sponges, suggesting an ancient genetic toolkit for diverse mineral utilization.
• The findings provide critical insights into the evolution of biomineralization and early animal-dominated reef ecosystems.