The palaeobiogeography of the alveolinoid Borelis species reveals the evolutionary patterns leading to the two extant representatives, which occur in shallow‐water tropical carbonate, coral reef‐related settings. Type material and new material of fossil Borelis species, along with Recent specimens were studied to assess their taxonomic status, species circumscriptions (based on proloculus size, occurrence of Y‐shaped septula, and the index of elongation), palaeobiogeography and evolutionary dynamics. The species dealt with here are known from exclusively fossil (B. pygmaea, B. inflata, B. philippinensis, B. melo, B. curdica), and from fossil and modern (B. pulchra, B. schlumbergeri) specimens. For the first time, fossil and Recent Borelis specimens are illustrated via micro‐computed tomography scanning images. Depending on the occurrence of Y‐shaped septula, two lineages are distinguished. Deriving from the middle–upper Eocene Borelis vonderschmitti, the first lineage includes B. inflata, B. pulchra and B. pygmaea, lacking Y‐shaped septula. The first species bearing Y‐shaped septula is the Rupelian B. philippinensis of the western Indo‐Pacific. The westward migrants of B. philippinensis into the Mediterranean gave rise to B. melo (Aquitanian–Messinian) and B. curdica (Burdigalian–Tortonian). These two species became isolated from the Indo‐Pacific by the Langhian eastern closure of the Mediterranean basin and disappeared during the Messinian Salinity Crisis. Since the Tortonian, B. schlumbergeri, which descended from B. philippinensis, has inhabited the Indo‐Pacific along with B. pulchra. From the central Pacific Ocean, B. pulchra reached the Caribbean area before the early Piacenzian closure of the Central America seaway.
Life was limited for most of Earth's history, remaining at a primitive stage and mostly marine until about 0.55 Ga. In the Paleozoic, life eventually exploded and colonized the continental realm. Why had there been such a long period of delayed evolution of life? Early life was dominated by Archaea and Bacteria, which can survive ionizing radiation better than other organisms. The magnetic field preserves the atmosphere, which is the main shield of UV radiation. We explore the hypothesis that the Cambrian explosion of life could have been enabled by the increase of the magnetic field dipole intensity due to the solidification of the inner core, caused by the cooling of the Earth, and the concomitant decrease with time of the high-energy solar flux since the birth of the solar system. Therefore, the two phenomena could be responsible for the growth and thickening of the atmosphere and the development of land surface life
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