Palaeobiogeography and evolutionary patterns of the larger foraminiferBorelisde Montfort (Borelidae)

Abstract

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.

Alien and cryptogenic Foraminifera in the Mediterranean Sea: A revision of taxa as part of the EU 2020 Marine Strategy Framework Directive

“…Fossil occurrences of other species of Borelis spp. from the Mediterranean region were reported by Reiss & Gvirtzman (1966), Adams (1976), Jones et al (2006), Makled et al (2017) and Bassi et al (2019). Unpublished records of modern B. schlumbergeri from northern Israel (Hyams-Kaphzan) show the species to be present in the year 1999 at Akhziv.…”

The Geographic, Environmental and Phylogenetic Evolution of the Alveolinoidea from the Cretaceous to the Present Day.

“…B. inflata is recorded as ranging from the Oligocene to the Miocene (Tortonian) of the Western Tethys (Sirel, 2003;Bassi et al, 2009;Braga and Bassi, 2011), and Zakynthos in Greece (Di Carlo et al, 2010;Benedetti, 2010). Borelis melo with a spheroidal shape and relatively large proloculus (60-65µm) has been reported from the Aquitanian to Messinian in the Tethyan province (Adams et al, 1983;Betzler and Schmitz, 1997;Jones et al, 2006;BouDagher-Fadel and Noujaim Clark, 2006;Brandano et al, 2016;Bassi et al, 2019). According to Bassi et al (2019), in B. melo the Y-shaped septula occur only in the adult growth stage, while in B. curdica the proloculus is smaller (30-50µm) and the Y-shaped septula occur in all whorls.…”

“…Borelis melo with a spheroidal shape and relatively large proloculus (60-65µm) has been reported from the Aquitanian to Messinian in the Tethyan province (Adams et al, 1983;Betzler and Schmitz, 1997;Jones et al, 2006;BouDagher-Fadel and Noujaim Clark, 2006;Brandano et al, 2016;Bassi et al, 2019). According to Bassi et al (2019), in B. melo the Y-shaped septula occur only in the adult growth stage, while in B. curdica the proloculus is smaller (30-50µm) and the Y-shaped septula occur in all whorls. These authors also postulated that all reliable records of B. melo and B. curdica are only from Western Tethys, and B. curdica is restricted to the Tethyan province.…”

“…In the Tethyan Eocene, Borelis is represented by the spheroidal B. vonderschmitti (Schweighauser), which was widespread throughout the Bartonian and Priabonian of Western Tethys (Bassi and Loriga Broglio, 1999;Bassi et al, 2019). Borelis is common in deposits laid down in Early Oligocene, low-latitude, shallow-marine environments, and differs from Alveolina in having only a pre-septal passage and a secondary small tier of chamberlets, which alternate with the larger ones producing "Y" shaped septa in axial section (BouDagher-Fadel and Noujaim Clark, 2006).…”

“…Borelis is common in deposits laid down in Early Oligocene, low-latitude, shallow-marine environments, and differs from Alveolina in having only a pre-septal passage and a secondary small tier of chamberlets, which alternate with the larger ones producing "Y" shaped septa in axial section (BouDagher-Fadel and Noujaim Clark, 2006). In the Oligocene, the sub-spheroidal, small (0.5-1.5 mm in diameter and 0.4-1.2 mm long), tightly coiled B. inflata (a form with no Y-shaped septula) is also recorded from the Oligocene to the Tortonian of the Western Tethys (Sirel, 2003;Di Carlo et al, 2010;Benedetti, 2010;Braga & Bassi, 2011;Bassi et al, 2019).…”