Steps of Morphogenesis and Iterative Evolution of Imperforate Larger Foraminifera in Shallow Carbonate Shelves During Mesozoic Times: Possible Relations to Symbiotic and Abiotic Factors

Abstract

The microgranular/agglutinated imperforate larger foraminifera (ILF, chiefly "lituolids") of Mesozoic shallow marine carbonate shelves are a polyphyletic group of K-strategists, ecologically homogeneous inhabitants of the photic zone (nutrient poor) and hosting symbionts as their larger porcelaneous recent equivalents. They contrast with deeper water "lituolid" taxa and other deeper marine dwellers (hyaline perforate and planktonics r-strategists). They are narrowly linked to the carbonate platform history and evolution, birth and demise (correlated to paleotectonics or sea-level variations), and global climatic or volcanic events, OAE, etc.2. General principles used in evolutionary sciences can be applied to decipher some morphological pathways among foraminifera through time to reconstruct phylogenetical arborescences, e.g., embryology (heterochronies of development), recapitulation law (Haeckel), size increase (Depéret), parallel evolution, and biostratigraphy.3.Iterative evolution is the main mode of morphological variation through time and biostratigraphy helps to reconstruct the time repartition of diverging advanced homeomorphic taxa and their distinction. The new characters are issued from a constant, more tolerant stock of smaller and simpler primitive atavic forms by the transformation of previous structures or the addition of new ones. Advanced homeomorphic taxa are temporarily preserved and their morphological innovations linked probably to (epi)genetic constraints and symbiotic history increasing their energy efficiency in a rather stable (but cyclical) environment.4.Morphological innovations appear slowly during the Jurassic and more rapidly (and frequently) during the Cretaceous following a probable saltative and allopatric mode of evolution during favorable periods after main environmental crisis, anoxia, and sea-level changes. The Cretaceous is a time of great diversification (adaptive radiation of microgranular lituolids and larger porcelaneous tests).5.Morphological changes at a scale of one or two stages in one evolutive bioseries (general trend: size and internal complications increase) cannot be linked to global events or other abiotic factors (e.g., the orbitopsellids in the Pliensbachian) but are rather driven by internal epigenetic factors related to algal symbiosis and coevolution. The constancy of the model (text Fig. 8.2) through time in variable clades could be explained that way. The structural incompatibility between pseudokeriotheca/alveolae within the wall and marginal microstructures (radial partitions or hypodermic network) could be explained by a biological incompatibility of bacterial symbionts to live aside with larger microalgae as dinoflagellates. Local discontinuous events like cyclic (metric) parasequences are common on carbonate platforms but have no apparent influence on morphogenesis or population composition.6.Conversely, global environmental crises affect deeply the larger foraminifera (chiefly advanced larger tests) and population compositions at a higher taxonomic ...

Agglutinated Conical Foraminifera (Orbitolinidae, Coskinolinidae) From the Upper Cretaceous (Campanian) of Greece, With Description of Paracoskinolina Klokovaensis N. Sp.

“…Iterative evolution as the main mode of morphological variation in Mesozoic imperforate larger benthic foraminifers has been recently discussed by Septfontaine (2020). This phenomen appears to be present also in the longlasting and complex history of the Orbitolinidae stretching from the upper Berriasian to the Paleogene (lower Oligocene) including two main-mass extinctions (Ce/T and K/T).…”

Comment on: “Evolutionary trend of Cenomanian alveolinids from Zagros Basin, SW of Iran” by Dousti Mohajer et al. (2021) in Geological Journal

“…Moreover, especially when working with fossils, evolutionary arguments could be based on a certain speciation model by considering a complex array of determining conditions (see e.g., Hohenegger, 2014, for a comprehensive discussion). Evolutionary models should rely on a solid, multidisciplinary‐based, corollary, such as the studies of Hottinger (2001) and Septfontaine (2020). The concept of “evolutionary trend” exposed by Dousti Mohajer et al (2021) is, however, based on an unrelated corollary that merely concerns some arguments classically used in foraminiferal taxonomy as stated (page 11): “The following features are of significance in the evolutionary study of alveolinids: Shell size (axial length), shell shape, number of chambers in each whorl, the ratio of axial length to the equatorial radius or the index of elongation, the status of aperture and internal structures, for example, septa, septula, floor, shape, and number of chamberlites”.…”

Siphopfenderina Gen. Nov. (Type-Species Arenobulimina Geyikensis Solak, 2022), a Primitive Pfenderinid Foraminifera From the Cretaceous of Neotethys

“…Other examples of foraminifera with pseudokeriothecal wall structure in-clude the Middle Jurassic Conicopfenderina Septfontaine in Kaminski, 2000, the Lower Cretaceous Melathrokerion Brönnimann & Conrad, 1967, the Upper Cretaceous-Paleogene Chrysalidina Orbigny, 1839(e.g., De Castro, 1991, Paleogene Coskinolina Stache, 1875, Coleiconus Hottinger & Drobne, 1980, and Barattolites Vecchio & Hottinger, 2007 It is worth noting that the presence of pseudokeriotheca within the wall seems to be incompatible with any exoskeletal microstructure (hypodermic network or radial partitions of larger foraminifera; Septfontaine, 1981, for details). It may be due to differential housing of symbionts (e.g., according to size) in different genera (Septfontaine, 2020). For the families Biokovinidae Gušić and the Charentiidae Loeblich & Tappan, the presence of pseudokeriotheca is interpreted as of suprageneric taxonomic importance (Loeblich & Tappan, 1985;Gušić, 1977).…”