Phylogeny Paleobiogeography of Caribbean Lepidocyclinds

Lepidocyclinids, a three layered orbitoidal larger benthic foraminifera group that appear at the base of the Eocene, often dominate the Paleogene fossils benthic communities of the American-Caribbean realm. Limited taxonomical and biostratigraphical data on lepidocyclinid populations including their response to ecological gradients have prevented yet an effective global view of their phylogenetical and paleo- biogeographical evolution in this realm. Available Eocene and Oligocene lepidocyclinid populations from shallow water carbonate deposits from Cuba have a considerable potential to unlock their extreme shell complexity, which can be only defined by morphometry. Therefore, this project strives a morphometric investigation of the internal morphology of the lepidocyclinids based on growth-independent and growth- invariant characters as only reliable means for species identification, and to differentiate the often subtle morphological changes that have been observed to occur with times. The overall goal of this project is to address the significance of ontogenetic studies based on growth-independent and growth-invariant characters to yield results going beyond the functional morphology, evolution, high-resolution biostratigraphy, and to include information about ther palaeogeographic distribution patterns and the environmental changes that these long-lived foraminifera may have experienced. The recent published works using growth-independent and growth invariant characters to describe the internal morphology of Caribbean Eocene nummulitids supported the present proposal, since have already lead to the first insights into this important topic in fossil record. These studies have documented results on species recognition, and much better interpretation of evolutionary tendencies separated from palaeoenvironmental and palaeogeographic diversification.

Lepidocyclinids belong to Larger Foraminifera, which are marine Protists with calcareous, multichambered tests of size > 2mm up to some centimeters. Tests consist of an embryonal apparatus called nepiont, surrounded by a row of periembryonal chambers and multiple rows (chambers) divided into chamberlets, ordered in an equatorial plane. Additional chamberlets are laterally positioned in multiple layers on both sides of the equatorial plane. According to these complex test structures, remarkable evolutionary tendencies can be found in Lepidocyclinids starting in the mid Eocene of Central America (47.8 Ma) and, after crossing the Atlantic Ocean, finishing at the end of the mid Miocene (11.6 Ma) in the Indo-Pacific region. Due to the Corona Crisis starting simultaneously with the project in February 2020, the proposed field work in Central and South America could not be done within the 4 years' time range, thus the project was extended. Fortunately, material from Cuba used for the PhD thesis of Ana I. Torres Silva investigating Nummulitids could be used studying the Lepidocyclinids in these samples. Results were published in 2023 in a large paper, where an objective grouping of specimens into species using multivariate statistics based on growth independent and growth invariant metrical characters was exercised. Besides the embryonal apparatus, which was used yet for the determination of species, differences in chamberlets of the equatorial rows strengthen the classification and confirm phylogenetic lines. Not till the end of the Corona restrictions could the following field work being performed: Colombia(10.12.2022 - 21.12.2022). Field trips in El Carmen de Bolivar und Sincelejo both in the Caribbean region of Colombia Panama (19.02.2023 - 03.03.2023). Field trips near Panama City and the Azuero Peninsula. Mexico (29-11.2023 - 12.12.2023). Field trips in San Cristobal de las Casas, Palenque and Tuxtla Gutierrez. Processing the samples from all locations is still in progress, results will be published in 2025 in two articles at least.