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

This article has been reviewed by Johann Hohenegger

The article on Alveolinoids by Marcelle K. BouDagher-Fadel and Geoffrey D. Price continues their former works on larger benthic foraminifera in a very comprehensive manner. The outstanding knowledge of published articles about this group of larger, symbiont-bearing Foraminifera allows a comprehensive view about mutual phylogenetic relations between the three families Alveolinidae, Rhapidioninidae and Fabulariidae. These families are solely based on morphological characters, which determines the generic status of the different morphologically (not biologically) determined genera. Therefore, the stratigraphic gap between Cretaceous and Paleogene representatives within the same morphological genera (e.g. in the Periloculina-Lacazina lineage) will be explained by canalizing strongly the possibilities of genetic alterations leading to identical morphospecies starting from a ‘simple’ forerunner. The second and more common explanation for similar forms at different stratigraphic levels is by homoplasy, again canalizing the pathways in genetic alterations, but not in the strict form as explained above. Therefore, differences in the outer and inner morphology between Cretaceous and Paleogene genera explains this separation.

The important point based on these morphological differences is the environmental and paleogeographic aspect of these induced phylogenetic lineages based on sea-level stands, where low stands has led to migrations across oceans and high stands create different ecological niches in the oceans, where differentiations within genera occur. Four transatlantic migrations based on low sea level stands can be found from the Mid-Cretaceous to the end of Cretaceous (Fig. 11), especially from the East to the West, while one migration based on low sea-level stands can be found in the Paleogene. The migration from the Tethys Ocean to the Indo-Pacific is caused by the connections between these oceans in the Paleogene and the following disconnection in the Neogene due to tectonic events. This explains the today distributions of the two genera Borelis and Alveolinella, where the first can be found in shallow waters of the whole tropical Indo-Pacific, possibly spread by the open Inter-American gateway to the Caribbean, while Alveolinella is restricted to the tropical East Indian and West Pacific Ocean.
All distribution are coincident with the directions of the paleo-currents.

Summing up, this is a well-written paper, where the reader can clearly understand the intensions of the authors. We have to keep in mind, that this are the opinions of the authors. Some specialists will not agree with some interpretations, but this does not impair the value of this paper. Published in this form, it is great information and shows possible interpretations of the phylogeny in this remarkable group of organisms, especially by the interruption of phylogenetic lines and the restart from primitive forms to extremely similar high evolved forms.

Level of importance: This manuscript details the evolution, distributions and dispersal of families of larger benthic foraminifers that are useful both biostratigraphically and paleoenvironmentally.

Level of validity:  The work is well researched and appears to be valid in the context of information presented.  As someone trained in ecology, this reviewer recommends that the authors not refer to taxa as occupying “the same niche” but rather using the terminology “a similar niche”, which communicates comparable information that is more defensible.  Similarly, from a paleoceanographic perspective, there is no reason to assume that the shallow waters occupied by these LBF would have experienced significant cooling (see text on pages 17 & 18). Rather, the high latitudes cooled and deep-ocean circulation accelerated, but low latitude temperatures probably did not fluctuate by more than a few degrees. On page 22, “The Indo-Pacific Province, 12 ^th line in the first paragraph regarding “more tolerant forms with more evolved characters” is problematic, because, as the authors note numerous times, the simpler forms are the long-term survivors and therefore presumable, “more tolerant”.

Level of completeness:  A Table of locations and coordinates for the new locations mention on pages 3 & 4 would be useful. This paper presents concepts that deserve additional discussion and recommendations for how to better define such issues in fossil phylogenies.  For example, although the information presented implies polyphyletic emergence of the three families, that issue is not mentioned in the discussion as a topic requiring further consideration in systematics and nomenclature. Similarly, the authors propose that some genera emerged more than once from the same primitive  ancestor, but don’t discuss the systematic implications thereof.  I am not proposing that the authors tackle these challenges in this paper, but could provide a paragraph in the Discussion noting that such challenges require further consideration in terms of appropriate nomenclature. Also, on page 7, there is a sentence that starts “Banner (1971)…” and an accompanying Figure 9 that are interesting, but clearly not pertinent to the evolutionary and distributional study as presented.  I recommend that the sentence and figure be deleted.

Level of comprehensibility: The topics in this manuscript, including morphological detail and paleo/evolutionary terminology, involve a lot of terms unfamiliar to most, including many researchers who work with foraminifers. Often terms are well defined, but other times, the reader will be forced to look them up. And sometimes it is challenging to determine what feature is being described for which species; and example is the short paragraph near the end of page 23, where the discussion of the Y-shaped septula is confusing.  Finally, several of the captions for figures need additional explanation of symbols, especially Figures 11 and 16.

Need for further editing: This is a long and detailed manuscript that could benefit from careful editing to deal with inconsistencies, wordiness, missing words, and occasionally poorly constructed sentences. Some common inconsistencies are in use of hyphens where en dashes should be used (both in the text and references) and in spacing (e.g., 6Ma vs. 6 Ma). Other issues include extraneous words, some confusing sentences that require clarification, and long sentences that can be broken up into two or more sentences.