Shiladri S. Das, Sandip Saha, Subhendu Bardhan, Subhronil Mondal, Shubhabrata Paul, Sumanta Mallick, Ranita Saha, Warren D. Allmon
Journal of Paleontology 98 (3), 434-445, (29 October 2024) https://doi.org/10.1017/jpa.2023.91
Turritellid gastropods are prey and naticid gastropods are predators and their oldest interaction was reported by us from the Oxfordian (157 million years ago). Recently, the Oxfordian age was disputed on the basis of mostly comments/opinion pieces. A map was reproduced based on data that are not correct. The only hard evidence provided, was the microfaunal assemblage. Against these claims, we hereby furnish several concrete examples, such as locality information, mode of occurrence, lithology (Fe-ooid-bearing beds), indigenous Oxfordian fossils, and the distinct assemblage of turritellid and naticid gastropods between the present and the Miocene beds of the Chhasra Formation, Kutch. Furthermore, the diversity curves and paleoecological analyses (both gastropods and bivalves) speak for two distinct and separate assemblages. We, therefore, reiterate our early claims about the age and evolution of prey–predator interaction and the development of the conchiolin layer in corbulid bivalves and other inferences that we have described in our previous publications.
We published a series of papers regarding the oldest turritellids, naticids, their paleoecological interaction, and gastropod biozonation, which are of Oxfordian in age, from the Jhura pond section, Kutch, western India. Recently, an Oxfordian age was challenged by Fürsich et al. (2023) and they argued for a Cenozoic age. The authors reproduced a local geological map based on regional data where the Jhura pond section sediments were overlying the Bhuj Formation. In the original regional data, there was no Bhuj Formation and the introduction of the Bhuj Formation served to show that Jhura pond section sediments were “allochthonous”. Other lines of argument against our conclusions (e.g., identification of associated bivalve fauna, foraminiferal assemblage, and geological context) were brought forward. There were additional inconsistencies, such as the reworking of Oxfordian fossils, in their comment/opinion pieces. The only hard evidence was the report of a microfaunal assemblage, but the taxa were identified at the generic level and most of the genera appear in the Jurassic or even earlier.
Here we provide detailed and concrete evidence explaining features at the Jhura pond section, such as the subvertical nature of the beds, the ooid-bearing lithologies, the presence of various Oxfordian fossils, the difference in turritellids, naticid assemblages, and differences in the diversity curves between the present beds and the lower Miocene Chhasra Formation of Kutch. Detailed paleoecological analyses (both gastropods and bivalves) speak for two paleocommunities. We, therefore, reiterate that the present Jhura pond section sediments are Oxfordian in age and validate all the interpretations and conclusions that we have made in our previous papers.