Cryptic speciation in the “ Marshallora nigrocincta ” species complex (Gastropoda, Triphoridae) from the Western Atlantic

How we study cryptic species and their biological implications: A case study from marine shelled gastropods

Methodological and biological considerations are intertwined when studying cryptic species. A potentially large component of modern biodiversity, the frequency of cryptic species among taxonomic groups is not well documented. The term "cryptic species" is imprecisely used in scientific literature, causing ambiguity when interpreting their evolutionary and ecological significance. This study reviews how cryptic species have been defined, discussing implications for taxonomy and biology, and explores these implications with a case study based on recently published literature on extant shelled marine gastropods. Reviewed gastropods were recorded by species. Records of cryptic gastropods were presented by authors with variable levels of confidence but were difficult to disentangle from inherent biases in the study effort. These complexities notwithstanding, most gastropod species discussed were not cryptic. To the degree that this review's sample represents extinct taxa, the results suggest that a high proportion of shelled marine gastropod species are identifiable for study in the fossil record. Much additional work is needed to provide a more adequate understanding of the relative frequency of cryptic species in shelled marine gastropods, which should start with more explicit definitions and targeted case studies.

Nomenclator, geographic and stratigraphic distribution of the family Triphoridae (Mollusca: Gastropoda)

The microgastropod family Triphoridae is one of the five most diverse marine molluscan families. It likely hosts a few thousand species worldwide, but its taxonomy has long been considered challenging due to the high diversity and subtle morphological characters needed for species delimitation. Consequently, only a small portion of the species appears to be formally described to date. However, further taxonomic work should be based on robust knowledge on the numerous names introduced so far. In this perspective, we have here compiled a list of all published names that can be attributed to the fossil and extant Triphoridae. We list 958 species and 75 genus names, of which 771 are known as extant species and 146 as fossil species, 41 are known from both fossil and extant records. We provide information on type locality and horizon, type material, synonymy and homonymy. Importantly, based on the review of hundreds of publications, we provide a preliminary overview of the geographic and stratigraphic distribution.