Abstract
Abstract. Morphologically similar benthic foraminiferal taxa can be difficult to separate. Aside from causing issues in taxonomy, incorrect identifications complicate our understanding of species-specific ecological preferences and result in flawed palaeoenvironmental reconstructions and geochemical results. Over the years, a number of studies have grouped together several key Arctic–North Atlantic species in various combinations, despite their distinct environmental preferences and/or stratigraphical differences, causing great confusion in the literature. These species include Cassidulina laevigata, Cassidulina neoteretis, Cassidulina teretis, Paracassidulina neocarinata, Islandiella helenae, and Islandiella norcrossi. Here, we provide for the first time a detailed comparison of these taxa. We present a compilation of the original species descriptions, along with clear, illustrated guidelines on how to separate these taxa to circumvent taxonomic confusion. We acknowledge that some features cannot easily be seen with a standard low-powered microscope, especially if specimens are not well preserved. In those cases, we recommend the following actions: (i) always strive to make a precise identification and at least differentiate between the three genera; (ii) where C. neoteretis and C. teretis cannot be separated, and where the stratigraphical context does not make the species identification obvious, specimens belonging to these taxa should be reported as C. teretis/C. neoteretis; and (iii) where specimens in a sample cannot be confidently assigned to a specific species of Islandiella or Cassidulina, specimens should be grouped as Islandiella spp. or Cassidulina spp., followed by naming the most dominant species in brackets. The improved identification of Cassidulina, Paracassidulina, and Islandiella specimens will ensure development of a better understanding of the ecological affinities of these key Arctic–North Atlantic taxa, consequently resulting in more accurate palaeoenvironmental reconstructions and geochemical data.
Highlights
A common problem in benthic foraminiferal studies is the persistent taxonomic confusion between morphologically similar taxa, even among species that are often abundant
We present an illustrated comparative study of these six morphologically comparable species C. laevigata, C. neoteretis, C. teretis, P. neocarinata, I. helenae, and I. norcrossi and highlight the distinguishing characteristics that allow them to be correctly identified at a species level
By providing clear guidance on the correct species identifications for C. laevigata, C. neoteretis, C. teretis, P. neocarinata, I. helenae, and I. norcrossi, we aim to curtail the misidentification of these morphologically similar species, elucidate ecological affinities, and improve accurate palaeoenvironmental reconstructions based on the differing environmental preferences of examined taxa
Summary
A common problem in benthic foraminiferal studies is the persistent taxonomic confusion between morphologically similar taxa, even among species that are often abundant. Sejrup and Guilbault, 1980; Mackensen et al, 1985; Polyak et al, 2002), resulting in the loss of important information when analysing foraminiferal assemblage composition It may cause mixing of taxa when picking specimens for geochemical analyses, leading to potentially flawed data, especially when considering vital effects. This problem is often exacerbated by poor access to well-illustrated and high-quality taxonomic resources (with clear scanning electron microscope (SEM), light microscope or line illustrations, and taxonomic descriptions), along with information on changes in synonyms over time or regional use of species names in disagreement with type descriptions Researchers lacking access to quality taxonomic resources would seek to examine type material available at museums or other institutions or visit experts for training; this is not always possible due to funding issues or lack of mobility and opportunity
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