Systematic taxonomy of theTrilobatus sacculiferplexus and descendantGlobigerinoidesella fistulosa(planktonic foraminifera)

Abstract

The extant morphospecies of the Trilobatus sacculifer plexus (T. sacculifer, T. quadrilobatus, T. immaturus and T. trilobus) have widespread biogeographical distributions and long stratigraphical ranges, and are thus routinely utilized in palaeoceanographical studies. The descendant morphospecies Globigerinoidesella fistulosa is comparatively shortranging (Pliocene-Pleistocene) and an important biostratigraphical marker. However, taxonomic concepts of these morphospecies are inconsistently applied between workers, leading to loss of information and incomparable datasets. We present a taxonomic appraisal of each morphospecies, including detailed taxonomic histories and refinement of their morphological concepts, using a combined population-based and typological approach. Morphometric data and scanning electron microscopy are used to illustrate morphological intergradation in the Trilobatus sacculifer plexus. The distinctive morphology of Globigerinoidesella fistulosa is shown to develop from T. sacculifer (as previously documented), but also from the other morphospecies in the plexus, providing the first fossil evidence demonstrating that the four morphospecies of the T. sacculifer plexus are the same species. Our new analyses support culturing and molecular genetic evidence from extant specimens that suggests the four T. sacculifer plexus morphospecies are the same biological species. However, we advocate using the four morphospecies concepts (T. sacculifer, T. quadrilobatus, T. immaturus and T. trilobus) and G. fistulosa, here refined, to increase their palaeoecological and biostratigraphical value.

Coiling directions in the planktonic foraminifer Pulleniatina: A complex eco-evolutionary dynamic spanning millions of years

“…For cases that are apparently randomly coiled throughout their existence and those with only slight biases it may be that the hypothetical ‘coiling gene’ is expressed only weakly during development, or not at all, so that randomness or ecophenotypic variation predominates at the moment the organism begins to build its shell. An interesting example of this is the modern species Trilobatus sacculifer which, unusually, has just one known genotype [ 80 ] but for which the coiling direction, as has been measured in hundreds of individuals, is consistent with being entirely random [ 81 ].…”

Evolution of the Oligotrophic West Pacific Warm Pool During the Pliocene‐Pleistocene Boundary

“…This species has been distinguished recently from its ancestor, the T . sacculifer plexus, based on morphological study and, in particular, the presence of elongate protuberances in the final chambers (Poole & Wade, 2019).…”

“…Globigerinoidesella fistulosa is a tropical to warm-subtropical, open-ocean, MLS with symbionts (Aze et al, 2011;Kennett & Srinivasan, 1983). This species has been distinguished recently from its ancestor, the T. sacculifer plexus, based on morphological study and, in particular, the presence of elongate protuberances in the final chambers (Poole & Wade, 2019).…”

Zooplankters in an oligotrophic ocean: contrasts in the niches of Globigerinoides ruber and Trilobatus sacculifer (Foraminifera: Globigerinida) in the South Pacific

“…The observed wide variability in the architecture of planktonic foraminifera, particularly evident in late ontogeny, has been simplified and structured by the proposal of morphospecies, usually using holotypes as exemplars (Scott, 2011). Poole and Wade (2019) interpreted Trilobatus sacculifer (Fig. 1 D-E, I-J, O-P) as a plexus of morphospecies (Globigerina quadrilobata (d'Orbigny, 1846); Globigerina triloba (Reuss, 1850); Globigerina sacculifera (Brady, 1877); Globigerinoides sacculifera var.…”