CATALOG OF ORIGINAL DESCRIPTIONS: Trilobatus Spezzaferri, Kucera, Pearson, Wade, Rappo, Poole, Morard and Stalder 2015

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> T -> Trilobatus
Other pages this level: Tectoglobigerina, Tenuitella, Tenuitellidae, Tenuitellinata, Texasina, Textilaria, Textularia, Thalmanninella, Ticinella, Tinophodella, Tinophodellini, Toddella, Trilobatus, Trinitella, Trochoguembelitria, Truncatulina, Truncorotalia, Truncorotaliini, Truncorotaloides, Truncorotaloididae, Truncorotaloidinoidea, Tubitextularia, Turbeogloborotalia, Turborotalia, Turborotalia (Acarinina), Turborotalia (Turborotalia), Turborotaliini, Turborotalita,

Trilobatus

Citation: Trilobatus Spezzaferri, Kucera, Pearson, Wade, Rappo, Poole, Morard and Stalder 2015
Rank: Genus
Type species: Globigerina triloba Reuss, 1850

Current identification/main database link: Trilobatus Spezzaferri et al. 2015


Original Description

Test low trochospiral, involute and compact in the initial whorls, later becoming slightly evolute to evolute. The test is from ovate to subtriangular or subrectangular to slightly lobate in outline with rounded peripheral margin with three to four subspherical chambers in the last whorl, increasing rapidly in size. The last chamber may become embracing and comprise one half of the test or it may become irregularly shaped and flattened. Sutures are depressed, straight to slightly curved on both sides, the umbilicus is often narrow and concealed. The primary aperture is an umbilical-extraumbilical elongated slit, tending toward the margin in many species. Supplementary apertures on the spiral side are irregular slits or low arches placed at the intersection of the spiral and radial sutures. The wall texture is cancellate, spinose and sacculifer–type sensu Hemleben et al. (1989).


Extra details from original publication

Distinguishing features. Differences and similarities between the genus Globoturborotalita Hofker, 1976, Globigerinoides Cushman, 1927, Globigerinoidesella El-Naggar, 1971 and new genus Trilobatus are outlined in Table 2. The descendant Praeorbulina differs from Trilobatus by possessing a last chamber tending to envelope the entire test and Globigerinoidesella by possessing irregular digitate projections on the final chambers. The potentially descendant lineage Sphaeroidinellopsis—Sphaeroidinella differs by developing a thick cortex covering the test surface.

Remarks. Hemleben et al. (1987) demonstrated that specimens attributed to T. trilobus and T. sacculifer are one single biological species based on culturing evidence. Their observation was later proved by genetic evidence (Weiner et al. 2013). These authors have recommended for all modern representative of this genetic species the name sacculifer because it was the only one described within modern plankton, by Brady 1887. They discuss also the possible priority of the name G. quadrilobatus as senior synonym. However, considering the possibility that the fossil representatives of the plexus with different morphologies could represent different species, they have proposed to retain trilobus for fossil populations and use the name sacculifer for all modern specimens of the plexus, with the use of ‘‘with sac” or ‘‘without sac” for the description of morphotypes within this species.

New observations of the PPFWG on G. quadrilobatus and its lectotype documented in Papp and Schmid (1985) have revealed that this species is not related to the trilobus/sacculifer but rather to the ruber lineage and therefore, it cannot be a senior synonym of trilobus/sacculifer. The holotype of this species was never described by its author (d'Orbigny 1846), therefore (Blow and Banner 1962) designated a lectotype, which no longer exists. This specimen was attributed to the “G. trilobus” group (Blow and Banner 1962; Bolli & Saunders 1985; Papp and Schmid 1985). Papp and Schmid (1985) designated a lectotype from the original material of d'Orbigny (1846). In particular, new SEM images of this lectotype shows a highly arched and symmetrical aperture, centered in the umbilicus, a ruber/sacculifer-type wall texture with strong affinities to the G. ruber group.

The occurrence of specimens with a tendency to develop a sac-like final chamber can be traced to the early Miocene (Fig 5), but their occurrence throughout the fossil record is often inconsistent, rendering the recommendation to keep both trilobus and sacculifer unnecessary. In line with Weiner et al. (2013), the development of the sac-like final chamber is considered as a phenotype. However, in the fossil record it is useful to separate these forms, which have different ecological preferences, and thus, to simplify the use of the new genus Trilobatus we consider acceptable naming them T. sacculifer and T. trilobus.

The name Trilobatus for the new genus has been chosen because it recalls the name of the designated type species T. trilobus, aiming to reduce confusion when searching on names in taxonomic databases and the literature. The first representative of this genus is T. primordius. Its presence within Paragloborotalia opima (Zone O5) reported by [60] is not presently proven. Many other authors (see Spezzaferri 1994 for a comprehensive list of references) reported its lowest occur- rence in the late Oligocene Zone O6-O7. Berggren et al. (1995) place the first appearance datum (FAD) of this species at 26.7 Ma and it Last Common Occurrence (LCO) at 24.3 Ma (as per the magnetochronology of Cande & Kent 1995). The genus diversifies at the base of Zone M1 (Fig 1) with the appearance of T. trilobus equated at 23.73 Ma [13]. The definition of the genus Trilobatus presently includes the species:

Note: We have followed the attribution of Turco et al. (2011) who do not include T. sicanus in the genus Praeorbulina. This species is here therefore attributed to Trilobatus.

 

References:

Spezzaferri, S. & others, (2015). Fossil and genetic evidence for the polyphyletic nature of the planktonic foraminifera "Globigerinoides", and description of the new genus Trilobatus. PLOS one: 1-20.


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Trilobatus compiled by the pforams@mikrotax project team viewed: 25-11-2017

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