Brönnimann and Resig (1971) considered this form as a subspecies of T. quadrilobatus and related it to T. quadrilobatus immaturus. The holotype they describe is covered by a relatively thick cortex (“secondary shell substance”) concealing the sutures of the last whorl. Trilobatus praeimmaturus has been overlooked and possibly attributed to other Globigerinoides species, although it is relatively abundant. [Spezzaferri et al. 2018]
Catalog entries: Globigerinoides quadrilobatus praeimmaturus
Type images:Distinguishing features: Like T. immaturus and T. trilobus but more subcircular and compact outline; aperture slit-like encompassing the penultimate chamber, and usually 4 chambers in the final whorl.
NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
Wall type: Normal perforate, spinose, sacculifer-type wall.
Morphology: Low trochospiral, subglobular to ovate, compact in outline consisting of about 2½-3 whorls, 3½-4 subglobular chambers in the last whorl, increasing rapidly in size. Sutures depressed, straight to slightly curved on both sides, umbilicus narrow and tending to close. Primary aperture umbilical to extraumbilical, a low arch encompassing the penultimate chamber, and lacking any lip or rim but sometimes showing short blunt or composite pustules fused together. A single triangular slit-like to low arched supplementary aperture is placed over the sutures separating the last and the penultimate chamber. [Spezzaferri et al. 2018]
Size: Maximum diameter of holotype 0.22 mm, its axial height is about 0.19 mm. [Spezzaferri et al. 2018]
Character matrix
test outline: | Ovate | chamber arrangement: | Trochospiral | edge view: | Equally biconvex | aperture: | Umbilical-extraumbilical |
sp chamber shape: | Globular | coiling axis: | Low-moderate | periphery: | N/A | aperture border: | |
umb chbr shape: | Globular | umbilicus: | Wide | periph margin shape: | Broadly rounded | accessory apertures: | Sutural |
spiral sutures: | Moderately depressed | umb depth: | Deep | wall texture: | Cancellate | shell porosity: | Macroperforate: >2.5µm |
umbilical or test sutures: | Strongly depressed | final-whorl chambers: | 3.5-4.0 | N.B. These characters are used for advanced search. N/A - not applicable |
Geographic distribution: Cosmopolitan, abundant in the South Atlantic and southwestern Pacific Oceans. [Spezzaferri et al. 2018]
Isotope paleobiology: No data available. [Spezzaferri et al. 2018]
Phylogenetic relations: Trilobatus praeimmaturus evolved from T. immaturus in the middle part of Subzones M1b. [Spezzaferri et al. 2018]
Most likely ancestor: Trilobatus immaturus - at confidence level 3 (out of 5). Data source: Spezzaferri et al. 2018.
Geological Range:
Notes: From the middle part of Subzone M1b to Zone M5 (Brönnimann and Resig, 1971). Additional investigations are needed to prove its presence in younger Miocene sediment. [Spezzaferri et al. 2018]
Last occurrence (top): within M5 zone (15.10-16.38Ma, top in Langhian stage). Data source: Spezzaferri et al. 2018
First occurrence (base): within M1b subzone (21.12-22.44Ma, base in Aquitanian stage). Data source: Spezzaferri et al. 2018
Plot of occurrence data:
Primary source for this page: Spezzaferri et al. 2018 - Olig Atlas chap.9 p.292
Brönnimann, P. & Resig, J. (1971). A Neogene globigerinacean biochronologic time-scale of the southwestern Pacific. Initial Reports of the Deep Sea Drilling Project. 7(2): 1235-1469. gs V O Spezzaferri, S. (1994). Planktonic foraminiferal biostratigraphy and taxonomy of the Oligocene and lower Miocene in the oceanic record. An overview. Palaeontographia Italica. 81: 1-187. gs Spezzaferri, S., Olsson, R. K. & Hemleben, C. (2018c). Taxonomy, biostratigraphy, and phylogeny of Oligocene to Lower Miocene Globigerinoides and Trilobatus. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication. 46(Chap 9): 269-306. gs V OReferences:
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Trilobatus praeimmaturus compiled by the pforams@mikrotax project team viewed: 17-1-2021
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