Streptochilus


Classification: pf_cenozoic -> Guembelitrioidea -> Chiloguembelinidae -> Streptochilus
Sister taxa: Chiloguembelina, Streptochilus,
Daughter taxa: (blue => in age window 0-300Ma)
Late Miocene to extant species

Rugose test, with globose chambers.
Rapidly expanding test, with smooth wall and aperture
Wall finely perforate and finely cancellate, becoming smooth in the later chambers.
Smooth walled with a lobulate periphery and straight sutures
Wall cancellate sometimes with coarse pores; test laterally compressed last two chambers slightly sub-inflated. Sutures oblique.
Oligo-Miocene Species
Triangular in shape and flared
Like S. cetacensis but more laterally compressed, more lobulate and pores smaller.
Test with straight lateral profile in early portion of the test followed inflation of the later chambers
Parallel-sided / rectilinear, often becomes staggered uniserial, ornament variable, aperture may be obscured
Test narrows towards apertural end, occasionally flared, laterally compressed, surface ornamentation of scattered circular pore mounds.
Paleogene Species
Gradually to moderately tapering test without surface ornamentation
Specimens which cannot be assigned to established species

Taxonomy

Citation: Streptochilus Bronnimann and Resig, 1971
Rank: Genus
Type species: Bolivina tokelauae Boersma, 1969 (in Kierstead and others, 1969; =Bolivina globulosa Cushman, 1933, according to Resig and Kroopnick, 1983)
Taxonomic discussion: Loeblich and Tappan (1988) removed Laterostomella from the Buliminidae, where it was originally assigned by de Klasz and Re½rat (1962), placed it in the Chiloguembelinidae and designated Streptochilus as its junior synonym. However, in their comparison of these two genera, de Klasz and others (1989) presented evidence that Laterostomella is a benthic taxon and agreed with other authors (e.g., Bronnimann and Resig, 1971; Kennett and Srinivasan, 1983; Resig and Kroopnick, 1983; Poore and Gosnell, 1985) that Streptochilus probably evolved from Chiloguembelina, and should be assigned to the Chiloguembelinidae. Stable isotopic evidence that Streptochilus is a planktonic taxon was presented by Resig and Kroopnick (1983). [Huber et al. 2006]

Catalog entries: Streptochilus;

Type images:

Distinguishing features: Like Chiloguembelina but with an internal plate connecting successive chambers, a prominent extension of an apertural collar, and a smoother surface texture.

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.
They are being edited as the site is developed and comments on them are especially welcome.

Description


Diagnostic characters: Distinguished from Chiloguembelina by the presence of an internal plate connecting successive foramina (Poore and Gosnell, 1985, pl. 1, figs. 11, 14), a prominent extension of an apertural collar, and a smooth to granular rather than pustulose to costate surface texture.
[Huber et al. 2006]

Test morphology: “Test biserial sometimes twisted; wall calcareous perforate; aperture high arch, eccentric in position, extending from the base of the last chamber onto the apertural face. On the outside margin a collar borders the aperture. Near the base of the inside margin, the collar and apertural edge are turned inward, producing a plate-like connection with the proximal margin of the collar of the previous aperture. The length of the test varies between 75 and 300 microns” (Bronnimann and Resig, 1971, p. 1288). [Huber et al. 2006]

Biogeography and Palaeobiology


Geographic distribution: Neptune records are predominantly from low-latitudes [editor's comment - JRY 2018]

Isotope paleobiology: Streptochilus globulosum indicate intermediate values for oxygen and carbon stable isotope values, suggestive of a thermocline-dwelling habitat (Resig and Kroopnick, 1983). No data available for Eocene taxa.
[Huber et al. 2006]

Phylogenetic relations: It is possible that the distribution of Streptochilus spp. represents one or more expatriation events from the coastal benthos to the pelagic zone (Darling and others, 2009), in addition to lack of observation of these small taxa, explaining its intermittent temporal distribution in the fossil record. Furthermore, it is likely that either no or not all species traditionally placed in the genus Streptochilus are descended from the genus Chiloguembelina. The name Streptochilus is used for planktonic species which morphologically cannot be distinguished from species in the benthic genus Bolivina. The genus, therefore, is polyphyletic, including potentially different clades. At present, however, we do not have enough information on evolutionary patterns to identify clades of biserial planktonic species, and it is proposed, therefore, that the name Streptochilus be retained provisionally until evolutionary relations are understood. [Smart & Thomas 2018]

Most likely ancestor: Benthic foraminifera - at confidence level 2 (out of 5). Data source: Smart & Thomas 2018.

Biostratigraphic distribution

Geological Range:
Notes: Middle Eocene (Zone E10) to Recent; intermittent. [Smart & Thomas 2018]
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): in upper part of Lutetian Stage (69% up, 43.2Ma, in Lutetian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Primary source for this page: Huber et al. 2006 - Eocene Atlas, chap. 16, p. 476; Smart & Thomas 2018 p.498; Kennett & Srinivasan 1983, p.21

References:

Brönnimann, P. & Resig, J., (1971). A Neogene globigerinacean biochronologic time-scale of the southwestern Pacific. Deep Sea Drilling Project, 7(2): 1235-1469.

Cushman, J.A., (1933). Some new foraminiferal genera. Contributions from the Cushman Laboratory for Foraminiferal Research, 9(2): 32-38.

Cushman, J.A., (1933). Some new Recent foraminifera from the Tropical Pacific. Contributions from the Cushman Laboratory for Foraminiferal Research, 9(4): 77-95.

Darling, K.F.; Thomas, E.; Kasemann, S.A.; Seears, H.A.; Smart, C.W. & Wade, C.M., (2009). Surviving mass extinction by bridging the benthic/planktic divide. Proc. Natl. Acad. Sci. U. S. A., 106: 12629–33.

Huber, B.T.; Olsson, R.K. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene microperforate planktonic foraminifera (Jenkinsina, Cassigerinelloita, Chiloguembelina, Streptochilus, Zeauvigerina, Tenuitella, and Cassigerinella) and Problematica (Dipsidripella). In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera. Cushman Foundation Special Publication. 41 Allen Press, Lawrence, Kansas, pp. 461-508.

Huber, B.T.; Olsson, R.K. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene microperforate planktonic foraminifera (Jenkinsina, Cassigerinelloita, Chiloguembelina, Streptochilus, Zeauvigerina, Tenuitella, and Cassigerinella) and Problematica (Dipsidripella). In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera. Cushman Foundation Special Publication. 41 Allen Press, Lawrence, Kansas, pp. 461-508.

Kennett, J.P. & Srinivasan, M.S., (1983). Neogene Planktonic Foraminifera. Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania, 1-265 pp.

Kierstead, C.H.; Leidy, R.; Fleisher, R.L. & Boersma, A., (1969). Neogene zonation of tropical Pacific cores. In: Brönnimann, P. and Renz, H.H. (Editors), Proceedings of the First International Conference on Planktonic Microfossiis, Geneva, . Brill, Leiden, pp. 328-338.

Loeblich, A.R. & Tappan, H., (1988). Foraminiferal Genera and Their Classification (Volume I-II)Van Nostrand Reinhold Co., New York, 1059 pp.

Poore, R.Z. & Gosnell, L.B., (1985). Apertural features and surface texture of upper Paleogene biserial planktonic foraminifers: Links between Chiloguembelina and Streptochilus. Journal of Foraminiferal Research, 15: 1-5.

Resig, J.M. & Kroopnick, P.M., (1983). Isotopic and distributional evidence of a planktonic habit for the foraminiferal genus Streptochilus Bronnimann and Resig, 1971. Marine Micropaleontology, 8(3): 235-248.

Smart, C.W. & Thomas, E., (2007). Emendation of the genus Streptochilus Brönnimann and Resig 1971 (Foraminifera) and new species from the lower Miocene of the Atlantic and Indian Oceans. Micropaleontology, 53(1-2): 73-103, 3 figures, 13 plates, 1 table.

Smart, C.W. & Thomas, E., (2018). Taxonomy, biostratigraphy, and phylogeny of Oligocene Streptochilus. In: Wade, B.S. et al. (Editors), Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research Special Pulbication. 46, pp. 495-511.


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Streptochilus compiled by the pforams@mikrotax project team viewed: 16-11-2018

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