Streptochilus subglobigerum Wall finely perforate and finely cancellate, becoming smooth in the later chambers.
Streptochilus inglei Smooth walled with a lobulate periphery and straight sutures
Streptochilus macdougallae Wall cancellate sometimes with coarse pores; test laterally compressed last two chambers slightly sub-inflated. Sutures oblique.
Streptochilus mascarenense Like S. cetacensis but more laterally compressed, more lobulate and pores smaller.
Streptochilus pristinum Test with straight lateral profile in early portion of the test followed inflation of the later chambers
Streptochilus rockallkiddense Parallel-sided / rectilinear, often becomes staggered uniserial, ornament variable, aperture may be obscured
Streptochilus tasmanense Test narrows towards apertural end, occasionally flared, laterally compressed, surface ornamentation of scattered circular pore mounds.
Paleogene Species
Streptochilus martini Gradually to moderately tapering test without surface ornamentation
Streptochilus sp. Specimens which cannot be assigned to established species
Taxonomy
Citation: Streptochilus Bronnimann and Resig, 1971Rank: GenusType species: Bolivina tokelauae Boersma, 1969 (in Kierstead and others, 1969; =Bolivinaglobulosa 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]
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
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: Within the Early Miocene Streptochilus is often abundant in the eastern Atlantic and western indian Oceans at paleo water depths of 1000-2500m - the "High Abundance of Bolivinid (HAB) event" - see Smart & Thomas (2006 - with references to earlier work). 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.
See also:Chiloguembelinidae - family in which it was previously classified;
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:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
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. Initial Reports of the Deep Sea Drilling Project. 7(2): 1235-1469. gsVO
Cushman, J. A. (1933d). Some new Recent foraminifera from the Tropical Pacific. Contributions from the Cushman Laboratory for Foraminiferal Research. 9(4): 77-95. gsVO
Cushman, J. A. (1933c). Some new foraminiferal genera. Contributions from the Cushman Laboratory for Foraminiferal Research. 9(2): 32-38. gsVO
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. Proceedings of the National Academy of Sciences, USA. 106: 12629-12633. gs
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., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication. 41(Chap 16): 461-508. gsVO
Kennett, J. P. & Srinivasan, M. S. (1983). Neogene Planktonic Foraminifera. Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania. 1-265. gs
Kierstead, C. H., Leidy, R., Fleisher, R. L. & Boersma, A. (1969). Neogene zonation of tropical Pacific cores. In, Brönnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967. Brill, Leiden 328-338. gs
Loeblich, A. R. & Tappan, H. (1988). Foraminiferal Genera and Their Classification (Volume I-II). Van Nostrand Reinhold Co., New York. 1-1059. gs
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. gs
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. gs
Smart, C. W. & Thomas, E. (2006). The enigma of early Miocene biserial planktic foraminifera. Geology. 34: 1041-1044. gs
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, 103 figures, 113 lates, 101 table. gs
Smart, C. W. & Thomas, E. (2018). Taxonomy, biostratigraphy, and phylogeny of Oligocene Streptochilus. 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 19): 495-511. gsVO
Streptochilus compiled by the pforams@mikrotax project teamviewed: 4-8-2021
