Catalog - Streptochilus macdougallae

CATALOG OF ORIGINAL DESCRIPTIONS: Streptochilus macdougallae Miranda-Martínez and Carreño 2017, in Miranda-Martínez et al. 2017

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 -> S -> Streptochilus -> Streptochilus macdougallae
Other pages this level: S. cetacensis, S. dubeyi, S. globiger infirmirugosus, S. inglei, S. latum, S. macdougallae, S. mascarenensis, S. pristinum, S. rockallkiddensis, S. subglobigerum, S. tasmanensis, S. tokelauae flexiserialis

Streptochilus macdougallae

Citation: Streptochilus macdougallae Miranda-Martínez and Carreño 2017, in Miranda-Martínez et al. 2017
Rank: Species
Type sample (& lithostrat): Sample IM-5, Unit III Marlstone and Mudstone (Dorsey et al., 2001), Carmen Formation.
Type locality: Loc. IGM-3972. 25°42′21.76′′ N, 111°03′10.23′′ W. Ensenada María, Monserrat Island, Baja California Sur, México.
Type repository: Mexico City; Colecci—n Nacional del Museo de Paleontolog’a Mar’a del Carmen Perrilliat, Instituto de Geolog’a, Universidad Nacional Aut—noma de MŽxico

Current identification/main database link: Streptochilus macdougallae Miranda-Martínez, Carreño & McDougall 2017


Original Description

Biserial, small to medium size test. Elongate and triangular shape in frontal view. Laterally compressed. Periphery slightly lobulate. 5 to 7 pairs of subrectangular chambers, which increase moderately as added. The last two chambers are larger, slightly semi-inflated and slightly overlapping. Faint lobes at the base of the chamber could be in contact with the suture. Sutures obscured by the ornamentation in the early portion, otherwise incised, curved, oblique from the midline and arched gently upward towards the periphery beneath the chambers lobes (Pl. IV, fig. 2a). Wall exhibits a cancellate texture and mural-like pores, sometimes with coarse pores. In some specimens, early middle portion of the test shows coarse interpore and anastomosing ridges displaying a rough texture (Pl. IV, fig. 5b); sometimes the roughness is extended with no clear pattern to the latest former chambers, which otherwise exhibit a low relief honeycomb-like surface (Pl. IV, fig. 2c), and a rugose texture at the top of the latest chambers (Pl. IV, fig. 2b). Aperture consists of a moderately wide elongate arch located perpendicular to the middle plane of the test, from the base of the last chamber onto apertural face, bordered by a thick rim/collar with a thick and wide internal plate formed by the infolding and downward extension of one margin of the rimmed aperture (Pl. IV, fig. 11).

Size:
Holotype. IGM-1586-Mi (Pl. IV, fig. 2). Length 257 μm, maximum width 140 μm, minimum width 36 μm. Size range: Length 133–312 μm (mean 225 μm, n = 27); maximum width 86–149 μm (mean 117 μm, n = 13); minimum width 15–27 μm (mean 20 μm, n = 13), maximum thickness 41–87 μm (64 μm, n = 19); minimum thickness 16–40 μm (mean 25 μm, n = 19).

Etymology:
In honor of Dr. Kristin McDougall for her contribution to the knowledge of the foraminifera from the Salton Trough.

Extra details from original publication
Stratigraphic occurrence. The latest part of the Miocene, from ~6 to 5.3 Ma. From the upper part of N17b to the basal part of N18/19 zones of Blow (1979, sensu Gradstein et al., 2012), equivalent to the M14 to the base of PL1 zones of Wade et al. (2011).


Remarks. The general outline of Streptochilus macdougallae sp. nov. is quite similar to morphotype B of S. globigerus (Schwager) identified in the Gulf (Pl. II, 3a), but differs in being laterally compressed; with the last two formed chambers slightly sub-inflated, instead of globose, with chamber slightly overlapping and exhibiting some faint lobes in the base, and distinctive sutures.
Darling et al. (2009; Fig. S1) illustrated adults of S. globigerus with a roughly texture wall with anastomosing ridges here described for the new species, also described in the initial portion of the test in some of the specimens here assigned to S. globigerus (Pl. II, fig. 6c). However, wall texture in Streptochilus macdougallae sp. nov. has coarse pores different to the fine perforate wall of S. globigerus and similar to that of Laterostomella guembeliniformis de Klasz and Rérat (1962).
S. subglobigerus
(length: 270 μm; width: 160 μm; Resig, 1989) is larger and S. globigerus (length:130μm; Schwager, 1866; length: 189 μm; max. width:170 μm, this study) is shorter than Streptochilus macdougallae sp. nov., which has a narrower test than these species.
The holotype of Streptochilus globigerus illustrated by Schwager (1866) has seven pairs of chambers, while Kennett and Srinivasan (1983) describe the species as having six to seven pairs and Resig (1989) illustrates specimens with five pairs. Six pairs of chambers are considered in the original diagnosis of S. subglobigerus, but specimens with five pairs are considered to illustrate the species (Resig, 1989). A similar number between five and six pairs of chambers is also present in the holotype and paratypes of Laterotomella guembeliniformis (de Klasz and Rérat, 1962). Numbers of chambers in these species are similar to S. macdougallae sp. nov. and therefore are not a diagnostic feature; only the adult specimens of S. globigerus illustrated by Darling et al. (2009; Fig. S1) have a greater number of chambers.
Specimens identified previously as Streptochilus cf. subglobigerus in Blythe Basin (McDougall and Miranda-Martínez, 2014; Plate 1, figs. 18–20, 24–25), are here considered as synonymous of S. macdougallae sp. nov. due to having the same form of the test, chambers, sutures (Pl. 1, figs. 20 & 21). Specimens with the same features, but subdued ornamentation that resemble Streptochilus subglobigerus are considered S. aff. macdougallae sp. nov., (McDougall and Miranda-Martínez, 2014; Plate 1, figs. 14–17) or as an ecophenotypic variant of the species due to their restricted distribution under estuarine conditions in Blythe Basin (McDougall and Miranda-Martínez, 2014).

Editors' Notes

References:

Miranda-Martinez, A. Y., Carreño, A. L. & McDougall, K. (2017). The Neogene genus Streptochilus (Brönnimann and Resig, 1971) from the Gulf of California. Marine Micropaleontology. 132: 35-52. gs


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Streptochilus macdougallae compiled by the pforams@mikrotax project team viewed: 30-11-2022

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