Acarinina pentacamerata

Classification: pf_cenozoic -> Truncorotaloididae -> Acarinina -> Acarinina pentacamerata
Sister taxa: A. medizzai, A. collactea, A. pentacamerata, A. aspensis, A. interposita, A. echinata, A. pseudosubsphaerica, A. alticonica, A. soldadoensis, A. cuneicamerata, A. angulosa, A. africana, A. sibaiyaensis, A. esnehensis, A. mckannai, A. subsphaerica ⟩⟨ A. bullbrooki, A. punctocarinata> >>


Citation: Acarinina pentacamerata (Subbotina 1947)
Rank: Species
Basionym: Globorotalia pentacamerata
Taxonomic discussion: The taxonomic history of Acarinina pentacamerata (Subbotina) is extremely complex and not without a considerable degree of uncertainty. We attempt a reconstruction here of this history in an effort to bring nomenclatural stability to a much (ab)used taxon.
1. In 1936, Subbotina mentioned and illustrated (her pl. 3, figs. 7-9) a new variety Globorotalia crassa (d’Orbigny) var. pentacamerata Subbotina. In failing to describe it, the form was instantly rendered nomen nudum according to the International Rules of Zoological Nomenclature, art. 25 (c), 1-2. The illustrated specimen is of a tightly coiled (involute) individual with 6 chambers in the final whorl (which may or may not be related to the Acarinina lodoensis -broedermanni group, cf. Blow (1979, p. 940) and was described from the “Globorotalia crassaformis Zone” (= probably
equivalent to Zone E7 of this work). Krasheninnikov and others (1988, pl. 8, fig. 8) figured as A. pentacamerata a specimen from the lower Eocene of the Campbell Plateau, south-west Pacific Ocean that is virtually identical with Subbotina’s (1947) strongly involute holotype figure.
2. In 1947, Subbotina formally described and illustrated Globorotalia pentacamerata for the first time. Three specimens were figured. The holotype (pl. 7, figs. 15-17) was recorded from the Globorotalia crassaformis Zone (which was considered middle Eocene in age but which is in fact probably stratigraphically equivalent to lower Eocene Zone E7 of this study). Two paratypes (her pl. 7, figs. 12-14 and pl. 9, figs. 24-26) were from the lower Eocene “Globorotalia velascoensis Zone” of (presumed) early Eocene age (the latter zone was subsequently termed, in 1953, the “Zone of conical globorotaliids”, and is characterized by Morozovella aragonensis [Nuttall] and M. caucasica [Glaessner]). However, Subbotina (1947, 1953) consistently misidentified M. caucasica with M. velascoensis which accounts for the persistent misuse of the term G. velasacoensis Zone in early literature (see further discussion in Blow, 1979, p. 993-996; Berggren and Norris, 1997, p. 75-76 and under Morozovella caucasica, Chapter 11).
3. It is doubtful/uncertain whether the three specimens illustrated in 1947 are of the same species. The form figured on pl. 7, figs. 24-26 by Subbotina (1953) shows the distinct lateral separation of chambers peripherally which is characteristic of Bolli’s (1957b) Globigerina angulosa ( =Acarinina angulosa). Indeed, Subbotina’s specimen is almost identical to that figured by Bolli (1957a, pl. 35, figs. 8a-c) from the Globorotalia palmerae Zone. There may be some question as to whether Bolli’s specimen from the G. palmerae Zone is conspecific with that figured (Bolli, 1957a, pl. 16, figs. 4-6) from the type locality of the Globorotalia formosa formosa Zone of Trinidad. They are considered conspecific here.
4. The paratype specimen figured by Subbotina (1947, pl. 7, figs. 12-14) shows the characters that have subsequently come to be associated with Acarinina pentacamerata as elucidated subsequently by Subbotina in 1953. It is curious that Subbotina (1947, p. 128) mentions that the “specimen described was found along the Kuban River”. This would presumably refer to the specimen illustrated on pl. 9, figs. 24-26 (from the Kuban River section) inasmuch as the holotype (pl. 7, figs. 15-17) and paratype (pl. 7, figs. 12-14) were recorded from the Khieu and Sunzha Rivers, respectively.
5. In 1953, Subbotina illustrated a number of specimens which she referred to Acarinina pentacamerata (Subbotina) including in the synonymy the specimens illustrated in her earlier (1947) work, but making no reference to the specimens illustrated on her pl. 23, figs. 8a-c and pl. 24, figs. 1a-5c, all from the Zone of conical globorotaliids— and if we ignore/ exclude the smaller upper Paleocene forms (pl. 24, figs. 6a-8c) and the anomalous 8-chambered acarininid (pl. 24, figs. 9a-c) from the G. marginodentata Subzone, it would appear that we have an homogenous group of morphotypes referable to a single taxon. Blow (1979, p. 940) noted that he based his interpretation of pentacamerata on Subbotina (1947, pl. 7, figs. 12-14) and he represented this concept with a specimen he illustrated on pl. 135, fig. 5 from Zone P8b (=Zone E5 of this work). The specimens illustrated by Subbotina (1953) and listed above all show a close similarity to that figured by her in 1947 pl. 7, figs. 12-14. It is interesting that none conform closely, let alone remotely, to the holotype illustration of 1936/1947. One thing is clear: Subbotina (1953) did not base her concept of A. pentacamerata on her (earlier illustrated) holotype of the taxon.
6. The holotype and paratype specimens of A. pentacamerata from Subbotina (1936/1947) were missing from the micropaleontologic collections of VNIGRI (Leningrad/St. Petersburg) on the occasion of several visits there by WAB in 1962, 1963 and in the 1970s. It is possible that they were lost or destroyed during the siege of Leningrad (1941-1943). On the other hand, all the specimens illustrated by Subbotina (1953) were examined during these visits and the taxonomic statements above reflect these observations. Thus the concept of A. pentacamerata in the work of one of us (WAB) has been based on these specimens. The 5-7
rounded chambers, relatively wide umbilicus and weakly developed circum-umbilical shoulder distinguish this species from associated forms in the lower Eocene.
7. Inasmuch as the holotype and paratypes of this taxon have been lost and it is virtually impossible to ascertain with certainty its taxonomic identity in terms of modern nomenclature, it would appear desirable, in the interest of nomenclatural stability, to base a concept of A. pentacamerata on the forms illustrated by Subbotina (1953) listed above and to designate a neotype from this series. Accordingly, based on observations of the material at VNIGRI, we designate as neotype the specimen illustrated on pl. 23, figs. 8a-c (no. 3088 in the micropaleontological collections at VNIGRI) from the Zone of conical globorotaliids, Green Formation, Kuban River section, North Caucasus.
8. A relatively large, robust morphotype exhibiting more relaxed, evolute coiling exposing/ opening the umbilical region has been described as Acarinina pentacamerata (Subbotina) var camerata by Khalilov, 1956 (see also Blow, 1979, p. 917). Placed in the synonymy of A. pentacamerata by Berggren (1977) and Berggren and Norris (1997), we maintain this view here and view this morphology as transitional to aspensis. [Berggren et al. 2006]

Catalog entries: Globorotalia pentacamerata, Acarinina pentacamerata camerata

Type images:

Distinguishing features: Compact, strongly muricate test with 5 globular, inflated chambers in last 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.
They are being edited as the site is developed and comments on them are especially welcome.


Wall type: Densely muricate on both sides, normal perforate, nonspinose. [Berggren et al. 2006]

Morphology: Low-trochospiral; generally 5 (ranging from 4½ to 6 or 7) rounded, inflated chambers, increasing gradually in size in last whorl; periphery weakly lobate; umbilicus generally small, deep with concentration of muricae around circumumbilical region; aperture a low umbilical-extraumbilical slit; 10-12 chambers arranged in 2½ whorls; early chambers elevated slightly above plane of final whorl; intercameral sutures weakly curved, tangential to peripheral margin in early chambers of last whorl; in edge view test is weakly biconvex, peripheral margin rounded; intercameral sutures radial, weakly retorse along rounded peripheral margin. [Berggren et al. 2006]

Size: Largest diameter 0.40-0.50 mm; thickness 0.20-0.25 mm. [Berggren et al. 2006]

Character matrix

test outline:Subcircularchamber arrangement:Trochospiraledge view:Inequally biconvexaperture:Umbilical
sp chamber shape:Inflatedcoiling axis:Lowperiphery:N/Aaperture border:N/A
umb chbr shape:Inflatedumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Strongly depressedumb depth:Deepwall texture:Finely muricateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:4.5-5.5 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology

Geographic distribution: Essentially global distribution in the early Eocene; not reliably reported from high austral latitudes. [Berggren et al. 2006]
Aze et al. 2011 summary: Cosmopolitan; based on Berggren et al. (2006b)

Isotope paleobiology: No data available. [Berggren et al. 2006]
Aze et al. 2011 ecogroup 1 - Open ocean mixed-layer tropical/subtropical, with symbionts. Based on very heavy δ13C and relatively light δ18O. Sources cited by Aze et al. 2011 (appendix S3): this study

Phylogenetic relations: Evolved from Acarinina interposita Subbotina and probably gave rise to A. aspensis (Colom) and A. collactea (Finlay). [Berggren et al. 2006]

Most likely ancestor: Acarinina interposita - at confidence level 4 (out of 5). Data source: Berggren et al. (2006) fig9.2.
Likely descendants: Acarinina aspensis; Acarinina collactea;

Biostratigraphic distribution

Geological Range:
Notes: Zone E5 to Zone E7. Given the intricate taxonomic discussion above, and in the light of our selection of a neotype, it is necessary to review the range of A. pentacamerata as described in Subbotina’s papers. Subbotina (1947) designated as the holotype of A. pentacamerata a specimen from the Globorotalia crassaformis Zone. This level is probably equivalent to Zone E7. She subsequently (1953, p. 234, table 3, p. 29) showed it to range from the G. crassata Subzone of the Zone of compressed globorotaliids (~/= Zone P5-E3) through the Zone of conical globorotaliids (~/= Zones E4-E6), but observed that this species reached its acme of development in the Zone of conical globorotaliids. However, in her chart showing the suggested phylogeny of the acarininids (Subbotina, 1953, p. 153, fig. 8) Subbotina showed A. pentacamerata evolving from A. interposita Subbotina at the base of the G. marginodentata Subzone (~/= Zones E4-E5) and ranging to the top of the Zone of conical globorotaliids. She mentioned (1953, p. 234) that the forms from the uppermost Paleocene of Mangyshlak Peninsula (illustrated as her pl. 24, figs. 6a-8c) differed from the lower Eocene forms in their significantly smaller size, indicating that she probably harbored some doubts/ reservations on the conspecificity of the two groups (see discussion above). [Berggren et al. 2006]
Last occurrence (top): in upper part of E7a subzone (80% up, 48.7Ma, in Ypresian stage). Data source: Eocene Atlas
First occurrence (base): within E5 zone (50.67-52.54Ma, base in Ypresian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Berggren et al. 2006 - Eocene Atlas, chap. 9, p. 296


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Acarinina pentacamerata compiled by the pforams@mikrotax project team viewed: 18-4-2021

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