Planorotalites pseudoscitula

Classification: pf_cenozoic -> Truncorotaloididae -> Planorotalites -> Planorotalites pseudoscitula
Sister taxa: P. capdevilensis, P. pseudoscitula, P. sp.,


Citation: Planorotalites pseudoscitula (Glaessner 1937)
Rank: Species
Basionym: Globorotalia pseudoscitula
Taxonomic discussion: Berggren (1968, 1977), McGowran (1968), Schmidt and Raju (1973), Hillebrandt (1976) and Blow (1979) placed renzi Bolli in the synonymy of pseudoscitula Glaessner and in this most workers have followed them for the past 20 years. The supposed synonymy of these two forms as well as G. pseudoscitula elongata was suggested to one of us (WAB) by Gohrbandt as early as the mid-1960s based on examination and illustrations of a topotype of G. pseudoscitula elongata from Il’skaya, northern Caucasus (sent to him by Glaessner) and 3 topotype specimens of renzi from Trinidad. Pertinent observations made at the time by Gohrbandt (pers. comm.) include the following:
1. “G. elongata has a more conical last chamber in axial profile (than G. renzi). G. renzi has a rather more acute periphery on the later chambers. However, G. pseudoscitula elongata shows signs of a ‘keel’; and the difference is a minor one. There are no other significant differences, so far as can be seen, in the surface texture of the two forms. The external appearance suggests that oriented thin sections would show the same wall structure”.
2. In spiral view the specimen of G. pseudoscitula elongata resembles the type figure of G. pseudoscitula s.s., whereas the axial profile resembles the variety elongata.
3. Russian workers no longer recognized elongata as a formal variety. In gross form G. renzi resembles the type figure of G. pseudoscitula very closely indeed. The similarity in surface texture has been confirmed; it had been strongly suspected from published data. The SEM was unavailable to Gohrbandt at the time he made his observations with the light microscope. SEM illustrations have shown that there is a difference in wall texture in the two forms, that of renzi ( =capdevilensis, see above) being considerably more coarsely muricate. Therefore, we have refrained from concluding that G. renzi/ capdevilensis is a junior subjective synonym of G. pseudoscitula (see above).
4. Gohrbandt also observed that G. pseudoscitula (which he regarded as conspecific with G. renzi) had its lowest occurrence in the lower Eocene Globorotalia aragonensis Zone (distinctly lower than the base of Zone P10 as given by Bolli, 1957b; cf. Berggren, 1960 who had noted earlier an extension into lower Eocene in Nigeria as well).
However, Blow (1979) presciently observed that earlier (early Eocene) and later (middle Eocene) forms of this plexus are characterized by a coarsening of the muricate wall texture and gradual enlargement of pores (similar observations were made on this plexus by Benjamini, 1980). Blow (1979) was also correct in surmising that the type level of G. pseudoscitula Glaessner (and of G. elongata Glaessner) is of early (not middle) Eocene age as most investigators had thought. Indeed, the type level is from what was subsequently designated (Subbotina, 1953) the “Zone of compressed globorotaliids” (the Abazin Fm.), stratigraphically equivalent to Zones E4, ?E5. Both he (Blow, 1979, p. 898) and Bolli (1957b, p. 168) gave the stratigraphic range of G. pseudoscitula s.s. (= G. renzi) as Zones E8/ E13 equivalents. However, in his text Blow (1979) referred to stratigraphically earlier morphotypes as Globorotalia cf. pseudoscitula with a range of Zones P7-P9; ? P10 (=E5-E7; ?E8) equivalents. Globorotalia renzi and G. capdevilensis partim were regarded as junior synonyms of G. pseudoscitula s.l.. Blow (1979) suggested that the wall texture pattern changes were one of degree rather than kind and that Globorotalia pseudoscitula s.s. (rather than Globorotalia cf. pseudoscitula based on his earlier, mistaken belief that the type level of G. pseudoscitula was middle Eocene) might be appropriate for the older (early Eocene) forms and G. renzi for the younger (middle Eocene) forms, while retaining the designation pseudoscitula s.l. for the entire plexus. Accordingly it is clear that Gohrbandt had made his observations on elongata (from the basal Eocene Zone E3-E5), and on renzi from upper middle Eocene Zone E12-E13.

At the same time Blow (1979) considered that Globorotalia elongata Glaessner is essentially unrelated to the G. pseudoscitula/renzi plexus. This was based upon the following lines of evidence:
1. Blow (1979) had submitted several specimens (subsequently illustrated as figures 6 and 7 of his plate 116 from [his] Zone P7 [=E5] of the Kilwa area, Tanzania), to Martin Glaessner who confirmed their identification as Globorotalia elongata; this led Blow (1979, p. 890) to assert that (Paleocene) records of G. elongata by Loeblich and Tappan (1957) and Bolli (1957a) did not correspond to Glaessner’s elongata.
2. G. elongata Glaessner is characterized by an acute to subacute peripheral margin and “nearly equally biconvex test”. Furthermore, elongata is a minute (0.15-0.2 mm; Glaessner, 1937; 0.167-0.249 mm: Blow, 1979) form. Confusion with G. pseudomenardii was not possible according to Blow because of the less ventrally inflated chamber surfaces and smaller umbilicus in pseudomenardii, “which, especially in stratigraphically younger specimens are virtually closed” (Blow, 1979, p. 891).
3. G. elongata was said to differ from G. pseudoscitula in having a “more open and lax trochospire so that the later chambers increase in size more rapidly than in pseudoscitula” (Blow, 1979, p. 891).

In the course of our work we have been unable to recognize a clear differentiation between morphotypes of elongata and pseudoscitula, considering the minor differences in coiling to be of degree rather than kind, and, accordingly, we include elongata in the synonomy of pseudoscitula.
Phylogenetic relationships within this group remain enigmatic. McGowran (1968, lineage 6) and Berggren (1968, lineage 2), in trying to lay a phylogenetic foundation for distinguishing different clades of Paleogene “globorotaliids”, recognized a morphologic and stratigraphic separation between Globanomalina and Planorotalites, although the former reserved Globanomalina for the planispiral forms (now referred to Pseudohastigerina) in the erroneous belief that the type species of Globanomalina (G. ovalis Haque) is planispiral (cf. Berggren 1968; Banner, 1989, p. 171, 173). Owing to the superficial similarity among smooth-walled, finely perforate forms in the Paleocene the generic names Globanomalina and Planorotalites have been used interchangeably for Paleocene and lower Eocene taxa. Globanomalina has been adopted by the Working Group for the smooth-walled Paleocene group typified by G. ovalis and having its origin in G. archeocompressa in the basal Danian (Olsson and others, 1999; see also Berggren and Norris, 1997; Fleisher, 1974, p. 1017).
Schmidt and Raju (1973) presented a detailed analysis of the morphology and evolution of the pseudoscitula plexus. Pertinent observations/conclusions include the following:
1. Globorotalia planoconica Subbotina is regarded as the stem form of the lineage and characterized by a small, finely perforate, unkeeled planoconvex test.
2. G. pseudoscitula Glaessner, 1937 is interpreted as a small, compressed, distinctly (coarsely) perforate, biconvex form with subcircular equatorial periphery and faintly keeled margin. G. pseudoscitula elongata Glaessner, 1937 is interepreted to represent varietal forms that develop a large, lobate last chamber. Globorotalia renzi is considered a junior synonym of G. pseudoscitula.
3. G. palmerae is considered to have evolved from pseudoscitula by “prolongation of the chambers at the axial periphery to a radially elongate shape terminating in a spine”(Schmidt and Raju, 1973, p. 179).
4. Globorotalia planoconica is shown to have originated in the G. velascoensis Zone (Zone P5 of this paper); G. pseudoscitula in the G. subbotinae Zone (Zone E3-E4 of this paper) and G. palmerae in the eponymous zone (i.e., within Zone E7).
It would seem that these subtle differences in wall texture are at the root of the disparate lower range given for the pseudoscitula/renzi group, which spans the interval of Zones P5-E6 (Hillebrandt, 1962; Samuel, 1972; Benjamini, 1980; Toumarkine and Luterbacher, 1985). Benjamini (1980) suggested that the transition from the relatively larger, typical pseudoscitula with depressed sutures to the relatively small, coarsely perforate, flush sutured typical renzi took place in the mid-part of the G. palmerae Zone (= Zone E7 of this work) in the Avedat Group of the northern Negev, Israel. Subbotina (1953) had earlier noted that pseudoscitula extends down into the highest levels of the “Zone of rotaliid-like globorotaliids” (=Zones P2/3) in the Elburgan Formation of the North Caucasus, but we believe that these references are to members of the superficially similar Igorina pusilla group. In like manner, Loeblich and Tappan (1957) identified forms as pseudoscitula in the mid-late Paleocene of the Gulf Coast that, while superficially similar to the Eocene morphotypes, belong to the distinctly different group of the albeari /laevigata plexus (Berggren, 1968).
If the finely perforate, superficially smooth-walled (but weakly muricate) to weakly cancellate, keeled, compressed, test of latest Paleocene-early Eocene pseudoscitula morphotypes are considered ancestral to the late early-middle Eocene, biconvex, keeled, coarsely perforate, muricate renzi, derivation from a juvenile morozovellid such as Morozovella occlusa would appear logical (cf. Berggren 1968; McGowran, 1968; Hillebrandt, 1976 for earlier, alternate interpretations). In the course of our studies we have found that pseudoscitula has its lowest/earliest occurrence at the base of Zone P5 (i.e, just above the HO of Globanomalina pseudomenardii).
The specimen illustrated by Shutskaya (1956, pl. 4, figs. 5a-c) from the Cherkessk Fm. of the north-west Caucasus is excluded from this taxon. It would appear to be a relatively large (maximum diameter 0.43 mm) robust form that was compared by Shutskaya with Globorotalia subbotinae, G. nartanensis and G. spinulosa and was recorded from the G. subbotinae Zone (=Zone E3-4 of this paper), whereas P. pseudoscitula is a relatively small form (with a maximum diameter of about half that of Shutskaya’s specimen; Bolli’s [1957a] holotype of Globorotalia renzi has a maximum diameter of 0.23 mm) and was shown to have its lowest occurrence considerably higher, in Zone P10.
The broadly rounded, seemingly densely muricate form illustrated by Hillebrandt (1962) from Zone P6 (equivalent) appears not to be referable to pseudoscitula/renzi as identified here and is more likely an acarininid referable to esnehensis (or a related form). [Eocene Atlas]

Catalog entries: Globorotalia pseudoscitula, Globorotalia pseudoscitula elongata

Type images:

Distinguishing features: Test small, weakly biconvex and muricate, distinctly carinate

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.


Diagnostic characters: The diagnostic features of Planorotalites pseudoscitula are its small, weakly biconvex and muricate, distinctly carinate test (see also under P. capdevilensis). [Berggren et al. 2006]

Wall type: Normal perforate, nonspinose, weakly muricate. [Berggren et al. 2006]

Test morphology: Peripheral outline oval to subcircular, weakly lobulate, coiled in low trochospire, weakly biconvex; in umbilical view 6-8 subtriangular chambers, compressed/flattened along peripheral margin, intercameral sutures radial (in early part of last whorl) to slightly curved in younger chambers, depressed in terminal 2-3 chambers, umbilicus narrow, shallow, aperture a low, umbilical-extraumbilical arch bearing a distinct lip; in spiral view 15-18 trapezoidal chambers arranged in 2½-3 whorls, sutures essentially flush with test chambers, distinctly curved, early part of test strongly muricate, elevated; in edge view test is biconvex, with distinct imperforate keel which extends at least to ante- or preantepenultimate chamber, test surface penetrated by normal-sized pores which do not open into distinct pore pits, aperture a typical umbilical-extraumbilical, low slit with distinct lip which extends to the periphery. [Berggren et al. 2006]

Size: Typical dimension given by Glaessner (1937, p. 32): 0.2-0.25 mm. [Berggren et al. 2006]

Character matrix

test outline:Subcircularchamber arrangement:Trochospiraledge view:Inequally biconvexaperture:Umbilical-extraumbilical
sp chamber shape:Crescenticcoiling axis:Lowperiphery:Imperforate bandaperture border:Thin lip
umb chbr shape:Trapezoidalumbilicus:Narrowperiph margin shape:Subangularaccessory apertures:None
spiral sutures:Flushumb depth:Shallowwall texture:Moderately muricateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Weakly depressedfinal-whorl chambers:6.0-8.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology

Geographic distribution: Ranges from tropics to temperate regions; central equatorial Pacific (ODP Site 865), New Jersey Coastal Plain (Bass River Borehole where it is a common form in Zone E1), Tethyan deposits of northern Africa (Egypt where it appears in the lower part of the Esna Shale Fm. in basal Zone P5) and northern Caucasus; not reliably reported (to date) from high austral or northern latitudes to our knowledge. [Berggren et al. 2006]
Aze et al. 2011 summary: Low to middle latitudes; based on Berggren et al. (2006a)

Isotope paleobiology: No data available. [Berggren et al. 2006]
Aze et al. 2011 ecogroup 2 - Open ocean mixed-layer tropical/subtropical, without symbionts. Based on δ13C lighter than species with symbionts; also with relatively light δ18O. Sources cited by Aze et al. 2011 (appendix S3): Pearson et al. (2001a)

Phylogenetic relations: Unresolved; probably evolved from a juvenile morozovellid (? M. occlusa) by neoteny. [Berggren et al. 2006]

Most likely ancestor: Morozovella apanthesma - at confidence level 2 (out of 5). Data source: Aze et al. 2011 - but no additional source given by them..
Likely descendants: Astrorotalia palmerae; Planorotalites capdevilensis;

Biostratigraphic distribution

Geological Range:
Notes: Zone P5-E7. [Berggren et al. 2006]
Last occurrence (top): within E7a subzone (48.31-50.20Ma, top in Ypresian stage). Data source: Berggren et al. 2006, f12.1
First occurrence (base): within P5 zone (55.96-57.10Ma, base in Thanetian stage). Data source: Berggren et al. 2006, f12.1

Plot of occurrence data:

Primary source for this page: Berggren et al. 2006 - Eocene Atlas, chap. 12, p. 393


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Planorotalites pseudoscitula compiled by the pforams@mikrotax project team viewed: 18-2-2020

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