CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia (Acarinina) praeangulata Blow 1979

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 -> G -> Globorotalia (Acarinina) -> Globorotalia (Acarinina) praeangulata
Other pages this level: G. (Acarinina) appressocamerata, G. (Acarinina) broedermanni anapetes, G. (Acarinina) cuneicamerata, G. (Acarinina) matthewsae, G. (Acarinina) praeaequa, G. (Acarinina) praeangulata,

Globorotalia (Acarinina) praeangulata

Citation: Globorotalia (Acarinina) praeangulata Blow 1979
Rank: Species
Type locality: ZDSDP Station 47 2 [lat. 33 0 26.9' N., long. 1570 42.7'E.]: holotype (pl. 84, fig. 7; pl. 212, figs. l , 2) and three paratypes (pl. 84, figs. l , 8; pl. 85, fig. l ) from sample 10-2, 80-82 cm; paratype (pl. 83, fig. 6) from sample 10-3, 78-80 cm; paratype (pl. 87, fig. 2) from sample 10-k, 72-74 cm. , Shatsky Rise; all at lat. 32 0 26.9' N. , long. 157 0 42.7' E. , northwestern Pacific Ocean. Three paratypes (pl. 82, figs. 5, 6; and figs. 10-12) from sample DB. 176, lower Lizard Spring Formation, west side of railroad track about 500 feet south of the Station Road crossing at the Point-a-Pierre railroad station, Trinidad.one P2, Sample DB 176, type locality of G. uncinata Zone, near Pointe a Pierre, S Trinidad
Type age (chronostrat): Middle Paleocene, lower Thanetian, Zone P.3 (Globorotalia angulata - Globorotalia pusilla pusilla Zone); ranges from upper Zone P.2 to lower Zone P.4, in the middle Paleocene.
Type specimens: Paratype PM PF 63824
Type repository: London, UK; NHM

Linked specimens: London, UK; NHM (PM PF 63830) London, UK; NHM (63824)

Current identification/main database link: Morozovella praeangulata (Blow 1979)


Original Description
The test is comprised of about 11-12 chambers coiled in a low, but comparatively lax, trochospire with 5 1/2 chambers visible in the last convolution of the test. In dorsal aspect, the chambers are longer tangentially than radially broad with the dorsal intercameral sutures strongly recurved to vorticiform in the earlier parts of the last convolution; the dorsal intercameral sutures are distinctly incised and are not pseudolimbate but are weakly muricate. The equatorial profile is lobulate and the peripheral margin does not bear a continuous muricocarina. However, the peripheral margin is strongly muricate but the muricae are not fused or coalesced together. In axial-aperture profile, the test is plano-conic with the dorsal side nearly flat and the ventral side strongly vaulted; the peripheral margin is seen to be subacute in this axial-apertural aspect. In ventral aspect, the umbilicus is open and deep and the ventral intercameral sutures are radially disposed and quite deeply incised. The primary aperture opens from the umbilicus to about two-thirds of the way towards the periphery. The wall is muricate with a peripheral concentration of muricae.

Size: Maximum diameter of holotype 0.32 mm.

Extra details from original publication
The paratypes figured on pl. 82, figs. 5 and 6, show two specimens wherein the later chambers of the last convolution become a little more nearly equidimensional in dorsal aspect and the coiling-mode more relaxed than seen In the holotypic specimen. On the other hand, the specimen figured by Bolli (1957, loc. cit., here considered a paratype of praeangulata) clearly links the holotypic form of Globorotalia (Acarinina)praeangulaia Blow to G. (A.) praecursoria praecursoria (Morozova) [Acaranina praecursoria, 1957] as implied by Bolli (1957, op. cit., p. 74; cf. Blow, 1979, op. cit., p. 945, where G. uncinata Bolli is considered as a junior synonym of praecursoria).
The paratypic specimen figured on pl. 83, fig. 6, in axial-apertural view, shows characters which closely link the (paratypic) specimen figured by Bolli (1957, loc. cit., fig. I I especially) to the holotypic form of praeangulata (cf. axial-apertural view of the paratype figured on fig. 7). The paratype on pl. 83, fig. 6 shows a more rounded, less subacute, peripheral margin than the holotypic morphotype. The paratype figured In oblique-dorsal view on pl. 85, fig. l, has a hole in its peripheral area and from this accidental breakage it can be seen that there is no muricocarinal structure developed. The paratype illustrated 01) pl. 87, fig. 2, also shows an axialapertural view of a specimen which does not show such an acute peripheral margin as the holotype.
In the development from G. (A.) praecursoria praecursoria (Morozova) to G. (A.) praeangulata, it would seem that the main trends to operate were the increasing peripheral acuteness combined with the development of chambers which were more nearly equidimensional in dorsal aspect, as compared to those of praecursoria (sensu  stricto), with the subsequent later loss of the vorticiform earlier dorsal intercameral sutures. In praeangulata, the dorsal intercameral sutures become more nearly radial in the phylogenetically advanced forms which lead into G. (Morozovella) angulata (sensu lato). However, the dorsal intercameral sutures usually show recurved features at least for the earlier ontogenetic stages of praeangulata. 
In general, G. (A.) praeangulata Blow, 1979 differs from G. (Morozovella) angulata (sensu lato), in having a less acute peripheral margin, more recurved dorsal intercameral sutures and, most importantly, no muricocarma.

References:

Blow, W. H. (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden. 2: 1-1413. gs


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Globorotalia (Acarinina) praeangulata compiled by the pforams@mikrotax project team viewed: 20-10-2020

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