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Hedbergella trocoidea


Classification: pf_mesozoic -> Hedbergellidae -> Hedbergella -> Hedbergella trocoidea
Sister taxa: << < H. mitra, H. modesta, H. occulta, H. praelippa, H. praetrocoidea, H. primare, H. quadricamerata, H. roblesae, H. ruka, H. semielongata, H. sigali, H. similis, H. speetonensis, H. tardita, H. tatianae, H. trocoidea, H. tunisiensis, H. tuschepsensis, H. sp.,

Taxonomy

Citation: Hedbergella trocoidea (Gandolfi, 1942)
Rank: Species
Basionym: Anomalina lorneiana var. trocoidea
Taxonomic discussion: H. trocoidea is the type species of Hedbergella. However this species shows features common both to Hedbergella and to Praehedbergella(sensu BouDagher-Fadel et al.,1997). It includes: 1. A larger test size (of 300 to 400 micron in diameter in Hedbergella compared to 100 to 200 micron in Praehedbergella) 2. A greater number of chambers in the last whorl (7 to 9 in Hedbergella vs. 4 to 7 in Praehedbergella). 3. Pore size varying between 1.8 to 2.9 micron in Hedbergella vs. pore size smaller than 1.5 micron in Praehedbergella. 4. Ornamented wall structure (on early chambers of last whorl, on both sides) in Hedbergella vs. a smooth wall structure in Praehedbergella. However H. trocoidea has retained morphological characters of Praehedbergella that includes: a presence of a thin lip rather than a flap or porticus; sporadic presence of weak perforation cones on last chambers of the spiral side of the last whorl.
Hedbergella trocoidea displays a moderate morphological variability regarding the number of chambers of the outer whorl (from 7 to 9), the height of the spiral side varying from almost flat to slightly convex, and the peripheral outline ranging from subcircular to slightly ovoid, more or less slightly lobate. [Huber & Leckie, 2011, p. 72]
Hedbergella trocoidea differs from its ancestor, Hedbergella praetrocoidea BouDagher-Fadel and others (1997), in having more numerous chambers in the outer whorl (7 to 9 instead of 6 to 6.5), a smaller and deeper umbilical area, and, possibly, a higher spiral side (Huber and Leckie, 2011).

Type images:

Original description: Test medium in size, low trochospiral, consisting of about 2 whorls, nearly flat to slightly concave on spiral side, broadly rounded, peripheral outline distinctly lobulate; chambers inflated, subglobular to radially rather elongate, about 7-8 in final whorl, increasing gradually in size as added; sutures distinct, depressed, nearly radial on both sides; wall calcareous, perforate, radial in structure, surface smooth; aperture a low interiomarginal, extraumbilical-umbilical arch bordered above with or without slight lip.

Interessante è notare che spesso l'avvolgimento tende a farsi nettamente trocoide, sì che la conchiglia diviene alquanto convessa, la camera finale viene così ad adagiarsi sulla faccia ombelicale e l'apertura sì estende sull'ombelico in un posizione nettamente asimmetrica (tav. IV, fig. 2-3). Forme analoghe si trovanogià descritte dal Berthelin (1880 p. 69, tav. IV, fig. 11) col nome di Placenta nitida (Reuss). Franke (1925) interpreta piuttosto tale forma come un sinonimo dell'Anomalina lenticula, ma a giudicare dalla stessa figura di Reuss ciò sembra escludersi, poichè questa è più piccola a bordo un po' depresso, giri interni nonvisibili. A giudicare dal nostro materiale sembra più evidente sussistere una relazione tra la forma di Berthelin e l'Anomalina lorneiana (d'Orbigny), forme che nei nostri sedimenti, sottolineano, non sono in alcun modo separabili, poichè troppi passaggi intermedi le uniscono.
Pertanto si può qui parlare di due gruppi di variazioni:
a) varietà quasi planispiralc: typica;
b) varietà nettamente convesa: trocoidea n. var.

[p. 134]:  L'Anomalina lorneiana tipica si distingue, come è evidente, per l'avvolgimento planispirale, pei giri interni più profondi che quelli esterni, sicchè poco visibili. Nelle fig. 2 e 3 (Tav. IV) si sono rappresentati due esemplari della varietà a spirale trocoide. L'individuo della fig. 2 è ancora poco trocoide e un po' involuto superiormente; quello della fig. 3 è per contro tipicamente evoluto. la forma convessa è ben accentuata sì che l'ultima camera si adagia un po' dal lato ombelicale. Da tale lato ambo gli individui sono completamente involuti, le camere della spira esterna si allungano irregolarmente fino al centro. in cui è solo visibile una piccola infossatura. L'Anomalina roberti Gandolfi mostra evidente. quale carattere differenziatore dalla precedente, un largo ombelico centrale; le camere appaiono per conseguenza più bassee larghe.

Entries in the Catalog of original descriptions: Anomalina lorneiana trocoidea


Emended description: Test medium to large, trochospirally coiled; dorsal side almost flat to slightly convex; 2 to 2.5 whorls; 7 to 9 chambers in the outer whorl increasing gradually and slowly in size as added; chambers subtriangular to triangular on the umbilical side, subspherical to trapezoidal in the spiral side, reniform in lateral view; equatorial periphery rounded, subcircular to ovoid, slightly lobate; sutures depressed, radial to slightly curved; umbilical area small and rather deep; aperture as a low to medium arch bordered by a lip. Wall finely perforate, with the first chambers of the last whorl covered by perforation cones; smooth wall was also observed in few specimens. [Huber & Leckie, 2011, p. 72]

Most likely ancestor: Hedbergella praetrocoidea - at confidence level 4 (out of 5). Data source: .

Geological Range:
Last occurrence (top): at top of P. rohri zone (99% up, 113.3Ma, in Aptian stage). Data source: [copied from Chronos database]
First occurrence (base): within G. ferreolensis zone (122.17-122.98Ma, base in Aptian stage). Data source: [copied from Chronos database]

Plot of occurrence data:

Dec 2017 - Plotting of Neptune data has been re-enabled on the Mesozoic pages following revision of the age-models in Neptune. The data is, however, still very sparse for the Early Cretaceous

  • Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
  • Note to users in China - the diagram may not plot unless you use a VPN since I use google services on the website. If this is a problem please contact me 谢谢.
  • Taxon plotted: Hedbergella trocoidea, synonyms included - Hedbergella trocoidea;
  • space-time plot :: Samples map :: Parent: Hedbergella

    Character matrix

    test outline:Lobatechamber arrangement:Trochospiraledge view:Planoconvexaperture:-
    sp chamber shape:Inflatedcoiling axis:Moderateperiphery:N/Aaperture border:Thin lip
    umb chbr shape:Subtriangularumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:N/A
    spiral sutures:Moderately depressedumb depth:Deepwall texture:Perforation conesshell porosity:Finely Perforate: 1-2.5µm
    umbilical or test sutures:Moderately depressedfinal-whorl chambers:7.0-9.0 N.B. These characters are used for advanced search. N/A - not applicable

    References:

    Ando, A., Huber, B. T. & Premoli Silva, I. (2013). Paraticinella rohri (Bolli, 1959) as the valid name for the latest Aptian zonal marker species of planktonic foraminifera traditionally called bejaouaensis or eubejaouaensis. Cretaceous Research. 45: 275-287. gs

    Gandolfi, R. (1942). Ricerche micropaleontologiche e stratigraphfiche sulla Scaglia e sul flysch Cretacici dei Dintorni di Balerna (Canton Ticino). Rivista Italiana di Paleontologia. 48: 1-160. gs


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    Hedbergella trocoidea compiled by the pforams@mikrotax project team viewed: 29-3-2020

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    Short stable page link: http://mikrotax.org/pforams/index.php?id=110269 Go to Archive.is to create a permanent copy of this page - citation notes



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