Catalog - Lilliputianella

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Lilliputianella

Citation: Lilliputianella Banner & Desai 1988

Type species: Lilliputianella longorii Banner & Desai 1988

Test trochospiral, evolute on spiral side, almost wholly involute on umbilical side, composed of two to three whorls of chambers; four to seven chambers in a whorl. The chambers are initially subglobular to reniform, becoming radially elongate and ovoid, and higher than broad, in the final whorl. The aperture is interiomarginal, umbilical-extraumbilical, with a porticus which is typically broadest at its posterior end. The relict parts of the primary aperture, with their portici, are visible on the last few chambers within the open umbilicus. The wall is microperforate, the external perforations being about 0.5 to 1.0µm in diameter and scattered irregularly over the surface of the test with no geometrical pattern of distribution.The surface of the test is smooth and lacks true muricae or spine bases.

The generic name Lilliputianella is derived from Lilliput (Swift, 1726) wherein organisms were of small proportions and where ovoids which displayed their pointed ends were preferred.

The radially elongate, pointed ovoid or clavate chambers of the last whorl, in which the chamber height is greater than the chamber breadth, distinguish this genus from both Hedbergella Bronnimann and Brown and from Blefuscuiana n. gen. Lilliputianella (Plate 4, figs. 11-12) is microperforate and nonmuricate and is therefore distinguished from Clavidhedbergella Banner and Blow, which is macroperforate (external perforations an order of magnitude larger and more densely and regularly packed) and which is wholly or partly muricate (Plate 4,fig. 10). We have not been able to find published records of pre-Aptian species which should be referred to Lilliputianella. Study of the numerically-rich planktonic foraminiferal assemblages from sidewall cores of the subsurface Kopervik formation, Central North Sea (well dated in BP Petroleum Development Ltd proprietary reports as Early Barremian to Middle/Late Barremian, on palynology and nannofossils) revealed the presence of abundant specimens of Blefuscuiana and rarer Praehedbergella, but none referable to Lilliputianella. Therefore, all evidence available to us suggests that Lilliputianella first appeared during the (Early to Middle?) Aptian.

Lilliputianella spp. appears to have been derived directly from Blefuscuiana spp. by radial elongation of some or all of the chambers of the last whorl. This parallels the independent evolution of Clavihedbergella spp. from Hedbergella (“Planogyrina”) in Albian and Later Cretaceous time, as well as the Cenozoic evolution of Clavatorella, Beella, etc. The radially elongate chambers of Lilliputianella often develop in only the later half of the last whorl (the early whorls being indistinguishable from the ancestral Blefuscuiana) and this parallels the development of radially elongate chambers in the later parts of the last whorl of many forms of Leupoldina (where the juvenile resembles the ancestral Blowiella, e.g. PI. 10, figs. 1, 2). The pointed ovoid form of elongate chamber, which is so common in species of Lilliputianella (pl. 8, figs. 5-7), gives the appearance of incipient sites for tubulospine development, but no tubulospines are known in any trochospiral schackoinid (they are confined to the planospiral Schackoina).

As in the evolution of Blefuscuiana, no species of Lilliputianella is yet known to extend and distally fuse its portici. The development of umbilical accessory apertures by the fusion of portici seems to be confined to the descendants of macroperforate Hedbergella. Therefore, the macroperforate Clavihedbergella has a rotaliporid relative with accessory umbilical apertures and elongate chambers (Claviticinella digitalis (Sigal) El-Naggar), but Lilliputianella has no such descendant. It seems that the microperforate descendants of Praehedbergella had only a limited capacity grossly to homeomorph the descendants of macroperforate Hedbergella (the microperforate forms not only lacked the capacity to parallel the evolution of Tzcinella, but in being nonmuricate, they never evolved peripheral keels).

A stratigraphically very early tendency radially to elongate later chambers is displayed by some specimens of Praehedbergella illustrated by Butt (1979, pl. 3, figs. 11-13). These have only four chambers in each whorl but the last one or two may become as high as long, producing a strongly lobulate peripheral outline. The age of these specimens is disputed, because the nannofossils suggest a Hauterivian age while the foraminifera indicate Barremian (Butt, 1979, p. 257). Such forms are likely to be directly ancestral to Blefuscuiana eocretacea (Neagu) and do not seem to have developed directly into true Lilliputianella.

References:

Banner, F. T. & Desai, D. (1988). A review and revision of the Jurassic-Early Cretaceous Globigerinina,with especial reference to the Aptian assemblages of Speeton (North Yorkshire, England). Journal of Micropalaeontology. 7: 143-185. gs

Swift, J. (1726). Travels into several remote nations of the world [also known as Gulliver's Travels]. Benjamin Motte, London. -. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Lilliputianella Banner & Desai 1988

Lilliputianella

References:

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