Catalog - Tenuitella

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Tenuitella

Citation: Tenuitella Fleisher 1974

Type species: Globorotalia gemma Jenkins

Tenuitella n. gen. is proposed to include a closely related group of small Cenozoic forms which are usually referred to either Globorotalia or Turborotalia, but which are unrelated to species of either genus. The primary diagnostic characteristic common to all species placed in Tenuitella is a microperforate surface wall texture. The wall in these forms consists of a smooth surface penetrated by extremely small perforations, approximately 0.5μ in diameter. Small pustules or crystallites are commonly present on the wall surface and may obscure the perforations. In some specimens, these pustules may be so common as to completely cover the fundamentally smooth surface, but in other forms the pustules may be rare or absent. The microperforate wall of Tenuitella spp. typically appears smooth and thin, but in specimens with major pustule development it seems slightly roughened. In well-preserved tests, it may appear translucent. All known species have a minute to small test, an umbilical to extraumbilical or peripheral aperture flanked by a narrow lip or rim, and a rounded periphery lacking a distinct carina. Chambers are arranged in a low trochospiral coil, but in some species (e.g., T. gemma) occasional specimens tend to become pseudoplanispiral.

Tenuitella can be differentiated from almost all other Cenozoic globorotaloid genera by the nature of the wall. The microperforate wall texture is quite different from the relatively smooth wall with large but optically indistinct pores of Globorotalia and the cancellate wall of Turborotalia. These species are differentiated from Acarinina spp. and Morozovella spp. by the absence of large, coarse pseudospines. Testacarinata Jenkins is a distinct but short-lived carinate offshoot of Tenuitella. Globigerinita is a primarily Neogene genus that evolved from Tenuitella in the Late Oligocene and is distinguished by the primarily umbilical aperture and the common presence of a bulla.

The purely morphological differences between Tenuitella and Globanomalina are more difficult to define. In general, species of the latter genus have more compressed and less inflated and distinct chambers than those in Tenuitella, and the wall of Globanomalina appears to be more coarsely perforate. The fundamental basis for recognizing Tenuitella, however, is the common and independent phyletic history of the species included in it, a separate phylogeny of which the distinctive wall texture is the primary reflection. The forms included in Globanomalina and Tenuitella have been evolutionarily separate since at least the early Middle Eocene and probably since the basal Tertiary.

In addition to the species discussed below (T. gemma, T. anfracta, T. clemenciae), a number of other species should apparently be included in this genus on the basis of published descriptions. These are:

T. aculeata (Jenkins) = Globorotalia inconspicua aculeata Jenkins
T. cifellii (Brönnimann and Resig) = Globorotalia (Turborotalia) cifellii Brönnimann and Resig, partim. (1971, pi. 42, figs. 1-5)
T. insolita (Jenkins) = Globorotalia insolita Jenkins
T. minutissima (Bolli) = Globorotalia minutissima Bolli
T. munda (Jenkins) = Globorotalia munda Jenkins
T. nkbrowni (Brönnimann and Resig) = Globorotalia (Turborotalia) nkbrowni Brönnimann and Resig
T. parkerae (Brönnimann and Resig) = Globorotalia (Turborotalia) parkerae Brönnimann and Resig, partim. (1971, pi. 43, fig. 7, not fig. 10; pi. 48, figs. 2, 3)
T. praestainforthi (Blow) = Globigerinita stainforthi praestainforthi Blow. The last species differs from T. gemma only in having an umbilical bulla.

References:

Fleisher, R. L. (1974a). Cenozoic planktonic foraminifera and biostratigraphy, Arabian Sea, Deep Sea Drilling Project, Leg 23A. Initial Reports of the Deep Sea Drilling Project. 23: 1001-1072. gs O

			Tenuitella fleisheri Li, 1987 = Tenuitellita fleisheri
			Tenuitella jamesi Li, Radford,&Banner 1992
			Tenuitella kyrtomina Loeblich&Tappan 1994
			Tenuitella neobrevispira Li 1987
			Tenuitella neoclemenciae Li 1987
			Tenuitella postcretacea subsp. pieste Fordham 1986

CATALOG OF ORIGINAL DESCRIPTIONS: Tenuitella Fleisher 1974

Tenuitella

References:

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