Catalog - Hoeglundina

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Hoeglundina

Citation: Hoeglundina Brotzen, 1948

Type species: Höglundina elegans (d’Orbigny) = Rotalia (Turbinuline) elegans d'Orbigny, 1826

The genus Epistomina Terquem 1883 is characterized by the lateromarginal or lateral aperture and by a partition in the inside of the chambers. This genus, as generally understood by palaeontologists, seems to consist of very different types, distinguished by the shape and position of the apertures.

Terquem (1883) and Berthelin (1863, Bull. Soc. Géol. France, sér. 3, Vol. XI) pronounced the importance of the shape of the aperture for the systematic position of this genus. Uhlig (1883, Jahrb. k. k. geol. Reichsanst., Wien, Vol. 33) observed the inner partition in the chambers and described in great detail the variations of the aperture. He distinguished types:

with lateromarginal and interiomarginal apertures,
with lateromarginal apertures and, in the septa in the inside of the test, areal apertures,
with lateral apertures and, in the inside of the chambers, as in the preceding type.

Sensu stricto only the last types belong to the genus Epistomina, but the other types have not so far been distinguished from Epistomina. The first types are not observed by the author. Types of the second group occur commonly in the Tertiary and Quaternary. For them a new genus shall be erected: the genus Höglundina. Its genotype is Rotalia elegans d’Orbigny. An interesting investigation was made by Rzehak (1885, Verh. k. k. geol. Reichsanst. 1888, Ann. nat. hist. Mus. Wien, Bd. III), disclosing that Tertiary and Recent specimens of “Epistomina” elegans lack an interiomarginal aperture on the last chamber and only have the lateromarginal aperture. Brady’s opinion that the lateral and lateromarginal aperture of Epistomina are “more or less abnormal” was erroneous and for many years restrained the progress of the taxonomy of the entire group of Epistominidae (Ceratobuliminidae Glaessner). But on the other hand Brady made the important discovery that the wall of “Epistomina” = Höglundina is built up of several layers. In the year 1934 (Amer. Midl. Nat., Vol. 15) Plummer continued Uhlig’s half-forgotten studies and described the interior structure of several genera (Epistomina, Epistominoides, and in 1936 Ceratobulimina (Amer. Midl. Nat., Vol. 17)). Glaessner, 1937 (Studies in Micropal., Moscow, Vol. I, Fasc. 3), concluded all these investigations and erected the family Ceratobuliminidae.

Plummer’s and Glaessner’s studies were the fundamental step toward a natural taxonomy of this branch of the Rotaliiformes. But contrary to Glaessner’s conclusions the author distinguished between forms with lateral or lateromarginal apertures, the Epistominidae, and forms with umbilical apertures and partitions in the inside of the chambers the Ceratobuliminidae (Brotzen, 1942, Sver. Geol. Unders., Årsb. 36, No. 8). These two groups are closely related.

The development of the genera and species in these two groups is characterized by a reduction of the inside partition and a simplification of the aperture. The Recent Höglundina shows many primitive characters and is a good example of the construction of the partition and the aperture. Only in the last chamber of the Recent or Miocene species does partition occur. (See Plummer. 1934, Amer. Midl. Nat., Vol. 15, no. 5, tf. 1 [Epistomina elegans (d’Orbigny)].) In the previous chambers the partition is reduced and what remains are some small ribs on the interior wall and the preceding septum (see Pl. 15, fig. 3b), and in the angle of the spiral and umbilical wall there is a short lamella. In the final chamber the partition continues from the spiral side into the chamber and forms a roof over the lateromarginal apertural slit (tec. = tectum). Downward the partition is fixed on the inner wall (l. inf. = latus inferior); along the entire height it is fixed on the preceding septum (sep. 2) (see Pl. 17, figs. 7-6; text-fig. 23). The opening from the preceding chamber into the last one lies interiomarginal and discharges into the inner part of the last chamber. This opening (foramen septale) is more or less elongate, but never a small slit as in other Rotaliiformes. The anterior part of the partition forms a free edge, curving rapidly backward (p. refl. = pars reflexa; see text-fig. 23).

Thus the inner part of the last chamber has an oriform opening to the exterior part. The function of this inner construction is stated by Plummer: “It is likely that the inner wall or chamber partition of Epistomina and Epistominoides is a protective device to prevent too ready exit of the protoplasm through a rather large and exposed aperture. The protoplasm passes readily from chamber to chamber through large foramina into the larger compartment of the final chamber, but to gain exit from the shell it must pass around the fold of the anterior edge of the partition and out through a comparatively narrow passageway or vestibule between the partition and the ventral wall to the aperture.

It is of interest to note that “Epistomina” spinulifera (Reuss) from the Gault of Folkestone has partitions in all chambers except the proloculum. The free edge, the pars reflexa, is very small, but distinct. In the early types the partition seems to be very complete in all chambers and is reduced in younger stages of evolution. Another ancestral character is that in the oldest species studied (from the Upper Jurassic) the septal foramen is areal, not interiomarginal as in Höglundina. During the evolution of the family Epistominidae the partition of the chambers will be reduced, so that more advanced genera only have rudiments of the inner structure or this structure has disappeared completely. The reduction cannot be followed step by step, but in many cases it is easy to correlate the strongly reduced parts with the primitive Epistomina stage (cf. Parrella Finlay, Alabamina Toulmin, Siphonina Reuss, etc.). In the uppermost Lias occur species of some new genera of Epistominidae, the aperture of which lies areal or lateral. Partly the aperture is rounded but never slit-shaped. Those forms seem to belong to an ancestral group, characterized by a very complete partition in all chambers of the specimens. From the phylogenetic point of view they can be regarded as ancestors of the Epistomininae and Ceratobulimininae.

The oldest known species for certain belonging to Epistomina or Höglundina occurs in the Lias. It is possible that such are known also from the uppermost Trias (Parker and Jones, 1860, Quart. Jour. Geol. Soc. [pp. 452, 455, pl. 20, fig. 46: Rotalia elegans d’Orbigny]). Uhlig supposed that Pulvinulina broeckiana Brady 1870 from the Namur Carbon [see Corrections, Supplement for 1949, Number 1] might belong to this genus, but that cannot be the case.

References:

Brotzen, F. (1948). The Swedish Paleocene and its Foraminiferal Fauna. Sveriges Geologiska Undersokning, Arsbok. 42(2): 1-140. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Hoeglundina Brotzen, 1948

Hoeglundina

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