Nannotax3 - ntax_cenozoic - Lithostromation obscurum

Nannotax3 - ntax_cenozoic - Lithostromation obscurum Nannotax3 - ntax_cenozoic - Lithostromation obscurum

Lithostromation obscurum

Classification: ntax_cenozoic -> Nannolith families inc sed -> Lithostromationaceae -> Lithostromation -> Lithostromation obscurum
Sister taxa: L. hohnensis, L. pyramidale, T. tripartitus ⟩⟨ L. martinii, L. nodosum, L. obscurum, L. reginum ⟩⟨ L. operosum, L. perdurum, L. simplex, L. biconvexitas, L. sp.

Bybell 1975 pl19-5.JPG
PN68 pl2-03.JPG
PN68 pl1-08.JPG
PN68 pl2-01.JPG
PN68 pl2-02.JPG
PN68 pl2-04.JPG
PN68 pl2-05.JPG
PN68 pl2-06.JPG
PN71 KDansk pl57-10.JPG
Steurbaut 1998 pl1 f14.jpg
PN68 pl1-07.JPG
Varol1998_7-06-4.jpg
Varol1998_7-06-1.jpg
Varol1998_7-06-2.jpg
Varol1998_7-06-3.jpg

Taxonomy:

Citation: Lithostromation obscurum (Martini 1958) Martini 1970

Taxonomic rank: species

Basionym: Discoaster obscurus Martini 1958

Synonyms:

Lithostromation obscurum (Martini 1958) Martini 1962
Marthasterites obscurus (Martini 1958) Perch-Nielsen 1968

Variants:

Polycladolithus deflandrei Stradner 1959 =Lithostromation deflandrei (Stradner 1959) [ornamentation different and possibly flatter, does not seem to have been recorded since orginal descrition]
Marthasterites reginus Stradner 1962 = Lithostromation reginum (Stradner 1962) Bybell 1975 [synonym according to Perch-Nielsen 1968 but arguably different in having knobs at the termination of each ray]
Trochoaster concavus Bona (1964) [my interpretation - JRY 2017] = Lithostromation concavum (Bona, 1964) Young 2023

Taxonomic discussion: This species has strong affinities with both Rhombasteraceae and Lithostromationaceae and arguably is an intermediate beween them. It is large and distinctive but appears to have a restricted distribution. The original description as M. obscurus Martini (1958) was based on a broken specimen but has priority over the better subsequent description as M. reginus Stradner (1962) - see Perch-Nielsen 1968 for discussion.

Distinguishing features:
Parent taxon (Lithostromation): Triangular to stellate nannoliths with porous structure formed from small crystallites. All show 3-fold symetry but with a wide range of forms.
This taxon: 6 long free rays at two levels, smooth/solid

Farinacci & Howe catalog pages: D. obscurus * , P. deflandrei * , M. reginus * , T. concavus *

Morphology:

Description of L. reginum from Bybell (1975): "This species has six long, slender rays arranged in the same pattern as the playing pieces for the children's game of jacks. There are six knobs at the termination of each ray. The surface is covered with circular depressions which are surrounded by hexagonal, knobby ridges. The perforations become more shallow and more oval toward the ray ends. L. reginum is similar to Marthasterites spineus Shafik and Stradner, which is distinguished by its lack of terminal nodes and the presence of small projections on either side of each ray." [Bybell 1975]

Description of M. obscurus from Perch-Nielsen 1968 (edited translation from google translate):
"Fragments of Marthasterites obscurus were described for the first time by MARTINI (1958) as Discoaster obscurus, and later were assigned by the same author (MARTINI, 1962), to the genus Lithostromation. In the same year, STRADNER (1962) described Marthasterites reginus without paying attention to Discoaster obscurus, which corresponds only to the central part of a half of Marthasterites reginus.
When observed in the light microscope, Marthasterites obscurus is distinguished by its size, 13-28 μm, and by the 6 slender arms. In the danish specimens, the lateral appendages adhering to the arms are not always developed, instead the arms extend uniformly outward and run to a fine point. Between crossed-nicols, Marthasterites obscurus, when flat, that is, on the ground surface of the flattened tetrahedron, is formed by three of the six arms. The optical c-axis in the calcite forming this form is perpendicular to the above-mentioned ground plane. Marthasterites obscurus is, therefore, optically similar to the other species in the genera Marthasterites and Discoaster. However, since it often stands obliquely and then brightens, it can easily be found between crossed-nicols. Damaged specimens with truncated arms are often to be found; The half-specimens, described first as the Discoaster obscurus, are somewhat less frequent.
With the scanning electron microscope, the large focal depth of this instrument and the possibility of rotating and tilting the preparation makes it easier to understand the construction. Two sets of three arms, each enclosing an angle of 120°, are twisted by 60° with respect to one another; The whole is like two flattened tetrahedrons, twisted by 60 °. In flat-lying specimens one can see that the arms have furrows on their inner side, which grow in the middle of the hollow and are separated by ribs in the direction of the other arms. The arms are very slender or, especially from the central body, thickened by lime deposits.

See also: Lithostromation simplex - similar but with all six rays in the same plane;

Search data:

LITHS: nannolith-radiate, star-shaped, CROSS-POLARS: V-prominent, 1ou,

Lith size: 15->30µm; Segments: 6->6;
Data source notes: lith length from ODs & illustrated specimens

The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: Probably all records of I. obscurus are from the Early Eocene but M. reginus has been recorded from the Middle Eocene (Bybell 1975) and Bona (1964) described T. concavus from the Miocene. So, large nannoliths formed of triplets of rays in two planes with secondary ornamentation are evidently long ranging.
Last occurrence (top): within Tortonian Stage (7.25-11.62Ma, top in Tortonian stage). Data source: Bona 1964
First occurrence (base): within Early Eocene Sub-Epoch (47.84-55.96Ma, base in Ypresian stage). Data source: Martini 1970

Plot of occurrence data:

Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Histogram - Neptune occurrence data from DSDP and ODP proceedings. Pale shading <50 samples in time bin. Interpret with caution & read these notes
Taxon plotted: Lithostromation obscurum, synonyms included - Discoaster obscurus; Imperiaster obscurus; Lithostromation deflandrei; Lithostromation reginum; Marthasterites reginus;
See also space-time plot :: Samples map :: Parent: Lithostromation

References:

Bona, J. (1964). Coccolithophorida-vizsgalatok a meceski retegekben (Coccolithopohriden-Unntersuchungen in der neogen Schichtenfolge des Meeskggerbirges). Földtani Közlöny - Bulletin of the Hungarian Geological Society. 94: 121-131. gs

Bybell, L. (1975). Middle Eocene calcareous nannofossils at Little Stave Creek, Alabama. Tulane Studies in Geology and Paleontology. 11(4): 177-247. gs O

Martini, E. (1958). Discoasteriden und verwandte Formen im NW-deutschen Eozän (Coccolithophorida). 1. Taxonomische Untersuchungen. Senckenbergiana Lethaea. 39: 353-388. gs

Martini, E. (1962). Neue Lithostromationidae-Arten aus dem NW-deutschen Tertiar. Senckenbergiana Lethaea. 43: 243-241. gs

Martini, E. (1970). Imperiaster n. g. aus dem europäischen Unter-Eozän (Nannoplankton, incertae sedis). Senckenbergiana Lethaea. 51: 383-386. gs

Perch-Nielsen, K. (1968). Beobachtungen im elektronenmikroskop an Micrantholithus mirabilis und Marthasterites obscurus (Nannoplankton). Meddelelser fra Dansk Geologisk Forening. 18(2): 251-254. gs

Perch-Nielsen, K. (1971c). Elektronenmikroskopische untersuchungen an Coccolithen und verwandten Formen aus dem Eozan von Danemark. Biologiske Skrifter, Kongelige Danske Videnskabernes Selskab. 18(3): 1-76. gs O

Perch-Nielsen, K. (1984). Validation of new combinations. INA Newsletter. 6(1): 42-46. gs

Steurbaut, E. (1998). High–resolution holostratigraphy of Middle Paleocene to Early Eocene strata in Belgium and adjacent areas. Palaeontographica Abteilung A Palaeozoologie Stratigraphie. 247: 91-256. gs

Stradner, H. (1962). Über neue und wenig bekannte Nannofossilien aus Kreide und Alttertiär. Verhandlungen der Geologischen Bundesanstalt (Wien). 2: 363-377. gs

Varol, O. (1998). Palaeogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 200-224. gs

Young, J. R. (2023). Some proposed changes to the systematics of Cenozoic and Mesozoic nannoplankton. Journal of Nannoplankton Research. 41(1): 15-25. gs