Nannotax3 - ntax_main - Amaurolithus

Nannotax3 - ntax_main - Amaurolithus Nannotax3 - ntax_main - Amaurolithus

Amaurolithus

Classification: ntax_main -> Nannolith families inc sed -> Ceratolithaceae -> Amaurolithus
Sister taxa: Amaurolithus, Ceratolithus, Nicklithus ⟩⟨ Orthorhabdus, Triquetrorhabdulus ⟩⟨ Nivisolithus

Daughter taxa (time control age-window is: 0-800Ma)
				Amaurolithus brevigracilis Like A. delicatus but shorter arms.
				Amaurolithus delicatus Simple horseshoe-shaped amauroliths. Grades into the other morphotypes, especially A. primus and A. tricorniculatus.
				Amaurolithus primus Simple form with short arms, broad arch and weakly developed keels.
				Amaurolithus tricorniculatus Right arm extended into apical spur.
				Amaurolithus sp. Specimens which cannot be assigned to established species

Taxonomy:

Citation: Amaurolithus Gartner & Bukry 1975

Taxonomic rank: genus

Type species: Ceratolithus tricorniculatus Gartner 1967

Taxonomic discussion: Raffi et al. (1998) documented likely evolutionary relationships between Ceratolithus and the fossil genera Amaurolithus and Orthorhabdus. They presented evidence that A. delicatus, A. amplificus and C. acutus all independently evolved from Orthorhabdus. Since this indicated that Amaurolithus was polypyhletic they proposed dividing the genus in two; Amaurolithus and Nicklithus. This is followed here.

Synonyms:

Amaurolithus * Gartner & Bukry 1975

Distinguishing features:
Parent taxon (Ceratolithaceae): Horseshoe-shaped rod-shaped nannoliths and simple hoop-coccoliths formed in one phase of life cycle, planolith heterococcoliths in the other.
This taxon: Ceratoliths non-birefringent or only weakly birefringent

Morphology:

Ceratoliths non-birefringent or only weakly birefringent. The c-axis is perpendicular to the plane of horseshoe, but spines on the surface may result it in being tilted from the horizontal and so showing some birefringence, but birefringence is lower than in Ceratolithus and extinction is rarely exactly in line with axis of the ceratolth.
In the SEM Amaurolithus ceratoliths (sometimes termed amauroliths) usually come to rest with the more ornamented surface upward, in this orientation the left hand arm is distinctly curved whilst the right hand arm is relatively straight, but more heavily ornamented.

Search data:

LITHS: nannolith-other, asymmetric, horseshoe-shaped, CROSS-POLARS: 1ou, V-prominent,

Lith size: 5->12µm; Segments: 1->1;

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

Geological Range:
Last occurrence (top): at top of NN14 zone (100% up, 3.9Ma, in Zanclean stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NN11b subzone (6.91-7.42Ma, base in Tortonian stage). Data source: Total of ranges of species in this database

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.
See also:

Parent: Ceratolithaceae

References:

Gartner, S. & Bukry, D. (1975). Morphology and phylogeny of the coccolithophycean family Ceratolithaceae. Journal of Research of the U.S. Geological Survey. 3: 451-465. gs

Raffi, I., Backman, J. & Rio, D. (1998). Evolutionary trends of tropical calcareous nannofossils in the late Neogene. Marine Micropaleontology. 35(1): 17-41. gs

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 225-265. gs

Amaurolithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 19-8-2026

Taxon Search:

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=40 Go to Archive.is to create a permanent copy of this page - citation notes

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