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Triquetrorhabdulus

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Cenozoic Taxa

Pseudotriquetrorhabdulus inversus (Bukry & Bramlette, 1969) Wise in Wise & Constans, 1976

Edited by Lyndsey on Fri, 11/03/2011 - 18:32

Pseudotriquetrorhabdulus inversus (Bukry & Bramlette, 1969) Wise in Wise & Constans, 1976

Description: Large, narrow, spine-like nannofossil that tapers towards both ends and has a narrow central canal.

Remarks: Originally compared with Neogene Triquetrorhabdulus due to presence of ‘keels' but may represent disarticulated rhabdolith spines.

Geological Time Data
Geological Time Periods: 
NP16
NP14b
Biblio Reference: 
Varol, O.  1998.  Palaeogene. Calcareous nannofossil biostratigraphy. :200-224.

Ceratolithus cristatus HET

Edited by Lyndsey on Thu, 10/03/2011 - 12:48

Ceratolithus cristatus Kamptner 1950 HET

Description: Circular heterococcoliths with a single shield and open central area, surrounded by a collar/tube. Formed of a single cycle of crystal-units with sub-vertical c-axes (Young et al. 1998).

Original description:

Neosphaera coccolithomorpha 020365.jpgNeosphaera coccolithomorpha 020366.jpg

Cer_HET_CSF0146.JPGCer_HET_166-06.JPGCer_HET_113-22.JPGCer_HET_114-96.JPG modern
5-21coccolithomorpha.JPG5-26coccolithomorpha.JPG5-27coccolithomorpha.JPGCerHet201 (471-0) 23NN14-15.JPG fossil

Remarks (relation to ceratoliths): A succesion of observations (Alcober & Jordan 1997, Young et al. 1998, Cros et al. 2000, and Sprengel & Young 2000) have shown that these heterococcoliths are formed during an alternate life-cycle stage of Ceratolithus cristatus and so should not be regarded as a discrete species.

Synonyms:

  • Neosphaera Lecal-Schlauder 1950
  • Craspedolithus Kamptner 1963

Variants: three different forms can be identified in the modern plankton (Kleijne 1993), and may represent discrete species, although given the life-cycle complexities it is simpler to place them all in C. cristatus.

  1. large coccolithomorpha type: 6-10 µm across, opening 0.4-0.5x total diameter [= Neosphaera coccolithomorpha Lecal-Schlauder 1950].
  2. small coccolithomorpha type: 4-5 µm across, opening 0.35-0.45x total diameter.
  3. nishidae type: 4-7 µm across, opening 0.15-0.3x total diameter [=Neosphaera coccolithomorpha var. nishidae Kleijne 1993].

Geological Time Data
Notes on occurrence information: 

Quite common in the Quaternary and has been observed back to at least the mid Pliocene, but is not routinely recorded since it is difficult to sperate from Umbilicosphaera in the LM. NB The first occurrence does seem to approximately conicide with that of Ceratolithus ceratoliths, but there is no obvious reason why this should be the case since the ancestor of Ceratolithus (Triquetrorhabdulus?) might be precidited to have formed heterococcoliths.

Pseudotriquetrorhabdulus Wise in Wise & Constans, 1976

Edited by Paul Bown on Fri, 02/04/2010 - 22:15

Description: Large, narrow spine like nannofossil that tapers towards both ends and has a narrow central canal.

Remarks:

Type species: Pseudotriquetrorhabdulus inversus (Bukry & Bramlette, 1969) [Triquetrorhabdulus]

Orthorhabdus serratus

Edited by Lyndsey on Thu, 10/03/2011 - 13:51

Orthorhabdus serratus Bramlette and Wilcoxon, 1967

Description: Triangular-shaped nannolith formed of three blades with c-axis perpendicular to length. The median blade is wider than the two lateral blades and the c-axis lies in the plane of this blade, hence in usual angle of rest the nannolith shows high birefringence, but inverse optical orientation (blue with gysum plate when orientated SW-NE). In alternative orientaton it is symetrical and shows low birefringence.

Typical forms are symmetrical but specimens with a spine developed from the median blade occur in upper part of range.

Remarks:

Original description:

Orthorhabdus serratus 080472.jpgOrthorhabdus serratus 080473.jpg

9-13serratus.JPG 9-16serratus.JPG 9-12serratus.JPG 9-11serratus.JPG

Synonym: Triquetrorhabdulus martinii Gartner, 1967.

Geological Time Data
Geological Time Periods: 
NN6
NN2
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Triquetrorhabdulus striatus

Edited by Lyndsey on Thu, 10/03/2011 - 13:49

Triquetrorhabdulus striatus Muller, 1974

Description: species of Triquetrorhabdulus similar to T. rugosus but with subsidiary ridges on one lateral blade.

Remarks: Some specimens are dramatically different from typical T. rugosus but they vary considerably, and weak ridges occur on some typical T. rugosus specimens (e. g. Gartner 1967 pl. 9/1).

Original description:

Triquetrorhabdulus striatus 090176.jpgTriquetrorhabdulus striatus 090177.jpg

9-26striatus.JPG 9-27striatus.JPG 9-29striatus.JPG 9-28striatus.JPG

Geological Time Data
Geological Time Periods: 
NN12
NN10
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Triquetrorhabdulus rugosus

Edited by Lyndsey on Thu, 10/03/2011 - 13:48

Triquetrorhabdulus rugosus Bramlette and Wilcoxon, 1967

Description: Triquetrorhabdulus species with three blades of variable width, c-axis perpendicular to length. Broadest blade usually rodded.

Remarks: The most common mid to late Miocene Triquetrorhabuduls species. Specimens vary noticeably in shape and in degree of development of secondary ridges, the most extreme of these have been described as separate species (T. striatus, T. extensus, T. finifer). It might also be worth subdividing the more normal forms, as noted by Perch-Nielsen (1985b).

Synonym: Ceratolithus farnsworthii Gartner, 1967.

Original description:

Triquetrorhabdulus rugosus 080355.jpgTriquetrorhabdulus rugosus 080356.jpg

9-21rugosus.JPG 9-22rugosus.JPG 9-25farnsworthii.JPG 9-24farnsworthii.JPG 9-23rugosus.JPG



Geological Time Data
Geological Time Periods: 
NN12
NN6
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Triquetrorhabdulus milowii

Edited by Lyndsey on Thu, 10/03/2011 - 13:44

Triquetrorhabdulus milowii Bukry, 1971

Description: Short (8-15μm), broad (5-8μm) species of Triquetrorhabdulus with curved sides. All blades similar.

Remarks:

Original description:

Triquetrorhabdulus milowii 060183.jpgTriquetrorhabdulus milowii 060184.jpg

9-14milowii.JPG 9-15milowii.JPG

Variant: T. auritus Stradner and Allram, 1982 - more wedge-shaped, occasionally with ridges at blunt end. Range: NN5 to 6.

Geological Time Data
Geological Time Periods: 
NN6
NN 1
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Triquetrorhabdulus challengeri

Edited by Lyndsey on Thu, 10/03/2011 - 13:43

Triquetrorhabdulus challengeri Perch-Nielsen, 1977

Description: Short broad species with two wide blades bearing one to four subsidiary ridges parallel to a shorted median lath. Optic axis parallel to length.

Remarks:

Size: 8-15 microns long, typically about half as wide as long.

Original description:

Triquetrorhabdulus challengeri 120414.jpgTriquetrorhabdulus challengeri 120415.jpg

9-9challengeri.JPG 9-10challengeri.JPG 9-3challengeri.JPG 9-4challengeri.JPG 9-5challengeri.JPG

Geological Time Data
Geological Time Periods: 
NN2
NN 1
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Triquetrorhabdulus carinatus

Edited by Lyndsey on Thu, 10/03/2011 - 13:42

Triquetrorhabdulus carinatus Martini, 1965

Description: Elongate (up to 50μm). All three blades identical, without ridges.

Remarks: As noted by Martini (1965) specimens vary considerably in dimensions with two main types:

  • (A) long thin specimens with parallel sides (entire specimens 25 - 50 x 1.5 - 2.5 microns, my obs.);
  • (B) shorter and broader specimens with distinct taper (15 - 25 x 2 - 4 microns, my obs.).

There does not, however, seem to be any consistent pattern to the distribution of these forms.

Original description:

Triquetrorhabdulus carinatus 020227.jpgTriquetrorhabdulus carinatus 020228.jpg

9-1carinatus.JPG 9-2carinatus.JPG
9-7carinatus.JPG
9-8carinatus.JPG
9-6carinatus.JPG Tq_car767 242-9-1 NN1.jpg Tq_car long_242-9-1 NN1.jpg  

 

Geological Time Data
Geological Time Periods: 
NN2
NP25
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.
Notes on occurrence information: 

Distribution rather sporadic.

Triquetrorhabdulus

Edited by Lyndsey on Thu, 10/03/2011 - 13:40

Genus Triquetrorhabdulus Martini 1965

Description: Elongate nannoliths formed of three blades. Entire nannolith formed of a single calcite crystal, but with variable c-axis orientation, see discussion of Family Triquetrorhabdulaceae.

Remarks: The genus contains two discrete sets of species

  • T. carinatus group , with c-axis parallel to length and so always strongly birefringent, with length-fast orientation
  • T. rugosus group , with c-axis perpendicular to length, show low biefringence in most common orientation, with length-slow orientation

Type species: T. carinatus Martini 1965

Original description:

Triquetrorhabdulus genus 100213.jpg

Geological Time Data
Geological Time Periods: 
NN12
NP24
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.
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