Nannotax3 - ntax_main - Ascidian spicules Nannotax3 - ntax_main - Ascidian spicules

Ascidian spicules


Classification: ntax_main -> other groups -> Ascidian spicules
Sister taxa: Haptophytes, Parmales, Silicoflagellates, Miscellaneous scale-bearing groups, Testate amoebae, Chrysophyte cysts, Dinophytes, Diatoms, Zooplankton groups, Ascidian spicules, C. and crud, Palaeozoic nannofossils, A. Agglutinations


Taxonomy:
Citation: Ascidian spicules
Taxonomic rank: informal group of genera
Taxonomic discussion:

Ascidians (common name sea squirts) are benthic tunicates, so nothing really to do with nannoplankton. However, the spicules they produce commonly occur in nannoplankton preparations, especially from shallow marine environments. So, nannoplankton workers need to be able to recognise them.

Durand (1948) first recognised fossil ascidian spicules and following this Deflandre & Delfandre-Rigaud (1956) proposed the new genus and species Micrascidites vulgaris for them. This name has often been used. Buge & Monniot (1972) provide further documentartion of French Eocen specimens

Varol & Girgis (1994) discussed ascidian spciules, suggested several Mesozoic nannofossils were likely to be Ascidian spicules and assigned them to the genus Didemnum, which is the most common extant genus of Ascidians. Varol & Houghton (1996) provide a useful overview for nannofossil specialists and also propose Linnean names for various different morphotypes. Varol (2006) developed this approach further, proposing names for many different Mesozoic morphotypes. 

Lukowiak (2012) and Lukowiak et al. (2016) record fossil specimens from the Eocene of Australia and Miocene of Moldova respectively and assign spicules to ascidian taxa as far as possible, in prefernce to using the parataxonomy of Varol & Houghton (1996). They also give modern references.


Synonyms:

Fossil taxa which are probably based on ascidian spicules include the following. NB Varol & Girgis 1994  also suggested that Tripinnalithus shetlandenis, Kokia borealis, Tetralithus? cascianus and Tetralithus pseudotrifidus were ascidians, we consider it is more likely that the first two are nannoplankton and the last two inorganic crystals

Variants:

The following taxa have been proposed for different morphotypes of Ascidian spicules. It is not clear that this type of parataxonomy is useful.  

Distinguishing features:
Parent taxon (other groups): Other nannoplankton and microplankton groups
This taxon: Typically spherically-radiate calcite bodies, formed of largish tapering, radiate elements with radial c-axes. Larger and less regularly-shaped than typical nannofossils.


Morphology:

Varol & Houghton (1996) state that ascidian spicules are aragonitic and support this with several references. It is not clear if this applies to all ascidian spicules, and I have not been able to find a modern source for this, but it seems likely that most ascidian spicules are aragontic and this would epxlain their sporadic fossil record [JRY 2026].  The spicules readily disaggregate into the consituent elements and these behave optically as single crystals. However in SEM it is ofen apparent that these elements have a fibrous-like substructure and in LM they often appear to contain inclusions.

In the Maldives ascidian spicules are a major component of micrite in reef-derived sediments [my obs, IODP expedition 359, JRY]

Search data:
Lith size: 0->0µm;
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 (100% up, 0Ma, in "Holocene" stage). Data source: Total of ranges of the species in this database
First occurrence (base): within (-Ma, base in "Holocene" stage). Data source: Total of ranges of species in this database

Plot of occurrence data:

References:

Bona, J. & Kernerne, K. (1966). Mikropaleontologiae vizsgalotok a tekeres 1. sz. Foldtani alapfuras Miocen kepzodmenyein. Magyar Allami Foldtani Intezet. Evi Jelentese. 1964: 113-137. gs

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

Bonet, F. & Benveniste-Velasquez, N. (1971). Espiculas de asicidias fosiles y actuales. Revista del Instituto Mexicano del Petroleo. 3(4): 8-35. gs

Bown, P. R. (2005d). Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research. 27(1): 21-95. gs O

Bown, P. R. (2010). Calcareous nannofossils from the Paleocene/Eocene Thermal Maximum interval of southern Tanzania (TDP Site 14). Journal of Nannoplankton Research. 31(1): 11-38. gs O

Bukry, D. (1973c). Coccolith stratigraphy, eastern equatorial Pacific, Leg 16, Deep Sea Drilling Project. Initial Reports of the Deep Sea Drilling Project. 16: 653-711. gs O

Deflandre, G. & Deflandre-Rigaud, M. (1956). Micrascidites manip. nov., sclerites de Didemnides (Ascidies, Tuniciers) fossiles due Lutétian du Bassin Parisien et du Balcombien d'Australia. Compte Rendu Sommaire des Séances de la Société Géologique de France. 1956: 47-48. gs O

Durand, S. (1948). Ascidians. Comptes rendus de l'Académie des sciences, Paris. 227: 683-684. gs

Filipescu, M. & Hanganu, E. (1960). Sur les Discoastérides du Tertiare du N-O de l'Olténie. Revue Roumaine de Géologie Géophysique et Géographie. 4(2): 217-232. gs

Hoffmann, N. (1970e). Taxonomische Untersuchungen an Coccolithen aus der Kreide Norddeutchlands anhand elektronenmikroskopischer Aufnamen. Hercynia. 7(1-3): 163-198. gs

Hoffmann, N. (1970c). Elektronenmikroskopische Untersuchungen an "stabförmigen" Nannofossilien aus der Kreide und dem Paläogen Norddeutschlands. Hercynia. 7: 131-162. gs O

Lukowiak, M. (2012). First record of Late Eocene Ascidians (Ascidiacea, Tunicata) from Southeastern Australia . Journal of Paleontology. 86(3): 521-526. gs

Lukowiak, M., Dumitriu, S. & Ionesi, V. (2016). First fossil record of early Sarmatian didemnid ascidian spicules (Tunicata) from Moldova. Geobios. 49: 201-209. gs

Menini, A., Mattioli, E., Spangenberg, J. E., Pittet, B. & Suan, G. (2018). New calcareous nannofossil and carbon isotope data for the Pliensbachian/Toarcian boundary (Early Jurassic) in the western Tethys and their paleoenvironmental implications. Newsletters on Stratigraphy. -. gs

Perch-Nielsen, K. (1988). New Lower Cretaceous calcareous nannofossil species from England. INA Newsletter. 10(1): 30-37. gs

Varol, O. & Girgis, M. (1994). New taxa and taxonomy of some Jurassic to Cretaceous calcareous nannofossils. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 192: 221-253. gs

Varol, O. & Houghton, S. D. (1996). A review and classification of fossil didemnid ascidian spicules. Journal of Micropalaeontology. 15: 135-149. gs

Varol, O. (2006). Didemnid ascidian spicules from the Arabian Peninsula. Journal of Nannoplankton Research. 28(1): 35-56. gs O

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

Missing or ambiguous references: Savigny 1816;

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Ascidian spicules compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 5-9-2026

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Comments (3)

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Thanks guys for such a possitive reactions to our latest paper! :) we are glad that you liked it. If you are interested in fossil ascidian spicules, I also recommend my article from 2012: _ukowiak, M. 2012. First Record of Late Eocene Ascidians (Ascidiacea, Tunicata) from Southeastern Australia: Journal of Paleontology 86 (3): 521–526
If any of you want a pdf of this paper, please, do not hesitate to write to me. Cheers!
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Very nice article about ascidian spicules at Researchgate published in April 2016 in Geobios. Unfortunatelly I couldn't add a link here. :(
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thanks for the tip - I just found it and and yes it is a nice paper , i will add mention of it on the page as it has modern references etc.

Lukowiak, M.; Dumitriu, S. & Ionesi, V., (2016). First fossil record of early Sarmatian didemnid ascidian spicules (Tunicata) from Moldova. Geobios, 49: 201-209.