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What exactly were Tentaculites?


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Mochaccino

The only descriptions I can find of these are just that they are fossil shells and have "uncertain affinity", whatever this means. Is it simply not known what organisms they were, animal, plant or otherwise? Are there some speculations?

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From the German Wikipedia  (Tentakuliten – Wikipedia ,which is much more detailed than the English-language version):  "The Tentaculita are usually assigned to the mollusks as a class, but some authors place them near the winged snails (pteropods) in the class of gastropods."

By the way, tentaculites is only a subgroup (genus) of the order Tentaculitida. The next higher level is the class Tentaculita (or Cricoconarida).

Edited by oilshale
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Mochaccino
16 hours ago, oilshale said:

From the German Wikipedia  (Tentakuliten – Wikipedia ,which is much more detailed than the English-language version):  "The Tentaculita are usually assigned to the mollusks as a class, but some authors place them near the winged snails (pteropods) in the class of gastropods."

By the way, tentaculites is only a subgroup (genus) of the order Tentaculitida. The next higher level is the class Tentaculita (or Cricoconarida).

 

Interesting, so they are some small mollusk or gastropod. I was wondering just maybe they were fragments of some exotic, bigger organism.

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Crusty_Crab

The Treatise on Invertebrate Paleontology, Part W (1962) lists them as "Small Conoidal Shells of Uncertain Affinities" in a chapter written by Donald Fisher. There is a short discussion about what they may be, but the short answer is that the jury is out since no soft tissue remains have been found.

 

21 hours ago, Mochaccino said:

 

Interesting, so they are some small mollusk or gastropod. I was wondering just maybe they were fragments of some exotic, bigger organism.

According to Fisher, this had been speculated as early as 1830, as possibly the spines of brachiopods or echinoids or crinoid arms. He rejects this since spine bearing brachiopods, echinoids or crinoids have not been found in the strata where Cricoconarids are most prolific.

 

 

On 1/22/2022 at 2:03 AM, oilshale said:

From the German Wikipedia  (Tentakuliten – Wikipedia ,which is much more detailed than the English-language version):  "The Tentaculita are usually assigned to the mollusks as a class, but some authors place them near the winged snails (pteropods) in the class of gastropods."

By the way, tentaculites is only a subgroup (genus) of the order Tentaculitida. The next higher level is the class Tentaculita (or Cricoconarida).

Fisher also listed the following reasons why they did not fit within the pteropods: 1. They lack an exceedingly thin shell. 2. They lack a notch or projection on the apertural brim and 3. They lack pteropodia. However, he did agree that they were likely Mollusks and proposed the class Cricoconarida in the phylum Mollusca. By the way, he rejected the name tentaculites because they implied the presence of tentacles when there is no evidence they had tentacles.

 

A 2012 paper did a phylogenetic study and found they are most likely lophophorates but they couldn't rule out the Molluscan hypothesis. 

https://www.researchgate.net/publication/234023270_Phenetic_phylogenetics_of_tentaculitoids_-extinct_problematic_calcareous_tube-forming_organisms

Historically, the hyoliths seem to have been in the same position as the Cricoconarids- listed as incertae sedis, with likely Molluscan affinities but in 2016 they were definitively identified as lophophorates https://pubmed.ncbi.nlm.nih.gov/28077871/.

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Mochaccino
23 hours ago, Crusty_Crab said:

The Treatise on Invertebrate Paleontology, Part W (1962) lists them as "Small Conoidal Shells of Uncertain Affinities" in a chapter written by Donald Fisher. There is a short discussion about what they may be, but the short answer is that the jury is out since no soft tissue remains have been found.

 

According to Fisher, this had been speculated as early as 1830, as possibly the spines of brachiopods or echinoids or crinoid arms. He rejects this since spine bearing brachiopods, echinoids or crinoids have not been found in the strata where Cricoconarids are most prolific.

 

 

Fisher also listed the following reasons why they did not fit within the pteropods: 1. They lack an exceedingly thin shell. 2. They lack a notch or projection on the apertural brim and 3. They lack pteropodia. However, he did agree that they were likely Mollusks and proposed the class Cricoconarida in the phylum Mollusca. By the way, he rejected the name tentaculites because they implied the presence of tentacles when there is no evidence they had tentacles.

 

A 2012 paper did a phylogenetic study and found they are most likely lophophorates but they couldn't rule out the Molluscan hypothesis. 

https://www.researchgate.net/publication/234023270_Phenetic_phylogenetics_of_tentaculitoids_-extinct_problematic_calcareous_tube-forming_organisms

Historically, the hyoliths seem to have been in the same position as the Cricoconarids- listed as incertae sedis, with likely Molluscan affinities but in 2016 they were definitively identified as lophophorates https://pubmed.ncbi.nlm.nih.gov/28077871/.


Thank you so much for showing me this detailed research. That is so intriguing that there is still no definitive identification past speculation, but that discussion is quite interesting and mysterious as well. I wonder if any soft tissue remains will ever be found.

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Crusty_Crab
1 hour ago, Mochaccino said:


Thank you so much for showing me this detailed research. That is so intriguing that there is still no definitive identification past speculation, but that discussion is quite interesting and mysterious as well. I wonder if any soft tissue remains will ever be found.

I think its just a matter of time. 20 years ago, someone might have asked the exact same question about the hyoliths. Then someone found fossils that answered that question. This is one of the reasons why I love the field of paleontology. Anyone, not just a trained scientist, can make that once in a lifetime find that leads to a major breakthrough. 

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FYI, Mollusks are a phylum not a class.  Gastropoda is a class within Mollusca.  

 

Try doing a Google Scholar search and start with the most recent papers or articles.  I think as Crusty has pointed out it is only a matter of time before either better specimens or better microscopy will reveal to whom they belong.

 

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doushantuo

 

 

 

Here's the thing: tentaculitid literature that one SHOULD read,but can't for accessability reasons(arrow points to the paper that i have read(*),and it;s a whopper:

(*albeit that was aound 1998)

 

 

tflitermarshtelaatjetentaculincsedis6 - 2020-07T065841.808.jpg

app.2009.tenpalynomacb0111.pdf

Organic remains of tentaculitids: New evidence from Upper Devonian of Poland
PAWEŁ FILIPIAK and AGATA JARZYNKA

Acta Palaeontologica Polonica 54 (1): 111–116.

 

 

 

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