A Very Little known Ctenacanthid Shark with massive evolutionary implications (and deserves to be studied more)

[Joseph Fossil]

The Ctenacanthiforms sharks emerged in the Late Devonian period and were one of the earliest evolutionary radiations in the Chondrichthyan lineage. They were also an incredibly successful group, surviving up to at least the Early Cretaceous in deep waters of what is now Southern France and Austria.

 

Image of Reconstructions by J.P. Hodnett of some Ctenacanthid Sharks (the three yellow sharks) from Permian formations at Yellowstone and Grand Teton National Parks, U.S.

Image Source: https://www.nps.gov/articles/000/fossil-inventories-uncover-permian-sharks-in-western-national-parks.htm

 

 

Unfortunately, this group is currently still relatively rarely studied by large sections of academia specializing in prehistoric sharks. This is the case even for species with preserved body fossils such as the magnificent, awe inspiring, and a personal favorite of mine, Saivodus striatus (Duffin and Glinter, 2006)!

 

Duffin, C. J., & Ginter, M. (2006). Comments on the Selachian genus Cladodus Agassiz, 1843. Journal of Vertebrate Paleontology, 26(2), 253–266. https://doi.org/10.1671/0272-4634(2006)26[253:cotsgc]2.0.co;2

 

 

However, one incredible genus that deserves more study and academic along with public spotlight is Amelacanthus (Maisey, 1982)!!

 

Maisey, J. G. (1982). Studies on the Paleozoic selachian genus Ctenacanthus Agassiz. No. 2, Bythiacanthus St. John and Worthen, Amelacanthus, new genus, Eunemacanthus St. John and Worthen, Sphenacanthus Agassiz, and Wodnika Münster. American Museum novitates; no. 2722.
https://digitallibrary.amnh.org/handle/2246/3536

 

[Joseph Fossil]

Described in 1982, the little-known genera Amelacanthus is known from four named species and three other unnamed species. 

 

What makes this genus so unique is it survived not one but two of the big seven mass extinction events!!

[Joseph Fossil]

Image Source: https://journals.pan.pl/Content/115543/PDF/3_Lebedev.pdf

 

 

The earliest geologic records of Amelacanthus date to the Famennian stage of the Late Devonian 360.7 Million Years ago.

 

 

Lebedev, O.A., Ivanov, A.O. and Linkevich, V.V. 2020. Chondrichthyan spines from the Famennian (Upper Devonian) of Russia. Acta Geologica Polonica, 70(3), 339–362. Warszawa. 
https://journals.pan.pl/Content/115543/PDF/3_Lebedev.pdf

 

http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&taxon_no=34480&max_interval=Mississippian&country=United Kingdom&is_real_user=1&basic=yes&type=view&match_subgenera=1

 

The youngest geologic records of Amelacanthus date to the Spathian stage of the Early Triassic 251.3-247.2 Million Years ago, meaning the genus survived both the two Devonian mass extinction events and Permian-Triassic extinction event 252 Million Years ago.

 

 

M. B. Koot, G. Cuny, M. J. Orchard, S. Richoz, M. B. Hart and R. J. Twitchett. (2015). New hybodontiform and neoselachian sharks from the Lower Triassic of Oman. Journal of Systematic Palaeontology 13:891-917 
https://www.researchgate.net/publication/270395486_New_hybodontiform_and_neoselachian_sharks_from_the_Lower_Triassic_of_Oman

 

This is also unequivocal proof, along with the genus Pkynotylacanthus, that the Ctenacanthiforms did indeed survive into the Mesozoic (with the presence of the group in Cretaceous southern France and Austria debated at times). 

 

http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&taxon_no=34480&max_interval=Triassic&country=Oman&is_real_user=1&basic=yes&type=view&match_subgenera=1

[Joseph Fossil]

This though begs the question of why, despite this genera’s importance in understanding the adaptability of the Ctenacanthiforms, still relatively poorly known and studied? This is a genera with massive implications in terms of the study of Ctenacanthiform evolution that could help answer the question of how this group of sharks survived the permian-triassic extinction event and made it all the way to the Early Cretaceous!!!

 

Why hasn't Amelacanthus, the earliest record of Mesozoic Ctenacanthiformes, been scrutinized and studied more?

[siteseer]

On 6/21/2023 at 1:01 PM, Joseph Fossil said:

This though begs the question of why, despite this genera’s importance in understanding the adaptability of the Ctenacanthiforms, still relatively poorly known and studied? This is a genera with massive implications in terms of the study of Ctenacanthiform evolution that could help answer the question of how this group of sharks survived the permian-triassic extinction event and made it all the way to the Early Cretaceous!!!

 

Why hasn't Amelacanthus, the earliest record of Mesozoic Ctenacanthiformes, been scrutinized and studied more?

 

There are fewer positions for paleontologists than there used to be.  Back in the 80's, a number of paleontologists worked for the USGS.  Starting in the 90's, the USGS stopped hiring another one when one retired.  I don't think any work there now.  This has happened at the university level too.  There are probably researchers out there who are interested in ctenacanths but they work on other groups as well.  It's a matter of getting around to it.  Sometimes, it's a matter of getting access to specimens.

 

[Joseph Fossil]

20 hours ago, siteseer said:

 

There are fewer positions for paleontologists than there used to be.  Back in the 80's, a number of paleontologists worked for the USGS.  Starting in the 90's, the USGS stopped hiring another one when one retired.  I don't think any work there now.  This has happened at the university level too.  There are probably researchers out there who are interested in ctenacanths but they work on other groups as well.  It's a matter of getting around to it.  Sometimes, it's a matter of getting access to specimens.

 

 

@siteseer Thanks for the input dude! I appreciate it and hopefully more people will be hired and join the field of Paleontology soon!!