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The Chondricthyans (including the sharks and rays) have been around and keeping the ocean's ecosystems healthy for about 420 Million Years. Today, in celebration of this, I've decided to do a little fun post and list the eight times in Earth's history truly massive chondricthyans have emerged. Hope you all enjoy!!! The First is the Devonian, where there is at least one confirmed fossil (CMNH 5238) of a large currently unnamed Ctenacanthiform shark that reached lengths of 4.2-5 meters (13-16 feet) in length. https://www.mdpi.com/1424-2818/15/3/318 The Second is the Mississippian stage of the Carboniferous (358.9-323.2 Million Years ago), a golden age for chondricthyans. The Early Carboniferous saw the emergence of Giant Ctenacanthiform sharks like Saivodus striatus, which grew up to 10-11 meters (32-36 feet) in length. https://www.uky.edu/KGS/fossils/fossil-of-the-month_2022-07_Saivodus.php https://www.uky.edu/KGS/fossils/fossil-of-the-month_2022-07_how-big.php https://www.nps.gov/articles/000/fossils-of-the-2023-national-fossil-day-artwork.htm The Third is the Pennsylvanian stage of the Carboniferous (323.2-298.9 Million Years ago). Like the Mississippian, the Pennsylvanian was also a golden stage for Chondricthyans where large Ctenacanthiforms continued to thrive and large Eugeneodontida edestoids like Edestus (which could grow up to 6.7 meters (22 feet) in length) emerged. Large Ctenacanthiforms from this time include the unnamed Graham Formation Gilkmanius sp., which grew up to 7 meters (22 feet) in length. https://bioone.org/journals/journal-of-vertebrate-paleontology/volume-37/issue-3/02724634.2017.1325369/A-Pennsylvanian-Supershark-from-Texas/10.1080/02724634.2017.1325369.short The Fourth is the Permian (298-252 Million years ago). There were some large sharks, like the Ctenacanthiform Kaibabvenator (which grew up to 4.8-5.48 meters (16-18 feet) in length). But Eugeneodontida by this point contained the largest Chondricthyans alive at this time including Helicoprion (which grew up to 7.6 meters (25 feet) in length) and Parahelicoprion (which could grow up to 12 meters (36 feet) in length). https://www.academia.edu/29941296/Chondrichthyan_and_actinopterygian_remains_from_theLower_Permian_Copacabana_Formation_of_Bolivia https://doi.org/10.1002%2Far.24046 The Fifth is the Early Cretaceous (145-100 Million Years ago). Though the time's aquatic ecosystems was dominated by large marine reptiles, large sharks managed to emerge and fill ecological niches from time to time. This includes the Early Cretaceous Shark Leptostyrax, which grew up to 6.3 meters (20 feet) in length. https://www.researchgate.net/publication/277782424_A_Gigantic_Shark_from_the_Lower_Cretaceous_Duck_Creek_Formation_of_Texas The Sixth is the Late Cretaceous (100-66 Million years ago). Aquatic ecosystems still were dominated by marine reptiles, but large sharks were indeed present. This includes Cretodus crassidens (which grew up to 9-11 meters (29-36 meters) in length) and Ptychodus (which grew up to 10 meters (32 feet) in length). https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0231544 https://www.cambridge.org/core/journals/journal-of-paleontology/article/morphology-and-paleobiology-of-the-late-cretaceous-largesized-shark-cretodus-crassidens-dixon-1850-neoselachii-lamniformes/A670012A44DDC68FC098BB8C73368408 The seventh is the Miocene-Early Pilocene (23-3.6 Million Years ago). This period saw the rise and reign of some of the largest sharks known currently in the fossil record, including Carcharocles (Otodus) megalodon (which grew up to 17 meters (55 feet) in length). https://www.uv.es/everlab/PUBLICACIONES/2017/2017 Martinez-Perez et al HB miocene sharks.pdf https://www.science.org/doi/10.1126/sciadv.abl6529 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9385135/ The eighth is the Early Pliocene-Late Pleistocene (3.6-0.012 Million Years ago). This period saw the last remnants of the large 20 foot + in size carnivorous sharks from the Miocene-Pilocene mega shark era not including the non-Great White shark (Carcharodon carcharias) and not including the large plankton eating sharks make their final stand. These include Hemipristis serra (which grew up to 6 meters (20 feet) in length) and Parotodus benedeni (which grew up to 7.6 meters (24 feet) in length). https://www.app.pan.pl/archive/published/app63/app004542018.pdf https://www.researchgate.net/publication/364591134_A_previously_overlooked_highly_diverse_early_Pleistocene_elasmobranch_assemblage_from_southern_Taiwan https://www.cambridge.org/core/journals/paleobiology/article/chondrichthyan-fossil-record-of-the-florida-platform-eocenepleistocene/2835CCEC27DC8EE0B24A5B62B1416618 I hope this is helpful?

At long last, I've found it! The near holy grail of Ctenacanthiform fossils!! I have been a bit perplexed at the small Ctenacanthiform tooth myself and @Tales From the Shale found on February 18th at a Bond Formation rock formation. dating to around 300 Million Years ago in Oglesby, Illinois. The tooth specimen is only 8mm in length and I almost overlooked it until I put it under a microscope and dissecting scope. I initially thought it was Gilkmanius. But the medial cusp of the tooth is too narrow and curved to be Gilkmanius. I also thought it could be Heslerodus, but the tooth didn't exactly match the shape of Heslerodus teeth. Last week I checked with my old college Geology Professor (an experienced fossil hunter of the Mazon Creek area) and emailed scientists from the American Museum of Natural History, New York and the University of Chicago, Illinois about what genus the specimen belongs. The following ID the scientists said was a reasonable assertion and my Geology Professor was in no doubt of it...It is an actual SAIVODUS STRIATUS TOOTH!!! The dead give away for the ID was apparently the Sigmoidal profile on the side of the tooth! This is the first truly confirmed record of Saivodus striatus from the Bond Formation that I'm aware of!!

As I have been researching large ctenacanthiform sharks from North America, I've been wondering if there are any known globally that are currently unnamed. I definitely know of the large Ctenacanthiformes Saivodus stratus (found in both what is now North America and Great Britain), the large Ctenacanthiform from the Permian Kaibab formation in Arizona, and the 'Texas supershark' (a likely large species of Gilkmanius) from the Pennsylvanian Texas Graham formation (all three as larger or larger than an adult Great White Shark (Carcharodon carcharias)). But are there any large ctenacanthiformes (at least in size comparable to a modern day adult Great white shark (Carcharodon carcharias)) currently unnamed that are also known? Ctenacanthiformes are known from North America, Greenland, Europe, Asia, and South America. https://www.mindat.org/taxon-P34476.html Even though study of Ctenacanthiformes as a whole is just starting to become more through within the past few decades, I'm wondering if anyone on the forum is aware of any currently unnamed Ctenacanthiform fossils from areas outside of North America of Great White Shark (Carcharodon carcharias)) size?

As I was recently doing some research on the prehistoric shark genus Cladodus, I came across some info that classifies the genus as a member of the family Cladoselachidae, Order Cladoselachiformes. https://en.wikipedia.org/wiki/Cladoselachidae This is somewhat confusing to me as mindat and the Paleontological Database aka fossilworks list Cladodus as a member of the family Ctenacanthidae, Order Ctenacanthiformes. https://www.mindat.org/taxon-8657177.html http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=104838 I'm personally leaning more towards Cladodus being a member of at least the Ctenacanthiformes. But I'm curious what are the origins of this taxonomic confusion on the genus Cladodus's phylogenetic placement in the Chondricthyan family? Is Cladodus a member of the Cladoselachiformes or Ctenacanthiformes? What do you guys think?

The Ctenacanthiformes are an impressive group of prehistoric sharks, emerging in the Devonian period before surviving the two Devonian extinction events that gave rise to the Carboniferous. During the Carboniferous, the Ctenacanthiformes diversified rapidly, even becoming some of the Carboniferous Oceans Apex Predators. But of all the members of this impressive (yet almost unknown to the general public) group, two species stand out as especially impressive and awe inspiring - Saivodus striatus and the Graham formation Gilkmanius (this species currently doesn't have a name yet). 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 Ivanov, A. O. (2005, September 1). The revision of "Cladodus" occidentalis, a late Palaeozoic ctenacanthiform shark. Acta Palaeontologica Polonica. Retrieved December 29, 2022, from https://www.academia.edu/49013029/The_revision_of_Cladodus_occidentalis_a_late_Palaeozoic_ctenacanthiform_shark Artist reconstruction of the skeleton and size of the Graham formation (Upper Pennsylvanian, Carboniferous) Gilkmanius sp. By J. Maisey. Image Source: https://www.amnh.org/explore/news-blogs/research-posts/ancient-supershark-fossils-found-in-texas Maisey, J. G., Bronson, A. W., Williams, R. R., & McKinzie, M. (2017). A Pennsylvanian ‘supershark’ from Texas. Journal of Vertebrate Paleontology, 37(3). https://doi.org/10.1080/02724634.2017.1325369 Artist reconstruction of an Adult Saivodus striatus and its size compared to an adult Human and adult Great White Shark (Carcharodon carcharias) by artist HodariNundu. Image Source: https://www.deviantart.com/hodarinundu/art/Super-Sized-Saivodus-866628428 Hodnett, J.-P. M., Tweet, J. S., & Santucci, V. L. (2022, August 8). The Occurrence of Fossil Cartilaginous Fishes (Chondrichthyes) within the Parks and Monuments of the National Park Service. researchgate.net. Retrieved December 30, 2022, from https://www.researchgate.net/publication/362806168_THE_OCCURRENCE_OF_FOSSIL_CARTILAGINOUS_FISHES_CHONDRICHTHYES_WITHIN_THE_PARKS_AND_MONUMENTS_OF_THE_NATIONAL_PARK_SERVICE Both were giant members of the Ctenacanthiformes and were on par in size with the largest Great White Sharks (Carcharodon carcharias) (which can reach lengths of 20 feet). But the question I have is which species was bigger (in weight and in length)? Which one was the biggest of the Ctenacanthiformes? @Elasmohunter @BobWill @connorp @deutscheben @jdp What do you think?