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I've recently read a 2020 scientific paper describing pretty accurately the multiple nurseries that Carcharocles (Otodus) megalodon had established to raise young between the Miocene-Pliocene 23-3.6 Million Years ago (not just a single nursery in what is now Panama as previously thought). Herraiz, J. L., Ribé, J., Botella, H., Martínez-Pérez, C., & Ferrón, H. G. (2020). Use of nursery areas by the extinct megatooth shark Otodus megalodon (Chondrichthyes: Lamniformes). Biology Letters, 16(11), 20200746. https://doi.org/10.1098/rsbl.2020.0746 https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0746 What I also found interesting about this paper was that the geologic latest nursery area the researchers identified is what is now the Yorktown Formation, North Carolina. Images Credit: https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0746 C. megalodon went extinct in the Mediterranean as a result of the Messinian Salinity crisis 5.59 Million Years ago. The emergence of Orcas (Orcinus) and the Great White Shark (Carcharodon carcharias), a decrease in diatom diversity during the middle miocene-pliocene, and the miocene formation of the Isthmus of Panama which changed ocean current patterns also helped caused a decline in C. megalodon's population by the Pliocene. But this 2020 paper has got me thinking about where did C. megalodon as a species make its last stand? Was the Yorktown Formation in North Carolina C. megalodon's last stronghold?

The era between the Miocene and Pliocene (23-2.3 Million Years ago) was, like the Carboniferous era 300 Million Years before, a golden age for the Chondricthyans. Not only was there a massive explosion in the diversity of grey sharks, but there was the emergence of perhaps the largest number of large macropredatory shark genera (sharks greater than 3 meters (10 feet) in length) currently known in Earth's geologic history. This includes the Giant Thrasher Shark Alopias grandis (which grew up to 13 meters (feet) in length) and the famous Carcharocles (Otodus) megalodon (which grew up to 17 meters (55 feet) in length). https://www.science.org/doi/10.1126/sciadv.abm9424 But this golden era of the giant macro predatory sharks wouldn't last, for between 3.8-2.4 Million Years ago there was an extinction event of large marine fauna that killed at least 14% of large marine fauna genera, including Carcharcoles (Otodus) megalodon. Though it's not entirely clear what caused this extinction event (some have hypothesized it could've been a mild gamma ray burst), C.megalodon's decline was due to the closing of the Isthmus of Panama by 4.5 Million Years ago (an area that was a C.megalodon nursery), a decline in diatoms that caused a decline in the food sources of many whales like Cetothere whales including Cetotherium (a known food source of C. megalodon), and Competition with the recently emerged Great White Shark (Carcharodon carcharias) and Orcas (Orcinus). By the extinction events end, most of the Miocene's large predatory sharks were extinct. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6377595/ https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0084857 https://www.researchgate.net/publication/318160879_The_Pliocene_marine_megafauna_extinction_and_its_impact_on_functional_diversity https://royalsocietypublishing.org/doi/10.1098/rsbl.2020.0746 But there was a few genera that survived the extinction event 3.6-2.4 Million Years ago and lived long after it. These surviving taxon (likely surviving due to relying on different food sources then other large sharks of the miocene-pliocene) lived previously alongside C. megalodon and some survived up to at least the early Pleistocene (120,000-100,000 years ago). Here's a list of the large (non Great White Shark (Carcharodon carcharias)) macropredatory sharks of the late Pliocene-Early Pleistocene (If I'm missing any examples, let me know and I'll quickly add them). Hemipristis serra (Hemigaleidae, grew up to 3-5 meters (10-16 feet) in length) (Miocene-Pleistocene (Pleistocene strongholds: What is now Indonesia, Taiwan, South Carolina (U.S.), Alabama (U.S.), and Florida (U.S.)), 23.03-0.012 Million Years ago) Reconstruction 1 and 2 Image by artist @Tetrtophoneus, Image credit: https://www.deviantart.com/teratophoneus/art/Hemipristis-serra-871902574 Image by artist @HodariNundu (the two sharks below and next to the juvenile C.megalodon at the middle top are adult Hemipristis serra), Image credit: https://www.deviantart.com/hodarinundu/art/Mobbing-Meg-885731702 http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=83182 https://www.fossilguy.com/gallery/vert/fish-shark/hemipristis/hemipristis.htm https://www.researchgate.net/publication/364591134_A_previously_overlooked_highly_diverse_early_Pleistocene_elasmobranch_assemblage_from_southern_Taiwan Parotodus benedeni (Otodontidae, grew up to 7.6 meters (24.9 feet) in length) (Oligocene-Pleistocene (Pleistocene strongholds: What is now South Carolina (U.S.)), 33.9-0.012 Million Years ago) Reconstructions 1 and 2 Image by artist @imAdro, Image credit: https://www.deviantart.com/imadro/art/Parotodus-benedeni-908901669 Image by artist @SameerPrehistorica, Image credit: https://www.deviantart.com/sameerprehistorica/art/Parotodus-Size-882947974 http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=389883 https://www.petit-fichier.fr/2013/01/27/kent-b-w-1999-taille-parotodus-benedenii/? https://www.researchgate.net/publication/337937278_2019-canevet-a-review-of_the-extinct-genus-Parotodus https://www.app.pan.pl/archive/published/app63/app004542018.pdf http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&taxon_no=389883&max_interval=Quaternary&country=United States&state=South Carolina&is_real_user=1&basic=yes&type=view&match_subgenera=1 https://www.cambridge.org/core/journals/paleobiology/article/chondrichthyan-fossil-record-of-the-florida-platform-eocenepleistocene/2835CCEC27DC8EE0B24A5B62B1416618 Cosmopolitodus hastalis (Lamnidae, grew up to 5-7 meters (16.4-22.9 feet) in length) (Oligocene-Pleistocene (Pleistocene strongholds: What is now Japan, South Carolina (U.S.), Alabama (U.S.), and Florida (U.S.)), 30-0.012 Million Years ago) Reconstruction Image by artist @artbyjrc, Image credit: https://www.deviantart.com/artbyjrc/art/Going-to-need-a-bigger-boat-Lamnid-sharks-837971394 http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=265174 https://actapalrom.geo-paleontologica.org/Online_first/Chan_Cosmopolidus_planus.pdf Note: Cosmopolitodus hastalis was an ancestor to the extant Great White Shark (Carcharodon carcharias), along with living alongside the Great White Shark (Carcharodon carcharias) between the Miocene-Pleistocene. However, Cosmopolitodus hastalis’s being a member of the genus Carcharodon has yet to be confirmed). I hope you all find this helpful?

Finally got a chance to take a break from school check out some land I got permission to collect on back in December. The site was pretty well documented in the Caprock member of the Ash Hollow formation, basically on the contact with the Valentine formation, and was known to produce Gomphothere. We made it out there and had found some bone within a few minutes of digging!

What opinion do you have, is a large bird jaw or is another structure? It was found in tufa calcareous with river bivalves of the late Pliocene of north of Mexico.