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To pass some time I've been recently researching early Paleocene life and I keep coming back to researching (in my view) the two strangest and controversial Late Cretaceous-Early Paleocene Formations I know of. These are the Hornerstown Formation dating 66.5-65.5 Million Years ago in what is now New Jersey, U.S. And the Takatika Grit Formation dating 66.5-60.0 Million Years ago in what is now the Chatham Islands, New Zealand. https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=0b3baee9ab1afc7973337f5047495b723fcfa4f2 https://www.researchgate.net/publication/315461615_The_age_of_the_Takatika_Grit_Chatham_Islands_New_Zealand https://www.sciencedirect.com/science/article/abs/pii/S0195667109000184?via%3Dihub I've read many reports about these formations and the pretty controversial stuff that's been found in both these areas (Paleocene ammonites and reports of archaic marine reptiles like Paleocene Mosasaurs). I'm really not 100% sure what to make of this as I've heard conflicting hypotheses on whether these more archaic marine reptile fossils were reworked from older formations while others say it's not too too likely? https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/maastrichtian-ammonites-from-the-hornerstown-formation-in-new-jersey/4F051D07668B7B893EEFECF0506E2F1B https://bioone.org/journals/acta-palaeontologica-polonica/volume-57/issue-4/app.2011.0068/Short-Term-Survival-of-Ammonites-in-New-Jersey-After-the/10.4202/app.2011.0068.full For most of these "controversial" specimens, I would say reworking is likely while some I'll admit I'm not sure? For the Mosasaurs, it's clear that the astroid impact 66 Million Years ago caused their total extinction, but I'm still not 100% convinced that none emerged from the event alive (at least barely) and swam the seas in the very first days of the Danian Paleocene but not too long after. Unlike the mostly terrestrial Non-Avian Dinosaurs, which could only hide in so many places and it's very unlike more than a tiny amount of individuals (not enough to support a population) made it into the Paleocene, the Oceans have slightly more areas to hide and more even for endothermic air breathing animals like Mosasaurs (though as an endotherm, food does become a major issue especially when the ocean food chain nearly collapsed completely). What I'm wondering is how valid are at least "some" of these supposed archaic marine reptile and ammonite fossils from the earliest Paleocene sections of the Hornerstown Formation and the Takatika Grit? Also, of all the Maastrichtian Mosasaurs known so far, which ones would have been the mostly likely to have (at least briefly) survived the Cretaceous-Paleocene Extinction Event of 66 Million Years ago (would it have been generalist feeders, ones that specialized in deep sea hunting, ones with cosmopolitan distributions, ones small by mosasaur standards but still around the same size of the few confirmed large reptiles that survived the event like the 8 meter (26 feet) in length Thoracosaurus, or ones with all these traits and advantages)?

I was curious what this might be. I am under the assumption it’s some marine mammal. However I’ve found nothing remotely similar as far as dolphins go, so your guess is as good as mine

I've been researching again large reptiles of the Paleocene (66.0-56.0 Million Years ago) and Eocene (56.0-33.9 Million Years ago) eras recently and I've come across something interesting - the sudden emergence of giant sea snakes in the Eocene. The Paleocene did see some large snakes, including the largest known snake in the fossil record the Boa relative Titanoboa (which grew up to 12.8-14.3 m. (42-47 feet) in length). But the sudden appearance of large sea snakes like Palaeophis colossaeus (which grew up to 12.3 m. (40 feet) in length) during the Eocene perplexes me as I've been struggling to find any large (or at least fairly large) sea snakes from the Paleocene. That is except one possible contender named Vialovophis from the late Paleocene as described in a Scientific Paper from 1997. https://www.researchgate.net/profile/Alexander-Averianov/publication/235806050_Paleogene_Sea_Snakes_from_the_Eastern_Part_of_Tethys/links/5437db850cf2027cbb205006/Paleogene-Sea-Snakes-from-the-Eastern-Part-of-Tethys.pdf I'm just a bit curious why this? Did these sea snakes evolve such gigantic sizes only during the Eocene and why?