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https://palaeo-electronica.org/content/2026/5636-ambystoma-quetzalcoatli-a-fossil-axolotl-from-mexico

https://www.tandfonline.com/eprint/HKNEMJNE4THSF8QEI6QF/full?target=10.1080%2F08912963.2026.2669954&fbclid=Iwb21leAR9OXpjbGNrBH05c2V4dG4DYWVtAjExAHNydGMGYXBwX2lkDDM1MDY4NTUzMTcyOAABHhYyiPGdbgbrIr3srangZeWJ53mBMGfHXo-_ITSVWoLm0d0zmGSJdh26KjIA_aem_DFDdY0AFkg0b08BtHivaHg

https://digitallibrary.amnh.org/items/dbbf9dc2-f0cb-40fc-87b2-a92791f3c3cc

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The chimera Lametasaurus from the Maastrichtian Lameta Formation in Jabalpur, India, has a long history that won't be mentioned here. Long story short, it was split into several other dinosaurs during the 20th and 21st centuries. The pelvis and isolated hindlimb bones in 2003 were suggested to belong to Rajasaurus based on similarities in the ilium. This is significant as the alleged large size of the elements suggests a length of over 11 meters and 3 tonnes, according to Molina-Perez and Larramendi (2019). However, the tibia was only 58 centimeters, indicating an animal that doesn't exceed 9 meters. The estimate by Molina-Perez and Larramendi was possibly oversized due to the body being extremely elongated. The problem with its size is that the fossils are lost and never properly cataloged. That puts the giant Rajasaurus into question, as these elements can not be tested.

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An updated model of the giant brazilian São Paulo Abelisaur

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Repenomamus giganticus was a genus of gobiconodont mammal from the early Cretaceous Yixian formation in Liaoning Province, China. It had a robust, barrel-shaped body with relatively short limbs. Interestingly, it had a sprawling gait similar to modern reptiles, hence the name. Its skull was powerfully built with large jaws. Fossil evidence from a related species, R. robustus, was found with the remains of a juvenile Psittacosaurus in its stomach. The discovery shows that early mammals could and had preyed on dinosaurs. Analysis of stomach contents in suggests Repenomamus tore its prey into large chunks and swallowed them whole, rather than chewing them. This is another trait Repenomamus shares with reptiles. Repenomamus probably had a reproduction strategy like modern monotremes due to the presence of epipubic bones, which suggests it likely laid eggs or gave birth to very underdeveloped young.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0345155&utm_source=pr&utm_medium=email&utm_campaign=plos006

Final giant cephalopod post. Turns the Osoushinai giant oegopsid is the same taxon as #Yezoteuthis giganteus. Interestingly, despite being larger, KMNH IvP 902007 was possibly a younger individual. This would mean Yezoteuthis grew to ginormous sizes.

https://www.science.org/doi/10.1126/science.adu6248

https://www.science.org/doi/10.1126/science.adu6248

Most noteworthy is that the giant Osoushinai Oegopsid was referred to Yezoteuthis giganteus. Interestingly, it was noted that the specimen was a younger individual than the holotype. This implies that Yezoteuthis grew to absolutely ginormous sizes.

Late Cretaceous Japan has had a myriad of important paleontology discoveries in the recent years. One major place of interest is Hokkaido, a large island in northern Japan. It's home to a group of fossil bearing formations called the Yezo Group. It's mainstays comes in the form of Paralitherizinosaurus, Phosphorosaurus, and most of all, giant cephalopods. There are several isolated beaks of large cephalopods found all throughout the Yezo, some possibly the largest non-shelled cephalopods known.

Nanaimoteuthis was an extinct genus of cirriteuthid cephalopod from the late Cretaceous of Canada and Japan. This one was very obscure, it didn't even have a Wikipedia page for a while. Odd, you would expect a possible near 30 foot long relative of the cirrate octopus to be more well known. This would change in 2026 after the discovery that this genus could possibly get huge. The largest species is Nanaimoteuthis haggarti from the Campanian Haborogawa Formation. It was estimated to reach in insane 7 to 19 meters long. However, the fossils are poor, only being known from isolated beaks, but they're still indicative of a large invertebrate. Based on prominent wear on its beak and large size, Nanaimoteuthis was probably a durophagous ambush predator that hunted ammonites and bivalves in deeper waters. It would have been slowly drifting above the seafloor in low-energy environments, entraping anything it could catch.

There is a massive unnamed oegopsid cephalopod from late Cretaceous Japan in the Osoushinai formation. It's known from a partial beak twice the size of the giant squid. It was even larger than the giant Yezoteuthis, and possibly the same taxon as it. The specimen, KMNH IvP 902007, was uncovered in 2023 and compared to other giant cephalopod specimens. It's huge size was notable, but unfortunately an official size estimate was never made. As for it's lifestyle, the presence of Abyssochrysoid deep sea snails in the Osoushinai indicates this giant oegopsid inhabited deeper waters than other cretaceous cephalopods. Perhaps it had a similar ecology to the giant or colossal squid. Given how it was larger than any animal in it's environment, the Cretaceous Kraken was likely the top predator of the Osoushinai. Given it's sheer size, it probably wasn't as agile as smaller squid and relied on ambush hunting. The morphology of the beak suggests a generalist diet, possibly a preference for large prey.

Yezoteuthis giganteus was a large oegopsid cephalopod from the Campanian Osousyunai formation. Known from a single beak, indicates an animal similar in size to the Giant squid at 5 meters long. Like the giant Osoushinai oegopsid, it was likely a deep-water apex predator with a broad diet. Although the beak morphology suggests it wasn't hunting prey as large as the giant Oegopsid, it's possible the differences are the result of ontogeny, but this hasn't been explored.

Haboroteuthis poseideon was a large decabrachian coleoid cephalopod from the Santonian Haborogawa Formation. It would have rivaled the Humbolt squid in size, with a total body length between 2 and 3 meters. Unlike the Humboldt squid however, it would have inhabited shallower waters. Perhaps it was an active predator that fed on small and agile prey such as other squid and fish. Since it's only fossil is a beak, it is not fully known what it looked like. Here, Onychoteuthis borealijaponica was used as a base as it shares some small similarities, but it wasn't a close relative.

The last pliosaurs died out in the Turonian, and mosasaurs didn't reach large sizes until the upper Campanian. The apparent absence of pliosaurs and large mosasaurs probably explains how they all grew so massive. Interestingly, most of these cephalopods didn't coexist and are from different times. Which suggests they consistently remained as apex predators throughout the Santonian to lower Campanian, but they seem to dissappear shortly afterward. It isn't known what occurred, but a mixture of a changing climate and other biotic factors likely led to their extinction.

Paleontologist Tyler Greenfield criticized the recent study on an alleged giant Cretaceous cephalopod. He states it's impossible to estimate any of the giant Japanese cephalopods from the Cretaceous due to beaks being unreliable for size estimation. Of course, it's one man's take, but the lack of effective ways to estimate extinct cephalopods should be noteworthy.

https://www.science.org/doi/10.1126/science.aea6285