My Prehistoric Saga: Dino Bios: Mosasaurus.

Mosasaurus:

Time: 84-66 million years ago, Campanian-Maastricthian of the late Cretaceous period.
Place: North America and Europe.
Length: 27-51 feet (8.1-15.5 meters).
Diet: Carnivore.

This was one of the largest marine reptiles of all time!

Description:
Mosasaurus was a prehistoric marine reptile that lived 72-66 million years ago, during the Campanian-Maastricthian of the late Cretaceous period. It lived in North America and Europe. It was 27-51 feet (8.1-15.5 meters), and was one of the top predator of the seas and oceans during its time. The largest species, M. hoffmanni, was 51 feet (15.5 meters) long. It's only enemies were either its own species, or a genus of prehistoric shark called Squalicorax.

It had a cone-shaped head, serpentine-like body, four flippers, and a long tail. At the end of its tail, it had a shark-like (Lindgren et al., 2013) (Bob Yirka, 2013). It, along with other mosasaurs, are descendants of the small terrestrial lizard, Dallasaurus.

Mosasaur Tail Fluke (Bob Yirka, 2013):

Prey:
Mosasaurus hunted an assortment of prey, including sharks like Squalicorax and the predatory fish Xiphactinus, plesiosaurs like Hydrotherosaurus and others, and ammonites.

Links:
Length:
https://psdinosaurs.blogspot.com/2019/07/size-calculations-for-mosasaurs.html
Time:
Campanian:

Takehito Ikejiri (2014):
https://www.researchgate.net/publication/271528820_Osteology_and_taxonomy_of_Mosasaurus_conodon_Cope_1881_from_the_Late_Cretaceous_of_North_America

James E. Martin (2006):
"Abstract":
https://sp.lyellcollection.org/content/258/1/101
Full Text:

https://books.google.com/books?id=MCapkbWiy2QC&pg=PA107&lpg=PA107&dq=tylosaurus+maastrichtian&source=bl&ots=qbbXCk-4O5&sig=ACfU3U0_aSzSucccdwXBeqZuwmC_AGlzhA&hl=en&sa=X&ved=2ahUKEwj0iL7KvrXjAhUICM0KHUYZC0gQ6AEwGXoECAMQAQ#v=onepage&q=tylosaurus%20maastrichtian&f=false

Fossilworks:

http://fossilworks.org/bridge.pl?a=taxonInfo&taxon_no=122603

Maastrichtian:

Eric Mulder (1999):

https://www.researchgate.net/publication/262901771_Transatlantic_latest_Cretaceous_Mosasaurs_Reptilia_Lacertilia_from_the_Maastrichtian_type_area_and_New_Jersey
Harrell and Martin (2014):

https://www.cambridge.org/core/journals/netherlands-journal-of-geosciences/article/mosasaur-from-the-maastrichtian-fox-hills-formation-of-the-northern-western-interior-seaway-of-the-united-states-and-the-synonymy-of-mosasaurus-maximus-with-mosasaurus-hoffmanni-reptilia-mosasauridae/69E1A6D0EC1FF1C6A5ACF3385DF4986C
Gallagher et al., (2012):

https://geology.rutgers.edu/images/stories/faculty/miller_kenneth_g/kgmpdf/12-Gallagher.GeolFrance.pdf
James E. Martin (2006):
"Abstract":
https://sp.lyellcollection.org/content/258/1/101
Full Text:

Grigoriev (2014):

https://www.zin.ru/journals/trudyzin/doc/vol_318_2/TZ_318_2_Grigoriev.pdf