Large mosasaurs like "Tylosaurus", which reached in excess of in length, may have competed with "Cretoxyrhina", and evidence of interspecific interactions such as bite marks from either have been found. There were also many sharks that occupied a similar ecological role with "Cretoxyrhina" such as the cardabiodontids "Cardabiodon" and "Dwardius", the latter showing evidence of direct competition with "C. vraconensis" based on intricate distribution patterns between the two. A 2010 study by paleontologists Corinne Myers and Bruce Lieberman on competition in the Western Interior Seaway used quantitative analytical techniques based on Geographical Information Systems (GIS) and tectonic reconstructions to reconstruct the theoretical competitive relationships between ten of the most prevalent and abundant marine vertebrates of the region, including "Cretoxyrhina". Their calculations determined that "Cretoxyrhina" was likely to have faced the most competition with "Squalicorax falcatus", "Squalicorax kaupi", and "Tylosaurus spp.", but was unlikely to face competition from other predators such as "Platecarpus spp." or "Xiphactinus spp.". The study also concluded that none of the competitive relationships were severe enough to apply candidate competitive replacement (CCR), which is when a species' distribution is affected due to being outcompeted by another. The causes of the extinction of "Cretoxyrhina" are uncertain. What is known is that it declined slowly over millions of years. Since its peak in size during the Coniacian, the size and distribution of "Cretoxyrhina" fossils gradually declined until its eventual demise during the Campanian. Siverson and Lindgren (2005) noted that the age of the youngest fossils of "Cretoxyrhina" differed between continents. In Australia, the youngest "Cretoxyrhina" fossils were dated approximately 83 Ma during the Santonian, while the youngest North American fossils known at the time (which were dated in the Early Campanian) were at least two million years older than the youngest fossils in Europe. The differences between ages suggests that "Cretoxyrhina" may have become locally extinct in such areas over time until the genus as a whole went extinct. It has been noted that the decline of "Cretoxyrhina" coincides with the rise of newer predators such as "Tylosaurus", suggesting that increasing pressure from competition with the mosasaur and other predators of similar trophic levels may have played a major contribution to "Cretoxyrhina" 's decline and eventual extinction.