Description

Parapuzosia is a genus of extinct desmoceratid ammonites found in Africa, Europe, and North America from the Cenomanian to the Campanian epochs. These ammonites are notably large, estimates of the complete shells vary from 2.5-3.5 metres. The largest known specimen of this ammonite exhibits a maximum diameter of approximately one hundred and eighty centimeters; however, this measurement applies to the incomplete shell. When reconstructed in its complete and living state, this shell is estimated to have measured anywhere between two hundred and fifty-five centimeters and three hundred and fifty centimeters in diameter. While the precise dimensions of Parapuzosia seppenradensis remain a topic of discussion, it remains acknowledged as the largest ammonite known to date. Their shells have a moderately involute shape and exhibit flat or slightly rounded sides. The inner whorls of the shell display distinct primary and secondary ribbing.

Movement, lifestyle and feeding habits

Ammonites like Parapuzosia are believed to have functioned as pelagic predators within the open waters of the ocean. Their potential prey could have encompassed various marine organisms, including fish, other cephalopods like squid, and even fellow ammonites. There's also a possibility that they could have targeted smaller marine reptiles if they were able to capture them. In terms of locomotion, Parapuzosia likely had a siphon protruding from its shell, capable of expelling water with force, similar to what we observe in other cephalopods such as squids, octopuses, cuttlefish, and nautilus.

It's likely that Parapuzosia possessed a broader range of vertical movement within the water column rather than extensive horizontal travel. This behavior aligns with observations in squid and nautilus.

When Parapuzosia captured a prey item, like a fish, with its tentacles, it likely maneuvered and positioned the prey near its mouth. Its mouth would have featured a robust, durable beak capable of both slicing flesh and crushing shells and bones. Nevertheless, Parapuzosia might have been subjected to predation as well. While in their juvenile stages, they could have fallen victim to predators such as sharks with sturdy teeth like Cretoxyrhina, as well as mosasaurs like Globidens and Prognathodon, which had specialized teeth for breaking through the shells of armored prey. Even larger Parapuzosia individuals might not have been immune to the largest mosasaurs like Tylosaurus and Mosasaurus, which, due to their immense size, might have possessed the jaw strength to crack open a Parapuzosia shell.