Cephalopods (Cephalopoda)

Ammonites (Ammonoidea)

Ammonoids are an extinct group of marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs are more closely related to living coleoids (i.e., octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species.The earliest ammonites appear during the Devonian, and the last species died out during the Cretaceous–Paleogene extinction event.

Parapuzosia seppenradensis is the largest known species of ammonite.

Parapuzosia was once named as a species of the Pachydiscus genus in 1895 by Hermann Landois, but was renamed as a distinct genus in 1913 establishing Parapuzosia seppenradensis as the type species. Today the species of the Parapuzosia genus are regarded as the largest ammonites that are currently known to us. The largest Parapuzosia bradyi had a shell that measured one hundred and forty by one hundred and eighty centimetres, making it the largest species of Ammonite known from North America.
Even bigger though was Parapuzosia seppenradensis from Europe.It lived during the Lower Campanian Epoch of the Late Cretaceous period, in marine environments in what is now Westphalia, Germany. A specimen found in Germany in 1895 measures 1.8 m (5.9 ft) in diameter, although the living chamber is incomplete. It is estimated that if complete, this specimen would have had a diameter of approximately 2.55 m (8.4 ft) or even 3.5 m (11 ft).The total live mass has been estimated at 1,455 kg (3,208 lb), of which the shell would constitute 705 kg (1,554 lb) The largest known shell of this has a maximum diameter of around one hundred and eighty centimetres, but this is the measurement for the incomplete shell. In life and when complete this shell is thought to have been anything between two hundred and fifty-five centimetres and three hundred and fifty centimetres across. Though the exact size of Parapuzosia seppenradensis is a matter of debate, it is still regarded as the largest ammonite currently known to us.
Ammonites like Parapuzosia are perceived to have been pelagic (open water) predators of other oceanic organisms. These may have included fish, other cephalopods including squid and even other ammonites, as well as possibly even smaller marine reptiles if they could catch them. As far as locomotion goes, Parapuzosia would have had a siphon pointing out of the shell that could shoot out water like a jet, just like we can see in other cephalopods such as squids, octopuses, cuttlefish and nautilus. It’s probable that Parapuzosia may have had a greater range of vertical movement in the water column as opposed to distance travel given that such behaviour has been observed in squid and nautilus.
When a Parapuzosia had a prey item such as a fish within its tentacles, the prey would have been manipulated and positioned to be near the mouth. This would have been a strong, very tough beak that could slice flesh as well as crush shells and bones. Parapuzosia may have been prey to other predators themselves however. When still growing up they may have been preyed upon by sharks with exceptionally tough teeth like Cretoxyrhina, as well as mosasaurs such as Globidens and Prognathodon which had specially adapted teeth for cracking and breaking up the shells of armoured prey. Even larger Parapuzosia may not have been safe from the largest mosasaurs such as Tylosaurus and Mosasaurus that through sheer size might have still had the jaw power to break open a Parapuzosia shell.

Belemnites (Belemnoidea)

Belemnoids are an extinct group of marine cephalopod, very similar in many ways to the modern squid and closely related to the modern cuttlefish. Like them, the belemnoids possessed an ink sac, but, unlike the squid, they possessed ten arms of roughly equal length, and no tentacles. Belemnoids include belemnites (which belong to order Belemnitida proper), aulacocerids (order Aulacocerida), phragmoteuthids (order Phragmoteuthida), and diplobelids (order Diplobelida).
Belemnoids were numerous during the Jurassic and Cretaceous periods, and their fossils are abundant in Mesozoic marine rocks, often accompanying their cousins the ammonites. The belemnoids become extinct at the end of the Cretaceous period along with the ammonites. The belemnoids" origin lies within the bactritoid nautiloids, which date from the Devonian period; well-formed belemnoid guards can be found in rocks dating from the Mississippian (or Early Carboniferous) onward through the Cretaceous.

Megateuthis gigantea is the largest known belemnite species.

The guard of M. gigantea, which has been found in Europe and Asia, can measure up to 46 centimetres in length (18 inches), giving the living animal an estimated length of 3 metres (10 feet).

Nautiloids

Nautiloids are a large and diverse group of marine cephalopods (Mollusca) belonging to the subclass Nautiloidea that began in the Late Cambrian and are represented today by the living Nautilus and Allonautilus. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, and developed an extraordinary diversity of shell shapes and forms. Some 2,500 species of fossil nautiloids are known, but only a handful of species survive to the present day. Specimens of the Ordovician nautiloid Endoceras have been recorded measuring up to 3.5 meters (11 feet) in length, and Cameroceras is (somewhat doubtfully) estimated to have reached 11 meters (36 feet). These large nautiloids must have been formidable predators of other marine animals at the time they lived.

The longest and largest-known of this group was Cameroceras with a shell length of 9 m (30 ft)

Cameroceras is widely regarded as one of if not the largest orthocone cephalopods to ever exist. Unfortunately only estimates for the upper size of the animal exist. More modern interpretations at the end of the twentieth century estimated the length of the shell at around six meters long, though estimates from earlier in the twentieth century suggested that it was as much as nine and even eleven meters long. Even at six meters long however, Cameroceras is still one of the largest cephalopods that we know about, especially for one that lived in the Ordovocian period.
 Cameroceras was a cephalopod, a type of mollusc that includes the octopuses, squids and cuttlefish that we know today, and because of this we can infer a few things about the living animal. The head of the animal would have been soft muscular tissue situated at the opening of the hard cone-like shell, with the mantle (main body) lying within the shell for protection. Tentacles would have grown from the base of the head like in a modern cuttlefish, and these tentacles would have been used to seize and manipulated prey as the Cameroceras prepared to feed. At the base of these tentacles within the buccal mass (analogous to the mouth) a hard keratinous beak would have bitten into the bodies of its prey, and would have been so strong that it could crunch straight through the hard shells of other orthocones or even the hard supposedly armoured exoskeletons of eurypterids. Within the beaks of modern cephalopods a ‘toothed’ tongue is used to rasp out soft tissue from within the preys shell, though it is not known for certain if Cameroceras had this feature. In addition to eurypterids and other Ordovician cephalopods, Cameroceras may have also hunted early jawless fish.
Occasionally when Cameroceras has been shown in popular culture it has been depicted as having poor eyesight. This is mostly speculation as the eyes of Cameroceras have never been found, but it is a curious decision to suggest such a thing since most cephalopods are visually orientated predators, and some of them actually have quite exceptional eyesight. We do not know for certain how good the eyesight of Cameroceras was but other cephalopods are noted for having a great ability to pick out colours as well as gather and filter light to see in very dark water.

Neocoleoidea

Neocoleoidea is a large group of marine cephalopods. This cohort contains two extant groups: Decapodiformes (squid, cuttlefish, and relatives) and Octopodiformes (octopuses and the vampire squid). Species within this group exist in all major habitats in the ocean, in both the southern and northern polar regions, and from intertidal zones to great depths.Whilst conventionally held to be monophyletic, the only morphological character for the group is the presence of suckers: although the presence of these features in the belemnites suggests that they do not support the Neocoleoidea, and hence that the group may be paraphyletic.

Yezoteuthis giganteus

Two isolated cephalopod jaws recovered from the middle Turonian of the Obira area and the Campanian of the Nakagawa area, Hokkaido, Japan, consist of short outer, and large and posteriorly elongated inner “chitinous” lamellae, with a sharply pointed rostrum in the outer lamella. These features are common with the upper jaws of Recent cephalopods. Comparison with the upper jaws of ammonoids and Recent cephalopods indicates that the two Cretaceous upper jaws are attributed to the Coleoidea other than the Octopodida. This assignment is also suggested by the cladistic analysis of the Nakagawa specimen compared with five upper jaw characters on 22 Recent cephalopod species. The Obira specimen differs from the Nakagawa specimen in having a much smaller jaw and a larger jaw angle, but its order-level assignment could not be determined because of imperfect preservation. The Nakagawa specimen shares several common features with the upper jaws of Recent Oegopsina; thus we assigned its higher systematic position to this suborder. Based on the extremely large upper jaw (97 mm maximum length), a new genus and species (Yezoteuthis giganteus) is proposed. This new taxon would have been as large as the modern giant squid Architeuthis, which commonly exceeds more than 5 m in body length. Our study postulates that studies of jaws are important to reconstruct the phylogeny of the Coleoidea.