Named By: Nowak - 1913.
Synonyms: Pachydiscus seppenradensis.
Classification: Mollusca, Cephalopoda, Ammonoidea, Desmoceratidae.
Species: P. seppenradensis (type), P. boesei, P. bradyi.
Size: Shell of P. bradyi up to around 1.8 meters across at the widest diameter. Largest fossil shell of P. seppenradensis is 1.8 meters at widest diameter, but this specimen is incomplete. Estimates of the complete shell range from 2.55 to 3.5 meters across. This are the largest known examples, most others smaller.
Known locations: Across Europe and the USA.
Time period: Cenomanian to Campanian of the Cretaceous.
Fossil representation: Many individuals.
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
and eighty centimetres, making it the largest species of Ammonite
known from North America.
Even bigger though was Parapuzosia seppenradensis from Europe. 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.
-Die Riesenammoniten von Seppenrade, Pachydiscus Zittel Seppenradensis - Jahresbericht des Westfälischen Provinzial-Vereins für Wissenschaft und Kunst 23: 99–108. - H. Landois - 1895.
- Parapuzosia (Parapuzosia) seppenradensis (Landois) und die Ammonitenfauna der Dülmener Schichten, unteres Unter-Campan, Westfalen. - Geologie und Paläontologie in Westfalen 33: 1–127 - W. J. Kennedy & U. Kaplan - 1995
- Ammonites and the Other Cephalopods of the Pierre Seaway. - Geoscience Press, Inc. p. 44 - Neal L. Larson, Steven D. Jorgensen, Robert A. Farrar & Peter L. Larson - 1997.
- Two-phase increase in the maximum size of life over 3.5 billion years reflects biological innovation and environmental opportunity. PNAS 106(1): 24–27 - Jonathan L. Payne, Alison G. Boyer, James H. Brown, Seth Finnegan, Michał Kowalewski, Richard A. Krause, Jr., S. Kathleen Lyons, Craig R. McClain, Daniel W. McShea, Philip M. Novack-Gottshall, Felisa A. Smith, Jennifer A. Stempien, and Steve C. Wang - 2009.