Name:
Prognathodon
(Forejaw tooth).
Phonetic: Pro-nayf-o-don.
Named By: Dollo - 1889.
Synonyms: Ancylocentrum hungerfordi,
Oronosaurus.
Classification: Chordata, Reptilia, Squamata,
Scleroglossa, Mosasauridae, Mosasaurinae.
Species: P. curri, P. giganteus,
P. kianda, P. overtoni, P. rapax, P. saturator, P.
solvayi, P. waiparaensis.
Diet: Carnivore.
Size: Depending upon the species, Prognathodon
could
range between 6 to possibly just under 14 meters in length.
Known locations: Fossil locations suggest a
worldwide
distribution, but especially well known from Europe and North America.
Time period: Campanian to Maastrichtian of the
Cretaceous.
Fossil representation: Many specimens. Usually
just skulls and skull material, more complete remains are known,
especially two specimens from Canada. Stomach contents have also
been found.
Prognathodon
was a late mosasaur
that showed a trend towards a different kind of
predation that saw it living like the much earlier basal placodont
reptiles of the Triassic such as Placodus.
This
means that
Prognathodon specialised in eating tough shelled
prey items like shellfish, ammonites and turtles. The diet of Prognathodon
was for a long time
just speculation based upon the teeth and jaw construction, but two
discoveries in Canada in the early years of the twenty-first century
not only revealed the full body shape of Prognathodon
but the diet as
well. One specimen revealed the presence of turtle and ammonite
fossils located where its stomach would have been. Interestingly it
also had a one-hundred
and sixty centimetre long fish in its gut, suggesting that while
Prognathodon was a specialised predator, it was
also opportunistic in
its feeding.
Prognathodon
had a robust and heavy jaw that would have been capable of withstanding
a high bite force supplied by powerful jaw muscles. However it’s the
teeth that should receive special note as not only are they strong and
well adapted for crushing, they have serrations which can be seen
under much more detailed inspection. This makes the teeth specialised
for a dual purpose, destroying the protective shells of prey while
shearing the flesh within. Another specialisation is the presence of
bony rings around the eye sockets. This is seen as a deep water
adaptation for the eyes to better withstand the higher water pressure
of deep water, something which may have often been necessary when
diving for ammonites.
Why
Prognathodon shifted towards this kind of diet when
mosasaurs are
generally perceived to be apex predators of other reptiles and fish
remains uncertain. It could have been that competition for the
ecological niche of apex predator was so fierce that the only way
Prognathodon could evolve and survive was by
adapting to a different
food source, removing the need for competition with other predators.
It could also be that numbers of large prey animals that mosasaurs are
traditionally associated with began to fall, necessitating a need to
switch to a different diet. It could have course been to simply
exploit an abundant food supply. What is certain is that Prognathodon
was not the only mosasaur to adjust to this diet with another named
Globidens
also having particularly large and rounded crushing teeth in
its mouth.
For
a time a particularly large specimen of Prognathodon
was split off from
P. curri into its own genus named Oronosaurus,
and a consequence of
this resulted in the upper size estimate being reduced to ten metres
long. However further study of the material has revealed that the
original interpretation was the correct one. Today Oronosaurus
is now
regarded as a synonym to Prognathodon. The largest
species of Prognathodon at the time of writing is P.
saturator
which
has an estimated body length of thirteen meters and seventy centimetres.
2013
saw the description of a Prognathodon specimen
first discovered in 2008
which led to the announcement that like with the genus Platecarpus,
Prognathodon too had a bi lobed tail. This basically
means that the
tail of Prognathodon did not just curve downwards
but had and
additional growth upwards, something quite more advanced than more
primitive formed mosasaurs. Although not as well developed as the bi
lobed tails of fish and advanced ichthyosaurs,
this tail would have
still provided extra push against the water meaning more efficient and
faster swimming. This probably allowed Prognathodon
to dive deeper
faster so that it could hunt for prey longer before returning to the
surface for air.
Further reading
- A new species of gigantic mosasaur from the Late Cretaceous of Israel
- Journal of Vertebrate Paleontology 22 (3): 629 - P. Christianson, N.
Bonde - 2002.
- A new species of Prognathodon (Squamata,
Mosasauridae) from the
Maastrichtian of Angola, and the affinities of the mosasaur genus
Liodon - Proceedings of the Second Mosasaur Meeting, edited by M. J.
Everhart, Fort Hays Studies, Special Issue number 3, p. 1-12. - A. S.
Schulp, M. J. Polcyn, O. Mateus, L. L. Jacobs & M. L. Morias -
2008.
- A new species of Prognathodon (Squamata:
Mosasauridae) from the
Maastrichtian of Harrana. Fossils of the Harrana fauna and the adjacent
areas. - H. Kaddumi - 2009.
- Another new species of Prognathodon from the
Maastrichtian of
Harrana. Fossils of the Harrana fauna and the adjacent areas. - H.
Kaddumi - 2009.
- New exceptional specimens of Prognathodon overtoni
(Squamata,
Mosasauridae) from the upper Campanian of Alberta, Canada, and the
systematics and ecology of the genus. - Journal of Vertebrate
Paleontology vol 31, issue 5 - T. Konishi, D. Brinkman, J. A. Massare
& M. W. Caldwell - 2011.
- Soft tissue preservation in a fossil marine lizard with a bilobed
tail fin. Nature Communications 4. - J. Lindgren, H. F. Kaddumi
& M. J. Polcyn - 2013.
- Redescription of Prognathodon lutugini (Squamata,
Mosasauridae). -
Proceedings of the Zoological Institute RAS. 317 (3): 246–261. - D, V.
Grigoriev - 2013.
- Redescription and phylogenetic assessment of 'Prognathodon'
stadtmani: implications for Globidensini monophyly
and character
homology in Mosasaurinae. - Journal of Vertebrate Paleontology:
e1784183. - J. R. Lively - 2020.