Tropeognathus
Name:
Tropeognathus
(Keel jaw).
Phonetic: Trop-e-o-nay-fuss.
Named By: Peter Wellnhofer - 1987.
Synonyms: Coloborhynchus mesembrinus,
Criorhynchus mesembrinus, Ornithocheirus mesembrinus.
Classification: Chordata, Reptilia,
Pterosauria, Ornithocheiridae.
Species: T. mesembrinus
(type), T. robustus?
Diet: Piscivore.
Size: Largest known individual based upon specimen
MN 6594-1 is estimated to have had a wingspan 8.2 meters across.
Known locations: Brazil - Santana Formation.
Time period: Aptian/Albian of the Cretaceous.
Fossil representation: Remains of at least three
individuals, together revealing the skull and parts of the post
cranial skeleton.
Tropeognathus
was first named in 1987 after the description of a pterosaur
skull
that had been purchased from a fossil dealer. In 2002 a set of
lower jaws was further attributed to the genus, and most recently at
the time of writing a third specimen was added in 2013, and this
was the first inclusion of post cranial remains. Today these
specimens all represent members of the type species Tropeognathus
mesembrinus which is held as valid, while a second species,
Tropeognathus robustus which was also named in
1987 and based upon
a more robust jaw, has a questionable validity.
Only
two years after Tropeognathus was established,
there was speculation
that it might have actually been a specimen of Anhanguera
(Kellner,
1989). Tropeognathus has also been considered
a synonym to
Coloborhynchus
(Veldmeijer, 1998), Criorhynchus
(Fastnacht,
2001) and Ornithocheirus
(Unwin, 2001). With the addition of
new post cranial remains in 2013 however, Tropeognathus
has now
gained a wider acceptance to its validity, and a 2013 taxonomic
review by Rodrigues and Kellner supported the view that Tropeognathus
is a valid genus.
Tropeognathus
is easily amongst the largest known ornithocheirid pterosaurs, a kind
that seem to have been best adapted for flying over bodies of water and
snatching fish from the water. Also with the addition of new fossil
material in 2013, Tropeognathus was the largest
pterosaur from
Gondwana, the amalgamation of the southern continents that were
largely separated from the northern continents that are known as
Laurasia. Only the largest azhdarchid pteroasurs such as
Quetzalcoatlus
from North America are known to have comfortably
exceeded Tropeognathus in size. Like relative
genera,
Tropeognathus had a toothed beak, and large
rounded growths
which have been dubbed ‘keels’ rising from the tips of both upper
and lower jaws.
The
wings of Tropeognathus seem to be very long while
at the same time
thin, similar to some other types of pterosaurs such as
pteranodonts. This may indicate that large ornithocheirds like
Tropeognathus may have used a flight principal
called dynamic soaring
to conserve energy. This is where air current passing over ocean
waves are exploited so that an individual can use them to pick up speed
and lift without having to expend energy to continuously flap the
wings. This idea of flight has also been proposed for the pterosaur
Pteranodon,
and can be seen in action by some modern sea birds such
as the albatross which although has a different wing construction,
has a roughly similar wing proportion. Glider pilots are also known
to use this flight principal, though usually more often on a grander
scale such as an air current rising over a mountain.
Further reading
- New crested pterosaurs from the Lower Cretaceous of Brazil. -
Mitteilungen der Bayerischen Staatssammlung f�r Pal�ontologie und
historische Geologie 27: 175–186; Muenchen - Peter
Wellnhofer - 1987.
- An overview of the pterosaur assemblage from the Cambridge
Greensand (Cretaceous) of Eastern England. - Mitteilungen aus
dem Museum f�r Naturkunde in Berlin, Geowissenschaftliche Reihe 4:
189–221. - D. M. Unwin - 2001.
- First record of Coloborhynchus (Pterosauria)
from the Santana
Formation (Lower Cretaceous) of the Chapada do Araripe of Brazil.
- Pal�ontologisches Zeitschrift, 75: 23–36. - M.
Fastnacht - 2001.
- Pterosaurs from the Lower Cretaceous of Brazil in the Stuttgart
collection, - Stuttgarter Beitr�ge zur Naturkunde Serie B
(Geologie und Pal�ontologie) 327: 1–27. - A. J.
Veldmeijer - 2002.
- The largest flying reptile from Gondwana: A new specimen of
Tropeognathus cf. T. mesembrinus
Wellnhofer, 1987
(Pterodactyloidea, Anhangueridae) and other large pterosaurs from
the Romualdo Formation, Lower Cretaceous, Brazil. Anais da
Academia Brasileira de Ci�ncias 85: 113. - A. W. A.
Kellner, D. A. Campos, J. M. Say�o, A. N. A. F.
Saraiva, T. Rodrigues, G. Oliveira, L. A. Cruz, F.
R. Costa, H. P. Silva & J. S. Ferreira -
2013.
- Taxonomic review of the Ornithocheirus complex
(Pterosauria)
from the Cretaceous of England. - ZooKeys 308: 1. - Taissa
Rodrigues & Alexander Kellner - 2013.
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