Acamptonectes
Name:
Acamptonectes
(Rigid swimmer).
Phonetic: Ah-camp-toe-nek-teez.
Named By: Valentin Fischer, Michael W. Maisch,
Darren Naish, Ralf Kosma, Jeff Liston, Ulrich Joger, Fritz J.
Krüger, Judith Pardo Pérez, Jessica Tainsh and Robert M.
Appleby - 2012.
Classification: Chordata, Reptilia,
Ichthyosauria, Ophthalmosauridae, Ophthalmosaurinae.
Species: A. densus (type).
Diet: Piscivore.
Size: Around 3 meters long.
Known locations: England - Cambridge Greensand
& Speeton Clay Formations. Germany, Cremlingen.
Time period: Hauterivian through to Cenomanian of
the Cretaceous.
Fossil representation: Several specimens but often
of incomplete remains.
The
first specimen of Acamptonectes was discovered in
1958 from the
Speeton Clay Formation, but was never officially described. A
second specimen from this formation was recovered in 1985. Early
interpretations of Acamptonectes led to the
conclusion that it was
similar to Platypterygius,
but a new discovery from Germany in
2003 was found to bear similarities to the 1958 material, a
discovery that sparked fresh interest in the fossils. A later study
that was a collaboration of all the palaeontologists involved with
these specimens saw the formal creation of Acamptonectes
as a valid
genus, as well as realisation that it was actually more similar to
ichthyosaurs
like Ophthalmosaurus
and Mollesaurus.
The
name Acamptonectes, which means ‘rigid
swimmer’, is a reference
to the tightly packed cervical (neck) vertebra which means that
Acamptonectes probably was not able to turn its head
from side to
side. Additionally the front half of the post cranial skeleton,
particularly the strongly developed ribs also hint towards a very
rigid forward body with the only real motion coming from the tail.
This might suggest that Acamptonectes relied upon
high forward speed
in chasing down prey like fast swimming fish rather than trying to out
manoeuvre them. This torpedo-like motion would be better suited for
high speed as Acamptonectes would not experience
unnecessary drag
caused by the side to side swaying of a body in motion. Additional
developments to reduce water resistance are the shallow snout and
slender but sharp teeth that would have helped improve the overall
streamlining of the body.
Further reading
- New Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous
Demonstrate Extensive Ichthyosaur Survival across the
Jurassic–Cretaceous Boundary. PLoS ONE 7 (1): e29234 - V. Fischer, M.
W. Maisch, D. Naish, R. Kosma, J. Liston, U. Joger, F. J. Krüger, J.
Pardo Pérez, J. Tainsh & R. M. Appleby - 2012.
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