Cyamodus
Name: Cyamodus
Phonetic: Sie-ah-mo-dus.
Named By: Christian Erich Hermann von Meyer -
1863.
Classification: Chordata, Reptilia,
Sauropterygia, Placodontia, Cyamodontidae.
Species: C. rostratus (type),
C.
hildegardis , C. kuhnschneyderi, C. orientalis, C.
munsteri, C.
tarnowitzensis.
Diet: Shellfish.
Size: 1.3 to 1.5 meters long.
Known locations: Europe.
Time period: Anisian to Ladinian of the Triassic.
Fossil representation: Several specimens including
those of juveniles.
As
dedicated eaters of shellfish, the placodonts
had no need to grow big
and were soon outsized by other marine reptiles such as the
nothosaurs.
As such placodonts like Cyamodus developed
turtle-like shells to try
and make themselves too tough for other marine reptiles to eat.
Cyamodus itself had two shells, the first and
largest covering the
main body while having a smaller one to the rear that protected the
pelvis. Although the shells would have been too cumbersome for high
agility swimming, Cyamodus would still likely
have been more agile
than other single shelled placodonts like Henodus.
The shells were
also covered in hexagonal plates that not only increased the level of
protection but also increased their weight. This was a typical
placodont adaptation as a higher weight just beyond the level of
neutral buoyancy allowing them to more easily reach bottom where the
shellfish were.
Further
adaptations for protection are the strongly built rear of the skull as
well as the limbs that that do not protrude too far from the extent of
the shell. However the reduced limbs mean that Cyamodus
could only
paddle itself through the water and this is where the heavy shell and
internal bones really helped Cyamodus in getting to
the bottom.
Cyamodus also would have been very cumbersome when
on the land and
probably only ventured out of the water for egg laying and possibly
periods of rest. Despite these developments however, juvenile
Cyamodus were still vulnerable to predation,
evidence for which has
been found with the presence of two Cyamodus
juveniles inside the
stomach area of a Lariosaurus
fossil.
A
placodont similar to Cyamodus was the much larger
Psephoderma.
Further reading
- A skull of Cyamodus kuhnschnyderi Nosotti
& Pinna 1993, from
the Muschelkalk of Wassonne (Alsace, France). - Palaeontologische
Zeitschrift 73(3/4):377-383. - O. Rieppel & H. Hagdorn - 1999.
- The shallow marine placodont Cyamodus of the
central European
Germanic Basin: its evolution, paleobiogeography and paleoecology. -
Historical Biology: An International Journal of Paleobiology. 24.3 (4):
1–19. - Cajus G. Diedrich - 2011.
- A new species of Cyamodus (Placodontia,
Sauropterygia) from the early
Late Triassic of south-west China. - Journal of Systematic
Palaeontology. Online edition (17): 1237–1256. - Wei Wang, Chun Li,
Torsten M. Scheyer & Lijun Zhao - 2019.
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