|
''Cyamodus'' (pron.: SIE-ah-MO-dus) is a genus of placodonts discovered from fossil remains in Germany in the early-to-mid-19th century and was named by Christian Erich Hermann von Meyer in 1863. The fossils have been dated to the Triassic Period, from the Anisian to Ladinian stages. 〔 Considered a possible turtle ancestor due to its wide flattened torso covered in dermal ossicles, but now is considered to only be closely related. Derived from a sister to ''Paraplacodus'', ''Cyamodus'' phylogenetically preceded ''Placochelys''. Meyer (1863) created the genus name ''Cyamodus'' for the "Schnabelplacodus" ''Cyamodus rostratus'' holotype skull material from Bindlach, which is today preserved and displayed in the Urwelt-Museum Oberfranken, Bayreuth. 〔 ==Discovery== ''Cyamodus'' is the type genus of the monotypic family Cyamodontidae. 〔 Thus far, five species of ''Cyamodus'' have been identified - ''C. rostratus'', ''C. munsteri'', ''C. tarnowitzensis'', ''C. hildegardis'', and ''C. kuhnschneyderi''. 〔 Initially considered to be an ancestral turtle due to its testudine-like head and large, bifurcated carapace. However further investigation resulted in its reclassification as a placodont, and it is closely related to other turtle-like reptiles of the Triassic period such as ''Henodus'' and ''Psephoderma''. Similar to these other placodonts, ''Cyamodus'' made its living by hovering close to the sea floor, vacuuming up various shellfish, and grinding them between its blunt teeth. 〔 Historically, the first ''Cyamodus'' remains were found in Upper Muschelkalk shallow marine limestones at near Bayreuth in Bavaria (Germany). They included the incomplete holotype skulls of ''Cyamodus muensteri'' and ''Cyamodus rostatus'', which along with all other placodont remains recovered from the six quarries on the Lainecker Range in northern Bavaria were originally considered to have been derived from fish. The earliest ''Cyamodus'' skull was later restored by Muenster, with the addition of four teeth that had not been present in the original skull, and was named ''placodus muensteri''. 〔 Further placodont remains were found by Muenster, who collected many placodont cranial remains in the Bindlach and Lainecker Range quarries. All placodont remains from those sites were then revised as being of reptilian origin by Owen (1858). The only known complete ''Cyamodus'' skeleton, including its skull, is that of ''C. hildegardis'', which was found outside the Germanic Basin in the northern Tethys in Switzerland. Middle Triassic sauropterygian placodonts have become increasingly important for developing new ideas to the evolutionary history of their relatives, the turtles, whereas modern analyses place placodonts not as their ancestors using morphological cladistic analyses based on the bone osteology. The study of these placodonts contributes to our understanding of the Germanic Basin and the reptile distributions. 〔 An intriguing placodont that appears to be intermediate between ''Cyamodus'' and the placochelyids, ''Protenodontosaurus italicus'', was described by Giovanni Pinna in 1990. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cyamodus」の詳細全文を読む スポンサード リンク
|