|mhorn||Дата: Wednesday, 15.06.2011, 15:11 | Сообщение # 1|
|Kruta I., Landman N.H. (2008) Injuries on nautilus jaws: implications for the function of ammonite aptychi // Veliger. Vol.50. Issue 3. P.241-247. |
Documentation of repaired injuries and abnormalities on the Jaws of modern nautilus sheds light on the ecology and behavior of these animals. It also helps elucidate the function of ammonite aptychi, which are traditionally interpreted as opercula. We examined 219 pairs of jaws belonging to Nautilus belauensis, N. macromphalus, N. pompilius, and Allonautilus scrobiculatus. Abnormalities occur in 68% of the sample and are only present on the lower jaw. The abnormalities consist of 1) repaired fractures, 2) small depressions, 3) radial grooves and ridges. and 4) flexures in the chitin. These abnormalities are either the result of injury or growth pathology. Injuries may be due to accidents during feeding (e.g., biting down on a hard crustacean carapace) or from predatory attacks. Alternatively, they may have been sustained during mating behavior or fighting between males. Most abnormalities Occur on the left side of the lower jaw. This may be related to the fact that in male nautilus, the jaws are displaced to the right side of the midline, so that during mating, for example, the apex of the jaws of the male lines up with the left side of the jaws of the female. The presence of injuries and other abnormalities on the jaws of nautilus suggest that similar features on aptychi may have been produced during the normal use of the Jaws, and do not necessarily imply an opercular function. Alternatively, aptychi may have served to strengthen and reinforce the lower jaw.
thanks to I. Kruta for pdf!
Middle Jurassic - Lower Cretaceous ammonites & aptychi