Endocerida

Artist's impression of life in the Ordovician.

• Worldwide

The Endocerida are an order of cephalopods ( Cephalopoda ) from the relationship of the nautilus ( Nautiloidea ). Representatives of Endocerida first appeared in the Lower Ordovician period ( J. approximately 488 million ) and died at the end of the Lower Silurian (before J. approximately 425 million) off again. Precursor forms, as a separate order ( order = Yanhecerida ) are summarized together with the Endocerida to superorder Endoceratoidea, but have been found in rocks of the Upper Cambrian ( about 495 million before J. ).

Features

The Endocerida usually have large, elongated, chambered body with a Siphonalstrang located at margins. A characteristic element of Endocerida are pointed bag -shaped, with the tip directed backwards so-called Intrasiphonalablagerungen, which gradually fill the back of the Siphonalstranges massive. These consist primarily of aragonite and to a lesser extent from organic deposits. The purpose of this filling of the posterior part of the Siphonalstranges is that the focus of the case ( including the animal in the living chamber ) has now moved to the center of the float. Without the ballast in the rear part of the housing, the focus in the front part of the case would be ( by the weight of the animal) and the cuttlebone would stand vertically in the water column. A move horizontally in the water column would be hardly possible. The lift generated by the housing enough to hold the weight of the housing and the animal itself floating in the water column. A climb or descend in the water column by changing the buoyancy in the housing was probably not possible as in today's Nautilus. The movement is probably as in today's Nautilus exclusively with the funnel and the reaction principle. The largest representatives of Endocerida such as Cameroceras reached a total length of no more than 10 to 11 meters (of which a maximum of 9 meters Case ).

Way of life

The representatives of the Endocerida lived exclusively in the sea ( like the other cephalopods ). They subsisted probably of fish, trilobites and arthropods (eg Seeskorpionen ). They were in the Ordovician seas to the Topräubern.

System

The order is classified as order within the subclass Nautiloidea in the classical classification of cephalopods in Nautiloidea, Ammonoidea and Coleoidea. In other classifications ( Shevyrev ) it is grouped with two other orders ( Yanhecerida and possibly also the Intejocerida ) to the Collection ( or subclass ) Endoceratoidea within the cephalopods. Also in the cladistic Altkopffüßer / Neukopffüßer - classification of cephalopods, the order with the Yanhecerida and Intejocerida be combined into a superorder Endoceratoidea. They are basal to the root of Altkopffüßer. There are also proposals to divide the order Endocerida in two or three submissions. These proposals have not been successful so far.

About 20 families are currently placed in the order:

• Allotrioceratidae Flower, 1956
• Botryoceratidae Flower, 1968
• Chihlioceratidae Grabau, 1922
• Cochlioceratidae Balashov, 1965
• Coreanoceratidae Chen, 1976
• Cyrtendoceratidae Hyatt in Zittel, 1900
• Cyrtovaginoceratidae Flower, 1958
• Emmonsoceratidae Flower, 1958
• Endoceroididae Lai, 1985
• Endoceratidae Hyatt, 1883
• Hemipiloceratidae Shimizu & Obata, 1936
• Manchuroceratidae Kobayashi, 1936
• Meniscoceratidae Flower, 1976
• Najaceratidae Flower, 1976
• Narthecoceratidae Flower, 1958
• Piloceratidae Miller, 1889
• Proterocameroceratidae Kobayashi, 1937
• Sinoendoceratidae Lai, 1985
• Suecoceratidae Shimizu & Obata, 1936
• Troedssonellidae Kobayashi, 1935
• Yorkoceratidae Flower, 1968