Rostroconchia

Ischyrinia winchelli

The extinct genus of beak Schaler ( rostroconchs ) belongs to the tribe of molluscs ( Mollusca ), where it is to subclass the shell molluscs expected ( Conchifera ). They are found fossil from the Cambrian to the Permian, ie only in the Palaeozoic ( Paleozoic ). Their heyday was in the Ordovician. It is believed that it is at the Scaphopoda a specialized branch of the beak Schaler ( rostroconchs ).

Construction

They had in the adult stage a pseudozweiklappiges housing similar to a shell, but without ligament. The two flaps are interconnected by a continuous shell to several layers; the two flaps so they could not move freely against each other as in the shells themselves. Only in growth, the two shell halves were opened by breaking the shell layers according to the rate of shell growth continues. The bottom of the case only slightly gaping; in the front part, there was a slightly larger opening through which a foot and / or the capture threads ( Captacula ) were protruded. The rear end is usually significantly prolonged, often drawn out into a hard tube rostrum. The rear end can also be flattened and rear-facing shell extensions to be surrounded (collar ). In the center of the collar is then located the rostrum.

Way of life

The original forms the beak Schaler lived probably similar to Kahnfüßern ( Scaphopoda ) half buried in the sediment of the sea floor in shallow water, with the rear end sticking out of the sediment. With the help of tentacles or coat appendages small organisms living in the sediment or in the gap of the sediment systems were captured. Specialized forms probably went into a symbiosis with unicellular algae, zooxanthellae, who sat in the upward oriented collar under a thin, translucent shell layer.

Orders

• Ribeiriida - Cambrian to Ordovician
• Ischyriniida - Cambrian to Ordovician
• Conocardiida - Ordovician to Permian