Specific features of the head region in euconodont animals

Abstract

New data on morphology of the head region of euconodonts are discussed based on a study of its imprint from the Lower Carboniferous deposits of the Polar Urals (Russia); on its external ventral surface, the animal had an oval expansion of the head region, supposedly, a mouth food sac. A similar structure is also described in one of the imprints from Granton (Great Britain) exposed from internal surfaces. A hypothesis is put forward on the mechanism of functioning of the feeding apparatus in euconodonts which consists of hard S, M, and P tooth elements and H attaching skeletal elements as well as soft connective structures. The food sac probably served for filtering food particles from the water which was removed through special openings and for formation of the food bolus and transferring the latter into the alimentary canal (gut). These data gave to reasons for a new interpretation of feeding behaviour of euconodonts. It is suggested that the euconodont animals were filter feeders adapted to the near-bottom dwelling over substrates, where there was greatest concentration of small food items available for filtration.