Systematic position and palaeoecology of a cavity-dwelling trilobite, Ityophorus undulatus Warburg, 1925, from the Upper Ordovician Boda Limestone, Sweden

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概要

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• The high level systematic position and autecology of the Upper Ordovician cavity-dwelling trilobite Ityophorus undulatus is discussed. The lectotype is here selected from syntypes. The Late Cambrian family Loganellidae Rasetti, 1959 appears to contain the ancestors of this species. Ityophorus is compared with the closely related Middle Ordovician trilobite Frognaspis to pick out the stable characters. These are the yoked free cheeks, the wide cephalic doublure in combination with a distinct narrow cephalic rim, pygidial pleural and interpleural furrows, and a smooth mesial part of the inner cephalic doublural margin (lack of an embayment of the hypostomal suture). Because of the presence of several characteristics unique to the two, they are best attributed to a subfamily Ityophorinae, which is interpreted as a relict group of the Loganellidae. The discussion of the autecology is based on the structural relationship of the mouth opening and position of basal podomeres in relation to the cephalic margin, and on the functional morphology of terrace lines on the brim margin. The appendages appear to have been long to reach the substrate. The cephalon appears to have held the body rigidly by means of the terrace lines. This made it possible for the animal to use its appendages freely, for instance, in scratching the substrate. Some cavities in the present study area show evidence of a gel-like consistency of the cavity walls, which best fits the behavior mentioned above. Ityophorus is interpreted to have been an animal adapted to cavities rich in bacterial mats, on which it may have fed.

• 日本古生物学会の論文
• 2002-04-28

著者

• Suzuki Yutaro

  Department Of Cardiology Surugadai Nihon University Hospital.

• Suzuki Yutaro

  Department Of Biology And Geosciences Faculty Of Sciences Shizuoka University

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