caa a22 4500 388016744 CHVBK 20180307124913.0 cr unu---uuuuu 161130e199807 xx s 000 0 eng 10.1017/S002233600004035X doi S002233600004035X pii (NATIONALLICENCE)cambridge-10.1017/S002233600004035X Bergman C. F. Department of Geology, Lund University, S-223 62 Lund, Sweden, <Claes.Bergman@geol.lu.se> Reversal in some fossil polychaete jaws [Elektronische Daten] [C. F. Bergman] Scolecodonts, the jaws of polychaetes, are the fossil evidence of the rich and diverse fauna that prospered in shelf seas. Among eunicid polychaetes, the largest jaws in the jaw apparatus occur in pairs. Normally these pairs are not exact mirror images of each other. Rarely, left and right jaws are found to be reversed, the jaw in the left position having the morphology of a mirror image of the normal right jaw and vice-versa. This type of morphological reversal (reversed handedness) is recorded with a frequency that varies from one reversed jaw in 430 to one in 5,838 of normal jaws. Reversed jaws so far are documented in four species from the Upper Ordovician of Indiana, USA, and one species from the Silurian of Gotland, Sweden. The reversed morphology is thought to be a natural, genetically induced feature. The polychaetes with morphological reversal grew to normal size, but never became common. Copyright © The Paleontological Society Journal of Paleontology Cambridge University Press 72/4(1998-07), 632-638 0022-3360 72:4<632 1998 72 JPA https://doi.org/10.1017/S002233600004035X text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S002233600004035X text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Bergman C. F. Department of Geology, Lund University, S-223 62 Lund, Sweden, <Claes.Bergman@geol.lu.se> NATIONALLICENCE 773 0- Journal of Paleontology Cambridge University Press 72/4(1998-07), 632-638 0022-3360 72:4<632 1998 72 JPA CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge