This is a interesting piece with two specimens (a complete Kettneraspis aff. pigra and an unidentified one) fossilized facing ventrally with respect to one another.
Two questions:
1) What period is this matrix?;
2) What species is the incomplete one? Dimensons of cranidium plus first thoraxic segments at the pictures: 1,3 x 1,9 cm
Thanks in advance for your opinions.
Miguel