Lemdadella


Lemdadella is an extinct genus of redlichiid trilobites that lived during the late Atdabanian stage, which lasted from 521 to 514 million years ago during the early part of the Cambrian Period.

Distribution

  • Lemdadella sp. occurs in the Lower Cambrian of Morocco
  • Lemdadella linaresae was collected in the Lower Cambrian of Spain
  • Lemdadella sp. was found in the Lower Cambrian of Antarctica
  • Lemdadella antarcticae occurs in the Lower Cambrian of Antarctica

Description

Glabella gently tapered forward. At the midline, a ridge between the glabella and the border of the cephalon may be present. Crescent-shaped eye-ridges. Thorax not divided in prothorax and opisthothorax, no macropleural segment.

Biostratigraphy

Lemdadella is currently the oldest trilobite genus known, dating back to about million years ago.
The International Commission on Stratigraphy has proposed that the first appearance datum of trilobites should be used as the lower boundary of Cambrian Series 2 and Cambrian Stage 3. If this proposal will be defined as a GSSP, it will most likely use the first appearance of Lemdadella, a species of Lemdadella, or a trilobite zone that includes Lemdadella. The age and global distribution of Lemdadella are therefore of key importance for the Stratigraphy of the Cambrian.
The following trilobite zones contain Lemdadella :
  • Fallotaspis zone
  • Eoredlichia-Yunnanocephalus zone