| Lemdadella | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Trilobita |
| Order: | Redlichiida |
| Suborder: | Redlichiina |
| Family: | Redlichiidae |
| Genus: | Lemdadella Sdzuy, 1978 |
| Species | |
| |
Lemdadella is the oldest trilobite that appeared on earth during the Cambrian in Cambrian Series 2. It is an extinct genus of redlichiid trilobites that lived during the late Atdabanian stage, which lasted from 530 to 524 million years ago.
Distribution[]
Description[]
Glabella gently tapered forward. At the midline, a ridge between the glabella and the border of the cephalon (a so-called plectrum) may be present. Crescent-shaped eye-ridges. Thorax not divided in prothorax and opisthothorax, no macropleural segment.
Biostratigraphy[]
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 (Brackets contain geographic distribution):
- Fallotaspis zone (Spain, Laurentia)
- Eoredlichia-Yunnanocephalus zone (Antarctica)