Marine Crabs from African Waters Housed in the Museo Nacional de Ciencias Naturales (MNCN-CSIC)—An Opportunity for Biogeographic and Systematic Studies—Part II: Thoracotremata

Zoological collections are essential for preserving regional biodiversity but often lack taxonomic updates, risking data loss. This work supposes the continuation of a review of the African marine crabs housed at the Crustacean collection of the Museo Nacional de Ciencias Naturales (MNCN) in Madrid. Part I, Heterotremata, revealed that only 21.9% of the specimens were correctly identified. In this new study focused on Thoracotremata species, 197 specimens (59 records) were reviewed, and this new study reveals similar results to Part I: 22.9% of the reviewed specimens were previously correctly identified (less than 29% when considering records), meaning that around 77.2% of the African Thoracotremata specimens housed in the MNCN were either misidentified or not identified at all. This highlights the importance of the taxonomic reviews made by specialists of specimens housed in both historical and non-historical scientific collections. This time we have used DNA barcodes (16S and COI) to confirm identifications or to add new molecular data to species without previous DNA sequences known. DNA sequences (16S and/or COI) were obtained for seven species. It has been a challenge to obtain sequences from specimens preserved 60 to 200 years ago.