NEW RECORDS OF THE ENIGMATIC NEOTROPICAL FOSSIL FISH ACREGOLIATH RANCII (TELEOSTEI INCERTAE SEDIS) FROM THE MIDDLE MIOCENE HONDA GROUP OF COLOMBIA

Abstract

Fossil scales of the enigmatic teleost Acregoliath rancii Richter, collected in 1945 and 1946, are described for the first time from finegrained sediments of the La Victoria Formation of the Honda Group in central Colombia. The specimens include one isolated but nearly complete scale from the anterior region of the body, and one isolated scale fragment. Although fragmentary, these specimens provide relevant anatomic and biogeographical information. Both specimens agree in most details with the type material of A. rancii; however, the almost complete scale differs in focus position and outline, thus suggesting topological variation. This aspect of lepidosis in A. rancii was previously unknown and could be relevant for future reassessment of the interrelationships of this taxon. The presence of A. rancii in the middle to late Miocene fossil assemblages from La Venta, Fitzcarrald, and Acre suggests a relationship between these areas during the middle Miocene. The relevance for paleodrainage evolution in northern South America is discussed in the context of these findings.