Lower Triassic Coelacanths of the Sulphur Mountain Formation (Wapiti Lake) in British Columbia, Canada

Abstract

The coelacanths from the Lower Triassic Sulphur Mountain Formation (Wapiti Lake) have been known for nearly 100 years, though they remained undescribed. Preliminary works identified them as belonging to a single undescribed species of Whiteia; however, six distinct coelacanths were identified: six new species, four new genera and a new family were erected thus bringing the total of known Lower Triassic coelacanths to near twenty-five, the highest recorded in the fossil record. Additionally, two of the new coelacanths, Rebellatrix, gen. nov., and Everticauda, gen. nov., have body forms that are new and distinct from forms previously attributed to coelacanths. These specimens represent the first major change in the coelacanth body form in 75 million years (since the Mississippian). These coelacanths are the first piece of evidence that morphological diversity may have actually peaked in the Lower Triassic. Finally, the various caudal morphotypes are examined to determine functional differences (related to locomotion) and the lifestyles (niches) that they suggest.