Trigoniidae [SEP] parent taxon
Trigoniidae
Trigoniidae is a taxonomic family of saltwater clams, marine bivalve mollusks in the superfamily Trigonioidea. There is only one living genus, "Neotrigonia", but in the geological past this family was well represented, widespread and common. The shells of species in this family are morphologically unusual, with very elaborate hinge teeth, and the exterior of the shell is highly ornamented. 
Description.
The most striking feature of the Trigoniidae, which has attracted attention for centuries, is their external ornamentation. This is usually present
Taxon in disguise
In bacteriology, a taxon in disguise is a species, genus or higher unit of biological classification whose evolutionary history reveals has evolved from another unit of similar or lower rank, making the parent unit paraphyletic. This happens when rapid evolution makes a new species appear radically different from the ancestral group, so that it is not (initially) recognised as belonging to the parent phylogenetic group, leaving the latter an evolutionary grade.
While the term is from bacteriology, parallel examples are found throughout the tree of