Relatives and Fossil Record
The genus Triops can be distinguished from the only other genus of Notostraca, Lepidurus, by the form of the telson, which bears a pair of long, thin caudal extensions in Triops, while Lepidurus bears a central platelike process. As soon as they are 24 hours old they represent the looks of their parents.
Triops are sometimes called "living fossils". Fossils attributable to this genus have been found in rocks of Carboniferous age, an estimated 300 million years ago, and one extant species, Triops cancriformis, has hardly changed since the Jurassic period (approximately 180 million years ago).
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