Notostraca
Triops longicaudatus
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Branchiopoda Order: Notostraca G. O. Sars, 1867 Family: Triopsidae Keilhack, 1909
Genera
Lepidurus Triops

Members of the order Notostraca (colloquially referred to as notostracans, called Triops, tadpole shrimp or shield shrimp) are small crustaceans in the class Branchiopoda. Triops have two internal compound eyes and one naupliar eye in-between, a flattened carapace covering its head and leg-bearing segments of the body. The order contains a single family, with only two extant genera. Their external morphology has apparently not changed since the Triassic appearance of Triops cancriformis around 220 million years ago. Triops cancriformis may therefore be the "oldest living animal species on earth." ^[1] The members of the extinct order Kazacharthra are closely related, having been descended from notostracans.