More recently it turned out that the "Anisozygopterans" form a paraphyletic assemblage of morphologically primitive relatives of the Anisoptera.

Hence they classified both Odontogriphus, and Wiwaxia with its "nearly identical" feeding apparatus, as primitive relatives of molluscs.

In particular, marsupials largely disappeared from North America, and the Asian deltatheroidans, primitive relatives of extant marsupials, became extinct.

They then disappeared, to be survived by their more primitive bushy relatives.

During the Jurassic, the area of Wyoming now called Dinosaur Canyon was home to primitive relatives of modern crocodilians and mammals.

Aetosaurs were traditionally referred to a (now obsolete) group called the thecodonts, which included all "primitive" crocodilian relatives that lived in the Triassic.

More primitive relatives such as Noasaurus and Ceratosaurus had longer, mobile arms with fingers and claws.

Researchers proved that the female preference predated the sword by sewing plastic swords to the hindquarters of male platyfish, primitive swordless relatives of swordtail fish.