Aptian first appearances

Palaeognathae (; ) is an infraclass of birds, called paleognaths or palaeognaths, within the class Aves of the clade Archosauria. It is one of the two infraclasses of birds, the other being Neognathae, both of which form Neornithes. Palaeognathae contains five extant orders consisting of four flightless lineages (plus two that are extinct), termed ratites, and one flying lineage, the Neotropic tinamous. There are 47 species of tinamous, five of kiwis (Apteryx), three of cassowaries (Casuarius), one of emus (Dromaius) (another became extinct in historic times), two of rheas (Rhea) and two of os

Protostegidae is a family of extinct marine turtles that lived during the Cretaceous period. The family includes some of the largest sea turtles that ever existed. The largest Archelon had a head long. Like most sea turtles, they had flattened bodies and flippers for front appendages; protostegids had minimal shells like leatherback turtles of modern times.

Calappoidea is a superfamily of crabs comprising the two families Calappidae and Matutidae. The earliest fossils attributable to the Calappoidea date from the Aptian.

Polycotylidae is a family of plesiosaurs from the Cretaceous. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous. Several species survived into the final stage of the Cretaceous, the Maastrichtian around . The possible latest surviving member Rarosaurus from the late Maastrichtian is more likely a crocodylomorph.

Deltatheroida is an extinct group of basal metatherians that were distantly related to modern marsupials. The majority of known members of the group lived in the Cretaceous; one species, Gurbanodelta kara, is known from the late Paleocene (Gashatan) of China. Their fossils are restricted to Central Asia and North America. This order can be defined as all metatherians closer to Deltatheridium than to Marsupialia.

Obaichthyidae (also known as "spiny gars" or "spike gars") is an extinct family of ginglymodian ray-finned fish that lived in what is now Africa, South America, and southern Europe during the Upper Cretaceous period (Aptian–Cenomanian ages). They were close relatives of the modern gars of the family Lepisosteidae, with the two groups making up the superfamily Lepisosteoidea. Though obaichthyids are generally similar to their extant relatives, they possessed a mobile maxilla along with a large posterior spine on their scales. The specializations of the skull seen in members of the family sugges

Deltatheridiidae is an extinct family of basal carnivorous metatherians that lived during the Cretaceous and Paleogene. They were closely related to marsupials. Their fossils are restricted to Central Asia (Mongolia and Uzbekistan) and North America (United States - Oklahoma, Texas, Utah, Wyoming). They mostly disappeared in the KT event, but a ghost lineage, currently represented by Gurbanodelta, survived until the late Paleocene by decreasing in size and becoming insectivorous.