Paleocene taxonomic orders

Anseriformes is an order of birds also known as waterfowl that comprises 178 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which includes the other 174 species of waterfowl, among them the ducks, geese, and swans. Most modern species in the order are highly adapted for an aquatic existence at the water surface. With the exception of screamers, males have penises, a trait that has been lost in the Neoaves, the clade consisting of all other modern birds except the galliformes and paleognaths.

The Gruiformes are an order containing a considerable number of living and extinct bird families, with a widespread geographical diversity. Gruiform means 'crane form'.

The Apodiformes is an order, or taxonomic grouping, of birds which traditionally contained three living families—the Apodidae (swifts), the Hemiprocnidae (treeswifts), and the Trochilidae (hummingbirds); however, in the Sibley-Ahlquist taxonomy, this order is elevated to the superorder Apodimorphae, in which hummingbirds are separated into a new order, the Trochiliformes. With nearly 450 species identified to date, it is the most diverse order of birds after the Passeriformes (the "perching" birds).

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Therapsida is a clade comprising a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more underneath the body, resulting in a more "standing" quadrupedal posture, as opposed to the lower sprawling posture of many reptiles and amphibians.

Gaviiformes () is an order of aquatic birds containing the loons or divers and their closest extinct relatives. Modern gaviiformes are found in many parts of North America and northern Eurasia (Europe, Asia and debatably Africa), though prehistoric species were more widespread.

Cariamiformes (or Cariamae) is an order of primarily flightless birds that has existed for over 50 million years. The group includes the family Cariamidae (seriemas) and the extinct families such as Phorusrhacidae, Bathornithidae, Idiornithidae, and Ameghinornithidae. Extant members (seriemas) are only known from South America, but fossils of many extinct taxa are also found in other continents including Europe and North America. Though traditionally considered a suborder within Gruiformes, both morphological and genetic studies show that it belongs to a separate group of birds, Australaves, w

The order Notostraca, containing the single family Triopsidae, is a group of crustaceans known as tadpole shrimp or shield shrimp. The two genera, Triops and Lepidurus, are considered living fossils, with similar forms having existed since the end of the Devonian, around 360 million years ago. They have a broad, flat carapace, which conceals the head and bears a single pair of compound eyes. The abdomen is long, appears to be segmented and bears numerous pairs of flattened legs. The telson is flanked by a pair of long, thin caudal rami. Phenotypic plasticity within taxa makes species-level ide

Choristodera (from the Greek χωριστός chōristos + δέρη dérē, 'separated neck') is an extinct order of semiaquatic diapsid reptiles that ranged from the Middle Jurassic, or possibly Triassic, to the Miocene (168 to 20 or possibly 11.6 million years ago). Choristoderes are morphologically diverse, with the best known members being the crocodile-like neochoristoderes such as Champsosaurus. Other choristoderans had lizard-like or long necked morphologies. Choristoderes appear to have been confined to the Northern Hemisphere, having been found in North America, Asia, and Europe, and possibly also N

Rheiformes is an order that contains the family Rheidae (rheas). It is in the infraclass Paleognathae, which contains all ratites. Extant members are found in South America. While the IOC World Bird List and the Clements Checklist categorise Rheiformes as its own order, the BirdLife Data Zone includes rheas, along with ostriches, tinamous, cassowaries, emu, and kiwis, in the order Struthioniformes. Of the two extant species of rheas recognized by the IUCN Red List, , Rhea americana is listed as near threatened, while Rhea pennata is listed as least concern. From 2014 to 2022, the IUCN recognis

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Synechodontiformes is an extinct order of prehistoric shark-like cartilaginous fish, known from the Permian to the Paleogene. They are considered to be members of Neoselachii, the group that contains modern sharks and rays.