Zygodactylidae is a family of extinct

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...

s found in Europe and North America from the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

epoch to the Middle

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

. First named in 1971, based on fragmentary remains of two species from Germany, a more complete description of the birds became possible in 2008 when a number of other, better-preserved fossil species were assigned to the family based on a number of shared characteristics. The name of the group comes from the presence of a

zygodactyl In biology, dactyly is the arrangement of digits (fingers and toes) on the hands, feet, or sometimes wings of a tetrapod animal. It comes from the Greek word δακτυλος (''dáktylos'') = "finger". Sometimes the ending "-dactylia" is used ...

foot, with two toes projecting forward, and two to the rear. This is the same arrangement as seen in living

parrot Parrots, also known as psittacines (), are birds of the roughly 398 species in 92 genera comprising the order Psittaciformes (), found mostly in tropical and subtropical regions. The order is subdivided into three superfamilies: the Psittacoid ...

s and

woodpecker Woodpeckers are part of the bird family Picidae, which also includes the piculets, wrynecks, and sapsuckers. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. ...

s, and the zygodactylids were at one time thought to be related to the woodpecker family. More recent analyses, however, have shown that they are more likely to be the sister

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

to the

passerine A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by t ...

or "perching" birds, the large clade that includes, among others, all living

songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 500 ...

s. Passerine birds are distinguished by an anisodactyl foot, but it is thought that their earliest ancestors may have been zygodactyl, likely using this arrangement of toes to cling to the bark of trees as woodpeckers do. Only later did the fourth toe rotate from the rear to face forward in the modern passerine fashion.

Species

† Family Zygodactylidae * Genus '' Eozygodactylus'', Weidig 2010 ** ''Eozygodactylus americanus'', Weidig 2010 * Genus '' Primoscens'', Harrison & Walker 1977 ** ''Primoscens minutus'', Harrison & Walker 1977 * Genus '' Primozygodactylus'', Mayr 1998 ** ''Primozygodactlyus ballmanni'', Mayr 1998 ** ''Primozygodactlyus danielsi'', Mayr 1998 ** ''Primozygodactlyus eunjooae'', Mayr & Zelenkov 2009 ** ''Primozygodactlyus major'', Mayr 1998 ** ''Primozygodactlyus quintus'', Mayr 2017 * Genus '' Zygodactylus'', Ballmann 1969 ** ''Zygodactlyus grandei'', Smith, DeBee & Clark 2018 ** ''Zygodactlyus grivensis'', Ballmann 1969 ** ''Zygodactlyus ignotus'', Ballmann 1969

References

{{Taxonbar, from=Q20072492 Neognathae Eocene first appearances Prehistoric birds of Europe Prehistoric bird families Prehistoric birds of North America