''Morsoravis'' is an extinct genus of

neoavian Neoaves is a clade that consists of all modern birds (Neornithes or Aves) with the exception of Palaeognathae (ratites and kin) and Galloanserae (ducks, chickens and kin). This group is defined in the ''PhyloCode'' by George Sangster and colleag ...

bird from the Early

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

Fur Formation of

Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...

. It contains a single named species, ''Morsoravis sedilis''. Fossils of Morsoravis have also been found in the

Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River (Colorado River), Green River in Colorado, Wyoming, and Utah. The sedimen ...

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

and possibly the

Nanjemoy Formation The Nanjemoy Formation is a Formation (geology), geologic formation pertaining to both the Wilcox Group and the Pamunkey Group of the eastern United States, stretching across the states of Virginia, Maryland, and the District of Columbia. The f ...

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

Discovery and naming

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

of ''Morsoravis'', MGUH 28930, consists of a complete but fully articulated and three-dimensionally preserved skeleton, found in the marine

Fur Formation The Fur Formation is a marine geological formation of Ypresian ( Lower Eocene Epoch, c. 56.0-54.5 Ma) age which crops out in the Limfjord region of northern Denmark from Silstrup via Mors and Fur to Ertebølle, and can be seen in many cliffs and ...

. There are several fish bones preserved within the body of the bird, although there are also other fish fossils surrounding the specimen. The fossil was collected from a site on the northwestern corner of the island of

Mors Mors may refer to: *Mors (mythology), the personification of death in Roman mythology *Mors, Latin for death *Mors (automobile), a French car manufacturer from 1895 to 1925 :* American Mors, Mors vehicles produced under licence in America by the S ...

, at the base of a cliff. Although ''Morsoravis'' belongs to its own family, Morsoravidae, and is related to the Psittacopedidae, it was first formally described as a relative of the

Charadriiformes Charadriiformes (, from '' Charadrius'', the type genus of family Charadriidae) is a diverse order of small to medium-large birds. It includes about 390 species and has members in all parts of the world. Most charadriiform birds live near water ...

by Bertelli ''et al.'' in 2010. Before that, it had been the subject of research in two unpublished doctoral theses in 2002 and 2007. Additionally, it had been inadequately described as a ''nomen nudum'' under the name "Morsoravis sedile" in Dyke & Tuinen (2004). The generic name ''Morsoravis'' comes from Mors, the name of the island on which the holotype was collected, Latin ''sor'', meaning "shore", and ''avis'', meaning bird. The specific ephitet, ''sedilis'', is from Latin "sedere", meaining to sit still, and ''ilis'', expressing capability, referencing ''Morsoravis capability to perch. A fossil from the

belongs to an unnamed species of ''Morsoravis'', and preserves the forelimbs, unlike the holotype. Remains of ''Morsoravis''-like bone fragments have been found from the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. However, the fragmentary nature of these specimens prohibits confident assignment to the genus. A further specimen from the Fur Formation, preserving elements of the wing and pectoral area not found in the holotype, belongs to ''Morsoravis'', but it is now lost.

Description

''Morsoravis'' had a rounded head totalling about , of which about half is accounted for by the relatively long beak, with a rounded braincase. The beak is straight and pointed at its tip, and has an elongated nostril. The beak is schizorhinal, suggesting the possibility of rhynchokinetism of the rostrum. The

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

is about the size of the

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calv ...

, and the

sclerotic ring The scleral ring or sclerotic ring is a hardened ring of plates, often derived from bone, that is found in the eyes of many animals in several groups of vertebrates. Some species of mammals, amphibians, and crocodilians lack scleral rings. The rin ...

is made of 12 segments. The interorbital septum, the bone between the two orbits, has a single fenestra. There is either a very weakly developed basipterygoid process or none at all. The skull of the holotype preserves many details of the inner ear and surrounding area well. In ''Morsoravis'' there are 21 presacral vertebrae, that is, vertebrae cranial of the synsacrum, which exhibit a pleurocoelous condition. There are 11 synsacral vertebrae and a further 7 caudal vertebrae. The pygostyle is large. The pelvis is incompletely fused to the synsacrum, which is true of adult ''Morsoravis''. The tarsometatarsus is highly similar to that of '' Pumiliornis'', a psittacopedid bird, and features an accessary trochlea of the trochlea of the fourth metatarsal, indicative of at least semi-

zygodactyly In biology, dactyly is the arrangement of digits (fingers and toes) on the hands, feet, or sometimes wings of a tetrapod animal. The term is derived from the Greek word () meaning "finger." Sometimes the suffix "-dactylia" is used. The derive ...

. The

hallux Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plantigrade''; ...

is relatively long and has a large, curved claw, and the proportions of the toes are not characteristic of ground-dwelling birds. The semi-zygodactyl foot also has a second toe with relatively little freedom of side-to-side motion, likely an adaptation for climbing.

Classification

The history of the classification of ''Morsoravis'' is convoluted. Dyke & van Tuinen (2004) figured the holotype of ''Morsoravis'' and classified it as a charadriiform bird, but provided no formal description, making their name, "Morsoravis sedile", a

nomen nudum In Taxonomy (biology), taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published ...

. The first formal description of the bird, by Bertelli ''et al.'', agreed with this assessment, partially due to details of the vertebrae. Mayr (2011) classified the bird together with Pumiliornis, and Mayr (2015) included ''Morsoravis'' in the new family Psittacopedidae. With new fossil evidence from the new genus Sororavis, Mayr (2023) described a new family, Morsoravidae, with ''Morsoravis'' as the type genus, and including Pumiliornis and Sororavis, to the exclusion of the other birds previously described as psittacopedids.

References

{{Taxonbar, from1=Q37302735, from2=Q16579299 Eocene life Prehistoric birds of Europe Prehistoric bird genera Green River Formation Taxa named by Luis M. Chiappe