''Tonsala'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

Plotopteridae Plotopteridae is an extinct family of flightless seabirds with uncertain placement, generally considered as member of order Suliformes. They exhibited remarkable convergent evolution with the penguins, particularly with the now extinct giant ...

, a family of

flightless Flightless birds are birds that through evolution lost the ability to fly. There are over 60 extant species, including the well known ratites ( ostriches, emu, cassowaries, rheas, and kiwi) and penguins. The smallest flightless bird is ...

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same envir ...

similar in biology with

penguin Penguins ( order Sphenisciformes , family Spheniscidae ) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere: only one species, the Galápagos penguin, is found north of the Equator. Highly adapt ...

s, but more closely related to modern

cormorant Phalacrocoracidae is a family of approximately 40 species of aquatic birds commonly known as cormorants and shags. Several different classifications of the family have been proposed, but in 2021 the IOC adopted a consensus taxonomy of seven ge ...

s. The genus is known from terrains dated from the Late

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but ...

of the

State of Washington Washington (), officially the State of Washington, is a state in the Pacific Northwest region of the Western United States. Named for George Washington—the first U.S. president—the state was formed from the western part of the Washingto ...

History and etymology

In 1979,

Storrs L. Olson Storrs Lovejoy Olson (April 3, 1944 – January 20, 2021) was an American biologist and ornithologist who spent his career at the Smithsonian Institution, retiring in 2008. One of the world's foremost avian paleontologists, he was best known ...

and

Hasegawa Yoshikazu (born 1930) is a Japanese vertebrate palaeontologist and honorary museum director. The Pleistocene anatid ''Shiriyanetta hasegawai'' was named in his honour, in recognition of his "outstanding contributions" to the field. Biography Born in ...

identified several fossilized specimens of Late

and Early

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 recent" ...

birds found in the

and in Japan as members of the family

, but distinct enough from '' Plotopterum'' in their general anatomy to warrant their own genus. The Washington fossils, collected by

Douglas Emlong Douglas Ralph Emlong (April 17, 1942–June 1980) was an amateur fossil collector from the Oregon Coast in the northwestern United States. His collections contributed to the discovery and description of numerous extinct marine mammal species, ma ...

in Late Oligocene terrains of the Pysht Formation, in the north of the

Olympic Peninsula The Olympic Peninsula is a large arm of land in western Washington that lies across Puget Sound from Seattle, and contains Olympic National Park. It is bounded on the west by the Pacific Ocean, the north by the Strait of Juan de Fuca, an ...

, were formally described the next year, 1980, by Olson himself, as the type of the new genus and species ''Tonsala hildegardae''. Olson ascribed to the genus the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

USNM 256518, an incomplete specimen comprising a fragmentary

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

, fragments of a distal wing, a

patella The patella, also known as the kneecap, is a flat, rounded triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. The patella is found in many tetrapods, such as m ...

and a

pectoral girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists ...

. The genus name, ''Tonsala'', is constructed with the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

prefix "''Tonsa''-", meaning "oar", and the suffix "-''ala''", meaning wing, referencing the adaptation of its forelimbs as a swimming apparatus ; the species name, ''hildegardae'', was given to honour

Hildegarde Howard Hildegarde Howard (April 3, 1901 – February 28, 1998) was an American pioneer in paleornithology, mentored by the famous ornithologist, Joseph Grinnell, at the Museum of Vertebrate Zoology (MVZ) and in avian paleontology.Joyce Harvey & Marilyn ...

, the American paleontologist who described '' Plotopterum''.

Description

''Tonsala'' was a very large and flightless seabird, comparable in size with a great penguin, and larger than its later relative '' Plotopterum''. The genus was heavily adapted towards swimming and diving ; the wings were paddle-shaped, and the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

had a thin and expanded blade, similar to that of penguins, to help the animal propel through water. The structure of the wing, and notably the shape of the

and

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

, shared more resemblances with early

s and flightless

auk An auk or alcid is a bird of the family Alcidae in the order Charadriiformes. The alcid family includes the murres, guillemots, auklets, puffins, and murrelets. The word "auk" is derived from Icelandic ''álka'', from Old Norse ''alka'' (au ...

s like '' Pinguinus'' and ''

Mancalla Mancallinae is an extinct subfamily of prehistoric flightless alcids that lived on the Pacific coast of today's California and Mexico from the late Miocene epoch to the early Pleistocene (ranging from at least 7.4 million to 470,000 years ago) ...

'' than with the related

Pelecaniformes The Pelecaniformes are an order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such n ...

, in a case of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...

. The appearance of the

ulnare The triquetral bone (; also called triquetrum, pyramidal, three-faced, and formerly cuneiform bone) is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones. It is on the ulnar side of th ...

also indicates the relatively low flexibility of the distal region of the wings. However, the genus retains some pelecaniform characteristics, such as an elongated acromion on the scapula, although thinner than its modern relatives, and the distinctive plotopterid coracoid was similar to those of

gannet Gannets are seabirds comprising the genus ''Morus'' in the family Sulidae, closely related to boobies. Gannets are large white birds with yellowish heads; black-tipped wings; and long bills. Northern gannets are the largest seabirds in the ...

s, while the ossified patella, only element known about the hindlimbs of the genus, was more reminiscent of

darter The darters, anhingas, or snakebirds are mainly tropical waterbirds in the family Anhingidae, which contains a single genus, ''Anhinga''. There are four living species, three of which are very common and widespread while the fourth is rarer and ...

s. Aside of its larger size, it is differentiated from ''Plotopterum'' through the more elongated glenoid facet, the lack of sinuation on the sternal margin, the projection of the furcular facet and the long and narrow coracohumeral surface.

References

{{Taxonbar, from=Q114554402 Fossil taxa described in 1980 Paleogene Japan Plotopteridae Extinct flightless birds Prehistoric bird genera