''Beorn'' is an extinct genus of

tardigrade Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them . In 1776, th ...

and the first known fossil tardigrade, discocered in

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

amber Amber is fossilized tree resin. Examples of it have been appreciated for its color and natural beauty since the Neolithic times, and worked as a gemstone since antiquity."Amber" (2004). In Maxine N. Lurie and Marc Mappen (eds.) ''Encyclopedia ...

from

Manitoba Manitoba is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

. The genus contains a single species, ''B. leggi'', and it was originally classified as the only member of its family, the Beornidae, but was later reclassified as belonging to the

Hypsibiidae The Hypsibiidae are a family of water bears or moss piglets, tardigrades in the class Eutardigrada. Subfamilies and genera * Subfamily Diphasconinae ** '' Diphascon'' ** '' Hebesuncus'' ** '' Paradiphascon'' * Subfamily Hypsibiinae ** ''Acutu ...

. It is one of three fossil tardigrades known from the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

, the others being '' Milnesium swolenskyi'' from the Turonian

New Jersey amber New Jersey Amber, sometimes called Raritan amber, is amber found in the Raritan Formation, Raritan and Magothy Formations of the Mid-Atlantic states, Central Atlantic (Eastern) coast of the United States. It is dated to the Late Cretaceous, Turoni ...

and ''

Aerobius ''Aerobius'' is a genus of extinct tardigrades ("water bears") of the superfamily Hypsibioidea. The genus contains a single species, ''A. dactylus'', known from a single individual preserved in amber. The ''Aerobius'' holotype is preserved in ...

'' from the same amber piece as ''Beorn''. The only other confidently known fossil tardigrade is the

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

'' Paradoryphoribius'' from the Dominican Republic. In addition to some other finds from the

and the

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

period, ''Beorn'' is an example of the early existence of tardigrades in

earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

's history, and its largely modern appearance suggests that tardigrades must have diversified considerably before this time.

Discovery and naming

William M. Legg collected the amber in the summer of 1940 in which the holotypes of both ''Beorn'' and ''

'' were found. He died in 1953 before finishing his thesis at

Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial ...

. Kenneth W. Cooper, Legg's friend and scientific mentor, named ''Beorn leggi'' after him in 1964. The type specimen is now in the Museum of Comparative Zoology at

Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...

Etymology

The generic name ''Beorn'' was chosen by Cooper in reference to a character of the same name from the children's book ''

The Hobbit ''The Hobbit, or There and Back Again'' is a children's fantasy novel by the English author J. R. R. Tolkien. It was published in 1937 to wide critical acclaim, being nominated for the Carnegie Medal and awarded a prize from the ...

'' by

J. R. R. Tolkien John Ronald Reuel Tolkien (, 3 January 1892 – 2 September 1973) was an English writer and philologist. He was the author of the high fantasy works ''The Hobbit'' and ''The Lord of the Rings''. From 1925 to 1945, Tolkien was the Rawlinson ...

, which can occur both in the shape of a man and that of a bear. The specific name ''leggi'' refers to Cooper's student William Legg.

Characteristics

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 ...

is enclosed in honey-colored amber. The animal itself is 0.3 millimeters long and 0.08 millimeters wide. As is the case with modern tardigrades, the cylindrical body is flattened on the ventral side. The cuticle is smooth, and slightly thickened on the backside, but does not harden to platelets (sclerites), making ''Beorn'' is one of the "naked" tardigrades. A total of four furrows extend transversely to the longitudinal axis of the body around the whole body, which divide these superficially into five regions: *The first or prostomial region forms the head on which there are no structures, such as filiform cirri or clavae, which are used in some modern modes of sensory perception. Eyes can not be identified. The

mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...

region is inconspicuous and does not have warren-like projections (papillae). *The second region contains the first pair of

legs A leg is a weight-bearing and locomotive anatomical structure, usually having a columnar shape. During locomotion, legs function as "extensible struts". The combination of movements at all joints can be modeled as a single, linear element cap ...

. A short transverse furrow is slightly displaced towards the back, opposite the center line of the segment. *The third and fourth regions bear the second and third pairs of legs. Here there are also shorter transverse furrows on the back, which run out laterally to the legs. They are shifted forward against the center line of the segment. *In the fifth region there is a transverse furrow on the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

, which runs out slightly laterally on the back line. The length ratio of the segments 2 to 5 is indicated as 1: 1.3: 1.3: 2. The legs are presumably telescopically retracted and each carry four unequally long claws arranged asymmetrically with respect to the middle of the leg. Other features, such as the structure of the stiletto apparatus or the mucous musculature, can not be recognized; Also the position of the sex opening (gonopore) with respect to the anus, which could have given further indications of the class belonging to the species, can not be ascertained.

Habitat

The origin of the present amber specimen is unknown. It was part of secondary sediment deposits on the lake shore of Cedar Lake, not far from the

Saskatchewan River The Saskatchewan River (Cree: , "swift flowing river") is a major river in Canada. It stretches about from where it is formed by the joining of the North Saskatchewan River and South Saskatchewan River just east of Prince Albert, Saskatchewan ...

outlet in the Canadian province of

. Observations suggest that the habitat of ''Beorn'' may have been a swamp-like wetland biotope. Another tardigrade specimen was identified in the same amber piece as ''Beorn''. It is much smaller than ''Beorn'', and is curled and notably shriveled. However, Cooper refrained from describing this individual in 1964 due to his inability to reliably determine its anatomical details. New imaging techniques developed since then allowed for later researchers to describe the smaller specimen in detail. It was named in 2024 as the new genus ''

''.

Classification

The affiliation of ''Beorn'' with the tardigrades is certain. Moreover, the species can even be assigned to one of the three modern classes - the absence of head structures such as cirri and clavae and back armoring suggests a placement within the

Eutardigrada Eutardigrada are a class of tardigrades (Tardigrada) without lateral appendages. Primarily freshwater bound, some species have secondarily gained the ability to live in marine environments ('' Halobiotus''). By cryptobiosis many species are able ...

. Within this class, ''Beorn leggi'' was originally placed in a separate family Beornidae. However, later studies based on more detailed imageing reinterpreted it as belonging to the

. To determine the relationships of ''Aerobius'' and ''Beorn'', Mapalo, Wolfe & Ortega-Hernández (2024) phylogenetically analyzed a combination of morphological features and

rRNA Ribosomal ribonucleic acid (rRNA) is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes. Ribosomal RNA is transcribed from ribosomal ...

sequences. They recovered these taxa as closely related members of the tardigrade family Hypsibioidea. These results are displayed in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below, with extinct species designated with a dagger ():

References

{{Taxonbar, from1=Q818582, from2=Q18520266, from3=Q20020090 Parachela (tardigrade) †Beorn (tardigrade) Fossil taxa described in 1964 Campanian genera Canadian amber