Beorn Temporal range: Late Cretaceous, | |
---|---|
Holotype specimen under various imaging techniques | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Tardigrada |
Class: | Eutardigrada |
Order: | Parachela |
Family: | Hypsibiidae |
Genus: | † Beorn Cooper, 1964 |
Species: | †B. leggi |
Binomial name | |
†Beorn leggi Cooper, 1964 | |
Beorn is an extinct genus of tardigrade and the first known fossil tardigrade, discocered in Late Cretaceous amber from Manitoba, Canada. 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. [1] [2] [3]
It is one of three fossil tardigrades known from the Cretaceous, the others being Milnesium swolenskyi from the Turonian New Jersey amber and Aerobius from the same amber piece as Beorn. [4] The only other confidently known fossil tardigrade is the Miocene Paradoryphoribius from the Dominican Republic. [5]
In addition to some other finds from the Cretaceous and the Cambrian period, Beorn is an example of the early existence of tardigrades in earth's history, and its largely modern appearance suggests that tardigrades must have diversified considerably before this time.
William M. Legg collected the amber in the summer of 1940 in which the holotypes of both Beorn and Aerobius were found. [4] He died in 1953 before finishing his thesis at Princeton University.
Kenneth W. Cooper, Legg's friend and scientific mentor, named Beorn leggi after him in 1964. [6] The type specimen is now in the Museum of Comparative Zoology at Harvard University.
The generic name Beorn was chosen by Cooper in reference to a character of the same name from the children's book The Hobbit by J. R. R. Tolkien, 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.
The holotype 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. [1]
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 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.
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 outlet in the Canadian province of Manitoba. Observations suggest that the habitat of Beorn may have been a swamp-like wetland biotope.[ citation needed ]
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 Aerobius . [4]
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. 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 Hypsibiidae. [7] [4]
To determine the relationships of Aerobius and Beorn, Mapalo, Wolfe & Ortega-Hernández (2024) phylogenetically analyzed a combination of morphological features and rRNA sequences. They recovered these taxa as closely related members of the tardigrade family Hypsibioidea. These results are displayed in the cladogram below, with extinct species designated with a dagger (†): [4]
Opabinia regalis is an extinct, stem group arthropod found in the Middle Cambrian Burgess Shale Lagerstätte of British Columbia. Opabinia was a soft-bodied animal, measuring up to 7 cm in body length, and its segmented trunk had flaps along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a clawed proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed, where they constitute less than 0.1% of the community.
Panarthropoda is a proposed animal clade containing the extant phyla Arthropoda, Tardigrada and Onychophora. Panarthropods also include extinct marine legged worms known as lobopodians ("Lobopodia"), a paraphyletic group where the last common ancestor and basal members (stem-group) of each extant panarthropod phylum are thought to have risen. However the term "Lobopodia" is sometimes expanded to include tardigrades and onychophorans as well.
Myxophaga is the second-smallest suborder of the Coleoptera after Archostemata, consisting of roughly 65 species of small to minute beetles in four families. The members of this suborder are aquatic and semiaquatic, and feed on algae.
Dominican amber is amber from the Dominican Republic derived from resin of the extinct tree Hymenaea protera.
The Stephanidae, sometimes called crown wasps, are a family of parasitoid wasps. They are the only living members of the superfamily Stephanoidea. Stephanidae has at least 345 living species in 11 genera. The family is considered cosmopolitan in distribution, with the highest species concentrations in subtropical and moderate climate zones. Stephanidae also contain four extinct genera described from both compression fossils and inclusions in amber.
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1964.
Sphecomyrma is an extinct genus of ants which existed in the Cretaceous approximately 79 to 92 million years ago. The first specimens were collected in 1966, found embedded in amber which had been exposed in the cliffs of Cliffwood, New Jersey, by Edmund Frey and his wife. In 1967, zoologists E. O. Wilson, Frank Carpenter and William L. Brown, Jr. published a paper describing and naming Sphecomyrma freyi. They described an ant with a mosaic of features—a mix of characteristics from modern ants and aculeate wasps. It possessed a metapleural gland, a feature unique to ants. Furthermore, it was wingless and had a petiole which was ant-like in form. The mandibles were short and wasp-like with only two teeth, the gaster was constricted, and the middle and hind legs had double tibial spurs. The antennae were, in form, midway between the wasps and ants, having a short first segment but a long flexible funiculus. Three additional species, S. canadensis, S. mesaki and S. nexa, were described in 1985, 2005, and 2024, respectively.
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 Kleiner Wasserbär'little water bear'. In 1776, the Italian biologist Lazzaro Spallanzani named them Tardigrada, which means 'slow steppers'.
Parachela is an order of tardigrades in the class Eutardigrada. Members of this order have existed for at least 72 million years, up to the present. The oldest known species are Beorn leggi and Aerobius dactylus.
Diania is an extinct genus of lobopodian panarthropod found in the Lower Cambrian Maotianshan shale of China, represented by a single species - D. cactiformis. Known during its investigation by the nickname "walking cactus", this organism belongs to a group known as the armoured lobopodians, and has a simple worm-like body with robust, spiny legs. Initially, the legs were thought to have a jointed exoskeleton and Diania was suggested to be evolutionarily close to early arthropods, but many later studies have rejected this interpretation.
Myanmymar is an extinct genus of fairyfly preserved in Burmese amber from Myanmar. It has only one species, Myanmymar aresconoides. It is dated to the earliest part of the Cenomanian stage of the Late Cretaceous, around 99 million years old. As of 2011, it is the oldest known fossil mymarid.
Tactopoda or Arthropodoidea is a proposed clade of ecdysozoan animals that includes the phyla Tardigrada and Euarthropoda, supported by various morphological observations. The cladogram below shows the relationships implied by this hypothesis.
Brownimecia is an extinct genus of ants, the only genus in the tribe Brownimeciini and subfamily Brownimeciinae of the Formicidae. Fossils of the identified species, Brownimecia clavata and Brownimecia inconspicua, are known from the Late Cretaceous of North America. The genus is one of several ants described from Late Cretaceous ambers of New Jersey. Brownimecia was initially placed in the subfamily Ponerinae, until it was transferred to its own subfamily in 2003; it can be distinguished from other ants due to its unusual sickle-like mandibles and other morphological features that makes this ant unique among the Formicidae. B. clavata is also small, measuring 3.43 millimetres (0.135 in), and a stinger is present in almost all of the specimens collected. The morphology of the mandibles suggest a high level of feeding specialization.
Myanmyrma is an extinct genus of ants not placed into any Formicidae subfamily. Fossils of the single known species, Myanmyrma gracilis, are known from the Middle Cretaceous of Asia. The genus is one of several ants described from Middle Cretaceous ambers of Myanmar.
Anbarrhacus is an extinct genus of millipede in the family Platyrhacidae known from a fossil found in North America. There is one described species in the genus, Anbarrhacus adamantis, which is one of three millipedes described from Mexican amber.
Gerontoformica is an extinct genus of stem-group ants. The genus contains thirteen described species known from Late Cretaceous fossils found in Asia and Europe. The species were described between 2004 and 2016, with a number of the species formerly being placed into the junior synonym genus Sphecomyrmodes.
Baikuris is an extinct genus of ant in the Formicidae subfamily Sphecomyrminae, and is currently placed in the tribe Sphecomyrmini. The genus contains four described species: the type species Baikuris mandibularis, along with Baikuris casei, Baikuris maximus, Baikuris mirabilis, B. ocellantis.
Milnesium swolenskyi is a species of tardigrade from the Cretaceous period. It, Beorn and Paradoryphoribius are the only known tardigrade genera in the fossil record. The type specimen AMNH NJ-796 was found in Turonian New Jersey amber, from about 93.9 to 89.8 million years ago (mya).
Paradoryphoribius is an extinct genus of tardigrades from the order Parachela. It is the third fossil tardigrade to be named, described in 2021 from Miocene Dominican amber from the Dominican Republic. The type, and currently only species, is P. chronocaribbeus.
Aerobius is a genus of extinct tardigrades 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 the same piece of Late Cretaceous amber as Beorn, another extinct tardigrade. The specimen was found near Cedar Lake in Manitoba, Canada.