''Mosura fentoni'' () is an extinct species of

hurdiid Hurdiidae (synonymous with the previously named Peytoiidae) is an extinct cosmopolitan distribution, cosmopolitan Family (biology), family of radiodonts, a group of Crown group#Stem groups, stem-group marine arthropods, which lived during the Pal ...

radiodont Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. Radiodonts are distinguished by their distinctive frontal appendages, which are morphologically diverse and were used for a variety ...

from 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 ...

Burgess Shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fos ...

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

, Canada. ''F. fentoni'' is the only species in the genus ''Mosura'', and is known from sixty specimens collected between 1990 and 2022.

Discovery and naming

''Mosura fentoni'' is known from sixty specimens. 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 ...

, ROMIP 67995 preserves a complete individual in dorsal view. Other notable specimens are ROMIP 66108, ROMIP 67998, ROMIP 68004, ROMIP 67999, and ROMIP 67979, which all preserve internal organs. The specimens were discovered in the Raymond Quarry and Marble Canyon localities within the

from 1990 to 2022, with the majority being placed in the invertebrate paleontology collection of the

Royal Ontario Museum The Royal Ontario Museum (ROM) is a museum of art, world culture and natural history in Toronto, Ontario, Canada. It is one of the largest museums in North America and the largest in Canada. It attracts more than one million visitors every year ...

(ROMIP). 2025, Moysiuk & Caron described ''Mosura fentoni'' as a new genus and species of radiodont based on these fossil remains. The generic name, ''Mosura'' (), is named after

Mothra is a fictional monster, or '' kaiju'', which first appeared as the title character in Ishirō Honda's '' 1961 film of the same name'', produced and distributed by Toho. Mothra has appeared in several Toho ''tokusatsu'' films, often as a recur ...

(モスラ, ''Mosura'') a moth-like

kaiju is a Japanese term that is commonly associated with media involving giant monsters. Its widespread contemporary use is credited to ''tokusatsu'' (special effects) director Eiji Tsuburaya and filmmaker Ishirō Honda, who popularized the ''kaiju'' ...

monster featured in films by the Japanese company

Toho is a Japanese entertainment company that primarily engages in producing and distributing films and exhibiting stage plays. It is headquartered in Chiyoda, Tokyo, and is one of the core companies of the Osaka-based Hankyu Hanshin Toho Group. ...

. The name was chosen for ''M. fentoni'' in reference to the animal's moth-like appearance. The name was romanized according to Hepburn style. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''fentoni'' (), honours Peter E. Fenton and his work as a technician in the Royal Ontario Museum Invertebrate Palaeontology section, and for his unwavering friendship to both authors.

Description

File:Moysiuk & Caron 2025 f07 (fig 7a).png,

Paleoart Paleoart (also spelled palaeoart, paleo-art, or paleo art) is any original artistic work that attempts to depict prehistoric life according to scientific evidence. Ansón, Fernández & Ramos (2015) pp. 28–34. Works of paleoart may be represen ...

File:Moysiuk & Caron 2025 f07 (fig 7b-d).png, Diagrammatic reconstruction File:20250526 Mosura size.png, alt=, Size estimation File:Moysiuk & Caron 2025 f07 (fig 7e-i).png, Reconstruction of frontal appendage ''Mosura'' is known from specimens ranging in length from , making this taxon one of the smallest radiodonts known. The head has three eyes: a pair of eyes on short stalks and a

median The median of a set of numbers is the value separating the higher half from the lower half of a Sample (statistics), data sample, a statistical population, population, or a probability distribution. For a data set, it may be thought of as the “ ...

(midline of the head) eye. The body is divided into 26 segments, the highest number found in any radiodont. The primary body sections are the head, the four-segmented neck, and the trunk. The trunk is divided into the

anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

(toward the front) six-segmented mesotrunk, and posterior (toward the back) posterotrunk, which has at most 16 segments. Like other radiodonts, the body bears pairs of swimming flaps, which are considerably larger on the mesotrunk than on the posterotrunk. The gills are very large compared to body size. ''Mosura'' is one of four radiodont taxa with known juvenile fossils (the other three being ''

Lyrarapax unguispinus '' Lyrarapax'' is a radiodont genus of the family Amplectobeluidae that lived in the early Cambrian period 518 million years ago. Its fossils were found in the Maotianshan Shales of China. The first species, ''Lyrarapax unguispinus'' was describe ...

'', ''

Amplectobelua symbrachiata ''Amplectobelua'' (meaning "embracing beast") is an extinct genus of late Early Cambrian amplectobeluid radiodont, a group of stem arthropods that mostly lived as free-swimming predators during the first half of the Paleozoic Era. Anatomy '' ...

,'' and ''

Stanleycaris hirpex ''Stanleycaris'' ("Stanley's shrimp") is an extinct genus of hurdiid radiodont from the Cambrian (Stage 3 to Miaolingian). The type species is ''Stanleycaris hirpex''. ''Stanleycaris'' was described from the Stephen Formation near the Stanley Gla ...

''). The juveniles in ''Mosura'' are distinguished by fewer segments in the posterotrunk, and possibly mesotrunk. An increase in total segment number during ontogeny (hemianamorphosis) is consistent with previous observations in ''Stanleycaris''. Moysiuk and Caron (2025) noted that an increase in mesotrunk segment number implies that some posterotrunk segments would have differentiated during ontogeny, incorporating with the mesotrunk. They note that this is uncommon, but not unprecedented, as this has been observed in other

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

groups, such as the

fuxianhuiid Fuxianhuiida is an extinct clade of arthropods from the Cambrian of China. All currently known species are from Cambrian Series 2 aged deposits in Yunnan Province, including the Chengjiang biota. Although historically suggested to be members of t ...

Fuxianhuia ''Fuxianhuia'' is a genus of Lower Cambrian fossil arthropod known from the Chengjiang fauna in China. Its purportedly primitive features have led to it playing a pivotal role in discussions about the euarthropod stem group. Nevertheless, despite ...

''.

Classification

''Mosura'' has a mixture of traits known from other basal hurdiids and non-hurdiids (elongate and multisegmented body, short head, distinct and constricted neck region, and small rounded H-element), traits

apomorphic In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

to Hurdiidae (single row of six elongate and mesially/toward the body midline curving endites on the frontal appendages), traits shared by other hurdiids (inner plates in the oral cone, tetraradial arrangement of the oral plates, absence of posterior auxiliary spines on the frontal appendage endites), and derived traits (median eye, specialised respiratory tagma). It is not known whether the median eye in this taxon was

compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive struc ...

or if it had a single lens, however Moysiuk and Caron (2025) favor the single lens theory, pointing to similarities between it, and the potentially homologous median eyes seen in

crown-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

euarthropods. Similar to ''Stanleycaris'', this taxon seemingly lacks lateral sclerites (formally known as P-elements), a trait only seen within hurdiidae between the two genera. In their

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

, Moysiuk and Caron (2025) recovered ''Mosura'' as a basal (early-diverging)

in the family

Hurdiidae Hurdiidae (synonymous with the previously named Peytoiidae) is an extinct cosmopolitan distribution, cosmopolitan Family (biology), family of radiodonts, a group of Crown group#Stem groups, stem-group marine arthropods, which lived during the Pal ...

, finding it to be

sister A sister is a woman or a girl who shares parents or a parent with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to ref ...

to all other hurdiids. Radiodonts are a diverse and long-lasting order of lower

Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...

marine

panarthropods Panarthropoda is a clade comprising the greatest diversity of animal groups. It contains the extant phyla Arthropoda (Euarthropoda), Tardigrada (water bears) and Onychophora (velvet worms), although the precise relationships among these remained ...

. The results reproduced 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 are based on their pruned maximum clade credibility tree, they also produced a majority rule consensus tree where ''Mosura'' was found to be in a

polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...

with ''

Stanleycaris ''Stanleycaris'' ("Stanley's shrimp") is an extinct genus of hurdiid radiodont from the Cambrian (Stage 3 to Miaolingian). The type species is ''Stanleycaris hirpex''. ''Stanleycaris'' was described from the Stephen Formation near the Stanley Gl ...

'', ''

Schinderhannes Johannes Bückler ( 177821 November 1803; ) was a German outlaw who orchestrated one of the most famous crime sprees in German history. He has been nicknamed Schinderhannes and Schinnerhannes () in German and John the Scorcher, John the Flayer ...

'', ''

Peytoia ''Peytoia'' is a genus of hurdiid radiodont, an early diverging order of stem-group arthropods, that lived in the Cambrian period, containing two species, ''Peytoia nathorsti'' from the Miaolingian of Canada and '' Peytoia infercambriensis'' fr ...

'' and the clade formed by ''

Aegirocassis ''Aegirocassis'' is an extinct genus of giant radiodont arthropod belonging to the family Hurdiidae that lived 480 million years ago during the early Ordovician in the Fezouata Formation of Morocco. It is known by a single species, ''Aegirocassis ...

'' and Hurdiinae. ''Mosura'' is one of three basal hurdiid

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

that show a mixture of traits expected from hurdiids and non-hurdiids, the others being ''Stanleycaris'' (the only other radiodont taxon currently known with a median eye) and ''Schinderhannes''. Regarding the specialised respiratory tagma, the authors speculate that they were—in conjunction with the reduced size—an adaptation for the oxygen-stressed environments that were proximal to the site of burial. However, while they find it unlikely, they could have been an adaptation to distinct behavioural traits such as the proposed nektobenthic sediment-sifting macropredatory ecology proposed for most hurdiids.

Ecology

''Mosura'' is interpreted as an actively swimming (

nektonic Nekton or necton (from the ) is any aquatic organism that can actively and persistently propel itself through a water column (i.e. swimming) without touching the bottom. Nektons generally have powerful tails and appendages (e.g. fins, pleopods ...

) predator of prey relatively large compared to its body size. Its large gills despite its small body size suggests it may have inhabited low oxygen environments such as the

outer continental shelf The Outer Continental Shelf (OCS) is a legally defined geographic feature of the United States. The OCS is the part of the internationally recognized continental shelf of the United States which does not fall under the jurisdictions of the ind ...

. This taxon was most likely a highly maneuverable swimmer, with Moysiuk and Caron (2025) suggesting the median eye in this hurdiid functioned similarly to those seen in modern odonates (specifically

dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...

), and would have helped the radiodont maintain its orientation when chasing fast moving prey.

References

External links

Mosura fentoni, a 2.5-inch radiodont found in the Burgess Shale of Canada

New York Times ''The New York Times'' (''NYT'') is an American daily newspaper based in New York City. ''The New York Times'' covers domestic, national, and international news, and publishes opinion pieces, investigative reports, and reviews. As one of ...

, May 13, 2025 {{Taxonbar, from=Q134466259 Fossil taxa described in 2025 Radiodonta Burgess Shale fossils

Discovery and naming

Description

Classification

Ecology

See also

References

External links