''Buenellus higginsi'' is an average size (about )

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

, which lived during the

Lower Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eight ...

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

period, in what is now North-West

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

. It is a prominent member of the

Sirius Passet Sirius Passet is a Cambrian Lagerstätte in Peary Land, Greenland. The Sirius Passet Lagerstätte was named after the Sirius sledge patrol that operates in North Greenland. It comprises six places in Nansen Land, on the east shore of J.P. Koch F ...

fauna. ''Buenellus higginsi'' is the only known species in the genus ''Buenellus'' (i.e., the genus is

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

Etymology

The genus name is a contraction of Buen, from the formation in which it was first collected, and ''

Olenellus ''Olenellus'' is an extinct genus of redlichiid trilobites, with species of average size (about long). It lived during the Botomian and Toyonian stages (''Olenellus''-zone), , in what is currently North-America, part of the palaeocontinent Lau ...

'', a somewhat related trilobite genus. The species

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

honors A. Higgins, who discovered the Sirius Passet ' in 1984 during the Geological Survey of Greenland.

Description

The general outline of the body is rounded n the front third, parallel sided in the middle third, and progressively tapering backwards in the back third, ending at an angle of approximately 45° with the midline. The headshield (or cephalon is approximately ⅝× as long as it is wide. The (in this case only slightly) vaulted central axis of the head or

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

tapers gently forward and does not reach the anterior margin. The outer backside of the cephalon (or genal angle) has short genal spines. The

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

has 17 or 18 articulating segments, maintaining width or widening slightly backwards up to the 8th segment, then tapering posteriorly. The posterior segment may be fused with the anterior part of a simple and small

pygidium The pygidium (plural pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compo ...

. Pleural spines are short, and the pleural regions are only slightly wider than the axis.

Differences with other Nevadiidae

The general shape of the body of other species in the Nevadid family (like ''

Nevadia ''Nevadia'' is an extinct genus of trilobites, fossil marine arthropods, with species of average size (about long). It lived during the Atdabanian stage, which lasted from 530 to 524 million years ago, in what are today Western Canada, the West ...

'' and '' Nevadella'') is shorter, with the greatest width across the back of the cephalon, and the entire thorax tapering backwards.

Distribution

''Buenellus higginsi'' has been collected from early to middle

Atdabanian Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approx ...

deposits at the lower

Buen Formation The Buen Formation is a geologic formation and Lagerstätte in Peary Land, North Greenland. The shale preserves fossils dating back to the Early Cambrian period (Atdabanian in the local timescale, about 520 to 513 Ma).

(“Nevadella” Zone),

lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These for ...

at its junction with the J. P. Koch Fjord, Peary Land, Greenland . It has also been reported from

Novaya Zemlya Novaya Zemlya (, also , ; rus, Но́вая Земля́, p=ˈnovəjə zʲɪmˈlʲa, ) is an archipelago in northern Russia. It is situated in the Arctic Ocean, in the extreme northeast of Europe, with Cape Flissingsky, on the northern island, ...

, Russian Republic.

Ecology

Mineral-filled gut tracts in ''B. higginsi'' suggest they were not filled with sediment at the time of burial, and that the species was a

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

of soft prey. Healed injuries, some of which are the result of unsuccessful predaceous attacks, are not uncommon in ''B. higginsi''. Carnivory on ''B. higginsi'' is also implied by the remains of

anomalocaridid Radiodonta is an extinct order of stem-group arthropods that was successful worldwide during the Cambrian period. They may be referred to as radiodonts, radiodontans, radiodontids, anomalocarids, or anomalocaridids, although the last two origi ...

s and other potential predators. Other exoskeletons show evidence of post-mortem disruption, perhaps because of scavenging. ''Buenellus higginsi'', one of the earliest known trilobites from

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although ...

, seems to have played an important role in the Sirius Passet ecosystem, serving both as predator on, and prey for, contemporary animals.

Habitat

''Buenellus higginsi'' was probably a marine bottom dweller, that lived in deeper water. This may be deduced from the dominance of eyeless forms and the absence of seaweeds at the collection site.

Soft tissue preservation

Many specimens of ''B. higginsi'' show some form of exceptionally preserved, non-biomineralised tissue. Structures interpreted as alimentary tracts and probable digestive glands are commonly preserved. The slender antennas are rarely preserved.

References

External links

* {{Taxonbar, from1=Q4985496, from2=Q18607686 Olenellina Prehistoric arthropod genera Cambrian trilobites Cambrian Greenland Fossils of Greenland Sirius Passet fossils Fossil taxa described in 1988