''Bolbolenellus'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

trilobites 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 ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

marine

arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

, with five species attributed to it currently. It can be easily distinguished from all other trilobites by the combination of the absence of dorsal sutures in the head shield like all

Olenellina Olenellina is a suborder of the order Redlichiida of trilobites that occurs about halfway during the Lower Cambrian, at the start of the stage called the Atdabanian. The earliest trilobites in the fossil record are arguably Olenellina, although ...

(which in all other trilobite suborders assist in moulding by splitting open), and a distinctly bulbous frontal lobe (L4) of the raised axial area in the head (or cephalon) called glabella. The species lived at the end of the

Lower Cambrian The Cambrian Period ( ; sometimes symbolized 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 years ago (m ...

Etymology

''Bolbolenellus'' is the combination of Greek (, “plant with round swelling on underground stem”), 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 ...

'', the rather distantly related genus to which all of the species were previously assigned. This refers to the bulb-like swelling of the frontal lobe of the glabella. The names of the species have the following derivations. * ''B. altifrons'' from the Latin altus (“high”) and from Latin frons (“forehead”), to express the species has a bulbous frontal glabellar lobe. * ''B. brevispinus'' from brevis the Latin word for "short" and spinus the Latin word for "spine". * ''B. groenlandicus'' is named for Greenland, where the species occurs. * ''B. sphaerulosus'' from the Latin sphaerula (small ball).

Description

As with most early trilobites, ''Bolbolenellus'' has an only thinly calcified

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

. Although most of the body is rather flat, the frontal lobe (L4) of the central area of the cephalon (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 ...

) is prominent, bulbous (or subglobular), and may overlap the border at the front in dorsal view. It also shares crescent-shaped eye ridges, but these rise above the exoskeleton. As part of the Olenellina suborder, '' Bolbolenellus '' lacks dorsal sutures. Like all other members of the Olenelloidea superfamily, the eye-ridges spring from the back of the frontal lobe (L4) of the glabella. The posterior margin of cephalon is nearly straight or angles to the front (anterolaterally) on the outside of the intergenal spine or intergenal angle. The short genal spine protrudes opposite or posterior to the most backward side lobe of the glabella (or L1). There may be an intergenal spine. The frontal lobe of the glabella touches the border of the cephalon (or the preglabellar field is absent). The most backward tips of eye ridges (or ocular lobes) are approximately opposite occipital furrow. Although the third

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 ...

) segment (or T3, this is counted from the headshield to the tailshield) has strongly enlarged side lobes (or pleurae), the spine on their end is not much enlarged compared to the spines of neighboring segments. The 14th segment carries an backward pointing axial spine that is approximately as long as the thorax axis. There seems to be no opistothorax.

Differences with some other Biceratopsinae

Most other Biceratopsinae, i.e. '' Biceratops nevadensis'', '' Emigrantia'' and '' Peachella'' and to a lesser extend '' Eopeachella'' have effaced cephalic features. ''Biceratops'' lacks genal spines. In ''Emigrantia'' the genal spines are longer than the cephalon and attach halfway down its side (or lateral margin). ''Peachella'' has club-like genal spines. In ''Nephrolenellus'' the eye ridges extend outwards, the second pair of side lobes of the glabella are very narrow, the genal spines attach further to the front of the cephalon, T3 carries massive pleural spines, the axial spine on T14 is absent, and there is a prominent opistothorax.

Relations with other Biceratopsinae

The closest relative of the six species of ''Bolbolenellus'' is the genus ''Nephrolenellus''. The other genera of the Biceratopsinae (''Biceratops'', ''Emigrantia'', ''Eopeachella'', ''Peachella'', and ''Olenelloides'') constitute the sister group.

Distribution

* ''B. euryparia'' is present in the Upper Olenellus-zone of California (lower half of the ''B. euryparia''-subzone of the Carrara Formation, Eagle Mountain, White-Inyo Mountains, and the middle part of the Latham Shale, East slope of hill 1440 in the southern end of the Marble Mountains, San Bernardino County). * ''B. altifrons'' occurs in the Middle ''Olenellus''-zone of the Northwest Territories (type section of the

type section A stratotype or type section in geology is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the stan ...

of the Sekwi Formation, 0.2 miles Southeast of June Lake, Mackenzie Mountains). * ''B. brevispinus'' has been collected in the Upper Olenellus-zone of Nevada (near Oak Spring Summit, Pioche Formation, Lincoln County). * ''B. groenlandicus'' is found in Northwestern Greenland, questionably from the Upper ''Olenellus''-zone (Wulff River Formation, Marshall Bugt,

Inglefield Land Inglefield Land is an unglaciated area along the northwestern coast of Greenland. It was named after English explorer Edward Augustus Inglefield. History Inglefield Land is noted for its archaeological sites, which show evidence of occupation by ...

). * ''B. hermani'' occurs in the Upper ''Olenellus''-zone of Vermont (Monkton Quartzite, near Clay and Red Rock Points on

Lake Champlain , native_name_lang = , image = Champlainmap.svg , caption = Lake Champlain-River Richelieu watershed , image_bathymetry = , caption_bathymetry = , location = New York/Vermont in the United States; and Quebec in Canada , coords = , type = , ...

, and Parker Slate, 2 miles west of Georgia Centre), of California (White, Inyo Mountain region) * ''B. sphaerulosus'' has been collected in the ''Olenellus''-zone of the Yukon Territory, Canada (Unit 6 of the Upper Illtyd Formation, Wernecke Mountains).

Habitat

''Bolbolenellus'' was probably a marine bottom dweller, like all Olenellina.

References

External links

Oblique picture of Bolbolenellus brevispinus

picture of Bolbolenellus brevispinus from a dorsal point of view
{{Taxonbar, from=Q4939012 Redlichiida genera Biceratopsidae Cambrian trilobites Extinct animals of North America