''Lochmanolenellus'' 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 one small species, ''L. mexicana''. It lived during the

Botomian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission on ...

stage (''Olenellus''-zone), 522–513 million years ago, in the South-West of the former continent of

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, althoug ...

, in what are today Mexico, and the South-Western United States.

Etymology

''Lochmanolenellus'' is named in honor of C. Lochman, who initially described the fossils that are assigned to this genus, and for its likeness to ''

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 distantly related genus. The species

epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...

''mexicana'' refers to Mexico, where the first specimen was found.

Taxonomy

''L. mexicana'' was first described as ''Wanneria mexicana prima''. There are however so many differences, that it is highly unlikely ''L. mexicana'' is more than distantly related. Later scholars assigned the species to ''Laudonia''. Although ''Laudonia'' is much more related than ''Wanneria'', ''L. mexicana'' must be considered an early representative of the subfamily Bristoliina, that further includes a handful species of the genus ''Bristolia'' and ''Fremontella halli''.

Description

The headshield (or cephalon) is not semi-circular but near pentangular, about 1¼ times wider than long. The front has a blunt angle at midline. The most frontal spines (or genal spines) are prominent, pointing backwards and outwards at about 65° compared to the midline. The genal angle (between the back of the spine and the cephalic border to the rear of the spine) is opposite the furrow between L2 and L3 – the scientific convention is to count glabellar lobes back to front, giving them the following names: occipital ring or lobe (OR, OL or L0), 1st lobe (L1), 2nd lobe (L2), 3rd lobe (L3), and anterior lobe (AL or L4). The base of the genal spine is equally far from the midline as the base of the intergenal angle. The most backwards spines (or intergenal spines) are prominent too, pointing backwards and outwards at about 45° compared to the midline. The intergenal angle is opposite the middle of the occipital ring (L0). The rounded ridge that borders the cephalon (or cephalic border) and the frontal lobe (L4) of the raised central part 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 ...

) touch. L4 bulges out the plain where cephalon rests. L4 is wider than the rearmost ring of the glabella (L0); L4 has the same length of L0 and L1 together. The eye-lobe (or ocular lobe) is stocky, reaching no further back than the furrow between L2 and L3. The medial part of posterior border flexing gently backwards.

Distribution

''L. mexicana'' occurs in the Lower Cambrian, (lower ''Olenellus''-zone,

) (Puerto Blanco Formation, west side of Proveedora Hills, 7 miles west of Caborca, Sonora, Mexico). It has also been collected in the Lower Cambrian, lower ''Olenellus''-zone (upper part of the Poleta Formation,

White White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White on ...

–

Inyo Mountains The Inyo Mountains are a short mountain range east of the Sierra Nevada in eastern California in the United States. The range separates the Owens Valley to the west from Saline Valley to the east, extending for approximately south-southeast fro ...

Death Valley Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. During summer, it is the Highest temperature recorded on Earth, hottest place on Earth. Death Valley's Badwater Basin is the ...

Habitat

''Lochmanolenellus'' was probably marine bottom dweller, like all Olenellina.

References

{{Taxonbar, from=Q16984783 Cambrian trilobites Cambrian trilobites of North America Redlichiida genera Biceratopsidae Cambrian genus extinctions