''Wanneria'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

from a well-known class of

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

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chiti ...

s, the

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 ...

s. It lived during the later part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the Cambrian Period. ''Wanneria walcottana'' is the only known species in this genus (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 "unispe ...

Description

As with most early trilobites, ''Wanneria walcottana'' has an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As part of the Olenellina suborder, ''Wanneria'' 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 central area of the cephalon, that is called

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 ...

. The dorsal exoskeleton of ''Wanneria'' has an inverted egg shaped outline, approximately 1½ times longer than wide, ignoring the pleural spines, and is at its widest at the back of the cephalon. The horizontal outline of the head (or cephalon) is semi-circular with the back (or posterior margin) perpendicular to the midline or somewhat arching backwards. The L4 is wider than the other lobes, and touches the raised ridge (or anterior border) at the front of the cephalon. The right and left furrow (S1) between the first (L1) and second (L2) pair of side lobes (counted from the back of the cephalon) do not join across the midline, and angle forwards from the middle to the side. The sickle shaped eyes are attached to the back of L4 and extend backwards to the most backward set of side-lobes of the glabella (or L1). The rim of the cephalon is extended into backward pointing genal spines, that reach back to approximately the 4th thorax segment. Its body (or

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 segments, with nodes on thorax segments 1 to 14, and a short spine on segment 15 that is at its base about ¼ as wide as the axis. The axis is about ¼ as wide as the thorax. Unlike in the majority of the Olenelloidea, in ''Wanneria'' thorax segment 3 is not macro-pleural, but equal in size and shape to neighboring segments. Pleural spines slightly arched backwards, extending sideward in the most frontal thorax segments, but gradually more backward and eventually even arching slightly inward in segment 17.

Distribution

''Wanneria walcottana'' occurs in the middle Upper ''Olenellus''-zone of Pennsylvania (Kinzers Formation, road metal quarry and walls of demolished tenant house on Noah L. Getz farm, on Harrisburg Pike, 1 mile (1.6 km) north of Rohrerstown, about 2.5 miles (4 km) west of Lancaster, Lancaster County, ), of Nevada (Harkless Formation, North-East of Goldpoint, Dyeran, Esmeralda County, ), Mexico (Buelna Formation, Cerro Rajon, Caborca Region, ) and of Greenland.

Taxonomy

Relationship within the Olenellidae

''Wanneria walcottana'' is close to the common ancestor of the

Holmiidae Holmiidae is a family of trilobites, that lived during the Lower Cambrian (Atdabanian). The Holmiidae is a diverse family of eight genera containing at least 17 species. It includes some of the earliest trilobites of Baltica. Holmiidae occur thro ...

, and of the clade comprising '' Fritzolenellus'', '' Mummaspis'', '' Laudonia'', the Biceratopsinae and the Bristoliinae. So far,

cladistic analysis Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived chara ...

could not determine which two of these groups are closer. This large group together is the sister group to '' Elliptocephala''.

Species previously assigned to ''Wanneria''

* ''W. halli'' = '' Fremontella halli'' * ''W. jaquetti'' p. 74-75, pl. VI, fig. 5 = '' Neltneria jaquetti'' * ''W. jaquetti'' p. 74-75, pl. VI, fig. 1-4 = '' Bondonella typica'' * ''W. logani'' = '' Elliptocephala logani'' * ''W. lundgreni'' = '' Elliptocephala lundgreni'' * ''W. macer'' = '' Mummaspis macer'' * ''W. mediocris'' = '' Elliptocephala mediocris'' * ''W. mexicana prima'' = '' Lochmanolenellus mexicana'' * ''W. occidens'' = '' Mummaspis occidens'' * ''W. mirabilis'' = '' Elliptocephala mirabilis'' * ''W. parvifrons'' = '' Elliptocephala parvifrons'' * ''W. ruginosa'' = ''Elliptocephala mediocris'' * ''W. subglabra'' = ''Elliptocephala mediocris'' * ''W. troelseni'' = ''Elliptocephala mediocris'' * ''W. walcottanus'' = ''Mummaspis macer''

References

{{Taxonbar, from=Q3169659 Cambrian trilobites Cambrian trilobites of North America Paleozoic life of Newfoundland and Labrador Olenelloidea Cambrian genus extinctions