''Wanneria'' 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 from a well-known class of fossil marine arthropods, the trilobites. 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 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 ...

. ''Wanneria walcottana'' is the only known species in this genus (i.e. the genus is monotypic).

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 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 Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont Company. Baldino s ...

) 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) 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, and of the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

comprising ''

Fritzolenellus ''Fritzolenellus'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites, with three known species. It lived during the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million year ...

'', ''

Mummaspis ''Mummaspis'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites, with five known species. It lived during the early part of the Botomian stage, which lasted from approximately 524 to 518.5 million years ago. T ...

'', ''

Laudonia ''Laudonia'' is an extinct genus of trilobites that lived during the early 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 The Cambrian Period ( ; ...

'', the

Biceratopsinae The Biceratopsinae is an extinct subfamily of redlichiid trilobites within the family Biceratopsidae, with species of small to average size. Species belonging to this subfamily lived during the Toyonian stage (Upper ''Olenellus''-zone), 516-513 ...

and the

Bristoliinae The Bristoliinae is an extinct subfamily of trilobites, fossil marine arthropods, with species of small to average size. Species belonging to this subfamily lived during the Botomian and Toyonian stage (''Olenellus''-zone), 522-513 million years ...

. So far, cladistic analysis could not determine which two of these groups are closer. This large group together is the sister group to ''

Elliptocephala ''Elliptocephala'' is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived from the later part of the Tommotian ( upper ''Schmidtiellus mickwitzi''-zone) to the upper Botomian ( early middle ''Olenellus' ...

''.

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