Elliptocephala

{{distinguish|Ellipsocephalus}} {{Italic title}} {{Taxobox | name = ''Elliptocephala'' | fossil_range = late Lower Cambrian (Upper Tommotian to Upper Botonian) {{Geological range|531|518.5}} | regnum = Animalia | phylum = Arthropoda | classis = Trilobita | ordo = Redlichiida | superfamilia = Olenelloidea | familia = Wanneriidae | subfamilia = Wanneriinae | genus = '''''Elliptocephala''''' | genus_authority = Emmons, 1844 | subdivision_ranks = Species | subdivision = * ''E. asaphoides'' Emmons, 1844 (Type)<ref name='Lieberman 1999'>{{cite journal|last1=Lieberman |first1=B.S. |year=1999 |title=Systematic revision of the Olenelloidea (Trilobita, Cambrian) |journal=Bulletin of the Peabody Museum of Natural History |volume=45 |pages=1–150 |url=https://elischolar.library.yale.edu/peabody_museum_natural_history_bulletin/45/ }}</ref> * ''E. bicensis'' (Walcott, 1910)<ref name='Lieberman 1999'/> synonym ''Callavia bicensis'' * ''E. laxocules'' (Fritz, 1972)<ref name='Lieberman 1999'/> synonym ''Olenellus laxocules'' * ''E. logani'' (Walcott, 1910)<ref name='Lieberman 1999'/> synonyms ''Olenellus logani'', ''Wanneria logani'' * ''E. lundgreni'' (Moberg, 1892)<ref name='Lieberman 1999'/> synonyms ''Wanneria lundgreni'', ''Kjerulfia lundgreni'', ''Holmia lundgreni'' * ''E. mediocris'' (Poulsen, 1958)<ref name='Lieberman 1999'/> synonyms ''Wanneria mediocris'', ''W. ruginosa'', ''W. subglabra'', ''W. troelseni'' * ''E. mirabilis'' (Poulsen, 1958)<ref name='Lieberman 1999'/> synonyms ''Holmia mirabilis'', ''Wanneria mirabilis'' * ''E. paraoculus'' (Fritz, 1972)<ref name='Lieberman 1999'/> synonym ''Olenellus paraoculus'' * ''E. parvifrons'' (Fritz, 1972)<ref name='Lieberman 1999'/> synonym ''Wanneria parvifrons'' * ''E. praenuntius'' (Cowie, 1968)<ref name='Lieberman 1999'/> synonym ''Olenellus praenuntius '' * ''E. sequomalus'' (Fritz, 1972)<ref name='Lieberman 1999'/> synonym ''Olenellus sequomalus'' * ''E. walcotti'' Lieberman, 1999<ref name='Lieberman 1999'/> synonym ''Olenellus truemanni'' pro parte }}

'''''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''-zone). ''Elliptocephala'' can easily be confused with ''Ellipsocephalus'', a trilobite genus of the Ptychopariida order.

== Etymology == The species ''E. walcotti'' was named in honor of Charles Doolittle Walcott, a renowned early paleontologist, that described many trilobite species.<ref name='Lieberman 1999'/>

== Taxonomy ==

=== Relations within ''Elliptocephala'' === According to Lieberman<ref name='Lieberman 1999'/> ''E. sequomalus'' is an early species, close to the common ancestor of the genus. The rest of the species fall into two distinct groups. The first consists of the closely related ''E. bicensis'' and ''E. asaphoides'', with ''E. walcotti'' and twin species ''E. praenuntius'' slightly less close and ''E. mediocris'' near the basis of this group. The second group consisting of the closely related ''E. mirabilis'' and ''E. lundgreni'', with ''E. logani'' and ''E. parvifrons'' slightly further removed, followed by ''E. paraoculus'', and ''E. laxocules'' near the basis of this second group.

=== Relationship within the Olenelloidea === ''Elliptocephala'' is the sistergroup of the clade comprising ''Wanneria walcottana'', the Holmiidae, ''Fritzolenellus'', ''Mummaspis'', ''Laudonia'', the Biceratopsinae and the Bristoliinae. Including ''Elliptocephala'', this clade is the sistergroup of the Olenellidae.<ref name='Lieberman 1998'>{{cite journal|last=Lieberman |first=B.S. |year=1998 |title=Cladistic analysis of the Early Cambrian olenelloid trilobites |journal=Journal of Paleontology |volume=72 |issue=1 |pages=59–78 |doi=10.1017/S0022336000024021 |bibcode=1998JPal...72...59L |s2cid=86307339 }}</ref>

== Distribution == * ''E. asaphoides'' was collected in the Middle ''Olenellus''-zone of eastern New York State (Greenwich Formation). * ''E. bicensis'' is found in Quebec, Canada and believed to be from the ''Olenellus''-zone (limestone boulder found in a conglomerate that has probably formed during the Lower Ordovician). * ''E. laxocules'' occurs in the Middle ''Olenellus''-zone of the Northwest Territories (type section of the type section of the Sekwi Formation, 0.2 miles Southeast of June Lake, Mackenzie Mountains). * ''E. logani'' was excavated from the Middle ''Olenellus''-zone of the Northwest Territories (type section of the type section of the Sekwi Formation, 0.2 miles Southeast of June Lake, Mackenzie Mountains, and the Illtyd Formation, Wernecke Mountains). * ''E. lundgreni'' is present in * ''E. mediocris'' was collected in Northwestern Greenland, questionably from the ''Olenellus''-zone (Wulff River Formation, Marshall Bugt, Inglefield Land). * ''E. mirabilis'' is found in Northwestern Greenland, questionably from the ''Olenellus''-zone (Wulff River Formation, Marshall Bugt, Inglefield Land). * ''E. paraoculus'' is present in the Middle ''Olenellus''-zone of the Northwest Territories (type section of the type section of the Sekwi Formation, 0.2 miles Southeast of June Lake, Mackenzie Mountains). * ''E. parvifrons'' was excavated from the Middle ''Olenellus''-zone of the Northwest Territories (type section of the type section of the Sekwi Formation, 0.2 miles Southeast of June Lake, Mackenzie Mountains, and the Illtyd Formation, Wernecke Mountains). * ''E. praenuntius'' occurs on the eastern Ellesmere Island, Canada, in what possibly belongs to the Lower ''Olenellus''-zone (430 feet above the basis of the Kane Formation, 6 miles Northwest of the head of Scoresby Bay). * ''E. sequomalus'' is found in the Middle ''Olenellus''-zone of the Northwest Territories (type section of the type section of the Sekwi Formation, 0.2 miles Southeast of June Lake, Mackenzie Mountains). * ''E. walcotti'' was collected in the Middle ''Olenellus''-zone of the Northwest Territories (type section of the type section of the Sekwi Formation.<ref name='Lieberman 1999'/>

== Description == As with most early trilobites, ''Elliptocephala'' has an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As part of the Olenellina suborder, ''Elliptocephala'' 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 head shield (or cephalon) of ''Ellipticephala'' carries backwards directed spines at the corner between the halfcircle shaped frontal and side margin and the backmargin that is roughly perpendicular to the midline. The frontal lobe of the glabella (L4) is roughly 1½× the length of the backward ring-shaped lobe (also called occipital ring or L0) and the most backward set of side lobes (L1) taken together, measured along the midline (or sagittally). L4 is also much wider than L0. Side lobes L2 and L3 do not merge with each other. The line between the backward tip of eye lobe and the junction of the back margin of lobe with glabella with the midline is 10-20°. L3 touches the eye ridge. L0 carries a node at the midline. The third thorax segment from the front (T3) is not larger than the neighboring segments and does not carry larger spines. Thoracic pleural furrows extend onto spines. Long backward directed spine on the midline of T15, and this spine is broad at its base.<ref name='Lieberman 1999'/>

==References== {{Reflist}}

Category:Cambrian trilobites Category:Prehistoric animals of North America Category:Olenelloidea Category:Taxa named by Ebenezer Emmons Category:Redlichiida genera