Elliptocephala

Elliptocephala; Temporal range: late Lower Cambrian (Upper Tommotian to Upper Botonian) 531–518.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Order:	Redlichiida
Suborder:	Olenellina
Superfamily:	Olenelloidea
Family:	“Wanneriidae”
Subfamily:	“Wanneriinae”
Genus:	Elliptocephala; Emmons, 1844
Species
	E. asaphoidesEmmons, 1844 (Type); E. bicensis(Walcott, 1910) synonym Callavia bicensis; E. laxocules(Fritz, 1972) synonym Olenellus laxocules; E. logani(Walcott, 1910) synonyms Olenellus logani, Wanneria logani; E. lundgreni(Moberg, 1892) synonyms Wanneria lundgreni, Kjerulfia lundgreni, Holmia lundgreni; E. mediocris(Poulsen, 1958) synonyms Wanneria mediocris, W. ruginosa, W. subglabra, W. troelseni; E. mirabilis(Poulsen, 1958) synonyms Holmia mirabilis, Wanneria mirabilis; E. paraoculus(Fritz, 1972) synonym Olenellus paraoculus; E. parvifrons(Fritz, 1972) synonym Wanneria parvifrons; E. praenuntius(Cowie, 1968) synonym Olenellus praenuntius ; E. sequomalus(Fritz, 1972) synonym Olenellus sequomalus; E. walcottiLieberman, 1999 synonym Olenellus truemanni pro parte ;

Last updated January 28, 2024

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.^[1]

Taxonomy

Relations within Elliptocephala

According to Lieberman^[1]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.^[2]

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.^[1]

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.^[1]

Related Research Articles

Olenellus is an extinct genus of redlichiid trilobites, with species of average size. It lived during the Botomian and Toyonian stages (Olenellus-zone), 522 to 510 million years ago, in what is currently North-America, part of the palaeocontinent Laurentia.

Olenelloides armatus is an extinct, small sized olenelloid redlichiid trilobite arthropod. 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 most conspicuous feature is the hexagonal head shield that carries 6 ray-like spines..

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Fremontella is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the part of the Toyonian stage. This faunal stage was part of the Cambrian Period. Fremontella shares with the other genera of the Bristoliinae subfamily, Lochmanolenellus and Bristolia conspicuous and long curved spines on the headshield. These reach back equal to 4-5 thorax segments. The furrows that separate border, eye ridges, glabella and its lobes are distinct. The area outside of the axis of the third segment of the thorax is enlarged, and carries large trailing spine on each side.

Archaeaspis is an extinct genus of redlichiid trilobites. It lived during the late Atdabanian stage, which lasted from 521 to 514 million years ago during the early part of the Cambrian Period. The first specimens were first found in Siberia, where they were originally thought to have been endemic. Later, though, more specimen were found in the Inyo Mountains in Southern California. An Ediacarian proarticulatan was given the same name, Archaeaspis Ivantsov, 2001. This is however a junior homonym. The name Archaeaspis Repina in Khomentovskii and Repina, 1965, for the trilobite has priority. The new valid name for the proarticulate is Archaeaspinus Ivantsov, 2007.

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<span class="mw-page-title-main">Holmiidae</span> Family of trilobites

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 throughout Baltica and Western Laurentia, and also in Morocco.

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Lochmanolenellus is an extinct genus of trilobites, fossil marine arthropods, with one small species, L. mexicana. It lived during the Botomian stage (Olenellus-zone), 522–513 million years ago, in the South-West of the former continent of Laurentia, in what are today Mexico, and the South-Western United States.

Bristolia is an extinct genus of trilobite, fossil marine arthropods, with eight or more small to average size species. It is common in and limited to the Lower Cambrian shelf deposits across the southwestern US, which constitutes part of the former paleocontinent of Laurentia.

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The Illtyd Formation is an up to 1000-m thick geologic formation in Yukon. It preserves fossils dating back to the Dyerian subdivision of the Cambrian period, which spans the Stage 3 / Stage 4 boundary; it's considered to belong to the mid-upper Bonnia-Olenellus trilobite Zone. Top of the unit corresponds, more or less, to the top of Stage 4. These fossils include Lower Cambrian trilobites'.

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References

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Lieberman, B.S. (1999). "Systematic Revision of the Olenelloidea (Trilobita, Cambrian)" (PDF). Bulletin of the Peabody Museum of Natural History. 45.^{[ permanent dead link ]}
↑ Lieberman, B.S. (1998). "Cladistic Analysis of the Early Cambrian Olenelloid Trilobites" (PDF). Journal of Paleontology. 72 (1): 59–78. Bibcode:1998JPal...72...59L. doi:10.1017/S0022336000024021. S2CID 86307339.^{[ permanent dead link ]}

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[Lieberman_1999-1] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Lieberman, B.S. (1999). "Systematic Revision of the Olenelloidea (Trilobita, Cambrian)" (PDF). Bulletin of the Peabody Museum of Natural History. 45.^{[ permanent dead link ]}

[Lieberman_1998-2] Lieberman, B.S. (1998). "Cladistic Analysis of the Early Cambrian Olenelloid Trilobites" (PDF). Journal of Paleontology. 72 (1): 59–78. Bibcode:1998JPal...72...59L. doi:10.1017/S0022336000024021. S2CID 86307339.^{[ permanent dead link ]}

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