Olenellina

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Olenellina
Temporal range: Cambrian - Series 2
Olenellus chiefensis CRF.jpeg
Olenellus chiefensis
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class:† Trilobita
Order:† Redlichiida
Suborder:† Olenellina
Superfamilies
Stemgroup genera: Elliptocephala , Fritzolenellus , Laudonia , Mummaspis , Wanneria
Stemgroup genera: Callavalonia , Callavia , Sdzuyomia

Olenellina is a suborder of the order Redlichiida of trilobites that occurs about halfway during the Lower Cambrian, at the start of the stage called the Atdabanian. The earliest trilobites in the fossil record are arguably Olenellina, although the earliest Redlichiina and Eodiscina follow quickly. [2] The suborder died out when the Lower passed into the Middle Cambrian, at the end of the stage called Toyonian. A feature uniting the Olenellina is the lack of rupture lines (or sutures) in the headshield, which in other trilobites assist the periodic moulting (or ecdysis), associated with arthropod growth. Some derived trilobites have lost facial sutures again (some Eodiscina, all Agnostina, and a few Phacopina), but all of these are blind, while all Olenellina have eyes.

Contents

Taxonomy

The suborder contains four superfamilies: Olenelloidea (with 3 families and 5 stemgroup genera), Judomioidea (with 1 family and 3 stemgroup genera), Nevadioidea, and Fallotaspidoidea (with 3 families and 3 stemgroup genera). Lieberman, 2002, considered that the Fallotaspidoidea are a paraphyletic group because it gave rise to the Redlichiina; he did not propose to restrict the Olenellina to the Olenelloidea, Judomioidea and Nevadioidea. Neither did he propose to assign this group of superfamilies to a newly formed order Olenellida, and consequently expand the Redlichiina to include the Fallotaspidoidea. This would imply that the Redlichiina would include taxa with and without dorsal sutures. [3]

Distribution

The Olenellina appear suddenly at the start of the Cambrian Series 2 (between Stage 2 Tommotian and Stage 3 Atdabanian) approximately 521 million years ago, and disappear at the end of this Series (between Stage 4 Toyonian and Stage 5 Amgan), 514 to 509 million years ago. The Olenellina probably first occurred on the paleocontinent Siberia and spread into the part of Gondwana that is now the Atlas Mountains, Baltica, Avalonia and Laurentia. In western Laurentia the first representatives to appear are Fallotaspididae, followed by Archaeaspididae, Nevadioidea and Holmiidae, and finally Biceratopsidae and Olenellidae. [4] The Olenellina are not known from South China, Australia and most of Latin America and Africa, where the first trilobites were Redlichiina, that had already developed dorsal sutures.

Description

As with most early trilobites, the Olenellina have an almost flat exoskeleton, that is only thinly calcified, and have crescent-shaped eye ridges. The suborder differs from all other trilobites by the lack of dorsal sutures in the head shield (or cephalon). There is a ventral mouth plate (or conterminant hypostome) with a very wide rostral plate extending between genal angles, with a perrostral suture (no connective sutures).

The thorax may be composed of a prothorax that generally has 14 or 15 segments, and an opisthothorax that has between 0 and up to 34 segments. In segment 3, the areas right and left of the axis (or pleural lobes) are often enlarged, sometimes carrying large trailing pleural spines. Segment 14 or 15 is often bearing a large spine at midline that points backwards.

The pygidium is mostly very small with few segments, that are often difficult to discern.

Unlike in other trilobite groups, the early larval stage called protaspid is not known, and it is generally accepted that this is because the protaspid was not calcified. [5]

Key to the superfamilies

Graphic of the relationship between the superfamilies within the Olenellina, and with other trilobites Olenellina cladogram.jpeg
Graphic of the relationship between the superfamilies within the Olenellina, and with other trilobites
1The frontal lobe of the glabella (L4) is longer than, or equal to, the length of the most backward lobe of the glabella (called occipital ring or L0) plus the first pair of side lobes counted from the back (L1), measured along the midline.→ 2
-L4 approximately equal in length to L0.
→ “Fallotaspidoidea”
2The eye ridge (or ocular lobe) merges with the frontal lobe of the glabella. → 3
-The ocular lobe touches, but not merges with L4.
→ Stemgroup “Nevadioidea“
3The ocular lobe merges with the entire margin of L4.
→ Crowngroup “Nevadioidea“ and Judomioidea
-The ocular lobe merges with the posterior margin of L4 only.
→ Olenelloidea

Related Research Articles

Trilobite Class of extinct, Paleozoic arthropods

Trilobites are a group of 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 Atdabanian stage of the Early Cambrian period, and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 20,000 species having been described.

Redlichiida Extinct order of trilobites

Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among the earliest are Fallotaspis, and Lemdadella, both belonging to this order. The first representatives of the orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid species. In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters. The last redlichiid trilobites died out before the end of the Middle Cambrian.

Emuellidae Extinct family of trilobites

Emuellidae are a small family of trilobites, a group of extinct marine arthropods, that lived during the late Lower Cambrian of the East Gondwana supercontinent, in what are today South-Australia and Antarctica. Emuellidae can be recognized among trilobites in having a set of unique features. The headshield or cephalon has large genal spines reaching back as far as the 3rd to 6th segment of the thorax. The eye-ridges contact the back of the frontal lobe of the glabella and extend laterally and backwards, roughly parallel to the frontal and lateral rim of the cephalon. There are small, clearly incised pits at the junction between the eye-ridge and the frontal lobe of the cephalic axis. The thorax reaches its greatest width at the 6th segment. The frontal part or prothorax consists of 6 segments, with number 5 and 6 fused, and the 6th carrying very large trailing spines. The rear part or opistothorax consists of a variable but extremely large number of segments.

<i>Wanneria</i>

Wanneria is an extinct 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. Wanneria walcottana is the only known species in this genus.

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 to the upper Botomian. Elliptocephala can easily be confused with Ellipsocephalus, a trilobite genus of the Ptychopariida order.

<i>Archaeaspis</i>

Archaeaspis is an extinct genus of redlichiid trilobites. It lived during the late Atdabanian stage, which lasted from 521 to 515 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.

<i>Nevadella</i>

Nevadella is an extinct genus of trilobites, fossil marine arthropods, with species of average size. It lived during the late Atdabanian stage, which lasted from 530 to 524 million years ago during the early part of the Cambrian Period.

<i>Nephrolenellus</i>

Nephrolenellus is an extinct genus of trilobite, fossil marine arthropods, of relatively small size. Currently two species are attributed to it. Nephrolenellus lived at the end of the Lower Cambrian. Species are known from the Great Basin of California, Nevada and Arizona, with one specimen from Canada.

<i>Mesonacis</i>

Mesonacis is an extinct genus of trilobite that lived during the Botomian, found in North-America, and the United Kingdom. Some of the species now regarded part of Mesonacis, have previously been assigned to Angustolenellus or Olenellus (Angustolenellus). Angustolenellus is now regarded a junior synonym of Mesonacis.

<i>Fallotaspis</i>

Fallotaspis is a genus of redlichiid trilobite genus found in Early Cambrian-aged strata of the United States and Morocco.

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 throughout Baltica and Western Laurentia, and also in Morocco.

<i>Peachella</i>

Peachella is an extinct genus of trilobites, fossil marine arthropods, with species of average size. It lived during the Toyonian stage, 516 to 513 million years ago, in what is today the southwestern United States. It can easily be distinguished from other trilobites by its club-like genal spines.

<i>Biceratops</i>

Biceratops is an extinct genus of olenelloid redlichiid trilobites, of average size, with the largest specimen 8 centimetres or 3.1 inches long, not including the huge pleural spines of the 3rd segment of the thorax. It lived during the Toyonian stage, in what is today the South-Western United States. Biceratops can easily be distinguished from other trilobites by the absence of genal spines, in combination with effaced features of the raised axial area of the head shield, that is bordering the two horn-like projections that carry the eyes. Biceratops nevadensis is the only known species in this genus.

Olenelloidea Extinct superfamily of trilobites

The Olenelloidea are a superfamily of trilobites, a group of extinct marine arthropods. They lived during the late Lower Cambrian and species occurred on all paleocontinents.

<i>Bristolia</i>

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.

<i>Emigrantia</i>

Emigrantia is an extinct genus of trilobites, fossil marine arthropods, of small to average size. It lived during the Toyonian stage, in what is today the South-Western United States. Emigrantia can easily be distinguished from other trilobites by the sturdy but not inflated genal spines, that are attached at midlength of the cephalon, in combination with effaced features of the raised axial area of the head shield.

Bolbolenellus is an extinct genus of trilobites, fossil marine arthropods, with five species attributed to it currently. It can be easily distinguished from all other trilobites by the combination of the absence of dorsal sutures in the head shield like all Olenellina, and a distinctly bulbous frontal lobe (L4) of the raised axial area in the head called glabella. The species lived at the end of the Lower Cambrian.

Fallotaspidoidea

The ”Fallotaspidoidea” are a superfamily of trilobites, a group of extinct marine arthropods. It lived during the Lower Cambrian (Atdabanian) and species occurred on all paleocontinents except for the Gondwana heartland. A member of this group, Profallotaspis jakutensis, has long been the earliest known trilobite, but recently the redlichiid Lemdadella has been claimed as occurring even earlier.

Repinaella is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived during the late Atdabanian stage.

Eodiscina

Eodiscina is trilobite suborder. The Eodiscina first developed near the end of the Lower Cambrian period and became extinct at the end of the Middle Cambrian. Species are tiny to small, and have a thorax of two or three segments. Eodiscina includes six families classified under one superfamily, Eodiscoidea.

References

  1. ↑ Lieberman, B.S. (1998). "Cladistic Analysis of the Early Cambrian Olenelloid Trilobites" (PDF). Journal of Paleontology. 72: 59–78. doi:10.1017/S0022336000024021.
  2. ↑ III, Sam Gon. "The Earliest Trilobites". www.trilobites.info. Retrieved 2021-10-28.
  3. ↑ Lieberman, B.S. (2002). "Phylogenetic analysis of some basal early Cambrian Trilobites, the biogeographic origins of the Eutrilobites, and the timing of the Cambrian radiation" (PDF). Journal of Paleontology. 76 (4): 692–708. doi:10.1666/0022-3360(2002)076<0692:paosbe>2.0.co;2. Archived from the original (PDF) on 2011-08-12.
  4. ↑ Hollingsworth, J.S. (2006). "Holmiidae (Trilobita: Olenellina) of the Montezuman Stage (Early Cambrian) in Western Nevada". Journal of Paleontology. 80 (2): 309–332. doi:10.1666/0022-3360(2006)080[0309:htootm]2.0.co;2. JSTOR   4095128.
  5. ↑ Palmer, A.R.; Repina, L.N. (1993), "Through a Glass Darkly: Taxonomy, Phylogeny and Biostratigraphy of the Olenellina", The University of Kansas Paleontological Contributions, 3: 1–35
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