Olenoides

Olenoides was a trilobite from the Cambrian period. Its fossils are found well-preserved in the Burgess Shale in Canada. It grew up to 10 cm long.

Olenoides
Temporal range: upper Middle to lower Upper Cambrian
Olenoides superbus from the Upper Marjum Formation
3D reconstruction of a Cambrian trilobite Olenoides serratus
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Trilobita
Order:
Corynexochida
Family:
Dorypygidae
Genus:
Olenoides

Meek, 1877
Species
  • O. nevadensis Meek, 1877 (Type) = Paradoxides nevadensis
  • O. serratus (Röminger, 1887) = Ogygia serrata, Neolenus serratus, Nathorstia transitans (fresh post-molting stage)[1]

Etymology

Olenoides – from Olenus, in Greek mythology a man who, along with his wife Lethaea, was turned to stone. Olenus was used for a trilobite genus name in 1827; the suffix -oides(“resembling”) was added later.

Discussion

Olenoides followed the basic structure of all trilobites — a cephalon (head shield), a thorax with seven jointed parts, and finally a semicircular pygidium. Its antennae were long, and curved back along its sides. Its thin legs show that it was no swimmer, instead crawling along the sea floor in search of prey. This is also evidenced by fossil tracks that have been found. Conspicuous W-shaped wounds, often partially healed, on Olenoides specimens may be due to predation by Anomalocaris.[2]

Its major characteristics are a large parallel-sided glabella, deep interpleural furrows on the pygidium, and slender pygidial spines, as well as the fact that it is the most common limb-bearing trilobite species in the Burgess Shale.

Specimens have been found in the Marjumian of the United States (Utah and New York). General Cambrian fossils have been found in Canada (British Columbia and Newfoundland), Greenland, Kazakhstan, Russia, and the USA (Idaho, Nevada for which O. nevadensis is named, New York, Pennsylvania for which O. pennsylvanicus is named, Virginia, Utah, and Wyoming).[3]

213 specimens of Olenoides are known from the Greater Phyllopod bed, where they comprise 0.4% of the community.[4] The Burgess Shale's preservative qualities have helped Olenoides become one of the best known of trilobites.

Synonyms
An exceptionally well preserved Olenoides serratus from the Burgess Shale. The antennae and legs are preserved as reflective carbon film

Olenoides was formerly known as Neolenus. Species of Kootenia are no longer considered different enough from those in Olenoides to warrant placement in a separate genus.[5]

Species
  • O. nevadensis
  • O. sassikaspa
  • O. serratus
  • O. dawsoni (formerly placed in Kootenia)
  • O. burgessensis (formerly placed in Kootenia)
  • O. buttsi (unrecognized)
  • O. convexus (unrecognized)
  • O. incertus (unrecognized)
  • O. pennsylvanicus (unrecognized)

Description

Olenoides is an average size trilobite (up to 9 cm long), broadly oval in outline. Its cephalon is semi-circular. The glabella is parallel-sided, rounded at its front and almost reaches the anterior border. Narrow occular ridges curve backwards from the front of the glabella to the small, outwardly-bowed eyes. The librigenae narrow backward into straight, slender genal spines that reach as far as the third thorax segment. Thorax consists of seven segments that end in needle-like spines. pygidium) has six axial rings that decrease in size backwards and four or five pairs of rearward pointing marginal spines. Cephalon, thorax and pygidium are of approximately equal length.[1]

Olenoides serratus is one of about twenty species of which the non-calcified parts are known, due to so-called soft tissue preservation. The antennae are the most anterior pair of appendages in trilobites. In O. serratus, these are attached about halfway the immediately adjacent to the hypostome, and appear from the dorsal side under the cephalon in front of the side of the glabella. They were flexible, having a tubular shape that became narrower towards anterior and composed of between 40 and 50 segments that are each shorter than wide. Olenellus serratus is the only known trilobite with cerci, uniramous appendages on ventral side of last pygidial segment, and these are shaped like the antennas.[6]

References
  1. team. "Olenoides serratus - The best-known trilobite from the Burgess Shale". The Burgess Shale. Royal Ontario Museum.
  2. Coppold, Murray and Wayne Powell (2006). A Geoscience Guide to the Burgess Shale, p.60. The Burgess Shale Geoscience Foundation, Field, British Columbia. ISBN 0-9780132-0-4.
  3. Paleobiology Database. "Chancia", accessed March 27, 2011
  4. Caron, Jean-Bernard; Jackson, Donald A. (October 2006). "Taphonomy of the Greater Phyllopod Bed community, Burgess Shale". PALAIOS. 21 (5): 451–65. doi:10.2110/palo.2003.P05-070R. JSTOR 20173022.
  5. Coppold, Murray and Wayne Powell (2006). A Geoscience Guide to the Burgess Shale, p.59. The Burgess Shale Geoscience Foundation, Field, British Columbia. ISBN 0-9780132-0-4.
  6. Moore, R.C. (1959). Arthropoda I - Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha. Treatise on Invertebrate Paleontology. Part O. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. pp. 1–560. ISBN 0-8137-3015-5.
This trilobite fossil is about 50 mm. long. It was found in the Marjum Formation in Utah. [Note - 25.4 mm=1 inch.]
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