Scutellum (trilobite)

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Scutellum
Scutellum fossil

Scutellum fossil

Temporal occurrence
Silurian to Frasnium
430 to 375 million years
Locations

Worldwide

Systematics
Trilobites (Trilobita)
Corynexochida
Illaenina
Styginidae
Scutelluinae
Scutellum
Scientific name
Scutellum
Push , 1833

Scutellum is a genus of trilobites from the Silurian and Devonian . These trilobites were widespread worldwide and so the fossils can be found in deposits on all parts of the world.

features

Side view of Scutellum flabelliferum

The carapace of these trilobites is relatively thin. The spindle (axial lobe) of the thorax is narrower than the pleura. As with the related Paralejurus species, the cephalon lacks many typical details due to smooth adhesions. Scutellum species, on the other hand, show even more details than Paralejurus species.

Scutellum species have an oval shape and are up to 11 inches long.

Cephalon : Scutellum species have a flat or slightly domed cephalon with a very narrow frontal hem. This frontal hem is also completely absent in some species. The glabella is compressed. The first side furrow is curved forward and reaches the second side furrow. The side lobes have therefore receded there and only appear as small knots. The third lateral lobes are not clearly delimited on the inside. Many species still have a small pit as a boundary between the second and third side furrow. The eyelids are crescent-shaped and relatively small.

Thorax : It consists of ten segments. The spindle is convexly curved dorsally.

Pygidium : The pygidium is flat, wide with a central, raised plate. The spindle ends in a triangular shape. On the pygidium, six to seven strong pairs of ribs radiate out from the spindle and end in a broad and concave envelope.

Evolutionary development

The genus existed for about 55 million years without changing significantly. It probably evolved from the genus Planiscutellum in the Silurian and disappeared like all Styginidae trilobites in the frasnium . A fusion of the thoracic segments into a solid pygidium as in Paralejurus species did not take place. Whether the Scutellum genus was a forerunner of the Paralejurus genus developed in the Pragium is still under discussion. This thesis is controversial because of some phylogenetic features. The Scutellum genus is probably also the forerunner of the genera Scabriscutellum , Thysanopeltis and Kolihapeltis .

Synonyms

  • Brontes , Fabricius 1801
  • Goldius , Konink 1841
  • Bronteus , Goldfuss 1843

Types (selection)

  • Scutellum alpinum GG Pusch 1833
  • Scutellum bromeliacearum (Rehm) Sacc. & P. Syd.
  • Scutellum calvum GG Pusch 1833
  • Scutellum costatum
  • Scutellum depressum GG Pusch 1833
  • Scutellum flabelliferum GG Pusch 1833
  • Scutellum hollandi
  • Scutellum paliferum (Beyrich 1845)
  • Scutellum umbonatum GG Pusch 1833
  • Scutellum whidbornei GG Pusch 1833

Individual evidence

  1. ↑ a b c d e Rudolf & Emma Richter, Basics for the assessment and classification of the Scutelluidae (Tril.). , Special print from Senckenberfiana lethaea , Volume 37, Frankfurt am Main, April 14, 1965, p. 84, p. 101
  2. ↑ a b c d e Hervé Chaumeton and Didier Magman: Small Encyclopedia of Fossils . Tandem Verlag, 2005, ISBN 3-8331-1312-X , p. 235
  3. ↑ Gunnar Schraut, Devonian Styginid Trilobite Paralejurus, with new data from Spain and Marocco in: Journal of Paleontology, 78 (4): 709-722, July 2004

Web links

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