Eldredgeops

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Eldredgeops
Temporal range: Givetian–Frasnian
Eldredgeops milleri, Middle Devonian, Silica Shale, Sylvania, Ohio, USA - Houston Museum of Natural Science - DSC01523.JPG
Eldredgeops milleri
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Trilobita
Order: Phacopida
Family: Phacopidae
Genus: Eldredgeops
Struve, 1990
Species
  • Eldredgeops rana(Green, 1832) type, = Calymene bufo rana, Phacops rana and see text
Eldredgeops norwoodensis; enrolled; Milwaukee Formation; Milwaukee County, Wisconsin. Eldredgeops norwoodensis.jpg
Eldredgeops norwoodensis; enrolled; Milwaukee Formation; Milwaukee County, Wisconsin.

Eldredgeops is a genus of trilobites in the order Phacopida, family Phacopidae, known from the late Middle and earliest Upper Devonian of Morocco and the USA.

Contents

Description

Like in all sighted Phacopina, the eyes of Eldredgeops are composed of very large (0.5mm in Eldredgeops rana ), separately set lenses without a common cornea (so called schizochroal eyes), and like almost all other Phacopina, the articulate mid-length part of the body (or thorax) in Eldredgeops has 11 segments.

In contrast to the related Phacops , Eldredgeops generally has a raised ridge along the ventral margin of the cephalon, the glabella is more inflated, the lateral parts of the preoccipital ring are rectangular (and not round), the palpebral area and palpebral lobe are larger than in P. latifrons (the type species of Phacops), and there is no fold right behind the posterior vertical row of lenses nor an isolated raised area just below the lenses. [1]

Distribution

All phacopids died out in North America during the Kačák Event at the end of the Eifelian. The phacopids returned to North America during the early Givetian with the emigration of Eldredgeops species from Morocco. [1]

Taxonomy

The species included in Eldredgeops were previously regarded as belonging to Phacops. It was considered however that the post-Eifelian North-American relatives of P. rana differ sufficiently from those found in Africa and Europe to be assigned to a separate genus. The new name is used for the North American species as the type species Phacops latifrons is European. However, old combinations like Phacops rana are widely used among fossil collectors. [1] Pre-Givetian North-American species previously included in Phacops have also been reassigned, such as P. cristatus (now referred to Viaphacops), P. microps and P. raymondi (now Kainops ), P. cambelli, P. birdsongensis, P. claviger and P. logani (now Paciphacops ). [2]

Species and occurrence

References

  1. 1 2 3 GerryK (9 June 2014). "Phacops vs Eldredgeops". The Fossil Forum.
  2. Hansen, George P. (2009). Trilobites of Black Cat Mountain. iUniverse.
  3. Eldredge, Niles (1972). "Systematics and Evolution of Phacops rana (Green, 1832) and Phacops iowensis Delo, 1935 (Trilobita) from the Middle Devonian of North America". Bulletin of the American Museum of Natural History. 147: 45–114.
  4. Burton, C.J.; Eldredge, N. (1974). "Two new subspecies of Phacops rana (Trilobita) from the Middle Devonian of North-West Africa" (PDF). Palaeontology. 17 (2): 349. Archived from the original on 2013-11-04. Retrieved 2015-08-19.