''Eldredgeops'' is a genus of

trilobite Trilobites (; meaning "three lobes") are 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 ...

s in the order

Phacopida Phacopida ("lens-face") is an order of trilobites that lived from the Late Cambrian to the Late Devonian. It is made up of a morphologically diverse assemblage of taxa in three related suborders. Characteristics Phacopida had 8 to 19 thoraci ...

, family

Phacopidae Phacopidae is a family of phacopid trilobites that ranges from the Lower Ordovician to the Upper Devonian, with representatives in all paleocontinents. Description As in all Phacopina, the eyes (if present) consist of very large (0.5 mm in ' ...

, known from the late Middle and earliest Upper Devonian of Morocco and the USA.

Description

Like in all sighted

Phacopina The Phacopina comprise a suborder of the trilobite order Phacopida. Species belonging to the Phacopina lived from the Lower Ordovician ( Tremadocian) through the end of the Upper Devonian (Famennian).Moore, R.C. (ed.). Treatise on Invertebrate Pal ...

, 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 The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

) in ''Eldredgeops'' has 11 segments. In contrast to the related ''

Phacops ''Phacops'' is a genus of trilobites in the order Phacopida, family Phacopidae, that lived in Europe, northwestern Africa, North and South America and China from the Late Ordovician until the very end of the Devonian, with a broader time range ...

'', ''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.

Distribution

All phacopids died out in North America during the

Kačák Event The Kačák Event (), also known as the Kačák-''otomari'' Event, is a widely recognised bioevent or series of events that occurred close to the end of the Eifelian Age (geology), Age of the Middle Devonian Epoch. It involved a global eustatic ris ...

at the end of the

Eifelian The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage. North American ...

. The phacopids returned to North America during the early

Givetian The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian The Frasnian is one of two faunal stages in the ...

with the emigration of ''Eldredgeops'' species from Morocco.

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 In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

''Phacops latifrons'' is European. However, old combinations like ''

Phacops rana ''Eldredgeops rana'' (formerly ''Phacops rana'') is a species of trilobite from the middle Devonian period. Their fossils are found chiefly in the northeastern United States, and southwestern Ontario. Because of its abundance and popularity wit ...

'' are widely used among fossil collectors. 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 ''Kainops'' is a genus of trilobites from the family Phacopidae, order Phacopida Phacopida ("lens-face") is an order of trilobites that lived from the Late Cambrian to the Late Devonian. It is made up of a morphologically diverse assemblage of ...

''), ''P. cambelli'', ''P. birdsongensis'', ''P. claviger'' and ''P. logani'' (now ''

Paciphacops ''Paciphacops'' is a genus of trilobites from the order Phacopida, suborder Phacopina. This genus is easily mistaken for the more common and popular genus ''Phacops'' and ''Kainops''. It takes a careful eye to spot the difference. One major diff ...

'').

Species and occurrence

* ''E. rana'' (Green, 1832) = ''Phacops rana rana'' is present in the Givetian (Middle Cazenovian, Stafford limestone, west New York State; Iowa and adjacent states; Tioughniogan of the Appalachians and New York State) and Frasnian ( Chemung sandstones, New York and Maryland). * ''E. africanus'' (Burton & Eldredge, 1974) = ''P. rana africanus'', occurs in Morocco * ''E. crassituberculata'' (Stumm, 1953) = ''Phacops rana crassituberculata'', appears in the Givetian (Lower Cazenovian) of the US (Delaware and Dundee Limestone, Ohio; and Soltsville siltstone, east central New York State). * ''E. milleri'' (Stewart, 1927) = ''Phacops rana milleri'', has been excavated from the Givetian (Middle and Upper Cazenovian, Tully Formation, New York State; Michigan and Iowa). * ''E. norwoodensis'' (Stumm, 1953) = ''Phacops rana norwoodensis'', found in Givetian strata ( Traverse Group of Michigan, Milwaukee Formation of

Wisconsin Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...

, and Cedar Valley Group of Iowa and Illinois). * ''E. paucituberculata'' (Eldredge, 1972) = ''Phacops rana paucituberculata'', can be found in the Givetian (Cazenovian) of the US (Plum Brook shale of north-central Ohio; and Upper Ferron Point shale of northeast Michigan). * ''E. tindoufensis'' (Burton & Eldredge, 1974) = ''P. rana tindoufensis'', is found in Morocco.

References

Paleobiology Database entry
{{Taxonbar, from=Q5354158 Phacopidae Devonian trilobites of North America Middle Devonian first appearances Frasnian extinctions Paleozoic life of Ontario