''Archaeaspis'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of redlichiid

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 At ...

s. It lived during the late

Atdabanian Cambrian Stage 3 is the still unnamed third stage of the Cambrian. It succeeds Cambrian Stage 2 and precedes Cambrian Stage 4, although neither its base nor top have been formally defined. The plan is for its lower boundary to correspond approx ...

stage, which lasted from 521 to 515 million years ago during the early part of the

Cambrian Period The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

. The first specimens were first found in Siberia, where they were originally thought to have been

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

. Later, though, more specimen were found in the

Inyo Mountains The Inyo Mountains are a short mountain range east of the Sierra Nevada in eastern California in the United States. The range separates the Owens Valley to the west from Saline Valley to the east, extending for approximately south-southeast fro ...

Southern California Southern California (commonly shortened to SoCal) is a geographic and Cultural area, cultural region that generally comprises the southern portion of the U.S. state of California. It includes the Los Angeles metropolitan area, the second most po ...

. An Ediacarian

proarticulata Proarticulata is a proposed phylum of extinct, bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately . The name comes from the Greek () = "before" and Articulata, i.e. pr ...

n was given the same name, ''Archaeaspis'' Ivantsov, 2001. This is however a

junior homonym In biology, a homonym is a name for a taxon that is identical in spelling to another such name, that belongs to a different taxon. The rule in the International Code of Zoological Nomenclature is that the first such name to be published is the se ...

. The name ''Archaeaspis'' Repina in Khomentovskii and Repina, 1965, for the trilobite has priority. The new valid name for the proarticulate is ''

Archaeaspinus ''Archaeaspinus fedonkini'' is an extinct proarticulatan organism from the Late Precambrian (Ediacaran) period. Background ''Archaeaspinus'' was discovered in Zimnii Bereg, the Winter Coast of the White Sea in Russia, by A. Yu. Ivantsov in 2001 ...

'' Ivantsov, 2007.

Etymology

The genus name is the combination of the

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

ἀρχαῖος (archaīos) meaning "ancient" and ἀσπίς (aspis) meaning "shield". The names of the species have the following derivations. * ''A. hupei'' is named in honor of Pierre Hupé, a distinguished French paleontologist. * ''A. nelsoni'' in named in honor of Clem Nelson, emeritus professor, who worked at the University of California at Los Angeles, and at the White Mountain Research Station. He collected the material the specimens the description of this species is based upon. * ''A. macropleuron'' is the combination of the Greek words μακρος (makros) meaning "large" and πλευρών (pleuron) meaning "rib", named for the macropleural spine of the 3rd thorax segment in this species.

Distribution

* ''A. hupei'' is found on the Siberian platform. * ''A. nelsoni'' was collected in the Lower Cambrian of California, USA (probably ''Nevadella''-zone), Inyo County; on a small hill just south of the east-west road leading to Silver Canyon, Montenegro Member of the Campito Formation, Blanco Mountains; and on a south facing dip slope on the North side of a small east-west canyon on the east side of the road, Campito Formation, near Bishop. * ''A. macropleuron'' occurs in the Lower Cambrian of California, USA (probably ''Nevadella''-zone), Inyo County; on a small hill just south of the east-west road leading to Silver Canyon, Montenegro Member of the Campito Formation, Blanco Mountains; Campito Formation near Waucoba Springs.

Description

As with most early trilobites, ''Archaeaspis'' has an almost flat exoskeleton that is only thinly calcified, and has crescent-shaped eye ridges. As part of the Olenellina suborder, ''Archaeaspis'' lack dorsal sutures. The superfamily Fallotaspidoidea, to which ''Archaeaspis'' belongs can be distinguished from all other

Olenellina 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 ...

by features of the cephalon and in particular the

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

. The glabella tapers forward. The frontal lobe of the glabella (because it is counted from the back, it is numbered L4) is as long as the most backward lobe (L0), less than in the other Olenellina. The eye ridges (or ocular lobes) contact, but do not merge with, the entire frontal margin of the glabella. In ''Archaeaspis'' the frontal lobe of the glabella (L4) does not contact the anterior border furrow, but is connected with it by a ridge at midline (called plectrum). There is an obvious ridge that crosses the area between the ocular lobe and the glabella backward and slightly outward at approximately 10° (called interocular ridge).

Species key

References

{{Taxonbar, from=Q4785349 Cambrian animals of North America Cambrian trilobites of Asia Fallotaspidoidea Cambrian genus extinctions