''Resserops'' is an
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
from a well-known class of
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
marine
arthropod
Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s, the
trilobite
Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...
s. It lived during the middle of the
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 approxi ...
or the early part of the
Botomian stage,
which lasted from approximately 524 to 518.5 million years ago. This faunal stage was part of the
Cambrian Period
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovici ...
. It has been found in Spain and southern Morocco. It can be recognised by the sabre-like spines of the headshield that are a smooth continuation of the frontal edge, and the enlarged spines on the 9th segment of the thorax.
Distribution
Lower Cambrian of Spain
and Southern Morocco (''Daguinaspis'' and ''Resserops''-zone near Amouslek, Ouijane and Tiout).
Taxonomy
The Treatise
[Whittington, H. B. et al. Part O, Treatise on Invertebrate Paleontology. Revised, Volume 1 – Trilobita – Introduction, Order Agnostina, Order Redlichiida. 1997] considers ''Resserops'' and ''
Richterops'' subgenera of ''Perrector'', which name was proposed by Hupé in the same publication as ''Resserops'' and ''Richterops'', but appears above it and thus has preference. Later publications use ''Resserops'' and ''Richterops'' however as separate
genera
Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
.
Description
As with most early trilobites, ''Resserops'' has an almost flat exoskeleton, that is only thinly calcified, and has crescent-shaped eye ridges. As a representative of the Redlichiina suborder, the headshield (or
cephalon
Cephalon, Inc. was an American biopharmaceutical company co-founded in 1987 by pharmacologist Frank Baldino Jr., Frank Baldino, Jr., neuroscientist Michael Lewis, and organic chemist James C. Kauer—all three former scientists with the DuPont ...
) has sutures where the exoskeleton ruptures to assist in
moulting
In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is a process by which an animal casts off parts of its body to serve some beneficial purpose, either at ...
. The cephalon is approximately ovate, more than twice as wide as long. There is no space between the raised axis (or
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 ...
) and the raised ridge (or anterior border) that defines the contour of the cephalon (in jargon: the preglabellar field is absent). The eye ridges are large, extend outward and arch backward near their tips. The cephalon carries massive sabre-like relatively short spines (or genal spines) that are a smooth continuation of the anterior border. The genal spines are connected at about half of the length of the cephalon (or are well-advanced). The tips of the genal spines are approximately as far out as their base. The thorax has 12 segments, the 9th segment (counted from the front) carries large spines at its tips, longer than the genal spines and longer than the thorax axis, extending about one pygidial length behind the body. The tailshield (or
pygidium
The pygidium (: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is compos ...
) has a smooth border, is large for a redlichiida, (about 60% of the length of the cephalon), both the axis and pleural regions of the pygidium have about 6 recognisable segments.
References
{{Taxonbar, from=Q7316025
Cambrian trilobites
Redlichiida genera
Saukiandidae
Trilobites of Europe
Trilobites of Africa