Editing Redlichiida (section)

== Description ==
[[Image:Olenellus chiefensis CRF.jpeg|left|thumb|''Olenellus chiefensis'', suborder Olenellina, showing the visual surface has broken away, the lack of dorsal sutures, and the enlarged pleurae of the 3rd thorax segment from the front]]
Most redlichiids are rather flat (or have low [[Anatomical terms of location#Dorsal and ventral|dorso–ventral]] convexity) and their [[exoskeleton]] typically has an oval outline, about 1½× longer than wide. Each back edge of the headshield (or [[Trilobite#Cephalon|cephalon]]) very often carries a spine, termed a genal spine.  The eye lobes are sickle-shaped, long and extend from the frontal lobe of the central raised area of the cephalon (or [[Trilobite#Cephalon|glabella]]) curving outward and increasingly backwards and sometimes eventually inwards again. The visual surface, that contains the calcite lenses is surrounded by fracture lines (or [[Trilobite#Facial sutures|circumocular sutures]]), so that it has most often broken away from the rest of the cephalon. The glabella tapers forward and is relatively long, with the frontal lobe boss-like or pointy, followed by three rings or pairs of lobes (defined by furrows that may or may not cross over the midline), and finally at the back of the cephalon the so-called occipital ring. On the ventral side of the cephalon, the palate (or [[Hypostome (trilobite)|hypostome]]) is attached to the part of the calcified exoskeleton that defines the contour at the ventral side (the so-called [[Trilobite#Morphology|doublure]]), a state called conterminant. The hypostomes of redlichiids have narrow borders, are not split into backward pointing forks, and have only small muscle attachment areas (or maculae). The articulate middle part of the exoskeleton (or [[Trilobite#Thorax|thorax]]) is composed of many of segments that often end in a spine at the side of the animal. To each side of the central axis, the third segment from the front may have an exta large and wide rib (a state called macropleural).<!--- to paraphrase: the articulation was nonfulcrate (Whittington, 1990) and allowed considerable arching of the body, if not complete enrollment.---> The tailshield (or [[Trilobite#Pygidium|pygidium]]) is small but appears to be composed of more than one segment. In Olenellina the earliest larval stage (called protaspis) has not been found, so it is presumed it was not calcified. The development of ''Redlichia'' from protaspis to adult was gradual without a metamorphosis at any stage.<ref name='Treatise'>{{cite book|last= Whittington|first= H.B.|year= 1997|title= Introduction, Order Agnostida, Order Redlichiida|publisher= Geological Society of America/University of Kansas Press|series= [[Treatise on Invertebrate Paleontology]]|volume= Part O.Revised, Volume 1 – Trilobita|pages= [https://archive.org/details/treatiseoninvert0002unse/page/400 400–481]|location= Boulder, Colorado/Lawrence, Kansas|isbn= 0-8137-3108-9|display-authors= etal|url= https://archive.org/details/treatiseoninvert0002unse/page/400}}</ref>

Two major [[Lagerstätte]]n where redlichiids are found are the [[Emu Bay shales]] of Southern Australia and the [[Maotianshan shales]] near Chengjiang in China.  Other regions include Morocco, Labrador, Canada, the western [[United States]], and [[Bohemia]], [[Czech Republic]].

The appendages have been preserved in a few specimens. They follow typical trilobite patterns in terms of the number, placement, and types of legs, antennae, [[gill]]s, etc.