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18-658: Fallotaspis is a genus of redlichiid trilobites found in Early Cambrian -aged strata of the United States and Morocco . The generic name, Fallotaspis , is a compound crassis word that honors Paul Fallot (1889-1960), a French paleontologist who researched Cambrian fossils in Spain, in combination with the Greek word ἀσπίς, aspis , meaning shield. As with most early trilobites, Fallotaspis has an almost flat exoskeleton, that

36-480: A few specimens. They follow typical trilobite patterns in terms of the number, placement, and types of legs, antennae, gills , etc. The order Redlichiida is divided into two suborders : Olenellina and Redlichiina . The main difference between the two groups is the lack of facial sutures in the Olenellina. This absence of the facial sutures is regarded as primitive by most scholars. Opisthoparian facial sutures are

54-404: A long spine that extends back to the fourteenth segment. The tail shield (or pygidium ) is very small, about the same length as the two most backward thorax segments combined. This key is based on the analysis of Lieberman. This key only includes the two Fallotaspis species that Lieberman included in his analysis, where the literature suggests there may be at least ten species. It complements

72-477: A non-mineralised membrane. Natant hypostomes appear to have been conservative over the course of the evolution of trilobites with overall form and shape of a simple ovoid without posterior extensions or ornamentation. Natant hypostomes are thought to be ancestral to other hypostome forms and thought to belong to trilobites with generalized particle feeding habits ( i.e. little need to modify mouth-parts to deal with specialized food items). A conterminant hypostome

90-472: A posterior lobe. Either side of the median body is a border with various extensions, including anterior and posterior wings, sometimes bearing knob-like processes. The hypostome is hollow, and encloses the mouthparts, the anterior digestive tract, and the bases of the antennae. Trilobite antennae pass through notches between the anterior and posterior wings, then forward. The anterior wings are designed to rest firmly against internal structures (ventral apodemes) on

108-540: A shared character of all Redlichiina. In other trilobites, dorsal sutures may be opisthoparian, gonatoparian, proparian or they may be lost secondarily. The absence in the fossil record of the earliest larval stage, the protaspid, suggests that it may have been uncalcified, which would be a second unique character that distinguishes the Olenellina from all other trilobites. Fossils of olenellinid trilobites are found in North America, and other associated areas that comprised

126-404: Is attached to the anterior doublure, aligned with the front edge of the glabella and found on trilobites thought of as predators. Anchoring the hypostome against the anterior doublure and cephalon provides structural bracing against which to tear apart prey. Different specializations of hypostome form might reflect different kinds of prey, or different feeding behaviors. An impendent hypostome

144-491: Is counted from the back, it is numbered L4) is as long as the most backward lobe (L0), less than in these other Olenellina subfamilies. The eye ridges (or ocular lobes ) contact, but do not merge with, the entire frontal margin of the glabella. The cephalon of Fallotaspis is semi-circular in shape, with rounded cheeks that are continuous with long spines that go back to the first half of the thorax. Sutures absent. The thorax has up to 21 segments. The third segment terminating in

162-403: Is only thinly calcified, and has crescent-shaped eye ridges. As part of the Olenellina suborder, Fallotaspis lacks dorsal sutures. As part of the superfamily Fallotaspidoidea Fallotaspis can be distinguished from Olenelloidea , Judomioidea and Nevadioidea by features of the cephalon and in particular the glabella . The glabella tapers forward. The frontal lobe of the glabella (because it

180-598: Is presumed it was not calcified. The development of Redlichia from protaspis to adult was gradual without a metamorphosis at any stage. Two major Lagerstätten 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

198-450: The glabella . Variation in trilobite hypostome morphology is crucial in modern discussions of trilobite phylogeny. Functional interpretations of hypostome shape also allow for reasonable speculation on the feeding habits of trilobite species. Although hypostome morphology is highly variable, three broad types are generally recognized: A natant hypostome is not attached to the anterior doublure , with support assumed to be provided by

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216-603: The Cambrian continent of Laurentia . They are very common and are used to define the extent of Laurentia. Their abrupt disappearance marks the boundary between the Lower and the Middle Cambrian. Fossils of redlichiinid are associated with Cambrian regions other than Laurentia. Hypostome (trilobite) The center of the hypostome is an ovoid, typically convex part called the median body, often divided into an anterior lobe and

234-423: The calcite lenses is surrounded by fracture lines (or 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

252-498: The earliest are Fallotaspis (suborder Olenellina), and Lemdadella (suborder Redlichiina), both belonging to this order. The first representatives of the orders Corynexochida and Ptychopariida also appear very early on and may prove to be even earlier than any redlichiid species. In terms of anatomical comparison, the earliest redlichiid species are probably ancestral to all other trilobite orders and share many primitive characters. The last redlichiid trilobites died out before

270-536: The end of the Middle Cambrian. Most redlichiids are rather flat (or have low dorso–ventral convexity) and their exoskeleton typically has an oval outline, about 1½× longer than wide. Each back edge of the headshield (or 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 glabella ) curving outward and increasingly backwards and sometimes eventually inwards again. The visual surface, that contains

288-426: The exoskeleton (or 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). The tailshield (or 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

306-520: The key in the Fallotaspidoidea article. Redlichiida Redlichiida is an order of trilobites , a group of extinct marine arthropods . Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficulty to relate sediments in different areas, there remains some discussion, but among

324-399: The ventral side of the cephalon, the palate (or hypostome ) is attached to the part of the calcified exoskeleton that defines the contour at the ventral side (the so-called 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

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