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A suborder of the Isopoda which are parasitic on various crustaceans, mainly marine forms. The females are sometimes modified so strongly as to leave almost no indication of their isopod nature. The female pierces the host's skin with the aid of styliform mandibles to suck blood. It seizes the host's skin by means of its prehensile pereiopoda. The pleopoda are respiratory in function. The dwarf male attaches to the female, from which it takes nourishment, and retains its isopod structure. The first larva, the epicardium, is free-living, while the second, the microniscium, is temporarily ectoparasitic on Copepoda. The third larval stage, the cryptoniscium, is free-swimming and seeks a final host, on which it undergoes final development to the adult. The suborder is divided into two tribes, the Cryptoniscina and Bopyrina.
Industry:Science
A suborder of trilobites (a class of extinct arthropods) and a diverse clade consisting of roughly 100 distinct species; they are among the first trilobites and thus the first definitive metazoans to appear in the fossil record. Olenellina first appear in rocks from Scandinavia and eastern Europe that are roughly 530 million years old; they persisted until the end of the Early Cambrian, roughly 510 million years ago. Their extinction coincided with a widespread global extinction.
They are known from all of the Earth's major Cambrian continents with fossiliferous strata, except Australia, Antarctica, and the south China region of Asia, but they reached their greatest abundance and diversity in North America. Charles Walcott, the famous paleontologist associated with the discovery of the Burgess Shale, did some of the first important studies on them.
Industry:Science
A subphylum of echinoderms, made up of members having a flattened theca or body lacking pentameral symmetry. Homalozoans (also called carpoids) include four extinct classes of relatively uncommon primitive echinoderms ranging in age from the Early or Middle Cambrian to the Late Carboniferous. Homalozoans have a flattened, asymmetrical to bilaterally symmetrical theca often composed of a marginal frame of large elongate plates surrounding top and bottom central areas that had numerous smaller plates and were probably flexible.
One homalozoan class (Ctenocystoidea) has no attached appendages; two classes (Stylophora and Homostelea) have a single plated armlike or taillike appendage used for feeding or swimming; and one class (Homoiostelea) has two plated appendages at opposite ends of the theca, one used for feeding, the other for swimming. The mouth is located either on one edge of the theca or at the base of the armlike appendage, while the anal pyramid is usually at the opposite margin or corner of the theca. All homalozoans were apparently mobile, benthic, detritus or suspension feeders that had adopted a flatfish way of life. Because they have a typical echinoderm skeleton with single-crystal, multiporous, sutured, calcite plates, most researchers consider homalozoans to be true echinoderms. However, they seem only distantly related to other echinoderms that have well-developed pentameral symmetry. It has been argued that one class of homalozoans (stylophorans or calcichordates) is intermediate between echinoderms and several groups of chordates, thus making the class directly ancestral to the vertebrates. However, this proposal has not been widely accepted by other echinoderm or vertebrate paleontologists.
Industry:Science
A subphylum of free-living echinoderms in which the body is essentially globoid with meriodional symmetry. They lack arms, brachioles, or other appendages, and do not at any time exhibit pinnate structure. The Echinozoa range from the Early Cambrian to the present day. There are four classes that can definitely be placed here:
# Edrioasteroidea, Lower Cambrian to lower Carboniferous echinozoans in which the mouth and anus were both directed upward and ambulacra (three to five in number) served as food-collecting areas;
# Echinoidea, the existing and fossil sea urchins, originating in the Middle Ordovician;
# Ophiocistioidea of the Lower Ordovician through Middle Devonian, with a domed aboral surface cover with large polygonal plates and a flat adoral side with a mouth and five radiating ambulacra; and
# Holothuroidea, the existing and fossil sea cucumbers, which apparently first appeared in the Devonian.
Two other extinct echinoderm classes can be placed here for convenience:
# Lower Cambrian Camptostromatoidea, conical or domal animals with plates of varying size that overlapped on the lower theca; and
# Lower Cambrian Helicoplacoidea, cylindrical animals with a spirally plated test and three ambulacra on the surface. The latter class may be the sister group of both echinozoans and crinozoans.
Industry:Science
A subphylum of Protozoa, typically with spores. The spores are simple and have no polar filaments. There is a single type of nucleus. There are no cilia or flagella except for flagellated microgametes in some groups. In most sporozoa there is an alternation of sexual and asexual stages in the life cycle. In the sexual stage, fertilization is by syngamy, that is, the union of male and female gametes. All sporozoa are parasitic.
Industry:Science
A subphylum of Protozoa. Sarcomastigophora replaces Rhizoflagellata for those protozoa that possess flagella or pseudopodia or both, according to a classification set up by an international committee of the Society of Protozoologists. Included organisms have a single type of nucleus, except the developmental stages of some Foraminiferida. Sexuality, if present, is syngamy, the fusion of two gametes. Spores typically are not formed. Flagella may be permanent or transient or confined to a certain stage in the life history; this is true also of pseudopodia. Both flagella and pseudopodia may be present at the same time.
Industry:Science
A subphylum of spore-producing Protozoa containing the two classes Myxosporidea and Microsporidea. Myxosporidea contains the three orders Myxosporida, Actinomyxida, and Helicosporida. Microsporida is the only order in the class Microsporidea. Cnidospora are parasites of cells and tissues of invertebrates, fishes, a few amphibians, and turtles.
Industry:Science
A subphylum of the Mollusca comprising members of the classes Monoplacophora, Gastropoda, and Cephalopoda. The use by paleontologists of subphyla, including Cyrtosoma and Diasoma, in the classification of the phylum Mollusca has not been generally adopted by students of living forms. There is no disagreement over the further division of the phylum into eight clearly distinguishable classes.
Industry:Science
A subphylum of the phylum Arthropoda in the long-established classification scheme which comprises three groups at subphylum level; it is almost certainly not a natural assemblage. Each of the other two subphyla (Trilobitomorpha and Chelicerata) is more likely to be monophyletic.
Industry:Science
A subphylum of the phylum Arthropoda. The Chelicerata can be defined as those arthropods with the anteriormost appendages as a pair of small pincers (chelicerae) followed usually by pedipalps and four pairs of walking legs, and with the body divided into two parts: the prosoma (corresponding approximately to the cephalothorax of many crustaceans) and the opisthosoma (or abdomen). There are never antennae or mandibles (lateral jaws). The Chelicerata comprise three classes: the enormous group Arachnida (spiders, ticks, mites, scorpions, and related forms); the Pycnogonida (sea spiders or nobody-crabs); and the Merostomata (including the extant Xiphosurida or horseshoe crabs).
Industry:Science
