1.
Anatomical terminology
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Anatomical terminology is a form of scientific terminology used by anatomists, zoologists, and health professionals such as doctors. Anatomical terminology uses many terms, suffixes, and prefixes deriving from Ancient Greek. These terms can be confusing to those unfamiliar with them, but can be more precise reducing ambiguity, also, since these anatomical terms are not used in everyday conversation, their meanings are less likely to change, and less likely to be misinterpreted. By using precise anatomical terminology such ambiguity is eliminated, an international standard for anatomical terminology, Terminologia Anatomica has been created. Anatomical terminology has quite regular morphology, the prefixes and suffixes are used to add meanings to different roots. The root of a term refers to an organ, tissue. For example, in the disorder hypertension, the prefix hyper- means high or over, the roots, prefixes and suffixes are often derived from Greek or Latin, and often quite dissimilar from their English-language variants. Latin names of such as musculus biceps brachii can be split up and refer to, musculus for muscle, biceps for two-headed. The first word tells us what we are speaking about, the second describes it, when describing the position of anatomical structures, structures may be described according to the anatomical landmark they are near. These landmarks may include structures, such as the umbilicus or sternum, or anatomical lines, the cephalon or cephalic region refers to the head. This area is differentiated into the cranium, facies, frons, oculus, auris, bucca, nausus, oris. The neck area is called the cervicis or cervical region, examples of structures named according to this include the frontalis muscle, submental lymph nodes, buccal membrane and orbicularis oculi muscle. Sometimes, unique terminology is used to reduce confusion in different parts of the body, for example, different terms are used when it comes to the skull in compliance with its embryonic origin and its tilted position compared to in other animals. Here, Rostral refers to proximity to the front of the nose, similarly, in the arms, different terminology is often used in the arms, in part to reduce ambiguity as what is the front, back, inner and outer surfaces. For this reason, the terms below are used, Radial referring to the radius bone, ulnar referring to the ulna bone, medially positioned when in the standard anatomical position. Other terms are used to describe the movement and actions of the hands and feet. International morphological terminology is used by the colleges of medicine and dentistry and it facilitates communication and exchanges between scientists from different countries of the world and it is used daily in the fields of research, teaching and medical care. The international morphological terminology refers to morphological sciences as a biological sciences branch, in this field, the form and structure are examined as well as the changes or developments in the organism
2.
Eye
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Eyes are organs of the visual system. They provide organisms vision, the ability to process visual detail, eyes detect light and convert it into electro-chemical impulses in neurons. Eyes with resolving power have come in ten different forms. Image-resolving eyes are present in molluscs, chordates and arthropods, the simplest eyes, such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. Complex eyes can distinguish shapes and colours, the visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception. In other organisms, eyes are located so as to maximise the field of view, such as in rabbits and horses, the first proto-eyes evolved among animals 600 million years ago about the time of the Cambrian explosion. The last common ancestor of animals possessed the biochemical toolkit necessary for vision, in most vertebrates and some molluscs, the eye works by allowing light to enter and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye. The cone cells and the rod cells in the retina detect, the visual signals are then transmitted to the brain via the optic nerve. The eyes of most cephalopods, fish, amphibians and snakes have fixed lens shapes, and focusing vision is achieved by telescoping the lens—similar to how a camera focuses. Compound eyes are found among the arthropods and are composed of many simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, each sensor has its own lens and photosensitive cell. Some eyes have up to 28,000 such sensors, which are arranged hexagonally, compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera, have eyes of only a few facets, each with a retina capable of creating an image. With each eye viewing a different thing, an image from all the eyes is produced in the brain, providing very different. Possessing detailed hyperspectral colour vision, the Mantis shrimp has been reported to have the worlds most complex colour vision system, trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes, in this, they differ from most other arthropods, which have soft eyes. The number of lenses in such an eye varied, however, some trilobites had only one, in contrast to compound eyes, simple eyes are those that have a single lens. For example, jumping spiders have a pair of simple eyes with a narrow field of view. Some insect larvae, like caterpillars, have a different type of simple eye which gives a rough image, some of the simplest eyes, called ocelli, can be found in animals like some of the snails, which cannot actually see in the normal sense
3.
Brain
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The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the organs for senses such as vision. The brain is the most complex organ in a vertebrates body, in a human, the cerebral cortex contains approximately 15–33 billion neurons, each connected by synapses to several thousand other neurons. Physiologically, the function of the brain is to exert centralized control over the other organs of the body, the brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment, the operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. This article compares the properties of brains across the range of animal species. It deals with the human brain insofar as it shares the properties of other brains, the ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because more can be said about them in a human context. The most important is brain disease and the effects of brain damage, the shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of architecture that apply across a wide range of species. Some aspects of structure are common to almost the entire range of animal species, others distinguish advanced brains from more primitive ones. The simplest way to gain information about brain anatomy is by visual inspection, Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the consists of areas of so-called grey matter, with a dark color, separated by areas of white matter. Further information can be gained by staining slices of tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, the brains of all species are composed primarily of two broad classes of cells, neurons and glial cells. Glial cells come in types, and perform a number of critical functions, including structural support, metabolic support, insulation. Neurons, however, are considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to target cells over long distances
4.
Mouth
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It is also the cavity lying at the upper end of the alimentary canal, bounded on the outside by the lips and inside by the pharynx and containing in higher vertebrates the tongue and teeth. This cavity is known as the buccal cavity, from the Latin bucca. Some animal phyla, including vertebrates, have a digestive system, with a mouth at one end. Which end forms first in ontogeny is a used to classify animals into protostome and deuterostome. In the first multicellular animals there was probably no mouth or gut, the particles became enclosed in vacuoles into which enzymes were secreted and digestion took place intracellularly. The digestive products were absorbed into the cytoplasm and diffused into other cells, the vast majority of other multicellular organisms have a mouth and a gut, the lining of which is continuous with the epithelial cells on the surface of the body. A few animals which live parasitically originally had guts but have secondarily lost these structures, the original gut of multicellular organisms probably consisted of a simple sac with a single opening, the mouth. Indigestible waste is ejected through the mouth, in animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the formation of the gut. In deuterostomes, the blastopore becomes the anus while the gut tunnels through to make another opening. In the protostomes, it used to be thought that the formed the mouth while the anus formed later as an opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the slit-like blastopore close up in the middle, apart from sponges and placozoans, almost all animals have an internal gut cavity which is lined with gastrodermal cells. In less advanced invertebrates such as the sea anemone, the mouth also acts as an anus, circular muscles around the mouth are able to relax or contract in order to open or close it. A fringe of tentacles thrusts food into the cavity and it can gape widely enough to large prey items. Food passes first into a pharynx and digestion occurs extracellularly in the gastrovascular cavity, annelids have simple tube-like gets and the possession of an anus allows them to separate the digestion of their foodstuffs from the absorption of the nutrients. Many molluscs have a radula which is used to scrape microscopic particles off surfaces, in invertebrates with hard exoskeletons, various mouthparts may be involved in feeding behaviour. Insects have a range of mouthparts suited to their mode of feeding and these include mandibles, maxillae and labium and can be modified into suitable appendages for chewing, cutting, piercing, sponging and sucking. Decapods have six pairs of appendages, one pair of mandibles. Sea urchins have a set of five sharp calcareous plates which are used as jaws and are known as Aristotles lantern, in vertebrates, the first part of the digestive system is the buccal cavity, commonly known as the mouth
5.
Evolution
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Evolution is change in the heritable characteristics of biological populations over successive generations. Evolutionary processes give rise to biodiversity at every level of organisation, including the levels of species, individual organisms. In July 2016, scientists reported identifying a set of 355 genes from the LUCA of all living on Earth. The fossil record includes a progression from early biogenic graphite, to microbial mat fossils, existing patterns of biodiversity have been shaped both by speciation and by extinction. More than 99 percent of all species that lived on Earth are estimated to be extinct. Estimates of Earths current species range from 10 to 14 million, more recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described. In the mid-19th century, Charles Darwin formulated the theory of evolution by natural selection. This teleonomy is the quality whereby the process of natural selection creates and preserves traits that are fitted for the functional roles they perform. The processes by which the changes occur, from one generation to another, are called evolutionary processes or mechanisms, the four most widely recognized evolutionary processes are natural selection, genetic drift, mutation and gene migration. Natural selection and genetic drift sort variation, mutation and gene migration create variation, consequences of selection can include meiotic drive, nonrandom mating and genetic hitchhiking. In the early 20th century the modern evolutionary synthesis integrated classical genetics with Darwins theory of evolution by natural selection through the discipline of population genetics, the importance of natural selection as a cause of evolution was accepted into other branches of biology. Moreover, previously held notions about evolution, such as orthogenesis, evolutionism, evolutionary computation, a sub-field of artificial intelligence, involves the application of Darwinian principles to problems in computer science. The proposal that one type of organism could descend from another type goes back to some of the first pre-Socratic Greek philosophers, such as Anaximander, such proposals survived into Roman times. The poet and philosopher Lucretius followed Empedocles in his masterwork De rerum natura, in contrast to these materialistic views, Aristotelianism considered all natural things as actualisations of fixed natural possibilities, known as forms. This was part of a teleological understanding of nature in which all things have an intended role to play in a divine cosmic order. In the 17th century, the new method of modern science rejected the Aristotelian approach, however, this new approach was slow to take root in the biological sciences, the last bastion of the concept of fixed natural types. The biological classification introduced by Carl Linnaeus in 1735 explicitly recognized the nature of species relationships. Other naturalists of this time speculated on the change of species over time according to natural laws
6.
Anatomical terms of location
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Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans. All vertebrates have the basic body plan – they are strictly bilaterally symmetrical in early embryonic stages. That is, they have left and right halves if divided down the centre. For these reasons, the directional terms can be considered to be those used in vertebrates. By extension, the terms are used for many other organisms as well. While these terms are standardized within specific fields of biology, there are unavoidable, sometimes dramatic, for example, differences in terminology remain a problem that, to some extent, still separates the terminology of human anatomy from that used in the study of various other zoological categories. The vertebrates and Craniata share a heritage and common structure. To avoid ambiguities this terminology is based on the anatomy of each animal in a standard way, for humans, one type of vertebrate, anatomical terms may differ from other forms of vertebrates. Thus what is on top of a human is the head, whereas the top of a dog may be its back, for example, many species are not even bilaterally symmetrical. In these species, terminology depends on their type of symmetry, all descriptions are with respect to the organism in its standard anatomical position, even when the organism in question has appendages in another position. This helps avoid confusion in terminology when referring to the organism in different postures. In humans, this refers to the body in a position with arms at the side. While the universal vertebrate terminology used in medicine would work in human medicine. Many anatomical terms can be combined, either to indicate a position in two axes simultaneously or to indicate the direction of a movement relative to the body, for example, anterolateral indicates a position that is both anterior and lateral to the body axis. There is no limit to the contexts in which terms may be modified to qualify each other in such combinations. Generally the modifier term is truncated and an o or an i is added in prefixing it to the qualified term, where desirable three or more terms may be agglutinated or concatenated, as in anteriodorsolateral. Such terms sometimes used to be hyphenated, but the tendency is to omit the hyphen. There is however little basis for any rule to interfere with choice of convenience in such usage
7.
Human head
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In human anatomy, the head is the upper portion of the human body. It supports the face and is maintained by the skull, which encloses the brain. The human head consists of an outer portion surrounding the bony skull. The head rests on the neck, and is provided bony support for movement by the seven cervical vertebrae, the face is the anterior part of the head, containing the sensory organs the eyes, nose and mouth. The cheeks, on side of the mouth, provide a fleshy border to the oral cavity. To either side of the sit the ears. The twelve pairs of cranial nerves provide the majority of control to the head. The sensation to the face is provided by the branches of the trigeminal nerve, the sensation to other portions of the head is provided by the cervical nerves. The head receives blood supply through the internal and external carotid arteries and these supply the area outside of the skull and inside of the skull. The area inside the skull also receives blood supply from the vertebral arteries, the head contains sensory organs, two eyes, two ears, a nose and inside the mouth a tongue. The human head typically weighs between 5 and 11 pounds, human faces are easily differentiable to us due to our brains predispositions toward discriminating human facial forms. When observing a relatively unfamiliar species, all faces seem nearly identical, ancient Greeks had a method for evaluating sexual attractiveness based on the Golden Ratio, part of which included measurements of the head. In many cultures, covering the head is seen as a sign of respect, often, some or all of the head must be covered and veiled when entering holy places, or places of prayer. For many centuries, women in Europe, the Middle East and this trend has changed drastically in Europe in the 20th century, although is still observed in other parts of the world. People may cover the head for other reasons, a hat is a piece of clothing covering just the top of the head. This may be part of a uniform, such as a uniform, a protective device such as a hard hat. Different headpieces can also signify status, origin, religious/spiritual beliefs, social grouping, team affiliation, occupation, while numerous charts detailing head sizes in infants and children exist, most do not measure average head circumference past the age of 21. Reference charts for adult head circumference also generally feature homogeneous samples, one study in the United States estimated the average human head circumference to be 55 centimetres in females and 57 centimetres in males
8.
Skull
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The skull is a bony structure that forms the head of the skeleton in most vertebrates. It supports the structures of the face and provides a cavity for the brain. The skull is composed of two parts, the cranium and the mandible, in the human these two parts are the neurocranium and the viscerocranium or facial skeleton that includes the mandible as its largest bone. The skull forms the anterior most portion of the skeleton and is a product of cephalisation—housing the brain, and several sensory structures such as the eyes, ears, nose, in the human these sensory structures are part of the facial skeleton. In some animals such as horned ungulates, the skull also has a function by providing the mount for the horns. The English word skull is probably derived from Old Norse skulle, while the Latin word cranium comes from the Greek root κρανίον, the skull is made up of a number of fused flat bones, and contains many foramina and processes, and several cavities or sinuses. For details and the constituent bones, see neurocranium and viscerocranium, the human skull is the bony structure that forms the head in the human skeleton. It supports the structures of the face and forms a cavity for the brain, like the skulls of other vertebrates, it protects the brain from injury. The skull consists of two parts, of different embryological origin—the neurocranium and the facial skeleton, the neurocranium forms the protective cranial cavity that surrounds and houses the brain and brainstem. The facial skeleton is formed by the supporting the face. Except for the mandible, all of the bones of the skull are joined together by sutures—synarthrodial joints formed by bony ossification, sometimes there can be extra bone pieces within the suture known as wormian bones or sutural bones. The human skull is considered to consist of twenty-two bones—eight cranial bones. In the neurocranium these are the bone, two temporal bones, two parietal bones, the sphenoid, ethmoid and frontal bones. The bones of the skeleton are the vomer, two nasal conchae, two nasal bones, two maxilla, the mandible, two palatine bones, two zygomatic bones, and two lacrimal bones. Some of these bones—the occipital, parietal, frontal, in the neurocranium, and the nasal, lacrimal, the skull also contains sinus cavities and numerous foramina. The sinuses are lined with respiratory epithelium and their known functions are the lessening of the weight of the skull, the aiding of resonance to the voice and the warming and moistening of the air drawn through the nasal cavity. The foramina are openings in the skull, the largest of these is the foramen magnum that allows the passage of the spinal cord as well as nerves and blood vessels. The many processes of the include the mastoid process and the zygomatic process
9.
Mandible
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The mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the face. It forms the lower jaw and holds the teeth in place. The mandible sits beneath the maxilla, the bone is formed from a fusion of left and right processes, and the point where these sides join, the mandibular symphysis, is still visible as a faint ridge in the midline. Like other symphyses in the body, this is a midline articulation where the bones are joined by fibrocartilage, the body of the mandible is curved somewhat like a horseshoe and has two surfaces and two borders. From the outside, the mandible is marked in the midline by a faint ridge and this ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. On either side of the symphysis, just below the teeth, is a depression, the incisive fossa, which gives origin to the mentalis. Below the second premolar tooth, on side, midway between the upper and lower borders of the body, is the mental foramen, for the passage of the mental vessels. From the inside, the mandible appears concave, near the lower part of the symphysis is a pair of laterally placed spines, termed the mental spines, which give origin to the genioglossus. Immediately below these is a pair of spines, or more frequently a median ridge or impression. In some cases the mental spines are fused to form a single eminence, in others they are absent, above the mental spines a median foramen and furrow are sometimes seen, they mark the line of union of the halves of the bone. Below the mental spines, on side of the middle line, is an oval depression for the attachment of the anterior belly of the digastric. Above the anterior part of line is a smooth triangular area against which the sublingual gland rests, and below the hinder part. To the outer lip of the border, on either side. The ramus of the mandible has four sides, two surfaces, four borders, and two processes. On the outside, the ramus is flat and marked by oblique ridges at its lower part, on the inside, the mandible presents about its center the oblique mandibular foramen, for the entrance of the inferior alveolar vessels and nerve. Behind this groove is a surface, for the insertion of the internal pterygoid muscle. The mandibular canal runs obliquely downward and forward in the ramus, and then horizontally forward in the body, on arriving at the incisor teeth, it turns back to communicate with the mental foramen, giving off two small canals which run to the cavities containing the incisor teeth. In the posterior two-thirds of the bone the canal is situated nearer the surface of the mandible
10.
Cephalon (arthropod head)
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The cephalon is the head section of an arthropod. It is a tagma, i. e. a specialized grouping of arthropod segments, the word cephalon derives from the Greek κεφαλή, meaning head. In insects, head is a preferred term, in chelicerates and crustaceans, the cephalothorax is derived from the fusion of the cephalon and the thorax, and is usually covered by a single unsegmented carapace. In the Late Precambrian or Lower Cambrian Proarticulata species Praecambridium sigillum, that resembles a trilobite. The head of the Thylacocephala is also referred to as a cephalon, the cephalon of trilobites is highly variable with a lot of morphological complexity. The glabella, the expression of the lobe in the cephalon. A toothless mouth and stomach sat upon the hypostome with the mouth facing backwards at the edge of the hypostome. Many variations in shape and placement of the hypostome have been described, the size of the glabella and the lateral fringe of the cephalon, together with hypostome variation, have been linked to different lifestyles, diets and specific ecological niches. The lateral fringe of the cephalon is greatly exaggerated in the Harpetida, highly complex compound eyes are another obvious feature of the cephalon. When trilobites moulted, the librigenae separated along the suture to assist moulting, leaving the cranidium exposed. Trilobite facial sutures can be divided into three main types according to where the sutures end relative to the genal angle. Early Cambrian trilobites belonging to the suborder Olenellina lacked facial sutures, other later trilobites also lost facial sutures secondarily. Carapace Facial suture Pygidium Tagma Thorax
11.
Arthropod
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An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods form the phylum Arthropoda, which includes the insects, arachnids, myriapods, arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages, the rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Their versatility has enabled them to become the most species-rich members of all guilds in most environments. They have over a million described species, making up more than 80% of all described living species, some of which. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab, arthropods primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates, they have open circulatory systems. Like their exteriors, the organs of arthropods are generally built of repeated segments. Their nervous system is ladder-like, with paired ventral nerve cords running through all segments and their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong, arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae that project through their cuticles. Aquatic species use internal or external fertilization. Almost all arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother, arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. The evolutionary ancestry of arthropods dates back to the Cambrian period, the group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall however, the relationships of Metazoa are not yet well resolved. Likewise, the relationships between various groups are still actively debated. Arthropods contribute to the food supply both directly as food, and more importantly indirectly as pollinators of crops. Some species are known to spread disease to humans, livestock. The word arthropod comes from the Greek ἄρθρον árthron, joint, and πούς pous, i. e. foot or leg, arthropods are invertebrates with segmented bodies and jointed limbs
12.
Trilobite
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Trilobites are a fossil group of extinct marine arachnomorph arthropods that form the class Trilobita. Trilobites form one of the earliest known groups of arthropods, Trilobites finally disappeared in the mass extinction at the end of the Permian about 250 million years ago. The trilobites were among the most successful of all early animals, by the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, a fossil record was left behind. The study of fossils has facilitated important contributions to biostratigraphy, paleontology, evolutionary biology. Trilobites are often placed within the arthropod subphylum Schizoramia within the superclass Arachnomorpha, Trilobites had many lifestyles, some moved over the sea bed as predators, scavengers, or filter feeders, and some swam, feeding on plankton. Most lifestyles expected of modern marine arthropods are seen in trilobites, some trilobites are even thought to have evolved a symbiotic relationship with sulfur-eating bacteria from which they derived food. The earliest trilobites known from the record are redlichiids and ptychopariid bigotinids dated to some 540 to 520 million years ago. Contenders for the earliest trilobites include Profallotaspis jakutensis, Fritzaspis spp, all trilobites are thought to have originated in present-day Siberia, with subsequent distribution and radiation from this location. All Olenellina lack facial sutures, and this is thought to represent the original state, other groups show secondary lost facial sutures, such as all Agnostina and some Phacopina. Earlier trilobites may be found and could shed light on the origin of trilobites. Three specimens of a trilobite from Morocco, Megistaspis hammondi, dated 478 million years old contain fossilized soft parts. Early trilobites show all the features of the group as a whole. Morphological similarities between early trilobites and other Cambrian arthropods make analysis of ancestral relationships difficult, however, that trilobites share a common ancestor with other arthropods before the Ediacaran-Cambrian boundary is still reasonable to assume. Changes also included narrowing of the thorax and increasing or decreasing numbers of thoracic segments, specific changes to the cephalon are also noted, variable glabella size and shape, position of eyes and facial sutures, and hypostome specialization. Several morphologies appeared independently within different major taxa, effacement, the loss of surface detail in the cephalon, pygidium, or the thoracic furrows, is also a common evolutionary trend. Notable examples of this were the orders Agnostida and Asaphida, effacement is believed to be an indication of either a burrowing lifestyle or a pelagic one. Effacement poses a problem for taxonomists since the loss of details can make the determination of phylogenetic relationships difficult, tectonic breakup of Pannotia then allowed for the diversification and radiation expressed later in the Cambrian as the distinctive olenellid province and the separate redlichid province
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