Erectus &/or Me

Skull low, broad and elongated Cranial capacity 900 cc Median sagittal ridge Supraorbital ridge Postorbital constriction Receding frontal contour Occipital bun or torus Nuchal area extended for muscle attachment Cranial wall unusually thick Brain case narrower than zygomatic arch Heavy facial architecture Alveolar (maxilla) prognathism Large jaw, wide ramus No chin (mentum) Teeth generally large Post-cranial bones heavy and thick

EUKARIOTES MITOCHONDRAL EUKARIOTES CROWN EUKARIOTES OPISTOCHONTA HOLOZOA FILOZOA KINGDOM: METAZOA (ANIMALIA) EUMETAZOA BILATERIA COELOMATA SUPERPHYLUM: DEUTEROSTOMIA PHYLUM: CHORDATA CRANIATA SUBPHYLUM: VERTEBRATA INFRAPHILUM: GNATHOSTOMATA MICROPHYLUM: TELEOSTOMI EUTELEOSTOMI SARCOPTERYGII CHOANATA SUPERCLASS: TETRAPODA AMNIOTA SYNAPSIDA THERAPSIDA CYNODONTIA MAMMALIAFORMES CLASS: MAMMALIA SUBCLASS: EUTHERIA (Placentals) SUPERORDER: EUARCHONTOGLIRES ORDER: PRIMATES SUBORDER: HAPLORHINI INFRAORDER:SIMIIFORMES PARVORDER: CATARRHINI SUPERFAMILY: HOMINOIDEA FAMILY: HOMINIDAE SUBFAMILY: HOMININAE TRIBE: HOMININI GENUS: HOMO SPECIES: SAPIENS SUBSPECIES: ERECTUS

The eukaryotes are distinguished from prokaryotes by the structural complexity of the cells characterized by having many functionall semi-autonomous elements, usually referred to as organelles.
Many of these are membrane bounded and include the nucleus, the rough endoplasmic reticulum, dictyosomes (= golgi apparatus) lysosomes, and in protists contractile vacuoles and extrusomes. Other membrane bound organelles that are not always present include chloroplasts and mitochondria. Non-membrane-bound organelles include cytoskeletal elements (mostly tubulin = microtubule or actin = microfilament - based), contractile (actin-myosin assemblages, centrin) or other motility devices (mitotic spindle, myonemes, cilia, flagella).

The synapomorphic features of the eukaryotes is the nucleus with associated mitotic division system. The first eukaryotic cells probably also had a small array of cytoskeletal elements but these have yet to be identified.

Mitochondrial eukaryotes include all cells with nuclear genomes that at one time in their evolutionary history contained mitochondria. This broad class includes all plants, fungi, animals and most protists.

Crown eukaryotes are an artificial group of eukaryotic organisms found at the top of molecular phylogenetic trees including both eukaryotes and prokaryotes. They were originally thought to represent a late step of eukaryotic evolution (somewhat similar to a crown group) because they include multicellular and macroscopic lifeforms that represent the majority of the biomass of the planet while accounting for less than 1% of the genetic diversity. However, they are in fact the result of an artificial clustering of eukaryotic organisms with slowly evolving gene sequences. They are thus not a crown that excludes simpler eukaryotes, but correspond roughly to the initial radiation of eukaryotes. All eukaryotic lineages branching below the "crown" in phylogenetic trees are misplaced because of the long branch attraction phenomenon.

The opisthokonts (Greek: opìsthios = "rear, posterior" + kontòs = "pole" i.e. "flagellum") or "Fungi/Metazoa group" are a broad group of eukaryotes, including both the animal and fungus kingdoms, together with the eukaryotic microorganisms that are sometimes grouped in the paraphyletic phylum Choanozoa (previously assigned to the protist "kingdom"). Both genetic and ultrastructural studies strongly support that opisthokonts form a monophyletic group.
One common characteristic of opisthokonts is that flagellate cells, such as most animal sperm and chytrid spores, propel themselves with a single posterior flagellum. This gives the group its name. In contrast, flagellate cells in other eukaryote groups propel themselves with one or more anterior flagella.

All animals are members of the Kingdom Animalia, also called Metazoa. This Kingdom does not contain the prokaryotes (Kingdom Mondera, includes bacteria, blue-green algae) or the protists (Kingdom Protista, includes unicellular eukaryotic organisms). All members of the Animalia are multicellular, and all are heterotrophs (that is, they rely directly or indirectly on other organisms for their nourishment). Most ingest food and digest it in an internal cavity.

Animal cells lack the rigid cell walls that characterize plant cells. The bodies of most animals (all except sponges) are made up of cells organized into tissues, each tissue specialized to some degree to perform specific functions. In most, tissues are organized into even more specialized organs. Most animals are capable of complex and relatively rapid movement compared to plants and other organisms. Most reproduce sexually, by means of differentiated eggs and sperm. Most animals are diploid, meaning that the cells of adults contain two copies of the genetic material. The development of most animals is characterized by distinctive stages, including a zygote, formed by the product of the first few division of cells following fertilization; a blastula, which is a hollow ball of cells formed by the developing zygote; and a gastrula, which is formed when the blastula folds in on itself to form a double-walled structure with an opening to the outside, the blastopore.

Somewhere around 9 or 10 million species of animals inhabit the earth; the exact number is not known and even our estimates are very rough. Animals range in size from no more than a few cells to organisms weighing many tons, such as blue whales and giant squid. Most animals inhabit the seas, with fewer in fresh water and even fewer on land.

Defined by a front and rear, an elongate trunk, and the presence of a specific cluster of unique developmental genes, the Hox cluster.
A complex of Hox genes was present in the last ancestor of all triploblast animals (Urbilateria). This cluster was already functioning in the patterning of the anterior-posterior axis of the animal. In contrast, there is until now no evidence for the existence of a Hox cluster in the cnidarians or the sponges, which have emerged earlier in the metazoan family tree.
The cluster presumably appeared by gene duplication in the ancestors of the Bilateria. A common view is that this process of gene duplication has more or less followed an increase of complexity of the body plan in Bilateria, passing through a four or five-gene stage when the nematodes diverged, to six or seven genes in the ancestor of the arthropods and vertebrates, to at least ten genes in the ancestor of the chordates and thirteen in the ancestor of the vertebrates.
A series of new discoveries challenge this view and raise the possibility that the whole cluster with numerous genes appeared in a single genetic radiation and that the history of the cluster since has been dominated by gene divergence and extinction.

Deuterostome means "second mouth", so called because the mouth develops from the second opening into the embryonic gut. The first opening (the blastopore) develops into the anus. The body cavity (coelom) develops from buds off the gut.

The notochord is an elongate, rod-like, skeletal structure dorsal to the gut tube and ventral to the nerve cord. The notochord should not be confused with the backbone or vertebral column of most adult vertebrates. The notochord appears early in embryogeny and plays an important role in promoting or organizing the embryonic development of nearby structures. In most adult chordates the notochord disappears or becomes highly modified. In some non-vertebrate chordates and fishes the notochord persists as a laterally flexible but incompressible skeletal rod that prevents telescopic collapse of the body during swimming.

The nerve cord of chordates develops dorsally in the body as a hollow tube above the notochord. In most species it differentiates in embryogeny into the brain anteriorly and spinal cord that runs through the trunk and tail. Together the brain and spinal cord are the central nervous system to which peripheral sensory and motor nerves connect.

The visceral (also called pharyngeal or gill) clefts and arches are located in the pharyngeal part of the digestive tract behind the oral cavity and anterior to the esophagus. The visceral clefts appear as several pairs of pouches that push outward from the lateral walls of the pharynx eventually to reach the surface to form the clefts. Thus the clefts are continuous, slit-like passages connecting the pharynx to the exterior. The soft and skeletal tissues between adjacent clefts are the visceral arches. The embryonic fate of the clefts and slits varies greatly depending on the taxonomic subgroup. In many of the non-vertebrate chordates, such as tunicates and cephalochordates, the clefts and arches are elaborated as straining devices concerned with capture of small food particles from water. In typical fish-like vertebrates and juvenile amphibians the walls of the pharyngeal clefts develop into gills that are organs of gas exchange between the water and blood. In adult amphibians and the amniote tetrapods (= reptiles, birds and mammals) the anterior most cleft transforms into the auditory (Eustachian) tube and middle ear chamber, whereas the other clefts disappear after making some important contributions to glands and lymphatic tissues in the throat region. The skeleton and muscles of the visceral arches are the source of a great diversity of adult structures in the vertebrates. For example, in humans (and other mammals) visceral arch derivatives include the jaw and facial muscles, the embryonic cartilaginous skeleton of the lower jaw, the alisphenoid bone in the side wall of the brain case, the three middle ear ossicles (malleus, incus and stapes), the skeleton and some musculature of the tongue, the skeleton and muscles of the larynx, and the cartilaginous tracheal rings.

The Craniata are characterized by a skull (initially cartilaginous and fibrous), which includes three types of sensory organs derived in ontogeny from ectodermal placodes; that is, thickened patches of the embryonic skin that sink inward toward the brain where they develop into sensory chambers. Anteriormost of these is the olfactory organ, which is initially unpaired, and becomes paired in the Vertebrata. Behind it are the paired eyes, the photo receptors that develop as lateral outgrowths of the brain. The skin and connective tissues adjacent to the neural (photoreceptive) part of the eye add secondary structures in the Vertebrata (lens, intrinsic muscles, and eye lids). Posteriormost of these sensory organs in the head are the paired acoustic organs or inner ears. The inner ears are mechanoreceptors concerned with hearing, balance, and perception of position of movement. The sensory cells of the inner ear are enclosed in a cavity filled with a liquid, the endolymph, and which develops from one to three semicircular canals. The acoustic organs also comprise a special component, the lateral sensory system, which is lost in most terrestrial craniates (Amniota). It consists of lateralis nerve fibres derived from the acoustic nerve and superficial mechanoreceptors, the neuromasts, which are housed in grooves or canals on the surface of the head. These extend onto the body in the Vertebrata. True neuromasts, however, seem to be unique to the Vertebrata, and have never been observed in hagfishes.

The craniates are characterized by a skull; that is, a complex ensemble of skeletal elements which surrounds the brain and sensory capsules. The skull of hagfishes (top) consists of cartilaginous bars (blue), but the brain is mostly surrounded by a fibrous sheath underlain by the notochord. The skull of lampreys has a more elaborate braincase and comprises a large "branchial basket" surrounding the gills. In the gnathostomes, the braincase is generally closed.

The skull also encloses the brain, always comprising five parts referred to as the rhombencephalon, metencephalon, mesencephalon, diencephalon, and telencephalon. The metencephalon is developed into a cerebellum in the Gnathostomata and some fossil jawless vertebrates. The nerve fibres are primitively non-myelinated and become myelinated only in the gnathostomes. The brain is continued posteriorly by the spinal cord, which is ribbon-shaped but becomes thicker in the gnathostomes. As in cephalochordates, the dorsal (sensory) and ventral (motor) spinal nerves are initially separate, but unite in the gnathostomes. In all craniates, the olfactory (I), optic (II), trigeminal (V), facial (VII), acoustic (VIII), glossopharyngeal (IX) and vagus (X) cranial nerves are present. Additional cranial nerves, the oculomotor (III), trochlear (IV) and abducent (VI) nerves occur only in the Vertebrata. Some consider that the latter have been secondarily lost in hagfishes.

The olfactory organ opens into a median duct, the nasopharyngeal duct, which also serves the intake of the respiratory water. In most vertebrates, however, this duct becomes a blind tube and the intake of respiratory water is made through the mouth or the gill slits. The nasopharyngeal duct lies ventrally against the diencephalon and there, in ontogeny, induces the formation of an important gland, the hypophysis, or pituitary organ, which comprises neural (neurohypophysis) and glandular (adenohypophysis) parts. The adenohypophysis is particularly complex in the Vertebrata, but very simple in hagfishes.

Craniates possess a unique embryonic tissue, the neural crest, that appears dorsal and lateral to the neural tube and which contributes to a great variety of adult tissues and structures including: sensory neurons (nerve cells), some skeletal and connective tissues in the skull, and some pigment containing cells and other integumentary tissues. In the skull, the neural crest cells give rise to the gill arches, jaws and parts of the braincase floor. In the gnathostomes and a number of fossil jawless vertebrates, the neural crest cells are also involved in the formation of the dermal skeleton (scales, teeth, and dermal bones).

The gills of craniates comprise gill filaments, made up by primary and secondary gill lamellae which insure gas exchanges. In hagfishes, the gills have no skeletal support, and are enclosed in pouches connected to the pharynx. Among vertebrates, a similar structure occurs in adult lampreys only, but here skeletal supports (gill arches) are present. The gills are derived from tissues of the embryonic gut (endoderm), but cells from the embryonic skin (ectoderm) are involved in their formation in the gnathostomes. The respiratory water flow is ensured by a special pumping and anti-reflux organ, the velum, situated at the limit between the mouth and the pharynx. There is a theory that the jaws of the gnathostomes are derived from the velum.

As chordates, all craniates develop a notochord, which is primitively large (hagfishes, lampreys), but becomes transitory in most vertebrates and is replaced by elements of the vertebral column, the centra and arcualia.

All craniates (except most tetrapods) possess a caudal fin strengthened by a number of cartilaginous radials. In vertebrates appear dorsal and anal fins, as well as radial muscles which ensure undulatory movements of the fin web. In the gnathostomes and some fossil jawless vertebrates, there are paired pectoral fins. Only the gnathostomes possess both pectoral and pelvic fins, which are modified into locomotory limbs in tetrapods.

All craniates possess an endoskeleton, which is primitively cartilaginous but becomes mineralized in various ways (bone, calcified cartilage) in the vertebrates. Only the gnathostomes and a number of fossil jawless vertebrates possess a mineralized exoskeleton which develops in the skin tissues. The exoskeleton is made up by a variety of tissues (bone, dentine, enamel).

Craniates have a circulatory system of arteries, capillaries and veins, and a chambered, muscular main heart located ventrally and anteriorly in the trunk. In the Vertebrata, the circulatory system is entirely closed. The two heart chambers, the atrium and ventricle are well apart. There are additional accessory venous hearts in the head and tail, which help in venous blood circulation, but these are lost in the Vertebrata. In gill-breathing craniates, the heart pumps venous blood anteriorly into arteries and capillaries in the gills for gas (oxygen and carbon dioxide) exchange with water. Oxygenated blood then collects dorsal to the gills and flows anteriorly to the head and posteriorly to the organs and muscles, and back to the heart. In some Vertebrata (Osteichthyes) diverticles of the digestive tract (lungs or air bladder) supplements or replaces gills as the repiratory organ.

The digestive tract of craniates is longitudinally differentiated into mouth and oral cavity, pharynx, esophagus, intestine, rectum and anus. A stomach is developed in the Gnathostomata and some fossil jawless Vertebrates. All craniates have a pancreas that produces digestive enzymes and hormones (insulin and glucagon) that regulate blood sugar level. The pancreas was ancestrally disseminated along the anterior part of the gut, but becomes condensed into a well-defined organ in the Vertebrata.

All craniates and the related cephalochordates have a liver or hepatic organ that serves many functions including food storage and production of fat emulsifiers (bile).

The kidneys are the chief excretory organs of vertebrates and these organs play an important role in water and salt balance. Although kidneys vary greatly in size, shape and position among species, all contain nephrons as the basic functional units. Each nephron is a nearly microscopic tubule that receives a filtrate of blood (lacking blood cells and very large molecules). The filtrate is processed by selective secretion and reabsorption of materials to produce an excretory product (generally called urine) that contains nitrogenous waste and other materials. Long and complex kidney tubules occur only in the vertebrates.

The Vertebrata have all the characteristics of the Craniata but share, in addition, a number of unique characteristics which do not occur in hagfishes (Hyperotreti). These characteristics are:

• Metamerically arranged endoskeletal elements flanking the spinal cord. There are primitively two pairs of such elements in each metamere and on each side: the interdorsals and basidorsals. In the gnathostomes, there are two additional pairs ventrally to the notochord: the interventrals and basiventrals. These elements are called arcualia and can fuse to a notochordal calcification, the centrum. The ensemble of the arcualia + centrum is the vertebra, and the ensemble of the vertebrae is the vertebral column.
  The vertebrates are characterized by a vertebral column; that is, a variable number of endoskeletal elements aligned along the notochord and flanking the spinal cord. In lampreys, the vertebral elements are only the basidorsal and the interdorsals . In the gnathostomes, there are in addition ventral elements, the basiventrals and interventrals , and the notochord may calcify into centra.
• Extrinsic eye muscles. These muscles are attached to the eyeball and orbital wall, and ensure eye movements
• Radial muscles in fins. These are small muscles associated with each of the cartilaginous radials of the unpaired and paired fins. They ensure the undulatory movements of the fin web.
• Atrium and ventricle of heart closely-set.
• Nervous regulation of heart. The heart in the embryo of the vertebrates is aneural, like the heart of adult hagfishes. In adult vertebrates, however, the heart is innervated by a branch of the vagus nerve.
• Typhlosole in the intestine. This is a spirally coiled fold of the intestinal wall. In the Gnathostomes, it can be developed into a complex spiral valve.
• At least two vertical semicircular canals in the labyrinth
• True neuromasts in the sensory-line system

Gnathostomes are characterized by:

• A vertically biting device called jaws, and which is primitively made up by two endoskeletal elements, the palatoquadrate and Meckelian cartilage, and a number of dermal elements called teeth, sometimes attached to large dermal bones.
  The skull of a gnathostome, or jawed vertebrates, are characterized by vertically biting jaws consisting of the palatoquadrate dorsally and the Meckelian cartilage ventrally. The gill arches are situated internally to the gill filaments, and the nasal capsules open to the exterior by means of paired nostrils.
• Pelvic fins. These are the paired fins or limbs situated just in front of the anus.
• Interventrals and basiventrals in the backbone. These are the elements of the backbone which lie under the notochord, and match the basidorsals and interdorsals respectively.
• Gill arches which lie internally to the gills and branchial blood vessels, contrary to the gill arches of all jawless craniates, which are external to the gills and blood vessels.
• A horizontal semicircular canal in the inner ear
• Paired nasal sacs which are independent from the hypophysial tube. In all extant and fossil jawless craniates, the nasal sacs, which contain the olfactory organs, open into a median duct, the nasohypophysial duct, which takes part to the formation of the pituitary gland and either leads postriorly to the pharynx (e.g. in hagfish and galeaspids) or ends as a blind pouch (e.g. in lampreys and osteostracans). In the gnathostomes, this pouch remains as a thin canal in the palate, the buccohypophysial canal, whereas the nasal sacs open separately to the exterior by external nostrils.

Teleostomi is a clade of jawed vertebrates that includes the tetrapods, bony fish, and the wholly extinct acanthodian fish. Key characters of this group include an operculum and a single pair of respiratory openings, features which were lost or modified in some later representatives. The teleostomes include all jawed vertebrates except the chondrichthyans and the placodermi.
The clade Teleostomi should not be confused with the similar-sounding fish clade Teleostei.
Teleostomes have two major adaptations that relate to aquatic respiration. First, the early teleostomes probably had some type of operculum, however, it was not the one-piece affair of living fish. The development of a single respiratory opening seems to have been an important step. The second adaptation, the teleostomes also developed a primitive lung with the ability to use some atmospheric oxygen. This developed, in later species, into the lung and (later) the swim bladder, used to keep the fish at neutral buoyancy.

The Sarcopterygii or lobe-finned fishes (from Greek sarx=flesh, and pteryx=fin) sometimes considered synonymous with Crossopterygii ("fringe-finned fish", from Greek krossos=fringe) constitute a clade (traditionally a class or subclass) of the bony fishes, though a strict classification would include the terrestrial vertebrates. The living sarcopterygians are the coelacanths, lungfishes, and the tetrapods.
Early sarcopterygians or crossopterygians are bony fish with fleshy, lobed, paired fins, which are joined to the body by a single bone. The fins of crossopterygians differ from those of all other fish in that each is borne on a fleshy, lobelike, scaly stalk extending from the body. Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates, amphibians. They also possess two dorsal fins with separate bases, as opposed to the single dorsal fin of actinopterygians (ray-finned fish).
The braincase of sarcoptergygians primitively has a hinge line, but this is lost in tetrapods and lungfish. Many early sarcopterygians have a symmetrical tail. All sarcopterygians possess teeth covered with true enamel.
Taxonomists who subscribe to the cladistic approach include the grouping Tetrapoda within this group, which in turn consists of all species of four-limbed vertebrates. The fin-limbs of sarcopterygians such as the coelacanths show a strong similarity to the expected ancestral form of tetrapod limbs.

The only animals with choana are the tetrapoda, and they could as well be called Choanata (they are also the only ones with a vomeronasal organ, which has an embryonic origin from the olfactory structure). These internal nasal passages evolved while the vertebrates still lived in water. At this point they already needed to gulp air to get enough oxygen, and rather than open their jaws each time to do this, those mutants who acquired small openings to breathe through were more successful at living in the new environment.
Fish
Fish do not have choanae, instead they have two pairs of external nostrils: each with two tubes whose frontal openings lie close to the upper jaw, and the posterior openings further behind near the eyes. Whether choanae of tetrapods are homologous to the posterior nostrils or not has been debated. Reasons for dispute have been that the posterior nostril in its evolution into choanae would have to switch position relative to other anatomical features, i.e. a nerve. Recent paleontologiclal findings support homology: a 400-million-year-old fossil lobe-finned fish called Kenichthys campbelli has something between a choana and the external nostrils seen on other fish, which makes it look like it has a cleft palate or cleft lip.
The reason seems to be that the posterior opening of the external nostrils has migrated into the mouth for some reason.
A similar evolution has taken place in lungfish. Here the inner nostrils have generally been accepted as homologous to the posterior nostrils, but the homology to true choanae as internal nostrils has been a matter of controversy. The fossil lungfish Diabolepis shows an intermediate stage between posterior and interior nostril and supports the independent origin of internal nostrils in the lungfish.
Tetrapods
Similar migration is still seen in the tetrapod embryo, and can cause a baby to be born with a cleft palate. Why it should migrate is a mystery, since the nostrils would be useless as a breathing device before their final position inside the mouth. They could also already breathe air through their spiracles.
Tetrapods are also equipped with a lacrimal duct, or tear duct. How it evolved is not known, but it has an internal connection with the choana. It is possible that the choana started as a natural crack between maxilla and premaxilla because of an incomplete fusion in air-breathing animals. If this gap got wider and deeper with time, the frontal part of it would have to fuse together to avoid weakening the upper jaw, creating a small opening on the upper lip. Some more migrating, and this gap would meet the anterior pair of the external nasal openings. The posterior pair of the openings was then free to form the lacrimal duct if a migration caused them to come in contact with the eyes.
Choanae analogues in other animals and fossils
This would not have been the first time the jaws evolved some sort of opening. For instance, snakes have evolved a cleft in the lower jaw, allowing them to stick out their tongues without having to open the jaw. For an animal living in water, the formation of a paired cleft on the upper jaw would be quite logical. Terrestrial vertebrates would in any case need a way to breathe without needing to open their jaws each time. Some fossil species are said to have both conventional external nostrils and a choana, but only more fossils will give a real answer to how the choanas evolved.
Lungfish and hagfishes
In addition to tetrapods, the lungfish has internal nostrils too. These seem to have a different origin than those of the tetrapods, and lungfish have no tear duct either.
Hagfishes have a single internal nostril that opens inside the mouth cavity, while Chimaerae have open canals that leads water from their external nostrils into their mouth and through their gills.

Tetrapoda is a crown group including modern amphibians and amniotes, their most recent common ancestor and all of its descendants. The animals have obvious, separate digits (fingers and toes) and well-defined joints in their limbs. Such limbs are called chiridii (chiridium, singular) (Laurin, 1998). Non-tetrapod tetrapodomorphs also possess chiridii, but true tetrapods always possess five or fewer functional digits per limb.

Interestingly, the name Tetrapoda means "four feet," yet snakes, whales, and limbless amphibians are tetrapods. These creatures have simply lost some or all of their limbs. Even when lost, the limbs are not lost uniformly.

Cephalization is the tendency for the head and anatomical units close to the head to form early in ontogeny (life development) and to be well-developed. Cephalization is characteristic of vertebrates and would, therefore, create expectations for patterns in limb development of animals. In most animal embryos, the head and front appendages form first and the lower extremities appear later. This might cause one to assume that if a limb were going to be lost, it would be the hind limbs to be lost because the front limbs appear earlier in ontogeny. Indeed, this is the case in whales where the forelimbs are preserved and the hindlimbs represented by only a vestigal splint for the femur and (in some species) a splint for the femur. This tendency does not hold true, however, in snakes where the hindlimb is represented by a vestigal ilium in primitive forms, but the forelimb is completely absent.

Tetrapods fall into two broad groups, Amphibia and Amniotamorpha. The former is known today from caecillians (amphisbaenians), which are limbless; urodeles (salamanders), which look like amphibian "lizards"; and anurans (frogs and toads). These three groups compose the clade Lissamphibia.

It is difficult to ascertain exactly when and in which group the amniote egg first appeared, but it is believed that diadectomorphs were approaching that condition. It seems likely that these creatures were spending a large amount of their time on land.

Many amniote synapomorphies are widely interpreted as adaptations to the rigors of life on land. Indeed Amniota owes its name to what may be its most distinctive attribute, alarge and hard-shelled "amniotic" egg which possesses of a unique set of membranes: amnion, chorion, and allantois. The amnion surrounds the embryo and creates a fluid-filled cavity in which the embryo develops. The chorion forms a protective membrane around the egg. The allantois is closely applied against the chorion, where it performs gas exchange and stores metabolic wastes (and becomes the urinary bladder in the adult).

As in other vertebrates, nutrients for the developing embryo are stored in theyolk sac, which is much larger in amniotes than in vertebrates generally. Hatchling amniotes also possess an egg-tooth and horny caruncle on the snout tip to facilitate exit from their hard-shelled eggs. The amniotic egg, together with a penis for internal fertilization, loss of a free-living larval stage in the life cycle, and the ability to bury their eggs, enabled amniotes to escape the bonds that confined their ancestors' reproductive activities to aquatic environments.

Some components of the amniotic egg have been variously modified within Amniota. Placental mammals, for example, have suppressed the egg shell and yolk sac, and elaborated the amniotic membranes to enable nutrients and wastes to pass directly between mother and embryo.

Development of extra embryonic membranes in an amniote egg (chick). In this early developmental stage, the yolk sac is expanding over the yolk. The amnion and chorion are expanding over the embryo and will eventually form the amniotic chamber. The allantois is expanding toward the chorion, with which it will form a respiratory membrane, in addition to storing metabolic wastes of the embryo.

The comparative aridity of the terrestrial environment affects all aspects of amniote biology, and not just their reproductive systems. Thus, amniotes have highly keratinized skins that are relatively impervious and reduce water loss. They also possess horny nails that, among other things, enable them to use their forelimbs to dig burrows into which they can retreat during the heat of the day.

The imperative to reduce water loss is equally evident in the density of renal tubules in the metanephric kidney of amniotes, in the larger size of their water-resorbing large intestines, and in the full differentiation of the Harderian and lacrimal glands in the eye socket whose antibacterial secretions help to moisten and, along with a third eyelid (the nictitans), to further protect the eye from desiccation.

The commitment of amniotes to a life on land is also revealed by anextensive system of muscle stretch receptors that enables finer coordination and greater agility during locomotion, their enlarged lungs (which are the only remaining organs of gas exchange owing to the loss of gills), and the complete loss of the lateral line system other vertebrates use to detect motion in water.

Many of these features are rarely preserved in fossils, but there are some novelties in the skeleton that are no less diagnostic of amniotes. For example, amniotes have at least two pairs of sacral ribs, instead of just one pair. They also have an astragalus bone in the ankle, instead of separate tibiale, intermedium, and proximal centrale bones. Finally, they have paired spinal accessory (11th) and hypoglossal (12th) cranial nerves incorporated into the skull, in addition to the ten pairs of cranial nerves present in amphibians.

Synapsida is one of two great branches on the amniote family tree. This is the branch that includes us. Synapsids are characterized by heterodont dentition and glandular skin. "Pelycosaurs" (non-therapsid synapsids) were once considered reptiles, but we now know that their lineage had separated very early.
According to some authorities all therapsids are characterized by some level of endothermy or "warm-bloodedness."

Perhaps the most famous non-mammalian synapsid is Dimetrodon. This animal was the top predator of the Permian. This genus lived in a variety of environments and would have been probably fed on numerous types of other vertebrates including other "pelycosaurs", the giant "amphibians" like Eryops, and diadectomorphs.

Basal therapsids would appear later with their potentially more advanced metabolisms and would have been able to exploit new environments. It is possible that the basal therapsids were covered with hair. It is unkown whether they would have possessed external ears (pinnae), gave birth to live young (a characteristic independently developed in many vertebrate groups), or even if they had fur. Based on the most primitive extant mammals (prototherians), it may be suggested that basal therapsids at the cynodont level may have lacked external pinnae, laid eggs, and had some form of insulation.

All known early synapsids had a lateral temporal fenestra (a hole in the lateral surface of the skull behind the orbit) that is still present in a modified form in mammals. Primitively, the lateral temporal fenestra was bordered by only three bones.

The occiput was broad and it faced posterodorsally. In other early amniotes, the endochondral bones of the braincase formed a narrower surface, and it was more or less vertical.

The pubis had a long, ridged anterodorsal edge.

Non-mammalian therapsids were a successful group in the Permian and earliest Early Triassic. It is interesting that that although they are much more closely related to us (as therian, mammalian, therapsids) than dinosaurs, yet the dinosaurs receive much more attention from the public.

Non-mammalian therapsids grew to a variety of sizes and filled many of the ecological niches we find in the world today. Similar in some respects to modern large ungulates were tapinocephalids. Basal theriodonts were similar to similar our terrestiral carnivorans, and many of the smaller forms filled niches that might correspond to our rodents. It was actually the small forms that were able to survive the extinction event that hit many therapsid groups. Ironically it was these small, insectivoran-style therapsids that would eventually give rise to mammals while the hippo- and carnivoran- mimics went extinct.

Basal therapsids may or may not have had "improved" metabolic conditioning. It seem likely that the relatively advanced forms like basal cynodonts might have been advanced well above the common basal amniote metabolism. If this is true, then it is not unreasonable to restore them with some form of insulatory structure; in this case, hair. Tenrecs and basal mammals (i.e., the duckbilled platypus) show the type of metabolism to which I refer. More basal forms may or may not have had more advanced metabolic rates than modern reptiles.

Cynodontia or cynodonts ("dog teeth") are a taxon of therapsids which first appeared in the Late Permian (approximately 260 Ma) and were eventually distributed throughout all seven continents by the Early Triassic (256 Ma). This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of therapsids. They are named after their dog-like teeth.
Cynodonts have nearly all the characteristics of mammals. Their teeth were fully differentiated, the braincase bulged at the back of the head, and many of them walked in an upright manner. Cynodonts still laid eggs, as all Mesozoic proto-mammals probably did. Their temporal fenestrae were much larger than in its ancestors, and the widening of the zygomatic arch allowed for more robust jaw musculature supporting the evidence of a more mammal-like skull. They also have the secondary palate that other primitive therapsids lacked, except the therocephalians, who were the closest relatives of cynodonts. Their dentary was the largest bone in their lower jaw, as other smaller bones moved into the ears. They were probably warm-blooded, and covered in hair.

All mammals share three characteristics not found in other animals: 3 middle ear bones, hair, and the production of milk by modified sweat glands called mammary glands.

Mammals hear sounds after they are transmitted from the outside world to their inner ears by a chain of three bones, the malleus, incus, and stapes. Two of these, the malleus and incus, are derived from bones involved in jaw articulation in most other vertebrates.

Mammals have hair. Adults of somespecies lose most of their hair, but hair is present at least during some phase of the ontogeny of all species. Mammalian hair, made of a protein called keratin, serves at least four functions. First, it slows the exchange of heat with the environment (insulation). Second, specialized hairs (whiskers or "vibrissae") have a sensory function, letting the owner know when it is in contact with an object in its external environment. These hairs are often richly innervated andwell-supplied with muscles that control their position. Third, through their color and pattern, hairs affect the appearance of amammal. They may serve to camouflage, to announce the presence of especially good defense systems (for example, the conspicuous color pattern of a skunk is a warning to predators), or to communicate social information (for example, threats, such as the erect hair onthe back of a wolf; sex, such as the different colors of male and female capuchin monkeys; presence of danger, such as the white underside of the tail of a white tailed deer). Fourth, hair provides some protection, either simply by providing an additional protective layer (against abrasion or sunburn, for example) or by taking on the form of dangerous spines that deter predators (porcupines, spinyrats, others).

Mammals feed their newborn young with milk, a substance rich in fats and protein that is produced by modified sweat glands called mammary glands. These glands, which take a variety of shapes, are usually located on the ventral surface of females along paths that run from the chest region to the groin. They vary in number from two (one right, one left, as in humans) to a dozen or more.

Other characteristics found in most mammals include highly differentiated teeth; teeth are replaced just once during an individual's life (this condition is called diphyodonty, and thefirst set is called "milk teeth); a lower jaw made up of asingle bone, the dentary; four-chambered hearts, a secondary palate separating air and food passages in the mouth; a muscular diaphragm separating thoracic and abdominal cavities; highly developed brain; endothermy and homeothermy; separate sexes with the sex of an embryobeing determined by the presence of a Y or 2 X chromosomes; and internal fertilization.

The Class Mammalia includes around 5000 species placed in 26 orders (systematists do not yet agree on the exact number or on how some orders are related to others). Mammals can be found in all continents and seas. In part because of their high metabolic rates (associated with homeothermy and endothermy), they often play an ecological role that seems disproportionately large compared to their numerical abundance.

Eutherians are a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals (such as humans) than to living marsupials (such as kangaroos). There are no living nonplacental eutherians, and so knowledge of their synapomorphies ("defining features") is entirely based on a few fossils, which means the reproductive features that distinguish modern placentals from other mammals cannot be used in defining Eutheria.
The features of Eutheria that distinguish them from metatherians, a group that includes modern marsupials, are:

• an enlarged malleolus ("little hammer") at the bottom of the tibia, the larger of the two shin bones.
• the joint between the first metatarsal bone and the entocuneiform bone in the foot is offset further back than the joint between the second metatarsal and mesocuneiform bones - in metatherians these joints are level with each other.
• various features of jaws and teeth.

• the presence of a malleolus at the bottom of the fibula, the smaller of the two shin bones.
• a complete mortise and tenon upper ankle joint, where the rearmost bones of the foot fit into a socket formed by the ends of the tibia and fibula.
• a wide opening at the bottom of the pelvis, which allows the birth of large, well-developed offspring. Marsupials have and nonplacental eutherians had a narrower opening that allows only small, immature offspring to pass through.
• the absence of epipubic bones extending forward from the pelvis, which are not found in any placental, but are found in all other mammals - nonplacental eutherians, marsupials, monotremes and mammaliformes - and even in the cynodont therapsids that are closest to mammals. Their function is to stiffen the body during locomotion. This stiffening would be harmful in pregnant placentals, whose abdomens need to expand.

Euarchontoglires (synonymous with Supraprimates) is a clade of mammals, the living members of which are rodents, lagomorphs, treeshrews, colugos and primates (including humans).
The Euarchontoglires clade is based on DNA sequence analyses and retrotransposon presence/absence data, combining the Glires clade, which consists of Rodentia and Lagomorpha, with that of Euarchonta, a clade consisting of Scandentia, Primates (which includes humans) and Dermoptera.
Euarchontoglires is now recognized as one of four major groups within Eutheria (containing placental mammals). These four clades are usually discussed without a Linnaean rank, but has been assigned the rank of cohort or magnorder, and superorder.
Relations within the four cohorts, Euarchontoglires, Xenarthra, Laurasiatheria, and Afrotheria, and the identity of the placental root, remain somewhat controversial. Euarchontoglires probably split from the Laurasiatheria sister group about 85 to 95 million years ago during the Cretaceous, developing in the Laurasian island group which would later become Europe. This hypothesis is supported by fossil as well as molecular evidence. The clade of Euarchontoglires and Laurasiatheria is recognized as Boreoeutheria.

The Primates are an ancient and diverse eutherian group, with around 233 living species placed in 13 families. Most dwell in tropical forests. The smallest living primate is the pygmy mouse lemur, which weighs around 30 g. The largest is the gorilla, weighing up to around 175 kg.

Primates radiated in arboreal habitats, and many of the characteristics by which we recognize them today (shortened rostrum and forwardly directed orbits, associated with stereoscopic vision; relatively large braincase; opposable hallux and pollex; unfused and highly mobile radius and ulna in the forelimb and tibia and fibula in the hind) probably arose as adaptations for life in the trees or are primitive traits that were retained for the same reason. Several species, including our own, have left the trees for life on the ground; nevertheless, we retain many of these features.

Primates are usually recognized based on a suite of primitive characteristics of the skull, teeth, and limbs. Some of these are listed above, including the separate and well-developed radius and ulna in the forearm and tibia and fibula in the hindleg. Others include pentadactyl feet and presence of a clavicle. Additional characteristics (not necessarily unique to primates) include first toe with a nail, while other digits bear either nails or claws, and stomach simple in most forms (sacculated in some leaf-eating cercopithecids). Within primates, there is a tendency towards reduction of the olfactory region of the brain and expansion of the cerebrum (especially the cerebral cortex), correlated with an increasing reliance on sight and increasingly complex social behavior.

The teeth of primates vary considerably. The dental formula for the order is 0-2/1-2, 0-1/0-1, 2-4/2-4, 2-3/2-3 = 18-36. The incisors are especially variable. In some forms, most incisors have been lost, although all retain at least 1 lower incisor. In others, the incisors are intermediate in size and appear to function as pincers or nippers, as they commonly do in other groups of mammals. In some, including most strepsirhines (see next paragraph), the lower incisors form a toothcomb used in grooming and perhaps foraging. In the aye-aye (Daubentoniidae), the incisors are reduced to 1 in each jaw and are rodent-like in form and function. Canines are usually (but not always) present; they vary in size, including within species between males and females. Premolars are usually bicuspid (bilophodont), but sometimes canine-like or molar-like. Molars have 3-5 cusps, commonly 4. A hypocone was added early in primate history, and the paraconid was lost, leaving both upper and lower teeth with a basically quadrate pattern. Primitively, primate molars were brachydont and tuberculosectorial, but they have become bunodont and quadrate in a number of modern forms.

Living primates are divided into two great groups, the Strepsirhini and the Haplorhini. Strepsirhines have naked noses, lower incisors forming a toothcomb, and no plate separating orbit from temporal fossa. The second digit on the hind foot of many strepsirhines is modified to form a "toilet claw" used in grooming. Strepsirhines include mostly arboreal species with many primitive characteristics, but at the same time, some extreme specializations for particular modes of life.

Haplorhines are the so-called "higher" primates, an anthropocentric designation if ever there was one. They have furry noses and a plate separating orbit from temporal fossa, and they lack a toothcomb. Haplorhines include many more species, are more widely distributed, and in most areas play a more important ecological role. Haplorhines are further divided into two major groups, the Platyrrhini and the Catarrhini. Platyrrhines have flat noses, outwardly directed nasal openings, 3 premolars in upper and lower jaws, anterior upper molars with 3 or 4 major cusps, and are found only in the New World (families Cebidae and Callitrichidae).
Catarrhines have paired downwardly directed nasal openings, which are close together; usually 2 premolars in each jaw, anterior upper molars with 4 cusps, and are found only in the Old World (Cercopithecidae, Hylobatidae, Hominidae).

Most primate species live in the tropics or subtropics, although a few, most notably humans, also inhabit temperate regions. Except for a few terrestrial species, primates are arboreal. Some species eat leaves or fruit; others are insectivorous or carnivorous.

Here, we follow Anderson and Jones (1984) in formally dividing living primates into two suborders, the Strepsirhini and the Haplorhini. We differ, however, in that we place humans and their close relatives, the chimpanzee, gorilla, and orang in the family Hominidae.

Technical characters (teeth)

Technical characters (strepsirhines)

Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia. Apes are the world's largest primates; the orangutan, an ape, is the world's largest living arboreal animal. Hominoids are traditionally forest dwellers, although chimpanzees may range into savanna, and the extinct australopithecines are famous for being savanna inhabitants, inferred from their morphology. Humans inhabit almost every terrestrial habitat. Hominoidea contains two families of living (extant) species:

• Hylobatidae consists of four genera and sixteen species of gibbon, including the lar gibbon and the siamang. They are commonly referred to as lesser apes.

• Hominidae consists of orangutans, gorillas, common chimpanzees, bonobos and humans.

Until recently, most classifications included only humans in this family; other apes were put in the family Pongidae (from which the gibbons were sometimes separated as the Hylobatidae). The evidence linking humans to gorillas and chimps has grown dramatically in the past two decades, especially with increased use of molecular techniques. It now appears that chimps, gorillas, and humans form a clade of closely related species; orangutans are slightly less close phylogenetically, and gibbons are a more distant branch. Here we follow a classification reflecting those relationships. Chimps, gorillas, humans, and orangutans make up the family Hominidae; gibbons are separated as the closely related Hylobatidae.

Thus constituted, the Hominidae includes 4 genera and 5 species. Its nonhuman members are restricted to equatorial Africa, Sumatra and Borneo. Hominid fossils date to the Miocene and are known from Africa and Asia.

Hominids range in weight from 48 kg to 270 kg. Males are larger than females. Hominids are the largest primates, with robust bodies and well-developed forearms. Their pollex and hallux are opposable except in humans, who have lost opposability of the big toe. All digits have flattened nails. No hominid has a tail, and none has ischial callosities. Numerous skeletal differences between hominids and other primates are related to their upright or semi-upright stance.

All members of this family have large braincase. Most have a prominent face and prognathous jaw; again, humans are exceptional. All are catarrhine, with nostrils close together and facing forward and downward. The dental formula is the same for all members of the group: 2/2, 1/1, 2/2, 3/3 = 32. Hominids have broad incisors and their canines are never developed into tusks. The upper molars are quadrate and bunodont; the lowers are bunodont and possess a hypoconulid. The uppers lack lophs connecting labial and lingual cusps and thus, in contrast to cercopithecids, are not bilophodont.

Hominids are omnivorous, primarily frugivorous or folivorous. All but humans are good climbers, but only the orangutan is really arboreal.

Members of this family are well-known for the complexity of their social behavior. Facial expression and complex vocalizations play an important role in the behavior of hominids. All make and use nests. Hominids generally give birth to a single young, and the period of parental care is extended.

Species included in database (Wikipedia):

Ponginae Pongo pygmaeus (Bornean Orangutan) Pongo abelii (Sumatran Orangutan) Homininae Gorillini Gorilla gorilla diehli (Cross River Gorilla) Gorilla gorilla gorilla (Western Lowland Gorilla) Gorilla beringei beringei (Mountain Gorilla) Gorilla beringei graueri (Eastern Lowland Gorilla) Hominini Homo sapiens Pan paniscus (Bonobo Or Pygmy Chimpanzee) Pan troglodytes troglodytes (Central Chimpanzee) Pan troglodytes verus (West Africa Chimpanzee) Pan troglodytes ellioti (Nigeria-Cameroon Chimpanzee) Pan troglodytes schweinfurthii (Eastern Chimpanzee)

See also:

• Early Modern Homo Sapiens
• Homo Sapiens

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