The bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven.

The primitive jawless fish have only a single testis, located in the midline of the body, although even this forms from the fusion of paired structures in the embryo.

The most famous is Myllokunmingia, possibly a very primitive agnathid ( i. e., jawless fish ).

While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed vertebrates ( the Gnathostomes ), which have seven arches, and primitive jawless vertebrates ( the Agnatha ), which have nine.

While there is no fossil evidence directly to support this theory, it makes sense in light of the numbers of pharyngeal arches that are visible in extant jawed ( the Gnathostomes ), which have seven arches, and primitive jawless vertebrates ( the Agnatha ), which have nine.

In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar to the other gill opening.

The only vertebrates to lack any structure resembling a vas deferens are the primitive jawless fishes, which release sperm directly into the body cavity, and then into the surrounding water through a simple opening in the body wall.

Ostracoderms (" shell-skinned ") are any of several groups of extinct, primitive, jawless fishes that were covered in an armor of bony plates.

Although the classical molecules of the adaptive immune system ( e. g. antibodies and T cell receptors ) exist only in jawed vertebrates, a distinct lymphocyte-derived molecule has been discovered in primitive jawless vertebrates, such as the lamprey and hagfish.

Anaspida (" without shield ") is an extinct group of primitive jawless vertebrates that lived during the Silurian and Devonian periods.

Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were lacking in oxygen.

The first vertebrates appeared in the form of primitive fish, which greatly diversified in the Silurian and Devonian.

Primitive fish have a four-chambered heart, but the chambers are arranged sequentially so that this primitive heart is quite unlike the four-chambered hearts of mammals and birds.

Though all but the most primitive bony fish lack a spiracle, the pseudobranch associated with it often remains, being located at the base of the operculum.

Lungfish larvae also have external gills, as does the primitive ray-finned fish Polypterus, though the latter has a structure different than amphibians.

Salmonids have a relatively primitive appearance among the teleost fish, with the pelvic fins being placed far back, and an adipose fin towards the rear of the back.

Their low diversity in Africa may explain why some primitive fish families and Cypriniformes coexist with them while they are absent in South America, where these fish may have been driven extinct.

The arrangement in lampreys, which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates.

In its primitive form, the air bladder was open to the alimentary canal, a condition called physostome and still found in many fish.

My thesis is that a branch of this primitive ape-stock was forced by competition from life in the trees to feed on the sea-shores and to hunt for food, shell fish, sea-urchins etc., in the shallow waters off the coast.

Ethan Van Sciver describes Ion as resembling a large, primitive whale or fish.

Cartilaginous fish, such as sharks, have also simple, and presumably primitive, skull structures.

The first that evolved is more primitive and resembles the visual system of animals such as fish and frogs.

The swim bladder normally consists of two gas-filled sacs located in the dorsal portion of the fish, although in a few primitive species, there is only a single sac.

In embryonal development, both lung and swim bladder originate as an outpocketing from the gut ; in the case of swim bladders, this connection to the gut continues to exist as the pneumatic duct in the more " primitive " ray-finned fish, and is lost in some of the more derived teleost orders.

In primitive fish, this ring consists of four plates, but the number is lower in many living ray-finned fishes, and much higher in lobe-finned fishes, various reptiles, and birds.

J M Conlon, J H Youson, T P Mommsen. 1993. Structure and biological activity of glucagon and glucagon-like peptide from a primitive bony fish, the bowfin: Amia calva. J. 295 ( Pt 3 ): 857 – 861.

Semionotiformes (" flag-back form ") is an order of primitive, ray-finned, primarily freshwater fish from the Triassic to the Cretaceous.

In the more primitive areas, where the capacity to absorb and utilize external assistance is limited, some activities may be of such obvious priority that we may decide to support them before a well worked out program is available.

Both Sudan and Ackermann are credited with discovering total computable functions ( termed simply " recursive " in some references ) that are not primitive recursive.

Even earlier examples of this sentiment may be found in Wild Talents by author Charles Fort where he makes the statement: "... a performance that may some day be considered understandable, but that, in these primitive times, so transcends what is said to be the known that it is what I mean by magic.

Early crochet hooks ranged from primitive bent needles in a cork handle, used by poor Irish lace workers, to expensively crafted silver, brass, steel, ivory and bone hooks set into a variety of handles, some of which were better designed to show off a lady's hands than they were to work with thread.

However, there are also some psychological differences in regard to how problems are dealt with and emotional perceptions and reactions that may relate to hormones and the successful characteristics of each gender during longstanding roles in past primitive lifestyles.

* Axiomatic proof: Proofs are deductive derivations of propositions from primitive premises that are ‘ true ’ in some sense.

Believed to have been composed in the wilds of Macedonia, Bacchae also happens to dramatize a primitive side to Greek religion and some modern scholars have therefore interpreted this particular play biographically as:

" Such definitions depend upon "( cultural ) processes rather than abstract musical types ...", upon " continuity and oral transmission ... seen as characterizing one side of a cultural dichotomy, the other side of which is found not only in the lower layers of feudal, capitalist and some oriental societies but also in ' primitive ' societies and in parts of ' popular cultures '.

Being one of the first film hyphenates ( film director, editor and engineer ) Porter also invented and utilized some of the very first ( albeit primitive ) special effects such as double exposures, miniatures and split-screens.

Most fighters up to this point had one engine but a number of twin engined fighters were built, however they were found defenseless against single engine fighters and were relegated to other tasks, some becoming night fighters, fitted with very primitive radar sets.

In some primitive way, early 4GL's were included in the Informatics MARK-IV ( 1967 ) product and Sperry's MAPPER ( 1969 internal use, 1979 release ).

Although some recent writers suggest that Homo georgicus was the first and most primitive hominid ever to live outside Africa, many scientists consider H. georgicus to be an early and primitive member of the H. erectus species.

" Hence although men had become less forebearing, and although natural pity had already undergone some alteration, this period of the development of human faculties, maintaining a middle position between the indolence of our primitive state and the petulant activity of our egocentrism, must have been the happiest and most durable epoch.

Viking navigational techniques are not well understood, but historians postulate that the Vikings probably had some sort of primitive astrolabe and used the stars to plot their course.

Like comets, chondritic asteroids are some of the oldest and most primitive materials in the solar system.

The first mirrors used by people were most likely pools of dark, still water, or water collected in a primitive vessel of some sort.

All programming languages have some primitive building blocks for the description of data and the processes or transformations applied to them ( like the addition of two numbers or the selection of an item from a collection ).

Daegling notes that in 1967, movie and television special effects were primitive compared to the more sophisticated effects in later decades, and allows that if the Patterson film depicts a man in a suit that " it is not unreasonable to suggest that it is better than some of the tackier monster outfits that got thrown together for television at that time.

* Patch, a 3-D Bézier curve used in computer graphics, or a primitive in some 3-D software packages

The ancient gods with tails of animals who stood for primitive bodily insticts, were considered to protect the flocks and herds, and some of them survived in the cult of Dionysos ( Satyrs and Seilinoi ) and Pan ( the goat-god ).

In fact, it is difficult to devise a computable function that is not primitive recursive, although some are known ( see the section on Limitations below ).

Other interpreters believe these references do not support the concept of transfer of the seventh-day rest, and some add that they do not sufficiently prove that Sunday observance was an established practice in the primitive New Testament church.

The idea that some languages were naturally superior to others and that the use of primitive languages maintained their speakers in intellectual poverty was widespread in the early 20th century.