Dog types are broad categories of dogs based on function; dog types are not identical to modern dog breeds but dogs identified primarily by specific function or style of work rather than by lineage or appearance, including ancestral forms (or landraces) that arose undocumented over a long period of time.
The terms dog breed and dog type are sometimes used interchangeably, but they have different meanings. Modern dog breeds are registered with one or more kennel club, which acknowledges a particular breed standard,[note 1] and keeps records of pedigree. Members of modern dog breeds share a common set of heritable characteristics, determined by the kennel club that recognizes the breed. These characteristics can be functional (e.g., the characteristic folds in a bulldog's skin serve to protect it during fights), but need not be (e.g., many breed standards require particular coat colors). Although many purebred dogs also belong to one or more types, dog types are not recognized by kennel clubs. A dog type can be referred to broadly, as in Bird dog, or more specifically, as in Spaniel. Dogs raised and trained for a specific working ability rather than appearance may not closely resemble other dogs doing the same work, or any of the dogs of the analogous breed group of purebred dogs.
With the beginnings of agriculture, approximately 12,000 years ago, humans began making use of dogs in various ways. Molecular biologist and founder of the Canine Genome Project Elaine Ostrander comments, "When we became an agricultural society, what we needed dogs for changed enormously, and a further and irrevocable division [between dogs and wolves] occurred at that point." There is a great deal of speculation about the early uses of dogs, but recent genetic analysis shows that the earliest ancestors of modern breeds (those with the least genetic divergence from the ancestral wolf) include lap dog types (Pekingese, Shih Tzu) along with hunting dog and working dog types.[note 2]
The earliest books in the English language to mention numbers of dog types are from the "Cynegetica" (hunting literature), namely The Art of Venery 1327 by the Anglo-French Master of game, Twiti (Twici), a treatise which describes hunting with the limer (a leashed bloodhound type), the pack of running hounds (scent hounds) greyhounds, and alaunts. More significantly in recording the use and description of various dog types, The Master of Game circa 1406 by Edward of York   a treatise which describes dogs and their work, such as the alaunt, greyhound, pack scent hounds, spaniel and mastiff used by the privileged and wealthy for hunting purposes. "The Master of Game" is a combination of the earlier Art of Venery and the famous French hunting treatise Livre de Chasse by Phébus (Gaston Phoebus) circa 1387. The Boke of St. Albans, written in 1486  a "school" book about hawking, hunting, fishing, and heraldry, attributed to one, Juliana Berners (Barnes), lists dogs of the time mainly by function: " First there is a greyhound, a bastard, a mongrel, a mastiff, a limer, a spaniel, raches (small-to-medium sized scenthounds),kennets (small hunting dogs), terriers, butcher's hounds, dung-heap dogs, trundel tails (lapdogs?) and prick-eared curs, and small ladies puppies that bear away the fleas and die".
Almost one hundred years later, another book in English, De Canibus Britannicus by the author/physician John Caius, translated (Fleming) from Latin in 1576, attempts the first systematic approach to defining different types of dogs in various categories, demonstrating an apparent increase in types, and population. "English dogs": the gentle (ie well-bred) kind, serving game - harriers, terriers, bloodhounds, gazehounds, greyhounds, limers, tumblers and stealers; "the homely kind"; "the currish kind", toys. "Fowling dogs" - setters and spaniels. As well as the pastoral or shepherd types, mastiffs or bandogs, and various village dogs. Sub-types describing the function of dogs in each group were also included.[note 4]
In 1758, Carl Linnaeus in Systema naturae named the domestic dog “familiaris” and added other dog classifications or species. More dog types were described as species by Johann Friedrich Gmelin in 1788, and by Robert Kerr in his English translation of Systema naturae (The Animal Kingdom) in 1792.[note 5] Today the species Linnaeus named are identifiable as dog types, not species or subspecies. Some, such as Canis aegyptius, a hairless dog type of Peru, have been documented and registered as breeds (Peruvian Hairless Dog). There are only two categories (subspecies) of domestic dog, Canis lupus familiaris and C. l. dingo, recognized by the International Code of Zoological Nomenclature (ICZN Code). 
Beginning with the advent of dog shows in the mid-1800s in England, dog fanciers established stud books and began refining breeds from the various types of dogs in use.
"It is important," reminds Ann Rogers Clark and Andrew Brace, "Not to claim great age for breeds, though it is quite legitimate to claim considerable antiquity for types of dogs." The attempts to classify dogs into different 'species' shows that dog types could be quite distinctive, from the 'Canis melitaeus' of lapdogs descended from ancient Roman pet dogs to the even more ancient 'Canis molossus', the Molossan types, to the 'Canis saultor', the dancing mongrel of beggars. These types were uniform enough to appear to have been selectively bred, but as Raymond Coppinger wrote, "Natural processes can produce, could produce, and do produce populations of unusual and uniform dogs, that is, dogs with a distinctive conformation." The human manipulation was very indirect. In a very few cases, Emperors or monasteries or wealthy hunters might maintain lines of special dogs, from which we have today Pekinese, St. Bernards, and foxhounds.
At the beginning of the 1800s there were only a few dogs identified as breeds, but when dog fighting was outlawed in England in 1835, a new sport of dog showing began. Along with this sport came rules and written records and closed stud books. Some of the old types no longer needed for work (such as the wolfhound) were remade and kept from extinction as show dogs, and other old types were refined into many new breeds. Sometimes multiple new breeds might be born in the same littler of puppies. In 1873 only 40 breeds and varieties were known; today there are many hundreds of breeds, some 400 are recognized by the Fédération Cynologique Internationale.
Dog types today are recognized in the names of Group or Section categories of dog breed registries.[note 6] But dog types have not disappeared. Types of feral dogs are being discovered and registered as breeds, as with the New Guinea Singing Dog and Carolina Dog. Types re-emerge from mixes of breeds, like the Longdogs from Lurchers and Greyhounds. Named types of dogs that are not dog breeds are still being used where function or use is more important than appearance, especially for herding or hunting, as with the herding dog types of New Zealand that are described by their exact function (Heading Dog, Huntaway, Stopping Dog, etc. - functional terms, not necessarily breed names).
For biologists, a type fixes a name to a taxon. Dog fanciers use the term breed type in the sense of “qualities (as of bodily contour and carriage) that are felt to indicate excellence in members of a group”. Breed type is specific to each dog breed’s written standard. A dog that closely resembles the appearance laid out in the standard is said to be typey. Type also is used to refer to "dogs of a well established line", an identifiable style of dog within the breed type, usually from a specific kennel.
Note 1. ^ Every modern dog breed has a written Standard, that describes in detail aspects of appearance. Standards are the basis of the sport of dog showing, as each dog is compared against the ideal of the written standard and awards are based on how closely the dog resembles the standard.
note 2. ^ Presumed to be of older lineage are modern dog breeds Shiba Inu, Chow Chow, Alaskan Malamute, Basenji, Shar Pei, Siberian Husky, Afghan Hound, Saluki, Tibetan Terrier, Lhasa Apso, Samoyed, Pekingese, and Shih Tzu.
Note 3. ^ Dog types in use in 1486: Grehoun, Bastard, Mengrell, Mastiff, Lemor, Spanyel, Raches, Kenettyes, Teroures, Butchers’ Houndes, Myddyng dogges, Tryndel taylles, Prikherid currys, and smalle ladyes’ poppees. Some of these dog types are still identifiable today.
Note 4. ^ Many modern breeds of dogs still use the names of early types, although they may or may not resemble the old types.Note 5. ^ Early attempts to categorize dogs as species (not actually species, today considered dog types) of Canis are described by Carl Linnaeus in Systema naturae, 1758, Gmelin in1788, Kerr in 1792.