Dogs have long been man's best friend, but research into a rise in pet surnames suggests they are now firmly part of the family.
Gravestones and epitaphs left by generations of animal lovers in memory of their dear departed pets show an increasingly close connection between humans and their companions.
A study of these tombs revealed a shift from cordial Victorian sorrow over deceased animals to 20th-century pet owners mourning their passing like that of a relative. The embrace of pets as part of the family unit is revealed by an increase in surnames being etched on to their memorials after the Second World War, research suggests.
Dr Eric Tourigny studied 1,000 gravestones from 1880 to 1980, and believes the increasingly elaborate tributes from owners, ranging from the touching to occasionally absurd, show the evolution of "from beloved pets to valued family members".
He has also suggested that the epitaphs show a growing acceptance of an animal afterlife, and the belief that dogs do indeed go to heaven.
"Unlike earlier gravestones, which were dedicated to Spot, Rex or Rover and erected by their owners, these later gravestones are dedicated to Spot Smith or Rex Robinson," Dr Tourigny said.
"This suggests that they are not only pets but members of the family by name.
"Many of the later gravestones will also mention grieving 'mums' and 'dads' as opposed to grieving owners."
At Hyde Park Pet Cemetery, which became the first such site in the UK in 1881, epitaphs mourn the dog Balu "poisoned by a cruel Swiss" and the 24-year-old cat Ginger Blyth who was a "king of pussies", but there are few surnames evident.
However, the practice of using these names rapidly increased to around 20 per cent of graves after the Second World War.
These familial designations have since become mandatory for dog collars, giving official status to the growing feeling among mourning post-war pet owners that their beloved animals were indeed part of the family.
Such expressions of grief, according to Dr Tourigny's research in the journal Antiquity, would have been "at odds with socially acceptable beliefs" of earlier decades.
Dr Tourigny researched memorials at The People's Dispensary for Sick Animals cemetery in London, Newcastle's Jesmond Dene, and Hyde Park Pet Cemetery.
As gravestones become more modern, they show a rise in epitaphs being signed by "mummy" or similar figures, indicating a sense of family belonging.
From 1880 to 1960, there is also an almost 30 per cent increase in the belief that "mummy" could one day be reunited with the departed, with research showing a rise in references to some kind of animal paradise.
Dr Tourigny said: "Few 19th-century gravestones reference an afterlife, although some may 'hope' to see their loved ones again. By the mid-20th century, a greater proportion of animal gravestones suggest owners were awaiting a reunion in the afterlife."