An emaciated dog found soaked in urine and covered in matted fur had been neglected for months, according to the RSPCA.
Marley, a 12-year-old Shih Tzu cross, was discovered in a life-threatening condition on a roadside near Weston-super-Mare, Somerset, last Thursday.
He had a 25cm-long dreadlock growing from the fur on his tail.
Vets also had to remove more than a kilogram of matted fur from his feet after it had formed “huge flippers".
RSPCA Animal Welfare Officer Alison Sparkes, investigating the case, said: "The matts were all soaked in urine and all of his feet had huge flippers of overgrown fur on them.
"The front feet had twisted overgrown nails which were 10cm long and caught up in the matted fur, which the vet said would have caused intense pain.
"His tail also had a dreadlock of fur, which was 25cm long, trailing from the end."
She added: "We really want to find the person who is responsible for allowing Marley to get in such a horrendous condition.
"It would have taken months for him to get like this, and he would have been in tremendous pain because of his matted fur and overgrown nails.
"If anyone recognises Marley or knows where he has come from, I would urge them to contact us in confidence on the RSPCA appeal line on 0300 123 8018.”
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Marley had been microchipped, allowing vets to learn his name, age and breed - a Shih Tzu crossed with a Yorkshire terrier.
However, this information had not been updated since the dog’s previous owners.
Ms Sparkes added: “We’re struggling to find out more about who may have recently owned or cared for him.”