The rat-like creature has been named Durlstotherium newmani, christened after Charlie Newman, the landlord of the Square and Compass pub in Worth Matravers, close to where the fossils were discovered on the Jurassic Coast of Dorset.
The new species was identified from just a handful of fossilised teeth, which were found by Portsmouth University undergraduate Grant Smith earlier this year.
A spokesman for the university said: “One of the specimens is named after a pub landlord because he is a keen amateur palaeontologist and has a small museum in his pub.
“He helped us collect samples and was otherwise very helpful and hospitable.”
Newman said the naming had come as a complete surprise.
“I am very honoured, it's not every day that you get something like this named after you - and it is a very significant fossil. It is quite an honour, I am very pleased.”
Newman, who said he was taught by his dad, has been collecting fossils for more than 45 years.
“I became aware there were some interesting micro fossils to be had in the Purbeck beds, and I discovered a particularly rich deposit down in Swanage that I started to collect. I spent two years just for personal study and interest collecting and sieving this material.
“On the strength of that, I found some mammal material. I have two or three teeth and a complete jaw from one of these early mammals similar to that just recorded.
“In this stuff there are tonnes and tonnes of crocodile, turtle, amphibians - there's a few birds, pterosaurs, and even large dinosaur material.”
Newman's family has owned the Square and Compass for more than 100 years, and Charlie is a fourth generation of landlord. The licensee not only spends time looking for fossils, but also makes 20,000 litres of cider a year for the pub.
“Most of the fossiling is a result of taking the dogs for a walk every day. I rarely come home without anything, to be honest,” he added.