He was a one-time plumber who gained unexpected renown pursuing his lifelong avocation as a fossil hunter who discovered some of the world’s most significant dinosaur fossils.

From Mexico to Montana, self-taught paleontologist and archaeologist Harley Garbani spent decades “prospecting for bones” in the badlands where bedrock is exposed. He also amassed one of the finest collections of American Indian artifacts in Southern California.

His prime fossil finds are on display at the Natural History Museum of Los Angeles County, the University of California Museum of Paleontology in Berkeley and the Museum of the Rockies in Bozeman, Mont.

Garbani died Thursday of natural causes at his home in Hemet, Calif., said his wife, Mary. He was 88.

“He was a very passionate fossil hunter and someone who understood the scientific value of fossils,” said Luis Chiappe, director of the Natural History Museum’s Dinosaur Institute.

“He didn’t have any academic training in the field, and he didn’t do any research,” Chiappe said. “He was primarily a field person, and he made some truly unique discoveries.”

Those finds include the partial skulls of the youngest-known Tyrannosaurus rex and the youngest-known Triceratops, two iconic dinosaurs, which will be on display in the museum’s new Dinosaur Hall when it opens July 16.

The skulls are among many of Garbani’s fossil finds that have been displayed over the years at the Los Angeles County museum, which paid him to lead fossil-hunting expeditions to Montana in the 1960s.

While leading such a trip in 1966, Garbani found the skull, jawbone and other parts of a T. rex on the Engdahl Ranch, 20 miles northwest of the small town of Jordan, Mont.

“That was only the third specimen that was in any way complete that had ever been found,” said paleontologist Lowell Dingus, who devoted a chapter to Garbani in his 2004 book, “Hell Creek, Montana: America’s Key to the Prehistoric Past.”

“He was certainly among the greatest fossil collectors that ever lived, and the greatest one that I have ever known and worked with,” said Dingus, who worked with Garbani while doing his dissertation fieldwork at UC Berkeley three decades ago.

During the summers from 1972 until several years ago, Garbani was part of the field crews of Berkeley’s Museum of Paleontology that made trips to Montana.

“He not only collected fossil vertebrates but fossil clams and snails and plants,” said Bill Clemens, a curator at the Berkeley museum who led the field trips.

“For us, one of the neat things that he found was the skull of a very young Triceratops, and already that’s been a focus of research as a number of people have been looking into the patterns of growth of that dinosaur,” Clemens said.

“He just had a sense for being able to find these amazing fossils — both large and small,” Dingus said. “He was an expert not only at finding dinosaurs, but also finding very tiny teeth that are small enough that you study them under a microscope. These teeth were from the small mammals that lived in the shadows of the large dinosaurs.

“His skill at this wasn’t simply based on luck. What he was able to do was figure out the kinds of rock layers and the kinds of outcrops that were most likely to have fossils because he had found them in similar-looking rock layers before.”

Garbani was a welcome visitor to the sprawling ranch owned by Robert and Jane Engdahl — and to neighboring ranches — in the rugged hill country of the Missouri Breaks in Montana.

“He called the Hell Creek Bar in Jordan ‘the office,’” Jane Engdahl said. “That’s where he always met with these other bone diggers.”

During the last four or five fossil-hunting trips Garbani made to the area, she said, “he’d have a potluck supper at the bar. He’d walk around with poker chips and give them to the friends to buy their drinks with. That would be ‘Free drinks from Harley.’

“He was well-loved by everybody in Garfield County,” she said.

Garbani — who had, among other things, a previously unknown gopher species and a small dinosaur named after him — received the Society of Vertebrate Paleontology’s first Morris F. Skinner Award in 1990, in recognition of his fossil collecting and contributions to science.