Mastodons, saber-toothed tigers, ice ages and laptops? Though named after a primordial era of Earth's past, the massive avant-garde act Pleistocene is one of Denver's most forward-looking and highly evolved ensembles. Drawing inspiration from such experimental entities as Godspeed You! Black Emperor and Sigur Ros, the ten-piece troupe incorporates guitar, bass, drums, saxophone, trumpet, trombone, banjo, cello, samples and computer manipulation in its quest for soaring, melody-laced magnificence. Ironically, the band was conceived as a solo project by Eric Gangloff, late of the transplanted New York outfit the Stephen Hero, but after being joined by former cohorts John Marbach and Chris Meckes, the lineup began to swell into its current form, which operates very much as an egalitarian and organic cooperative. No wonder, then, that the group is aligned with the radical Breakdown Book Collective (1409 Ogden Street), which will be hosting Gangloff and comrades' performance at 9 p.m. Saturday, July 16, along with George and Caplin and Sandusky. Pleistocene will be working on its debut recording this summer, even as it searches for a new drummer. With any luck, though, its progressive sound and spirit won't face extinction any time soon.