Earliest Cambrian find beyond algae/sponge life: Kimbrella. Earliest mollusks: 535 mya.
All known fossilizable phyla (including vertebrates) were created by the tenth stage of Cambrian, 495 mya (or earlier, possibly), a time frame of 60 million years or less.
Earliest known dinosaur: 245 mya, china; Nyasasaurus parringtoni
http://www.reuters.com/article/2012/12/05/us-science-dinosaur-idUSBRE8B400B20121205
(Reuters) - Researchers have found what could be the earliest known dinosaur to walk the Earth lurking in the corridors of London's Natural History Museum.
A mysterious fossil specimen that has been in the museum's collection for decades has now been identified as most likely coming from a dinosaur that lived about 245 million years ago - 10 to 15 million years earlier than any previously discovered examples.
The creature was about the size of a Labrador dog and has been named Nyasasaurus parringtoni after southern Africa's Lake Nyasa, today called Lake Malawi, and Cambridge University's Rex Parrington, who collected the specimen at a site near the lake in the 1930s.
"It was a case of looking at the material with a fresh pair of eyes," Paul Barrett from the Natural History Museum, who worked on the study, told Reuters. "This closes a gap in the fossil record and pushes back the existence of dinosaurs."
Hence, the worst case time for development of dinosaurs from pre-mollusks is actually 250 mya or less, probably 245 mya or even less than that. The time from mollusk to bony fish (420 mya) is 115 my. Acanthodii, cartilaginous fish, came into existence circa 420 mya, with a time from mollusks of 92 my.
The earliest vertebrate, ostracoderm, is dated to at least 435 mya, or 100 my from mollusks.
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