Brachipods, mollusks, and sponges are generally recognized from the basal
Tommotian small shelly faunas that are older than the oldest published
records of trilobites. These faunas are known worldwide.
Precambrian mollusks (Kimbarella) are known from Siberia and Australia.
Precambrian sponges are known from China.
Some of the worldwide Ediacaran fauna is generally accepted to be
cnidarian, and many others are believed by some to be cnidarian while
others think they are not.
The oldest record of trilobites I can find is in the Chenjiang fauna, which
also has lobopods. The reference suggests that other trilobites of this
age are known. I did not spot any references on lobopods while quickly
browsing the geology library, so I cannot verify my vague recollection that
some of the older small shelly fossils have been tentatively identified as
lobopod sclerites.
>I do not
>>remember whether other phyla are definitely known from the pre-trilobite
>>basal Cambrian, though there are now some summary papers on the subject.
>>
>>However, if nothing of certain affinity is found below the trilobites, then
>>nothing is known about when taxa appeared and we cannot say whether the
>>trilobites appeared before, after, or simultaneously with the lobopods
>>except by extrapolation.
>
>It is no extrapolation on my part to say that based on presently available
>evidence, the trilobites appear in the record before their putative
>ancestors. That was what this thread was about!
Trilobites appear about the same time as forms putatively resembling their
ancestors. It is extrapolation to conclude anything about their origins
from this information.
David C.