GMAT Sentence Correction (SC) | Re: Scientists have recently discovered what could be the

The reason why there is so much confusion here is that the principles of participle usage have not been understood well. A participle though called present or past participle per se does not indicate the sense of the tense. It goes along with the tense of the main clause.

In the above simple sentence, if the intruding descriptive structures are removed, the clause will read under

Scientists have recently discovered a giant fungus, spawned by a single fertilized spore some 10,000 years ago