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

Scientists have recently discovered what could be the largest and oldest living organism on Earth,a giant fungus that is an interwoven filigree of mushrooms and rootlike tentacles spawned by a single fertilized spore some 10,000 years ago and extending for more than 30 acres in the soil of a Michigan forest.

In the 2nd part of this sentence - after the comma
If spawned & extending are participles
then there would be no Verb for the noun " a giant fungus " in this clause.

Is it