Sentence Correction

This question is from OG11

#39. 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 root-like 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.


Here the original sentence as shown is correct. My doubt is regarding the explanation in OG.

OG Explanation: The present participle "extending" parallels the past participle "spawned".

My doubt: isnt the past participle of a verb is "had + correct verb form".
how is "spawned" a past participle?

dumb.doofus wrote:This question is from OG11

#39. 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 root-like 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.


Here the original sentence as shown is correct. My doubt is regarding the explanation in OG.

OG Explanation: The present participle "extending" parallels the past participle "spawned".

My doubt: isnt the past participle of a verb is "had + correct verb form".
how is "spawned" a past participle?

2 cents

Has/had/have + past tense - past perfect tense/ present perfect tense

Base form of verb + ing - present participle

Base form of verb + ed - past participle

In other words you can say that

has/have/had + past participle - past perfect or present perfect tense

Cheers
Piyush