请帮助答疑一题！感激~

joyviva

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.

答案就是原文。解释说，spawned by 与extending 并列，修饰filigree，而且体现了动作先后顺序。完全不理解……修饰的词也太远了吧。而且如果这样的话，逗号后面a giant fungus that...就不是一句话啊。。。

请大牛们指教！！！

cx_ding

逗号之后的好像是同位语，解释organism，不用是句子。
我也不太理解这个句子，只是机械的记住了答案，请nn指正。

joyviva

顶顶，谢谢大家

因为还在练习中遇到过另外一道，特别像。也是科学家发现了一个东西，逗号之后就不是一句话了。请问这个句型怎么理解？