For every Avatar of Lord MahaVishnu will Himself uphold the presence of Lord Shiva.

This very rare and enigmatic picture of Lord Shiva astride a giant tortoise seems to signify that He has always been around in this world,since the beginning of time. 

In the beginning of Brahma's creation, there was said to be only the ocean, so the 

First Avatar of Vishnu was Matasya 

1)Matasya, the sacred fish, representing all those life forms of the ocean. When, over the passage of time, those ocean life forms  slowly evolved into land species as amphibians.Then we had

Second Avatar of Vishnu was Kurma

 2) Kurma, the giant tortoise.

Interestingly even at the Samundra manthan, where Shiva played the pivotal role of swallowing poison, it was Kurma who served as the pedestal for churning the ocean, symbolising a cosmic path to evolution.

So we can see that the acts of the

 Trinity of Hindu Gods...

 Brahma Vishnu Maheshawara can very well be seen even with the scientific periscope of theory of evolution. 

Now, Shiva seated on Kurma, seems to suggest that every Avatar of Vishnu will Himself uphold the presence of Shiva.

Om Namah Shivaya 🕉 🙏 

Om sivaya Namha 

Om Tatpurushaay Vidmahe Vidmahe Mahadevaay Deemahi Tanno Rudrah Prachodayat🙏🙏🙏

🕉Har Har Mahadev shambo shankara 🕉