At first I thought this fallen leaf might be showing black spots due to a leaf spot fungal disease, however this helpful site:

https://ag.purdue.edu/btny/ppdl/Pages/WH_old/hot07/7-24.html

when talking about Tulip Tree Leaf premature yellowing and leaf drop said those are:

"...symptoms most likely related to root stress. Previous extended periods of hot, dry, weather in combination with various site stress factors, are likely contributing factors. An added symptom that frequently accompanies the leaf yellowing is the appearance of circular, black spots between the veins of the yellowing leaves. The black spots are often mistaken for a fungal leaf spot disease. Though alarming in appearance these symptoms do not usually affect long-term tree vigor or health."