Found on an Oak Tree

After seeing a blip by Maurice1948 ( https://www.blipfoto.com/entry/3403038846571512133 ), I went to see what was to be found on my local oak trees.
I found 5 different galls plus something that was a puzzle to me.  I have made a collage of three of the galls plus the (now resolved) puzzle.

Top L. is a Knopper gall which deforms an acorn.  It is caused by the knopper gall wasp, Andricus quercuscalicis.

Top R. are two oak oyster galls caused by another gall wasp, Neuroterus anthracinus.  When the grub is mature, the gall falls off onto the ground and they overwinter on/in the soil to emerge as adults in the spring.

Btm L. is the common oak spangle gall caused by the gall wasp Neuroterus quercusbaccarum.

Finally the image bottom right is a sputnik - the egg cocoon of the sputnik spider, Paidiscura pallens.  I found half a dozen of these and quickly realised they weren't galls because they were soft and attached by silken threads.