Rupelramphastoides knopfi Mayr
Well, the head appears to have also been found, yet in another specimen, so here’s the reconstruction after measuring the skull.:
*********************

It does not really differ that much from the previous version.:
*********************

*********************
References:
[1] Gerald Mayr: A tiny barbet-like bird from the Lower Oligocene of Germany: the smallest species and earliest substantial fossil record of the Pici (woodpeckers and allies). The Auk 122(4): 1-9. 2005
[2] Gerald Mayr: Avian Evolution: The Fossil Record of Birds and its Paleobiological Significance. Wiley-Blackwell 2016
*********************
edited: 18.07.2017