Harrisonavis, the French Flamingo
For various reasons I procrastinated wrapping up my Wikipedia work on flamingos (Phoenicopteridae), but I finally had the motivation to finish the final species on my list, Harrisonavis croizeti.
Harrisonavis was a genus of flamingo from the Late Oligocene to Early Miocene of central France ( Saint-Gérand-le-Puy), first described in 1852 as Phoenicopterus croizeti based on a nearly complete skull, a rarity for fossil flamingos which are typically only known from assorted leg material. Although now considered a distinct genus, this early assignment did make sense given that the skull was remarkably similar to modern flamingos of the Phoenicopterus genus.
Alas the skull was lost and since fossil flamingo skulls are so hard to co...hang on they found an upper bill....and two parts of a lower bill...and the upper bill of a juvenile....and a nearly complete cranium. Yeah, turns out Harrisonavis has all the luck its relatives lacked and has gotten several referred specimens preserving the skull material. These fossils show two ironic things. 1) It is very similar to modern flamingos 2) It also differs subtly enough to actually make a difference.
Sounds weird but hear me out. Basically, it already has the needed parts to be a filter feeder, which is pretty obvious since you don't develope this kind of skull just for the hell of it. The bill is curved, the lower side deep to make room for a large tongue and the upper bill has a central keel where the lamellae can attach to (which later filter water). However, the curvature of the bill is rather weak, the lower bill not all that deep and the maxillary keel is shallow. All of this indicates that while already filter feeding, Harrisonavis was not as good at it as modern species. It does show one thing tho. The greater flamingo type skull has been around for approximately 20 million years and seems to represent the ancestral condition, which only later became the bulbous beak seen in the genera Phoenicoparrus (see below) and Phoeniconaias.
As said before, Harrisonavis was found at Saint-Gérand-le-Puy, which seems to represent a complex of lake environments from the Oligocene and Miocene. Far as I've seen, its hypothesized that these lakes underwent cycles of wet and dry conditions, with the dry conditions in particular leading to evaporation, increased salinity and the brackish water favored by flamingos. Harrisonavis wasn't the only flamingo from the region either. Fossils also show the presence of members of the Palaeolidae (perhaps a topic for a future deep dive), specifically Palaelodus ambiguus and Megapaloelodus goliath (maybe Palaelodus goliath?). Illustrations below by @alphynix for Palaeolodus, Scott Reid (@DinosaurDrawing) / Twitter for Megapaloelodus and artbyjrc - Hobbyist, Digital Artist | DeviantArt for Harrisonavis itself.
And below you can see the difference between the Wikipedia page as it was originally compared to the new version following my brief dive into the literature, tho I admittedly relied mostly on the comprehensive paper by Torres et al. 2015 that went over the new cranial remains and dealt with the older stuff as well.