Everyone loves the budgerigar!
(genus: Melopsittacus undulates), but few people know it has an unusually large/long lacrimal (tan) that curls under the orbit to contact the postfrontal (Fig. 2), as in it’s larger relative, Ara, the macaw. It looks like a typically jugal on other reptiles. The actual very birdy jugal appears beneath it (cyan).
And where is the maxilla?
Hidden inside the premaxilla and overlapping nasal. The last of it is contacting the anterior jugal.
Melopsittacus undulatus (Linneaus 1758; extant ) is the extant budgerigar, a tiny parrot. Here the nasal wraps around the ventral naris. The lacrimal forms a send jugal below the orbit and contacts the postorbital and squamosal.
Linnaeus C 1758. Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.
The anterior portion is the lacrimal, but the posterior triangular portion is the squamosal, and the middle portion is an ossified ligament sheet between the two bones (Tokita, 2003:756, fig. 6A). Also note the absence of a prefrontal or postfrontal even when all the other circumorbital elements are unfused. They really are absent in modern birds. Note even when the lacrimal first forms in hatchlings (fig. 5D) it includes that dorsal portion you color orange as the prefrontal. So there was never any fusion between separate elements and thus no remnant of any separation for DGS to recover. I don’t know what better evidence you could ask for that DGS isn’t actually recovering boundaries between elements.
Oh, and the reference- Tokita, M. (2003). The skull development of parrots with special reference to the emergence of a morphologically unique cranio-facial
hinge. Zoological Science, 20, 749–758.
It’s downloadable for free.
Okay. I’ve seen it. It’s important to remember, Mickey, that when two bones fuse, both bones are still there.
I have requested the paper. We’ll see. I hope you are correct. I don’t want this to be another situation where one bone has been traditionally misidentified, as in turtles.