Figure 1. Skull of the basal hard-shell turtle, Baena. Some of these bone IDs and their sutures differ from those from Gaffney 1979. Principally, the gray/red bone is the supratemporal, considered absent by all turtle experts when they do not recognize the pareiasaur origin of the clade.
Yesterday we looked at several turtles with a lateral temporal fenestra. Today a few more are presented including Baena and Kayentachelys, turtles recently added to the large reptile tree (LRT, 1201 taxa).
Figure 2. Kayentachelys skull with bones colored differently than in the original drawings.
These two extinct turtles
nest between basalmost forms and extant turtles.
several turtle clades (Fig. 3) developed various skull fenestrae, including soft-shell turtles beginning with Arganaceras (not sure if it’s a turtle or not yet) and Odontochelys.
Figure 3. Subset of the large reptile tree (LRT, 1199 taxa) with the addition of three basal turtles. The Mongolochelys/Chubutemys clade did not develop temporal fenestrae. Foxemys and Macrochelys had tentative occipital invagination that extended further with more derived taxa in their respective clades.
Among the most striking of the fenestrated turtle skulls
are the [cryptodire = straight neck in dorsal view, S-curve in lateral view] common Eastern box turtle (genus: Terrapene, Fig. 4) and the [pleurodire = S-curve side neck in dorsal view] matamata (genus: Chelus, Fig. 5). It’s difficult to label these two ‘anapsids’ based on their skull morphology, but that’s the traditional label.
Figure 4. Terrapene, the box turtle, with skull bones colorized. Note the fenestrated skull. See how colors make bones so much easier to understand. You’ll note many academic papers have been following this trend lately.
Figure 5. Chelus frmbiata, the mata-mata has a temporal fenestra. Not sure if it’s a lateral or upper type. Note also the mistake made by Dr. Gaffney in overlooking the squamosal and quadratojugal, and mislabeling the supratemporal. This is one skull you can easily get lost in—if you don’t color the bones. Finally, note the sidesweep of the cervicals in this pleurodire turtle.
Gaffney ES 1979. The Jurassic Turtles of North America. Bulletin of the American Museum of Natural History 162(3):91-136.