Earlier work by yours truly
on Acleistorhinus relied on drawings of the specimen (Fig. 3). Here (Fig. 1) a DGS tracing (colorizing skull bones) of photos from the original paper (Daly 1969) reveals a slightly new interpretation of the skull, and the jugal in particular.
Acleistorhinus pteroticus (Daly 1969) Early Permian, ~3.5 cm skull length was consiered by DeBraga (2001, 2003) and DeBraga Reisz (1996) to be a Parareptile related to Lanthanosuchus, which is a clear mismatch. Daly (1969) considered Acleistorhinus a procolophonid. Here, in the large reptile tree, Acleistorhinus is derived from a sister to the RC14 specimen of Milleretta, is a sister to Delorhynchus (below; Reisz, Macdougall and Modesto 2014) and phylogenetically precedes the turtle-like (but not related) Eunotosaurus (Fig. 2).
The middle posterior process of the jugal in Acleistorhinus
is broken in situ and overlying the lower posterior process. Essentially both Delorhynchus and Acleistorhinus had dual lateral temporal fenestrae.
Since both Eunotosaurus and Milleretta
had expanded ribs, it is likely that Acleistorhinus did so too. We do not know the post-crania at present.
The new data
on Acleistorhinus did not change its placement in the large reptile tree. I did not have access to any of the specimens listed above. Even so, the new data further unites two taxa, Delorhynchus and Acleistorhinus, that had been earlier united by a suite of traits. Colorizing the bones greatly helps produce the reconstruction.
Daly E 1969. A new procolophonoid reptile from the Lower Permian of Oklahoma. Journal of Paleontology 43: 676-687.
DeBraga M 2001. The postcranial anatomy of Procolophon (Parareptilia: Procolophonidae) and its implications for the origin of turtles. PhD thesis, University of Toronto.
DeBragra M 2003. The postcranial skeleton, phylogenetic position and probable lifestyle of the Early Triassic reptile Procolophon trigoniceps. Canadian Journal of Earth Sciences 40: 527-556.
DeBraga M and Reisz RR 1996. The Early Permian reptile Acleistorhinus pteroticus and its phylogenetic position. Journal of Vertebrate Paleontology 16(3): 384–395.
Reisz RR, Macdougall MJ and Modesto S 2014. A new species of the parareptile genus Delorhynchus, based on articulated skeletal remains from Richards Spur, Lower Permian of Oklahoma. Journal of Vertebrate Paleontology 34:1033–1043.