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Endothiodon tolani, new dicynodont species from Permian of Tanzania
A new online paper:
C.B. Cox & Kenneth D. Angielczyk (2015)
A new endothiodont dicynodont (Therapsida, Anomodontia) from the
Permian Ruhuhu Formation (Songea Group) of Tanzania and its feeding
Journal of Vertebrate Paleontology (advance online publication)
Cranial material of the dicynodont Endothiodon from the middle
fossiliferous horizon of the Permian Ruhuhu Formation (Ruhuhu Basin,
Tanzania) is described as a new species, E. tolani is distinguished
from other Endothiodon species by the absence of a pineal boss and the
presence of tusks in most specimens. Although some parts of the Ruhuhu
Formation probably correlate with the Eodicynodon or Tapinocephalus
assemblage zones of the South African Karoo Basin, it is uncertain
whether E. tolani is older than E. bathystoma or E. mahalanobisi.
There is less evidence for extensive anteroposterior translation of
the mandible in E. tolani than in other dicynodonts. The jaw joint is
specialized for allowing some medial-lateral motion. Mastication
involved unilateral chewing. Flexure of the postdentary bones relative
to the fused dentaries permitted the posterolaterally directed rows of
teeth on one side of the skull and mandible to move past one another.
The long tooth rows and prominent horn-covered ridges and grooves on
the palate and mandible of Endothiodon are unique among dicynodonts.
Comparisons with other taxa suggest that its feeding system may have
been specialized for cutting three-dimensional objects such as stems
or rhizomes. The dicynodont feeding system is very stereotyped
throughout the clade's history, but Endothiodon escaped the
constraints that affected other dicynodonts, allowing it to evolve a
unique skull morphology. This evolutionary flexibility did not
translate into high taxonomic richness (we recognize only three
species of Endothiodon), but Endothiodon was able to achieve high
levels of relative abundance in some basins.