Data from: Tooth microwear and occlusal modes of euharamiyidans from the Jurassic Yanliao Biota reveal mosaic tooth evolution in Mesozoic allotherian mammals

‘Haramiyidans’ are extinct mammaliaforms often clustered with
Multituberculata as Allotheria, and with a fossil record extending from
the Upper Triassic to possibly the Upper Cretaceous. For many decades,
‘haramiyidans’ were known only from isolated teeth, and their
relationships to other mammaliaforms remain unclear. With the discovery of
several euharamiyidans represented by skeletal specimens from the Jurassic
Yanliao Biota, north‐western China, our knowledge of this group has
significantly advanced. Nonetheless, much morphology, including dentition
and occlusal patterns, has only been briefly described for most taxa, and
phylogenetic reconstruction and interpretation of the biology of the group
still remain unclear or controversial. Here we provide systematic
descriptions of the dental wear of shenshouids (Qishou and Shenshou) from
the Yanliao Biota. We reconstruct the occlusal mode of shenshouids and
compare it with those of other taxa based on our observation of specimens
of most known ‘haramiyidan’ taxa. Several occlusal patterns are
recognized. In particular, that of Thomasia, Haramiyavia and Maiopatagium
is similar to the multituberculate M1/m1 occlusal relationship and
probably represents the primitive occlusal condition in ‘haramiyidans’.
The occlusal mode of shenshouids resembles the multituberculate M2/m2
occlusion. The double‐engaged mode in Arboroharamiya and Vilevolodon, as
well as that of Eleutherodon, represents a more advanced occlusal pattern.
The diverse dental occlusions suggest diverse diet adaptations and
resource partitioning from co‐existing taxa in the Jurassic forests; they
also reflect mosaic evolutionary transformations and complicated
phylogenetic relationships within the group. Some aspects of the dental
evolution remain challenging and require further vigorous testing.