Nannaroter

Nannaroter is an extinct genus of Recumbirostran tetrapod within the family Ostodolepidae.

Nannaroter Temporal range: Early Permian
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Order:	†Microsauria
Family:	†Ostodolepidae
Genus:	†Nannaroter Anderson et al., 2009
Species
N. mckinziei Anderson et al., 2009 (type)

History of study

Nannaroter was named in 2009 by Canadian paleontologists Jason Anderson, Diane Scott, and Robert Reisz. It was known from only the holotype specimen, which was found at the Richards Spur locality in Oklahoma. The holotype, a well preserved skull, was found in early Permian-aged fissure fill deposits in Ordovician limestone. The specific name is given for Mark McKinzie, who found and donated the specimen to the Sam Noble Oklahoma Museum of Natural History.

In 2021 a second specimen was referred, ROMVP 86541, a skull with right lower jaw.

Anatomy

Nannaroter is the smallest known ostodolepid and is diagnosed by: (1) the high subtemporal recess that separates the postorbital from the squamosal; (2) four premaxillary tooth positions; (3) 12 maxillary tooth positions; circumorbital walls formed by medial laminae of the prefrontal, lacrimal, and jugal; (5) a ventral flange of the frontal meeting the sphenethmoid; (7) an anterolaterally bulbous sphenethmoid; and (8) a massive epipterygoid. Like other ostodolepids, it has a wedge-shaped skull, a pointed snout, and a temporal emargination. The skull is highly ossified in order to resist anteroposteriorly directed forces, as indicated by the markedly interdigitated sutures.

Ecology

The high degree of ossification in the skull of Nannaroter is seen as an adaptation to a fossorial, or burrowing, lifestyle. More specifically, the animal would likely have used its recumbent snout to push forward into the substrate, facilitated by increased epaxial musculature that inserted into the broad, sloping occiput, as in amphisbaenians. As Nannaroter was known from only one specimen, it has been suggested that it was either a naturally rare component of the assemblage or that its inferred burrowing ecology did not lend itself well to preservation in the fissure fill system.

Relationships

Below is the placement of Nannaroter in the analysis of Huttenlocker et al. (2013):

	Microbrachis Asaphestera Tuditanus Hapsidopareion Saxonerpeton Recumbirostra Pantylus Stegotretus Carrolla Batropetes Rhynchonkos Eocaecilia Nannaroter Pelodosotis Micraroter Proxilodon bonneri Tambaroter Huskerpeton englehorni Pariotichus Euryodus dalyae Euryodus primus Cardiocephalus sternbergi Cardiocephalus peabodyi