PV R 37363) in dorsal view (from above). The distinctive anteriorly broad preparietal bone with a spur-like anterior process is discernible in front of the
pineal foramen.
Madumabisa is mostly known by its complete skull, including the lower jaws. The largest skulls have lengths approaching , mid-sized amongst dicynodonts. Some postcranial remains are also known, but they mostly belong to young juveniles (except for a partial
femur and
rib fragments) and have not been thoroughly prepared or described, and so little can be said of its postcranial anatomy. Like other dicynodonts,
Madumabisa has a short snout with a
turtle-like beak and only a pair of
tusk-like teeth in its jaws.
Madumabisa is characterised by two unique traits (
autapomorphies) amongst dicynodonts. Below the on the back side of the skull (the
occiput)
Madumabisa has an additional pair of deep and well-defined depressions (
fossae) excavated into the , the "paroccipital fossae". Each paroccipital fossa is directly beneath the post-temporal fenestra, and they are separated only by a sharp ridge. No other dicynodonts have paroccipital fossae. Likewise, the shape of the preparietal bone is unique. The preparietal is a singular midline bone unique to dicynodonts and some other therapsids that sits in front of the parietal foramen. In
Madumabisa it has a tab-like shape that broadens towards the front, before constricting into a pointed spur at the tip. This shape is unique to
Madumabisa, and the front of the preparietal is usually more bluntly rounded in other dicynodonts.
Skull Madumabisa has the most generalised skull shape of all recognised lystrosaurids, broadly resembling that of
Dicynodon and other "
Dicynodon-grade"
taxa (i.e. non-kannemeyeriiform, non-lystrosaurid
dicynodontoids) instead of the highly specialised morphologies of other lystrosaurids. For example, the intertemporal bar (the strut of the skull between the two
temporal fenestra) is narrow with the midline
parietal bones compressed together, typical of "
Dicynodon-grade" taxa but unlike the wide and flat intetemporal bar of
Lystrosaurus. Likewise, the
pineal foramen (the opening of the
parietal or "third" eye) is smaller than in
Lystrosaurus but like
Dicynodon. The
secondary palate of the
premaxillary beak is also more like
Dicynodon than other lystrosaurids—the paired palatal ridges at the front are not as narrowly spaced as in
Lystrosaurus and are joined to the midline posterior ridge behind them by a broad, flat plate that is not found in
Lystrosaurus.
Madumabisa also has a distinct bone in the palate, present in most dicynodontoids but characteristically absent in
Lystrosaurus. Nonetheless,
Madumabisa still shows incipient development of some characteristic lystrosaurid features. The snout is deflected downwards, with the rim of the beak drawn down below the level of the eyes and nostrils compared to
Dicynodon-grade taxa, but only slightly so relative to the extreme condition of
Lystrosaurus. The
orbits (eye sockets) are relatively larger than "
Dicynodon-grade" dicynodontoids, as in other lystrosaurids. The , a bone found in the nostril of various early tetrapods, has a thin extension reaching out of the naris to meet the
lacrimal (a bone in front of the eye), narrowly separating the maxilla from the
nasal bone above. This contact is not present in non-lystrosaurid Permian dicynodontoids. On the palate, the premaxilla is almost completely separated from the
palatine bone by an extension of the maxilla, which completely separates them in
Lystrosaurus. The interpterygoid vacuity (a space between the two front arms of the
pterygoid bones) is very low, almost level with the median pterygoid plate behind it (where the pterygoids join) as in
Lystrosaurus but not
Dicynodon or the lystrosaurid
Euptychognathus. PV R 17197) The skull of
Madumabisa is relatively lightly built and unornamented compared to other lystrosaurids and Permian dicynodontoids. The
postorbital bars that rim the back of the orbit are relatively narrow and unornamented by thickened bosses as in some other dicynodonts. Bosses are present on the
prefrontal bones in front of the eyes that project outwards, typical of many dicynodontoids, but they are relatively narrow front-to-back as in
Lystrosaurus, albeit not as strongly developed. A single rugose nasal boss is also present on top of the snout, typical of dicynodontoids, though it is not greatly developed. The caniniform processes, bony extensions of the
maxilla that house the tusks, are relatively narrow and lack a lateral buttress projecting out laterally beyond the width of the tusk. The premaxilla lacks a median ridge found in most species of
Lystrosaurus and many other "
Dicynodon-grade" taxa, save for a slight ridge at the highest point of the premaxilla. There is a distinct keel along the bottom of the front end of each anterior pterygoid arm, unlike
Euptychognathus.
Mandible Relative to the skull, the mandible of
Madumabisa is much more like that of
Lystrosaurus, with a relatively short and deep symphysis at the tip where the two
dentary bones are fused together. The lateral dentary shelf, a site for jaw muscle attachment in dicynodonts, starts out thickened and diffuse in front of the mandibular fenestra, but becomes extremely thin and sheet-like where it forms the upper border of the fenestra. Due to its extreme thinness, the rear edge of the fenestra is tapers to an upward curving point, creating an
airfoil shape (as seen in some
Lystrosaurus specimens) compared to the oval opening typical of dicynodontoids. Above the anterior edge of the shelf, the dentary bears rugged, corrugated muscle scars, a feature characteristic of lystrosaurids. The rest of the mandible is otherwise typical of
bidentalian dicynodonts. ==Classification==