Tramuntanasaurus was a medium-sized captorhinid, measuring about long from head to tail. The
skull is long and wide. It is distinctly triangular in dorsal view, where it shows a gradual narrowing towards its anterior end but without a sharp decrease in width in the snout area (unlike most moradisaurines). In the upper jaw, the
maxillae form medially extending plates, each bearing up to five rows of teeth. After an anterior area with a single row of four teeth, further rows of teeth begin to appear, up to five, arranged diagonally to each other. These teeth are bulbous, with narrowed bases and subquadrate/subtrapezoidal section. They clearly show wear facets on their
distal side, producing a lateral "heel" outline. In the
mandible, the two most anterior teeth are conical, widened and directed forwards. They are followed by a single row of three smaller teeth directed upwards. Immediately afterwards, on an enlarged area of the dentary bone, several rows of teeth arranged diagonally begin to appear. In the widest area of the dentary plates, five rows of teeth can be distinguished. Like the maxillary teeth, the dentary teeth have a subquadratic-subtrapezoidal section and are bulbous, with a narrowed base. Tooth wear is visible, developing a "heel" on the mesial side of the teeth.
Tramuntanasaurus differs from all other moradisaurines by a combination of characters such as the presence of a double row of teeth anterior to the tooth plate (unlike
Captorhinikos and
Moradisaurus), the absence of a
diastema (unlike
Gansurhinus and
Kahneria), the anteriormost dentary teeth oriented forward (unlike
Captorhinikos and
Gecatogomphius), the presence of five tooth rows on the maxillae and dentaries, a broad snout relative to the length of the skull (unlike
Labidosaurikos,
Moradisaurus, and
Rothianiscus), a postorbital cheek with little lateral convexity, a long anterior process of the
frontal, an anterior process of the
jugal reaching the anterior margin of the
orbit, and
pterygoids without teeth. ==Paleobiology==