page_title: Euchambersia
section_title: Maxillary fossa and associated canals
hierarchical_section_title: Euchambersia / Description / Maxillary fossa and associated canals
caption_attribution_description: English: Fig 9. Three-dimensional reconstruction of the maxillary canal in Euchambersia and other therapsids in lateral view. A, BP/1/4009; B, NHMUK 5696 (mirrored for comparison); C, Bauria; D, Olivierosuchus; E, Thrinaxodon. Abbreviations: AlvRam, alveolar rami; Chan, channels excavating the maxilla; ExtNas, external nasal rami of the infraorbital nerve; IntNas, internal nasal rami of the infraorbital nerve; ION, infraorbital nerve; MxCan, maxillary canal; RosSul, sulcus on the rostral-most part of the maxilla and premaxilla for a branch innervating the ventral margin of the upper jaw; SupLab, supralabial ramus of the infraorbital nerve; SptMxC, Septomaxillary canal.
context_page_description: Euchambersia is a genus of therocephalian therapsid that lived during the Late Permian, approximately 255 million years ago, in what is now South Africa. The genus contains a single species, Euchambersia mirabilis, named by paleontologist Robert Broom in 1931 from a skull missing the lower jaws; a second skull, belonging to an immature individual, was later described. It is a member of the family Akidnognathidae, which historically has also been referred by as the synonymous Euchambersiidae.
  Euchambersia was a small and short-snouted therocephalian, possessing large canines as is typical of the group. However, it is notable among therocephalians for possessing ridges on its canines and a large indentation in the side of the skull. Under the erroneous assumption that the canines are grooved instead of ridged, it has been proposed that these structures supported a venom delivery mechanism. More recently, the internal structure of the skull of Euchambersia has been used as stronger evidence in favour of the hypothesis that it was venomous; other possibilities, such as the indentation supporting some sort of sensory organ, still remain plausible.
context_section_description: Behind the incisors and canines, there were no additional teeth in the jaw. Where teeth would be located in therocephalians that do have teeth behind the canines, there is instead a large depression, or fossa, on the side of the maxilla, which is also bounded below by part of the lacrimal and possibly part of the jugal. This fossa is 48% the length of the jaw in the type specimen, and 38% in the second skull. In both skulls, this fossa is divided into two parts: a shallower ridge on top, and a larger and deeper depression on the bottom. A wide furrow beginning behind the canine contacts the bottom of the fossa and then passes into the interior of the mouth. The bottom portion of the fossa is strongly pitted and bears a small opening, or foramen, on both the front and back surfaces.
  CT scanning shows that these openings lead to canals that connect to the trigeminal nerve, which controls facial sensitivity. The forward-directed canal also splits into the three main branches of the infraorbital nerve, all of which connect to the socket of the canine; the junction occurs about 3–6 millimetres (0.12–0.24 in) along the canal, another point of variation between the two skulls. The top branch, the external nasal ramus, splits into four branches in the type skull, but it does not split in the second skull. In other therapsids like Thrinaxodon, Bauria, and Olivierosuchus, the external nasal ramus generally splits into three or more branches. All of these canals would have brought nerves and nutrient-rich tissue to the root of the canines and the rest of the upper jaw.
caption: 3D reconstruction of the maxillary canals from CT scans, compared with those of other therapsids
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