Fig 1.
Three-dimensional rendering of the skulls of Euchambersia mirabilis.
A, NHMUK 5696 (right) and BP/1/4009 (left). B, C close-up views of their respective maxillary fossa in lateral (B) and ventral (C) views showing the sulcus leading from the fossa to the buccal cavity (white arrows). Abbreviations: D, deep part of the maxillary fossa; C, canine; I, incisor; Orb, orbit; S, shallow part of the maxillary fossa.
Fig 2.
Micro-CT sections through BP/1/4009.
A, cross section through the nasal cavity at the level of the fossae; B, cross section through the braincase at the level of the orbits; C, axial section through the snout; D, cross section through the snout at the level of the right canine.
Table 1.
Measurements.
Fig 3.
Procedure to correct the diagenetic deformation on NHMUK 5696 using 3D landmarks (red dots).
Fig 4.
Three-dimensional rendering of the tooth rows of Euchambersia mirabilis.
A, B, C, BP/1/4009; D, E, F, NHMUK 5696. A, D, lingual face of the left teeth seen through the transparent skull; B, E, lingual view of the right teeth seen through the transparent skull; C, F, ventral view showing the position of the tooth sockets (reconstructed in yellow). The fourth replacement incisor of BP/1/4009 is coloured in orange. Abbreviations: 2, second incisor; 3, third incisor; 4, fourth incisor; 5, fifth incisor; C, canine. The white arrow points to a crack on the right canine of BP/1/4009.
Fig 5.
Three-dimensional rendering of the replacement fourth incisor of BP/1/4009.
A-D, the fourth incisor alone; E-H, the fourth incisor and the replacement tooth in orange; I-L, the replacement fourth incisor only. A, E, I, labial view; B, F, J, lingual view; C, G, K, mesial view; D, H, L, distal view. The arrows point to the ridge on the replacement tooth.
Fig 6.
Location of the upper replacement incisor and the ex situ lower? incisor of BP/1/4009.
A, transparent skull in lateral view showing the labial face of the left hand side; B, teeth and transparent skull in ventral view; C, teeth and transparent skull in rostral view. The fourth replacement incisor is coloured in orange; the ex situ incisor is coloured in blue. Abbreviations: 2, second incisor; 3, third incisor; 4, fourth incisor; 5, fifth incisor; C, canine; I, ex situ incisor. The white arrows point to a crack on the right canine of BP/1/4009.
Fig 7.
Three-dimensional rendering of the ex situ incisor of BP/1/4009.
A, labial view (the empty arrow points to the wear facet); B, lingual view; C, mesial view; D, distal view; E, cross CT section through the middle of the ex situ incisor showing the conspicuous ridge (white arrow); F, cross section of the first right incisor of the lower jaw of an unidentified scylacosaurid therocephalian (= Glanosuchus?), redrawn after [51, 52].
Fig 8.
Transverse CT sections through the right canine of NHMUK 5696.
The position of each section is shown on the canine (A, the tooth root is up). The white arrows point to the shallow invagination at the base of the ridge.
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.
Fig 10.
Cross sections through the teeth of various mammals redrawn from literature and compared to Euchambersia.
Mesial is on the top, labial is on the right. * indicates venomous species.
Fig 11.
Three-dimensional rendering of the transparent skulls of (A) a rinkhals (Hemachatus haemachatus) and (B) a python (Python sp.). Oblique view showing the relationship of the mummyfied venom gland (in red), with the fang (in yellow) and the maxillary canal (in green). Abbreviations: Fang, functional fang; Mand, mandible; MxCan, maxillary canal; Orb, orbit; Pits, foramina for the pit organ; VenGl, venom gland.
Fig 12.
Reconstruction of Euchambersia.
Oblique ventro-lateral view showing the ridged dentition. Artwork by Alex Bernardini (Simplex Paleo 2017).
Fig 13.
Three-dimensional rendering of the hypothetical organ that filled the maxillary fossa and its relationship with the maxillary canal (in green).
A, B, BP/1/4009; C, D, NHMUK 5696 (mirrored for comparison). A, C, lateral view; B, D, medial view. Abbreviations: Chan, channels excavating the maxilla; MxCan, maxillary canal; MxOrg, maxillary organ; SptMxC, septomaxillary canal.