FIG. 39 in Transverse Canal Foramen And Pericarotid Venous Network In Metatheria And Other Mammals

FIG. 39. Sipalocyon gracilis AMNH VP-9254 (Hathliacynidae, Sparassodonta), adult caudal cranium, selected coronal segments in rostrocaudal order (data source, table 2). As in extant marsupials, large carotid canals probably carried internal carotid vein as well as artery. However, channels for transverse canal veins resembling those of most marsupials or Prothylacynus (fig. 40A) are not in evidence. Small channels on lip of extracranial carotid foramen, thought by Archer (1976) to be possible transverse foramina, are for components of nerve of pterygoid canal and another structure that cannot be securely identified (features 1, 2; cf. fig. 38). Right and left internal carotid veins could have interacted with each other and with caudal portion of transverse basisphenoid sinus via features 3 and 4 (cf. fig. 38D). Key: AS, alisphenoid; BS, basisphenoid; cc, carotid canal; ctbs, caudal portion of transverse basisphenoid sinus; encf, endocranial carotid foramen; encg, endocranial carotid groove; excf, exocranial carotid foramen; fo, foramen ovale; hpf, hypophyseal fossa; mdnc, canal for mandibular nerve (to foramen ovale); mxns, sulcus for maxillary nerve; onvs, sulcus for ophthalmic neurovascular bundle; rtbs, rostral portion of transverse basisphenoid sinus; SQ, squamosal; 1, pterygoid canal; 2, sulcus of unknown function; 3, small canaliculus joining right and left carotid canals (presumably venous, for anastomosis between internal carotid veins); 4, small connector between 3 and rest of caudal transverse basisphenoid sinus; possibly retained portion of notochord canal.