PRIMATES, Linnaeus, 1758

MacPhee, Ross D. E., Gaillard, Charlène, Forasiepi, Analía M. & Sulser, R. Benjamin, 2023, Transverse Canal Foramen And Pericarotid Venous Network In Metatheria And Other Mammals, Bulletin of the American Museum of Natural History 2023 (462), pp. 1-125 : 63

PRIMATES

GALAGO (LORISIFORMES, GALAGIDAE ) AND MICROCEBUS (LEMURIFORMES, CHEIROGALEIDAE ) (figs. 36C, 37A–D). Unlike other primates, lorisiforms, and cheirogaleid lemuriforms exhibit well developed transcranial venous channels in the mesocranial region. In these strepsirhines a venous plexus surrounds the ascending pharyngeal artery as it enters the carotid foramen ( Saban, 1963; Cartmill, 1975; MacPhee, 1981). (The internal carotid artery, reduced to a thread in these taxa, is functionally replaced by an anastomosis between the ascending pharyngeal artery and the circulus arteriosus [Cartmill, 1975]; this anastomosis is not known to occur in marsupials [Aplin, 1990].) The plexus is found where the PVP and BVP occur in other mammals and presumably incorporates them in whole or in part. The plexus is connected to the cavernous sinus by a large emissarium, regarded here as a primary homolog of the ICV (= sinus carotidien of Saban, 1963) (fig. 37A). Other primates do not exhibit ICV hypertrophy of this kind, and likely possess only a small internal carotid venous plexus along the lines of the one in Homo .

In Galago both the ascending pharyngeal artery and the ICV are retiform and intertwined (fig. 37A), which may mean that they function as a counter-current heat-exchange mechanism (see Cartmill, 1975; Caputa, 2004). However, in Microcebus the artery is a single tube, not a rete, and the function of this arrangement in mouse lemurs is obscure (fig. 37D). According to Saban (1963: fig. 36), two emissaria leave the rostral carotid foramen in Cheirogaleus (a close relative of Microcebus ) to anastomose with the maxillary vein or EJV. Indicators are ambiguous regarding whether these qualify as TCVs; their destinations are similar to those of marsupial TCVs, but separate TCFs are absent. Both the ICV/BVP (= sinus pétro-occipital of Saban, 1963) and IJV are depicted as rather small in this lemur, but Saban’s figure is impressionistic and actual dimensions are not provided.