MACROSCELIDEA, Butler, 1956

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

MACROSCELIDEA

ELEPHANTULUS ( MACROSCELIDIDAE ) (fig. 37E). In the macroscelidean afrothere Elephantulus fuscipes the carotid foramen transmits a large vein in addition to the internal carotid artery ( MacPhee, 1981: fig. 46c). Although it might be assumed that this vessel is a version of the ICV, its morphological relations in sengis are quite different from those seen in marsupials. Homology is therefore unlikely; however, showing this in developmental terms illustrates how ontogeny can help inform character analysis.

The vein departs from the temporal (= prootic) sinus on the interior sidewall of the skull and crosses the tympanic roof to enter the intratympanic carotid foramen, where it merges with the CS. The vessel never leaves the skull and therefore does not conform to either an emissarial CBV or emissarylike RBV as seen in marsupials. The vein may be a remnant of a portion of the prootic sinus that is lost in most placentals, but this needs to be corroborated. Van der Klaauw’s (1929) paper on the development of the macroscelidean bulla includes section drawings that show a vein that is unidentified but positionally like the one described here for E. fuscipes . Something similar may occur in the chrysochlorid Eremitalpa granti: Roux (1947 : fig. 41) depicts a large unidentified vein passing between the ossifying basisphenoid and the location of the trigeminal ganglion in a 45 mm embryo, but does not discuss its relations. If this vein is widespread in afrotheres—which is completely unknown—it may mark a shared retention, perhaps lost in adult stages of other placental clades.