Anatomy and phylogenetic value of the mandibular and coronoid canals and their associated foramina in proboscideans (Mammalia)

Abstract

Characters associated with the mandibular canal are differently distributed amongst proboscidean lineages and provide useful information on the systematics and relationships of proboscideans. The aim of this paper is to describe the pattern of the mandibular canal and its associated foramina in proboscideans in order to fully appreciate the extent of interspecific variation of these structures within the group and to discuss its systematic and phylogenetic value. Outgroup comparison indicates that the condition presented by the basal proboscidean Phosphatherium is morphotypic for proboscideans. Primitive proboscidean characters are: the low position of the mandibular foramen, and its crescent-shaped outline, the occurrence of a coronoid foramen (canal), the occurrence of two lateral mental foramina, the posterior one at the level of (or slightly behind) the posterior margin of the symphysis, the anterior one in a more distal position, the absence of a medial mental foramen (MMF), the mandibular canal set just below the tooth row. The occurrence of a single lateral mental foramen may represent a shared derived character of Daouitherium, Numidotherium, and Barytherium. A unique derived feature of the Elephantinae mandible is the occurrence of a medial mental foramen on the medial side of the incisive part of the mandible. MMFs have never been observed in other proboscideans excluding elephantines. The very high frequency of MMFs observed in Mammuthus meridionalis-Mammuthus trogontherii-Mammuthus primigenius (>93 per cent of the studied specimens) could be considered a synapomorphy of this group.

New stem elephant‐shrews (Mammalia, Macroscelidea) from the Eocene of Dur At‐Talah, Libya

“…In proboscideans (including the basal forms Eritherium and Phosphatherium ), the coronoid canal pierces the mesial base of the coronoid process; it extends from behind m3 to a foramen in the medial side of the ascending ramus, near the mandibular foramen (Gheerbrant 2009; Delmer 2005; Ferretti and Debruyne 2011). In Moeritherium , since the observation of Thewissen and Domning (1992), and Savage et al.…”

Jaw anatomy ofPotamogale velox(Tenrecidae, Afrotheria) with a focus on cranial arteries and the coronoid canal in mammals

“… The section in Elephas corresponds to the same individual and mirror-imaged μCT slice figured by Ferretti & DeBruyne (2011: their fig. 2G) .…”

Mammuthus meridionalis (Nesti, 1825) from Apollonia-1 (Mygdonia Basin, Northern Greece) and its importance within the Early Pleistocene mammoth evolution in Europe

“…The taxonomically important cranium and tusks for the distinction between the two genera are missing from the APL collection; however, several lines of evidence exclude an assignment to Palaeoloxodon: a) Palaeoloxodon is characterized by tight enamel folding and presence of midline sinuses; in the APL molars, the moderate enamel folding (APL-687, 716) and midline swellings (APL-687) are traits seen generally in much worn elephantid molars, and are without taxonomic significance; b) in early wear, the plates of Palaeoloxodon are typically subdivided into two short lingual and labial rings, and with a long central ring; in contrast, in all APL molars, their plates in early wear consist of sub-equal rings; c) the M3 of P. antiquus are more hypsodont (mean value HI > 1.9) than the APL one; d) the lamellae of Palaeoloxodon commonly have "cigar-shape" and blunt lingual and labial ends; in the APL molars the enamel bands run almost parallel to each other; and e) a medial mental foramen is absent in P. antiquus, whereas it is present in the APL mandible (Palombo & Ferretti 2005;Ferretti & Debruyne 2011;Lister et al 2012;Stimpson et al 2016). The APL molars are further differentiated from Elephas, which is characterized by: a) dental wear, which progresses from a row of small rings at the apex, to three subequal rings that finally fuse to form (Ferretti & Debruyne 2011;Lister et al 2013). Finally, the lozenge-shaped dental wear figure in contact in the successive lamellae in the midline, typical for Loxodonta (Maglio 1973), is not present in the APL molars.…”