Protemnodon, Owen, 1874

Kerr, Isaac A. R., Camens, Aaron B., Van Zoelen, Jacob D., Worthy, Trevor H. & Prideaux, Gavin J., 2024, Systematics and palaeobiology of kangaroos of the late Cenozoic genus Protemnodon (Marsupialia, Macropodidae), Megataxa 11 (1), pp. 1-261 : 9-10

Genus PROTEMNODON Owen, 1874

Protemnodon Owen, 1873 ; Proc. Roy. Soc. Lond. 21, p. 128 (nomen nudum).

Protemnodon Owen, 1874 : Phil. Trans. Roy. Soc. 164, p. 274–275.

Type species: Protemnodon anak Owen, 1874, p. 278 .

Revised diagnosis:

Within Macropodinae , the species of Protemnodon most closely resemble those of Congruus McNamara, 1994 and Wallabia in craniodental features. Species of Protemnodon differ from all known macropodines in having: an ilium with a highly reduced cranial iliac spine, a craniocaudally deeper caudal iliac spine and an associated deeply concave gluteal fossa; and a middle pedal phalanx IV that is short, broad, and highly dorsoplantarly compressed, with its shaft only slightly narrower than the distal end.

Protemnodon vs Congruus

Species of Protemnodon and Congruus share 14 thoracic and five lumbar vertebrae to the exclusion of all other macropodines, which have 13 and six, respectively. Dentally, the species of Protemnodon are distinguished fromthoseof Congruus byhavinglongerpremolarsrelative to molars and a more dorsally inclined lower incisor. Species of Protemnodon differ from species of Congruus in the following cranial attributes: cranium larger and more robust; premaxilla lacks an anterior sulcus within the nasal cavity, and is taller and more robust anteriorly; nasal less domed and less anteriorly projected; larger masseteric process; thicker, less laterally projected orbital lip on jugal; taller zygomatic arch; foramen ovale with a single anteroposterior ridge abutting the medial margin, rather than being abutted at the anterior by a shallow but distinct anteroposterior groove; occipital condyles that project posteriorly well beyond the posterior margin of the nuchal crest and occiput; and a broader foramen magnum relative to occipital height and width. The dentary of the species of Protemnodon differs from those of Congruus in its more inflected diastema, more posteriorly situated mental foramen, and deeper medial pterygoid fossa with higher posterior margin.

The forelimb differs by having: humerus more robust, with more dorsally projected greater and lesser tubercles and a deeper proximal shaft that deepens proximally; proximal ulna more transversely compressed; more elongate metacarpals; and manual phalanges considerably more dorsopalmarly compressed, particularly the distal phalanges. Within the hindlimb, species of Protemnodon are distinguished from those of Congruus by: a pelvis with a broader ilium and a smaller, blunter iliopubic eminence; straighter femur in dorsal view with a larger, more dorsally deflected head, more distally extensive lesser trochanteric ridge, less medially displaced quadratus tubercle, and a more proximally situated lateral gastrocnemial fossa; tibia with a deeper, flatter and more distinct distal fibular facet; talus with a more caudoplantarly extensive navicular facet, and a cuboid facet on the navicular head; a taller, narrower navicular; a more robust metatarsal IV; metatarsal V with a proximal plantar groove present, larger lateral plantar tuberosity and medial plantar tubercle, and lacking a slight kink of the arch of the shaft immediately proximal to midpoint in lateral view; and dorsoplantarly shorter distal phalanges with a more rounded dorsal peak and a less plantarly curved shaft.

Protemnodon vs Wallabia

Besides greater size, species of Protemnodon differ from those of Wallabia bicolor in the following ways. Their dentitions are distinguished by: P3 with larger posterolingual basin relative to length of P3; and upper molars with postparacrista and premetacrista that curve or deflect lingually toward the centre of the interloph valley, rather than continuing straight from the cones along the buccal margin of the lophs to merge above the buccal edge of interloph valley. The cranium differs in: a more ventrally projected anterior part of the premaxilla; nasal less convex and less anteriorly projected; masseteric process anteroposteriorly shorter and more ventrally projected; occipital condyles that project posteriorly well beyond the posterior margins of the nuchal crest and occiput; foramen magnum broader relative to the posterior cranium height; a more raised anteroposterior ridge meeting the medial margin of the foramen ovale; and a more laterally projected postglenoid process.

The forelimb differs in its humerus with a more medially projected humeral head, lower (less raised) and less elongate deltoid tuberosity, straighter pectoral crest, and a broader lateral supracondylar ridge; and ulna with olecranon lacking cranial deflection. The manus differs in its deeper, squarer capitatum. The hindlimb differs in its pelvis with broader ilium and more rounded, less projected iliopubic eminence; and femur with larger, more dorsally deflected femoral head and less dorsoventrally compressed distal shaft. The pes is differentiated by: calcaneus with a broader medial talar facet; talus with a more rounded posterior plantar process in medial view; metatarsal IV more robust; metatarsal V with larger proximolateral process relative to metatarsal V length; and broader pedal phalanges relative to length.

Etymology:

Greek, neutral gender; pro (before), temno (to cut), odous (tooth). ‘…in reference to the sectorial form of the anterior molar or premolar’ ( Owen 1874, p. 274).

Remarks:

We contend that Protemnodon anak was designated the type species for the genus by Owen (1874) when he described Protemnodon mimas Owen, 1874 on the page following the description of P. anak : “The postbasal ridge though narrow is definite; the parabasal ridge is proportionately as well developed as in Protemnodon Anak ; its ‘link’ also, and that of the two chief lobes, are more distinct than in the type species” ( Owen 1874, p. 278). Here, Owen clearly referred to P. anak as the type species, demonstrating his intent, not otherwise stated, that P. anak be given this status, contra Mahoney & Ride (1975), who stated that P. anak is the type species ‘by subsequent designation... by Simpson, 1930 ’.