Hoplitomeryx Leinders 1984
Creators: name: Van Der Geer, Alexandra A. E.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Artiodactyla
Hoplitomerycidae
Hoplitomeryx

description: Genus Hoplitomeryx Leinders, 1984
Type species. Hoplitomeryx matthei Leinders, 1984.
Original diagnosis. Hoplitomeryx has two horn cores above each orbit and one horn core in the sagittal plane on the posterior part of the nasalia. The rest of the diagnosis corresponds to that of the family (Leinders 1984: p. 6).
Emended diagnosis. Cheek teeth are low crowned and have rugose enamel (shared with all other cervoids except for Antilocapra), lacking the Palaeomeryx -fold in lower molars, lacking the Dorcatherium -fold in lower molars, bifurcated posterior wing of the protocone (=postprotocrista) (uniting advanced cervoids) and of the metaconule (derived pecoran condition), bilophed posterior lobe of lower m3 that is distally open in unworn molars and closed in worn molars, at most faint traces of the anterior cingulum on the molars, p4 is not molarized, three lower incisors are present and the lower canine is incisiform. Additional diagnosis of the postcranial of Hoplitomeryx. The glenoid of the scapula is round or subcircular. The humerus has a greater trochanter that clearly extends above the level of the head, and a conical distal epiphysis that may have a small supracondylar foramen. The ulna is loosely or more firmly fused to the radius with a proximally situated spatium interosseum of varying size. The radial facet on the distal radius extends further palmar than the intermedial facet, and is deeper and broader than the intermedial facet. The facets for the lateral metapodials are very pronounced on the proximal metacarpals but indistinguishable on the metatarsals. The first phalanges are robust with often pronounced ligament attachment areas and small or very small facets for the sesamoids at the volar part of the proximal articulation. The second phalanges have a post-articular volar platform. The third phalanges have a more or less flat sole and lack the prominent thickening below the lower end of the articulation area as seen in bovids. The articulation area lacks a horizontal part. A very small extensor process may be present. The femur is robust with a cylindrical or subspherical head, which may bear a slight concavity just before the transition to the saddle. The medial trochlear ridge is enlarged relative to the lateral trochlear ridge, runs parallel to it and may have a proximal extension or thickening. The lateral condyl extends clearly further distally than the medial condyl. The fossa intercondylaris is deep and narrow. The lesser trochanter is pronounced. The patella has an elongated or even extremely elongated distal apophysis independent of size. The medial half of the articular surface is twice as large as the lateral half and may form a hook-like extension. The tibia is generally S-shaped with a triangular crosssection and a high and long tibial crest; only in the largest specimens the tibia is straight. The astragal is compact and has a slightly asymmetrically placed median gorge, an internal condyl that is smaller than the external condyl and generally a non-parellel sided trochlea. The calcaneum has a sustentaculum that extends beyond the articular surface, a corpus that terminates in a head and an inwardly pointing distal end of the cubo-navicular facet. The articular facet for the os malleolare is longer than wide and has a rectangular shape. The sustentaculum does not project until the rear margin. The tuber calcanei is slender and midway compressed in anterior view and bears a massive head with a pronounced tendon groove on its top. The metatarsals have a dorsal longitudinal gully that is distally closed, pronounced, and extends proximally into the cubonavicular. The metatarsals are always shorter than the metacarpals.
Remarks. Material, including holotypes and paratypes, of the newly described species below are taken only from chronological levels with a proven existence of a full radiation of Hoplitomeryx to exclude the possibility of chronospeciesThe type species Hoplitomeryx matthei meets this criterion. Hoplitomeryx from the oldest fissures are all small but need not necessarily be equivalent to one of the two small sizes of Hoplitomeryx from the younger fissures. In other words, even if the size of the oldest specimens equals that of the smallest size of the younger specimens, this is no guarantee that the latter is an unchanged continuation of the former after cladogenesis has taken place. Theoretically, a different, new species might be needed for this first, ancestral stage. At present there is insufficient material and support to do so and the lack of the other morphotypes from the older fissures could in principal also be just a sampling bias.
description: Published as part of Van Der Geer, Alexandra A. E., 2014, Systematic revision of the family Hoplitomerycidae Leinders, 1984 (Artiodactyla: Cervoidea), with the description of a new genus and four new species, pp. 1-32 in Zootaxa 3847 (1) on pages 21-22, DOI: 10.11646/zootaxa.3847.1.1, http://zenodo.org/record/286815