Ovibos moschatus

Ovibos moschatus (Zimmermann, 1780)

M a t e r i a l. Skull fragment, Buryn district local history museum.

L o c a l i t y a n d g e o l o g i c a l a g e. Chasha River bed alluvium (51°10´N, 33°52´E), near Buryn, Sumy Region, Ukraine; Late Pleistocene.

D e s c r i p t i o n. The skull (fig. 2) belongs to a young, probably 4-year-old individual, which is evidenced by the presence of thickened horncores whose bases not yet fused together (according to the scheme in Henrichsen & Grue, 1980). Only cranium cerebrale with unequally preserved horncores is available for the study. Basis cranii as well as occipital part of the skull are completely destroyed; however jugular processes are preserved. Imprint of the brain is well pronounced on the inner surface of calvaria. The skull is dark brown in colour, which is usual for the fossil material that has been in water for a long time. The horncores are wide, compressed dorso-ventrally; they come down almost vertically, slightly deviating laterally in lower part. Their surface is rather loose and bears the traces of exostoses.

M e a s u r e m e n t s (according to Walker, 1982). See table 1.

C o m p a r i s o n.The muskox skull from Buryn as compared to those of adult individuals of O. moschatus from the Pleistocene (Vangengeim, 1961; Sher, 1971; Krakhmalnaya, 2007 b) is characterized by well-developed cerebral part, high occiput and large foramen magnum. Maximum occipital breadth of the studied specimen is comparable to those in skulls obtained from the Yana River (Tchersky, 1891), Tomsk Region (Shpansky, 2000), and to a lesser extent — to those from Zbranky (Ryziewicz, 1995). These four skulls have the widest occipital region in comparison with others, whose measurements are presented in table 1. According to the minimum occipital breadth, the specimen from Buryn is also similar to those from the Tomsk.

1 Measurements: 1 — skull breadth at the anterior margin level of orbits; 2 — maximum occipital breadth; 3 — minimum occipital breadth; 4 — akrocranium-basion height; 5 — height of akrocranium-upper margin of foramen magnum; 6 — diameter of horncore base; 7 — distance between inner margins of horncore processes; 8 — breadth of foramen magnum. 2 Skulls of males, mean values. 3 Skulls of females, mean values.

The height of the occipital region can only be compared with material from Ukraine. It is smaller than those in the specimen from Khodoriv. The breadth of foramen magnum in the studied specimen slightly exceeds those few measurements, which are indicated in table 1.

Diameter of horncore base is greater than those in an adult female from Mezyn (Belan, 1985) and male from Zbranky, but considerably smaller than in the skull from Khodoriv (Krakhmalnaya & Kovalchuk, 2017). Minimum distance between inner margins of horn processes does not exceed 10 mm which is typical for muskox males (Tchersky, 1891; Sher, 1971). Muskoxen from Siberia have more powerful horns, especially males from the Yana and Lena Rivers (Tchersky, 1891), as well as from other localities of this region, except of the skull from the Mamontova Gora (Rusanov, 1968) and some female skulls (Sher, 1971; Lazarev & Tomskaya, 1987).

R e m a r k s. Late Pleistocene muskox of Eurasia has uncertain taxonomic status in the scientific literature. Recently, this species is increasingly referred to O. moschatus (Zimmermann, 1780), emphasizing its relatedness with the extant American muskox. However, not all the researchers agreed with the unification of the extinct representative of the genus with the living one. There is no doubt that they differ significantly in a number of morphological characters noted in the comparative analysis of their skulls (Ryziewicz, 1955; Sher, 1971; Tikhonov, 1994; Chubur, 2015). These differences allowed C. H. Smith to describe the extinct muskox as O. pallantis in 1827. However, “the Fossil Musk Ox, O. pallantis, with the horns pressed against the temples behind the orbits, found on the coasts of Siberia, is not definitively ascertained to be a separate species” (Smith, 1827, p. 370).

Recognizing the close proximity of the two species, but wanting to confirm the significance of the morphological differences between them, a number of researchers considered the extinct Late Pleistocene muskox as a sub-species of the extant O. moschatus and identified it as O. moschatus pallantis (Lydekker, 1900; Andrée, 1933; Gromova, 1935; Baryshnikov, 1981; Belan, 1985; Krakhmalnaya, 2007 a; Krakhmalnaya & Kovalchuk, 2017). Khant (1996) described a new subspecies Ovibus pallantis rhenanus from the Rhine Valley, Germany. Using modern research methods, e. g. ancient DNA analysis supports the attribution of the Late Pleistocene and extant muskoxen to the same species (MacPhee et al., 2005; Campos et al., 2010). Taking these data into account, researchers began to recognize the species name O. moschatus for the Pleistocene muskox instead of O. pallantis or O. moschatus pallantis.