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New fossils of small and medium-sized bovids from the Early Site of Shanshenmiaozui in Nihewan Basin, North China
TONG Hao-Wen, ZHANG Bei, CHEN Xi, WANG Xiao-Min
Vertebrata Palasiatica    2022, 60 (2): 134-168.   DOI: 10.19615/j.cnki.2096-9899.220413
Abstract   (181 HTML34 PDF(pc) (11536KB)(259)  

Shanshenmiaozui site in Nihewan Basin in North China is a recently discovered Early Pleistocene site which yields rich and diverse mammalian fossils. In the fauna, the small and medium-sized bovid fossils are well represented and can be referred to the following taxa: Spirocerus wongi, Gazella sinensis, Ovis shantungensis and Megalovis piveteaui respectively, among which G. sinensis is the dominate species. S. wongi and G. sinensis are mainly represented by horn-cores and partial skull bones as well as mandibles; in addition, metacarpal and/or metatarsal bones were also recognized for all of the four species. The horn-cores are easy to be identified to the species level, while the dentitions and the postcranial bones underwent a series of examinations and comparisons before getting properly determined and referred to the most approximate taxa. Among the postcranial bones, the metapodials, especially to the metacarpal bones special attentions were paid, which are crucial not only for taxonomic identification, but also for phylogenetic and paleoecological reconstructions; the previously misidentified metapodial specimens in Nihewan fauna were reconsidered in this paper. In the SSMZ fauna, the bovid guild is dominated by Gazella and Bison, which indicates steppe was the most important biome in Nihewan Basin during Early Pleistocene.

Fig. 3 CT scan images and 3-D reconstructions of the horn-core of Spirocerus wongi from SSMZ (IVPP V 28650)
A1-A2. CT scan images showing the general canal system (A1) and a longitudinal slice (A2);C1-C5. CT scan slices showing the changes of cross sections and the canal system at different levels;B1-B4. CT image reconstruction of the right horn-core in anterior (B1), lateral (B2), posterior (B3) and medial (B4) views
Extracts from the Article
Skull bones: One partial adult skull (Fig. 2A) and one partial juvenile skull (Fig. 2B1-3) can be referred to the the species S. wongi. The adult one has very limited frontal bone, but with almost complete horn-cores of both sides. In front view, the frontal bone shows two moderately developed supraorbital pits which accommodate the two prominent supraorbital foramina which are connecting directly to the anterosuperior corner of the orbit and each has a very large internal opening, even larger than in an ox. The eye socket is very large and deep, and has a trench-like roof with flat superior wall rather than domed as in other taxa. The horn is very close to the orbit, which is only 30 mm apart; the postorbital constriction is also obvious. The cranial width at the horn bases is 149.0 mm, and the two horn-cores are 65.6 mm apart at the base. The frontal sinus (pneumatization) is also quite developed, but the diverticulum doesn’t extend to the cornual process ( Fig. 3A2).
Horn-core: The horn-core is a typical form of Spirocerus wongi, with rugose surface and only one spiral carena (or carène or keel) ( Fig. 3B1-4), rather than two as in S. peii and S. kiakhtensis. The carena derives from the basal anterior part and heteronymously spirals upwardly (the left horn spirals anticlockwise but the right one spirals clockwise) and ends near the tip after finishing one complete revolution. The pedicle is quite short. The interior of the horn-core is nearly solid but with a complicated minor canal system ( Fig. 3A1-2, C1-5), which resembles those of the true gazelles. The cross-section of the horn-core is elliptical ( Fig. 3C1-5). Around the basal part of the horn-core, there are many nutrient foramina, among which the ones above the orbit are the largest ( Fig. 3B2). The dimensions of the horn-cores are shown in Table 2.
Spirocerus has developed frontal sinuses, but they do not extend to the horn-core at all ( Fig. 3A2). According to Farke’s paper of 2010, the frontal sinus doesn’t always have phylogenetic significance. But the present authors think it’s more important if the frontal sinus extends to the horn-core, i.e. if there is a cornual diverticulum of the frontal sinus or if the horn-core is hollowed.
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