Sinomegaceros

Sinomegaceros is an extinct genus of deer known from the Late Pliocene/Early Pleistocene to Late Pleistocene of Central and East Asia. It is considered to be part of the group of "giant deer" (often referred to collectively as members of the tribe Megacerini), with a close relationship to Megaloceros. Many members of the genus are noted for their distinctive palmate antler brow tines.

Taxonomy
The first species of the genus S. ordosianus and S. pachyosteus were named by pioneering Chinese paleontologist C. C. Young as species of Cervus in 1932 for material from Zhoukoudian. In a review of the paper the subsequent year Dietrich created the name Sinomegaceros as a subgenus of Cervus to house the species, with S. pachyosteus as the type species. Due to the fact that the name was not published in a formal research paper, it was not widely used for several decades after publication. The species S. yabei was named in 1938. In the following decades various researchers considered it a subgenus of Megaloceros, or a distinct genus. Several named species are likely to be junior synonyms.

Named species include:

Indeterminate remains of Sinomegaceros are also known from the Late Pleistocene of the Korean Peninsula.
 * Sinomegaceros tadzhikistanis, known from the Late Pliocene-Early Pleistocene of Tajikistan
 * Sinomegaceros konwanlinensis, from Gongwaling in Northern China, dating to the Early Pleistocene, around 1.6 million years ago.
 * Sinomegaceros fabellatus, known from the late Early Pleistocene-Early Middle Pleistocene of China
 * Sinomegaceros sangwonensis known from the mid-Middle Pleistocene of China
 * Sinomegaceros luochuanensis known from the late Middle Pleistocene of China
 * Sinomegaceros baotouensis known from the Late Pleistocene of China
 * Sinomegaceros pachyosteus known from the early Middle Pleistocene to the late Middle Pleistocene or Late Pleistocene of China
 * Sinomegaceros ordosianus, known from the late Middle Pleistocene-Late Pleistocene of China and small adjacent areas of Russian Siberia
 * Sinomegaceros yabei late Middle Pleistocene-Late Pleistocene of Japan

Sinomegaceros has often been considered closely related to other genera "giant deer", like Praemegaceros and Megaloceros, as part of the tribe Megacerini.  Mitochondrial genomes from Late Pleistocene Chinese and Siberian Sinomegaceros (including S. ordosianus and S. pachyosteus) indicate that the mitochondrial diversity of Megaloceros giganteus is nested within the diversity of Sinomegaceros, suggesting that the two lineages interbred after their initial split. This interbreeding may have occurred in the contact region between the two groups in Siberia. Relationships of Sinomegaceros mitochondrial genomes after Xiao, et al. 2023

Description
Species of Sinomegaceros were large deer, with estimated body masses for Chinese Pleistocene species ranging from 220 kg in S. pachyosteus to 365 kg in S. konwanlinensis, with S. ordosianus estimated at 330 kg. Remains attributed to the genus in Central Asia are even larger, with the body mass of S. tadzhikistanis being estimated at 465 kg, while an indeterminate species from the Pleistocene locality of Lakhuti 2 in Tajikistan was estimated 560 kg, making it one of the largest deer known. The antlers have palmate brow tines, with the palmation generally orientated transversely and vertically. The mandibles of Sinomegaceros, like those of Megaloceros giganteus, are robust and display pachyostosis with the robustness being the most extreme in S. pachyosteus.

Ecology
S. yabei and S. pachyosteus are suggested to have been grazers.

Evolution
One of the oldest species in the genus is Sinomegaceros tadzhikistanis, known from the Late Pliocene-Early Pleistocene of Tajikistan. The oldest species of the genus in China is Sinomegaceros konwanlinensis, from Gongwaling in Northern China, dating to the Early Pleistocene, around 1.6 million years ago. S. fabellatus is known from fossils spanning the latest Early Pleistocene to early Middle Pleistocene. S. sangwonensis is known from fossils spanning the mid-Middle Pleistocene. The oldest fossils of S. pachyosteus date to around 700,000 years ago, during the early Middle Pleistocene. While some authors suggest youngest fossils of the species date to the late Middle Pleistocene, other sources have suggested that the species persisted into the Late Pleistocene, with reported radiocarbon dates as recent as 35,000 years ago. The species S. yabei and S. ordosianus first appeared during the late Middle Pleistocene. It has been suggested that both S. pachyosteus and S. yabei ultimately derive from S. konwanlinensis. While often stated to have become extinct around 12,000 years ago, a lack of high-quality radiocarbon dates makes the time of extinction uncertain for S. yabei, with the only certain radiocarbon dates dating to around 40,000 years ago. Radiocarbon dates for S. ordosianus in Northeastern China extend as recently as the Last Glacial Maximum, around 22,000 years ago.

Relationship with humans
Remains of S. yabei at Lake Nojiri in Nagano Prefecture of Honshu, Japan, dating to approximately 37,900 to 42,600 years Before Present have been found associated with spear-shaped wood pieces and large pebbles, with the long bones fractured, with their fragments bearing percussive marks, suggesting that these deer (alongside elephants belonging to the species Palaeoloxodon naumanni) were butchered by humans at the site, with the long bones likely cracked to extract bone marrow. S. ordosianus is suggested to have likely been hunted by archaic humans, based on the finds of its remains in Chinese Paleolithic archaeological sites.