|Genus:|| Rucervus |
| Cervus duvaucelii |
Rucervus is a genus of deer from India, Nepal, Indochina, and the Chinese island of Hainan. The only extant representatives, the barasingha or swamp deer (R. duvaucelii) and Eld's deer (R. eldii), are threatened by habitat loss and hunting; another species, Schomburgk’s deer ( R. schomburgki), went extinct in 1938.  Deer species found within the genus Rucervus are characterized by a specific antler structure, where the basal ramification is often supplemented with an additional small prong, and the middle tine is never present. The crown tines are inserted on the posterior side of the beam and may be bifurcated or fused into a small palmation.
|Male||Female||Scientific name||Common name||Distribution|
|Rucervus duvaucelii (Cuvier, 1823)||barasingha or swamp deer||northern and central India and southwestern Nepal|
|Rucervus eldii (McClelland, 1842)||Eld's deer or thamin||South Asia and Southeast Asia.|
According to the old tradition of zoological taxonomy, swamp deer originally were regarded as members of the genus Cervus. Rucervus was originally proposed by Hodgson  as a subgenus of the genus Cervus. The original definition of Rucervus was mostly based on antler shape believed to be intermediate between that of 'elaphus' and 'hippelaphus'. Hodgson  reported that upper canines are present only in males of barasingha, but the additional craniological material shows that upper canines are present in both sexes.  Eld's deer was regarded as another species of the genus Rucervus, however, the recent genetic evidences suggest that Eld's deer is most closely related to Père David's deer   and should be placed in its own genus, Panolia.   However, it has recently been place back into Rucervus by the American Society of Mammalogists  despite Eld's deer is not closely related to barasingha in genetics and antler structure. 
Rucervus is an ancient cervid lineage that--together with the genus Axis --represents the oldest evolutionary radiation of the subfamily Cervinae (plesiometacarpal deer). 
The fossil species of Rucervus of Europe were included in the genus Arvernoceros Heintz, 1971 (the type species: Cervus ardei Croizet & Jobert, 1828) or in the genus Eucladoceros , as in the case of R. giulii. Today, Arvernoceros is regarded as a subgenus of Rucervus.  The European fossil forms of Rucervus are distinguished from the South Asian species by more compact crown part of the antler and by the frequent development of a small distal palmation as for instance in R. ardei and R. radulescui. South Asian fossil forms of Rucervus are represented by large-sized R. simplicidens and R. colberti. The late Early Pleistocene of Greece has yielded the remains of a giant species R. gigans that rivaled in size Irish elk Megaloceros giganteus , The giant Rucervus from Greece is distinguished by unusually for such a large animal long limbs and apparently is closely related to R. simplicidens and R. colberti from the Sivaliks.  The Southwest-Europe endemic Mid to early Late Pleistocene genus Haploidoceros is regarded as closely allied. 
Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including muntjac, elk (wapiti), red deer, and fallow deer; and the Capreolinae, including reindeer (caribou), white-tailed deer, roe deer, and moose. Male deer of all species, as well as female reindeer, grow and shed new antlers each year. In this, they differ from permanently horned antelope, which are part of a different family (Bovidae) within the same order of even-toed ungulates (Artiodactyla).
Antlers are extensions of an animal's skull found in members of the Cervidae (deer) family. Antlers are a single structure composed of bone, cartilage, fibrous tissue, skin, nerves, and blood vessels. They are generally found only on males, with the exception of reindeer/caribou. Antlers are shed and regrown each year and function primarily as objects of sexual attraction and as weapons.
Eld's deer, also known as the thamin or brow-antlered deer, is an endangered species of deer endemic to South Asia and Southeast Asia.
The Irish elk, also called the giant deer or Irish deer, is an extinct species of deer in the genus Megaloceros and is one of the largest deer that ever lived. Its range extended across Eurasia during the Pleistocene, from Ireland to Lake Baikal in Siberia. The most recent remains of the species have been carbon dated to about 7,700 years ago in western Russia.
Megaloceros is an extinct genus of deer whose members lived throughout Eurasia from the early Pleistocene to the early Holocene. The type and only certain member of the genus, Megaloceros giganteus, vernacularly known as the "Irish elk" or "giant elk", is also the best known. Fallow deer are thought to be their closest living relatives.
The chital or cheetal, also known as the spotted deer, chital deer and axis deer, is a deer species native to the Indian subcontinent. It was first described and given a binomial name by German naturalist Johann Christian Polycarp Erxleben in 1777. A moderate-sized deer, male chital reach 90 cm (35 in) and females 70 cm (28 in) at the shoulder. While males weigh 70–90 kg (150–200 lb), females weigh around 40–60 kg (88–132 lb). It is sexually dimorphic; males are larger than females, and antlers are present only on males. The upper parts are golden to rufous, completely covered in white spots. The abdomen, rump, throat, insides of legs, ears, and tail are all white. The antlers, three-pronged, are nearly 1 m long.
The Schomburgk's deer is an extinct species of deer once endemic to central Thailand. It was described by Edward Blyth in 1863 and named after Sir Robert H. Schomburgk, who was the British consul in Bangkok from 1857 to 1864. It is thought to have gone extinct by 1938, when the last records of the species were published.
The barasingha, also known as the swamp deer, is a deer species distributed in the Indian subcontinent. Populations in northern and central India are fragmented, and two isolated populations occur in southwestern Nepal. It has been extirpated in Pakistan and Bangladesh, and its presence is uncertain in Bhutan.
Eucladoceros or bush-antlered deer is an extinct genus of deer whose fossils have been discovered in Europe, the Middle East and Central Asia. This genus was formally described by Hugh Falconer in 1868.
Cervus is a genus of deer that primarily are native to Eurasia, although one species occurs in northern Africa and another in North America. In addition to the species presently placed in this genus, it has included a whole range of other species now commonly placed in other genera. Additionally, the species-level taxonomy is in a state of flux.
The Cervinae or the Old World deer, are a subfamily of deer. Alternatively, they are known as the plesiometacarpal deer, due to their ankle structure being different from the telemetacarpal deer of the Capreolinae.
Candiacervus is an extinct genus of deer native to Pleistocene Crete. Due to a lack of other herbivores, the genus underwent an adaptive radiation, filling niches occupied by other taxa on the mainland. Due to the small size of Crete, the genus underwent insular dwarfism, the smallest species, C. ropalophorus, stood about 40 cm at the shoulders when fully grown, as can be inferred from a mounted skeleton. Some species are noted for their peculiar, spatula-shaped antlers, though other species have normal albeit miniaturized antlers. Other features are the relatively short limbs, the massivity of the bones and the simplified antler.
The Philippine deer, also known as the Philippine sambar or Philippine brown deer, is a vulnerable deer species endemic to the Philippines. It was first described from introduced populations in the Mariana Islands, hence the specific name.
The sangai is an endemic and endangered subspecies of Eld's deer found only in Manipur, India. It is also the state animal of Manipur. Its common English name is Manipur brow-antlered deer or Eld's deer and the scientific name is Rucervus eldii eldii. Its original natural habitat is the floating marshy grasslands of the Keibul Lamjao National Park, located in the southern parts of the Loktak Lake, which is the largest freshwater lake in South Asia.
The Finnish forest reindeer(Rangifer fennicus fennicus, also known as Eurasian or European forest reindeer is a rare subspecies of the reindeer native to Finland and northwestern Russia. They are found primarily in Russian Karelia and the provinces of North Karelia, Savonia and Kainuu in Finland, though some range into central south Finland. They are distinct from the semi-domesticated mountain reindeer in their larger size, longer legs and preference for dense boreal forest habitat, where they are rarely seen by humans, over the open tundra. The Finnish herd migrates seasonally back and forth across the long Russo-Finnish border.
Praemegaceros is an extinct genus of deer, known from the Pleistocene and Holocene of Western Eurasia. It contains the subgenera Praemegaceros,Orthogonoceros and Nesoleipoceros. It has sometimes been synonymised with Megaloceros and Megaceroides, however they have been found to be generically distinct.
Croizetoceros is an extinct genus of deer which lived throughout much of Europe, first appearing during the last stages of the Miocene and living until the Early Pleistocene.
Megaceroides algericus is an extinct species of deer known from the Late Pleistocene to the Holocene of North Africa. It is one of only two species of deer known to have been native to the African continent, alongside the Barbary stag, a subspecies of red deer. It is considered to be closely related to the giant deer species of Eurasia.
Haploidoceros is an extinct genus of deer that lived in Europe during the Pleistocene. It contains a single species, Haploidoceros mediterraneus. Fossils have been found mainly in France, as well as the Iberian peninsula.