Khirtharia is an extinct genus of raoellid artiodactyl that inhabited what is now northern India and Pakistan during the middle-upper Eocene (early Lutetian, 48 to 45 million years ago). There are three species of "Khirtharia": "K. dayi," "K. inflata," and "K. aurea". There is also a possible fourth species, "K. major". "Khirtharia" is found primarily from Jammu and Kashmir and Northern Pakistan. More specifically, it is most commonly found in the Upper Subathu Group within Jammu and Kashmir. "Khirtharia" is notable for a well preserved skull of "K. inflata", which allowed for obtaining an endocranial cast of the brain cavity.
The endocranial cast of "K. inflata" showed that the brain of "Khirtharia" was slightly smaller than that of the related "Indohyus." The brain cavity had a volume of approximately 5.5 cubic centimeters, less than in contemporary artiodactyls, giving strong evidence that whales evolved from artiodactyls of relatively small brain sizes. It was also hypothesized that the small brain of "Khirtharia" could be an adaptation to a semi-aquatic life, supporting the position of Raoellidae as the sister group to whales (Cetacea).
Discovery.
The first remains of "Khirtharia" were unearthed by E.S. Pinfold, who then stored them in a museum. He found the remains in the Khirthar fold belt, which is a foldbelt found in Pakistan created by the formation of the Himalayan mountains. "Khirtharia" was then named by Guy Ellcock Pilgrim in 1940 after the fossils of "Khirtharia" were given to him by the museum they were stored at. Guy Pilgrim named the type species "K. dayi". It was named from a fragmentary mandible and maxilla with some of their respective premolars and molars. In 1972, the new species "Bunodentus inflatus" was discovered by A. Ranga Rao, which was synonymized with "Khirtharia" as "K. inflata". "Indohyus major" was described by Hans Thewissen and colleagues (1978) from a single tooth. Orliac and Ducrocq (2012) found that the tooth was more similar to "Khirtharia", and thus assigned the species to it, as "K. major". "K. aurea" was named by Thewissen and colleagues (2001) from northern Pakistan.
Classification.
External classification.
The placement of "Khirtharia" has varied throughout the history of the taxon. Generally, it has been assigned to basal groups of artiodactyls, although it is currently a member of Raoellidae. When "Khirtharia" was first discovered by Pilgrim (1940), it was assigned to Helohyidae. However, Dehm and Oettingen-Spielberg (1958) moved "Khirtharia", along with "Haqueina," to Dichobunidae. When Coombs and Coombs (1977) reevaluated Helohyidae, they determined that the remains of "Khirtharia" were not diagnostic of any particular family of artiodactyls, and therefore left "Khirtharia" as an artiodactyl of uncertain position. In 1981, the family Raoellidae was created, with "Khirtharia" being one of the three genera included, along with "Raoella" (a junior synonym of "Indohyus") and "Kunmunella." After the results of a phylogenetic analysis by Orliac and Ducrocq (2012), it was determined that "Khirtharia", along with "Metkatius", were the most derived members of Raoellidae. This result was confirmed by a phylogenetic analysis performed by Rana et al. (2021) in their description of "Rajouria".
Internal classification.
The first species of the genus "Khirtharia" to be named was "K. dayi", which is also the type species. "K. dayi" was named in 1940 by Guy E. Pilgrim. In 1980, Robert M. West suggested that "Bunodentus", at the time known only from an isolated molar and fragmentary mandible, was synonymous with "Khirtharia dayi", although this change was only officially enacted by Kumar and Sahni (1985) who believed "B. inflatus" was different enough from "K. dayi" to warrant being placed under a different species. Since there was only one species of "Bunodentus", "B. inflatus", "Khitharia" gained the species "K. inflata". Likewise, "Indohyus major" was named by Thewissen et al. (1978) from a single molar in Pakistan. It was named "I. major" due to the size of the tooth, being approximately twice the size of other raoellid teeth. Orliac and Ducrocq found that this tooth was more similar to "Khirtharia", however, and assigned it to the new species "K. major". "K. aurea" was named by Thewissen et al. (2001) from the remains of a single molar in northern Pakistan. The species name (meaning gold in Latin) refers to the color of the sediments which the fossil was found in.
Description.
"Khirtharia" is a raoellid that lived during the early Lutetian age. It is most similar to "Metkatius" in that it had bunodont teeth. As a raoellid, "Khirtharia" was relatively small, although there was large interspecific variety in size.
"Khirtharia dayi".
"Khirtharia dayi" is the type and smallest species of "Khirtharia", and one of the two smallest species of Raoellidae as a whole. Within "K. dayi", there are two similar but distinct morphs: a more common one with relatively small molars and the other, more rare, one with relatively large molars.
By being in the same genus, "K. dayi"'s skull is probably similar to the better-preserved skull of "K. inflata". The snout is broad. There is a prominent preorbital foramen above the third premolar. The orbits are open posteriorly and there is no postorbital bar, showing that "Khirtharia" was likely omnivorous. The jugal bone connects to the maxilla above the second molar. The internal nares connect to the throat just after the third molar. There is a large parietal crest, although a relatively minor sagittal one. There is a specimen of "K. dayi" where the entire mandible is preserved except for the most posterior portion of the coronoid. Symphysis occurs before the first premolar in one specimen, although in another it ends at the seconds premolar. The mandible is shallow for the first two premolars, but it quickly grows in height by about 20% with the last two. The ramus begins immediately after the third molar. It is tall and vertical. The angle is enlarged, especially posteriorly so that it extends bast the head of the mandible.
For the upper dention of "K. dayi", the first premolar is single-rooted, while the second is double-rooted. The second premolar is narrow and non-molarized; in life it would have appeared similar to a canine. The tooth is widest posteriorly because of a relatively large postero-lingual (tongue-side) shelf. The third premolar is similar to the second; it is non-molarized and has a postero-lingual shelf. However, the third molar was slightly larger and there were large vertical grooves. The fourth premolar represents a transition from the canine-like first to third premolars to the molars. There are only two cones on the tooth, both situated in the front portions. Because of this, the posterior section of the tooth is low and flattened. The cone on the labial (lip) side of the tooth is larger than the protocone, which it is connected to by a ridge. The first lower molar is square-shaped. There are four large cusps which are rounded; they were likely used for crushing plant matter. The paracone is the largest cusp while the hypocone is the smallest. The first molar is very transverse. The second lower molar is significantly larger than the first and, as opposed to being square in shape, is trapezoidal. Cingulum are less apparent than the first molar. The second molar is has bulbous cusps. As with the first molar, the paracone is the largest of the cusps.While the first and second premolars were not preserved, Ranga Rao postulated that the first lower premolar was single-rooted while the second premolar was double-rooted. The third premolar is large and triangular, with prominent cingulum. The fourth premolar is slightly larger than the third. It is more premolariform than the upper fourth premolar. The lower molars of "Khirtharia" lack the paraconid. The lower molars are highly bunodont. There is a large ridge connecting the protoconid and metaconid and a large ridge connecting the hypoconid and entoconid. The largest molar is the third.
"Khirtharia inflata".
"Khirtharia inflata" differs from "K. dayi" in terms of size in that it is between the size of the two morphs and slight dental differences. The premaxilla is elongated and the maxilla is tall. The incisors are caniniform and raptorial, likely adapted to seizing prey. Compared to "K. dayi", "K, inflata" has more bunodont and squarish upper molars; the upper molars of "K. inflata" are similar to the lower molars of "K. dayi". The lower molars are also more bunodont and the hypoconid is the largest cusp (in "K. dayi" the metacone is the largest cusp). The lower molars are also longer than in "K. dayi". All molars have cusps separated from each other by valleys. The skull is relatively rectangular, with the height staying of the skull slowly decreasing anteriorly until the beginning of the nostril openings, where it is about half of its maximum height. While there is a sagittal crest, it is minor.
"Khirtharia aurea".
"Khirtharia aurea" is known from relatively sparse remains. Depending on the validity of "K. major" as a species of "Khirtharia", "K. aurea" is either the largest or second largest species of "Khirtharia". The molars of "K. aurea" have more prominent cingulum than in both "K. dayi" and "K. inflata". Unlike "K. inflata", the hypocone is reduced to the point of being smaller than the protocone and the cusps are (unsurprisingly) less inflated than in "K. inflata". The two known upper molars are large and bunodont. In the left first molar, the metacone is taller and narrower than the protocone, which is the largest cusp overall. The hypocone is much smaller than the protocone and shifted labially. In the third molar, the paracone being the largest cusp. The protocone is less tall than the paracone, although roughly the same in the other dimensions. In 2007, a study came out stating that the holotype specimen, previously identified as a third molar, could possibly be a second molar.
"Khirtharia major".
"Khirtharia major" is a possible species of "Khirtharia" known only from two molars. It is the largest species of "Khirtharia" and the largest raoellid as a whole; it is twice the size of "Indohyus indirae". It is different from all other species of "Khirtharia" in that it has an elongated third molar, larger hypocone, and a variety of other small morphogical differences.
Paleobiology.
"Khirtharia" was most similar to "Metkatius" in terms of its paleobiology due to the shared bunodont nature of their teeth, although "Khirtharia"'s teeth were even more bunodont than those of "Metkatius". The incisors of "Khirtharia" were caniniform, which is an adaptation for catching and holding onto potential prey. The molars are bunodont, which is a characteristic of omnivorous taxa. Since "Khirtharia" also had the most bunodont teeth of any raoellid, this suggests it had the most carnivorous diet of any raoellid. Due to being a raoellid, "Khirtharia" was almost certainly semi-aquatic. Therefore, "Khirtharia" was probably an omnivorous semi-aquatic chevrotain-like creature.