| Indraloris | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Primates |
| Suborder: | Strepsirrhini |
| Family: | †Sivaladapidae |
| Subfamily: | †Sivaladapinae |
| Genus: | †Indraloris Lewis, 1933 |
| Species | |
| |
Indraloris is a fossilprimate from theMiocene of India and Pakistan in the familySivaladapidae. Two species are now recognized:I. himalayensis fromHaritalyangar, India (about 9 million years old) andI. kamlialensis from thePothohar Plateau, Pakistan (15.2 million years old). Other material from the Potwar Plateau (16.8 and 15.2 million years old) may represent an additional, unnamed species. Body mass estimates range from about 2 kg (4.4 lb) for the smallerI. kamlialensis to over 4 kg (8.8 lb) for the largerI. himalayensis.
Indraloris is known from isolated teeth and fragmentary lower jaws. The jaw is deep under the lastpremolars, but becomes shallower towards the front. The lower premolars are elongate. The lower molars are shorter and broader than those ofSivaladapis.Indraloris may have been arboreal and at least partlyfrugivorous. When the firstIndraloris fossils were discovered in the early 1930s, one was misidentified as acarnivoran and the other as aloris. The carnivoran identification was corrected in 1968, and in 1979Indraloris and the relatedSivaladapis were identified as late survivors ofAdapiformes, an archaic primate group.
Currently,Indraloris is considered to be a valid genus within the familySivaladapidae, containing two named species:I. himalayensis from India andI. kamlialensis from Pakistan. A third species may be represented in the Pakistani material ofIndraloris. However,Indraloris has had a complicatedtaxonomic history, and some of the known material was misidentified as members of other mammalian groups for decades.
In 1932, British paleontologistGuy Pilgrim described two species from theMiocene of what is now India and Pakistan,Sivanasua palaeindica fromChinji (Pakistan) andSivanasua himalayensis fromHaritalyangar (India). He attributed both toSivanasua, acarnivoran genus otherwise known from Europe.[1] The next year, American scientistG. Edward Lewis described the new genus and speciesIndraloris lulli from Haritalyangar, which he provisionally allocated to the familyLorisidae. Thegeneric name,Indraloris, combines the name of the godIndra with the generic nameLoris, and thespecific name,lulli, honorsRichard Swann Lull, at the time director of thePeabody Museum of Natural History.[2] It was not until 1968 that American anthropologistIan Tattersall noted that Pilgrim'sSivanasua species had been misidentified; he suggested thatSivanasua himalayensis was probably the same asIndraloris lulli, but left the affinities ofSivanasua palaeindica open.[3] Tattersall, who also described additional material ofIndraloris, continued to regard the animal as a lorisid.[4]
Lewis had suggested thatIndraloris might derive from theAdapidae, a primitive group of primates,[5] and in the 1970s some authors provisionally placedIndraloris among the Adapidae.[6] In 1979, American and Indian paleontologistsPhilip Gingerich andAshok Sahni reviewedIndraloris and the Indo-Pakistani "Sivanasua" species. They recognizedSivanasua himalayensis andIndraloris lulli as representing the same species,Indraloris himalayensis, and created the new genusSivaladapis forSivanasua palaeindica and another species that had been named later,Sivanasua nagrii.[1] Gingerich and Sahni considered bothIndraloris andSivaladapis to be adapids.[7]
Several other authors suggested similar taxonomic rearrangements around the same time. In 1979, Herbert Thomas and Surinder Verma agreed thatIndraloris andSivaladapis were adapids, but placed them in asubfamily of their own, Sivaladapinae. Also in 1979,Frederick Szalay and Eric Delson placedIndraloris in its owntribe, Indralorisini, within Adapidae.[8] In 1980, Indian paleontologists S.R.K. Chopra and R.N. Vasishat placed both of Pilgrim'sSivanasua species inIndraloris and argued thatIndraloris lulli,Sivanasua himalayensis andSivanasua nagrii all represented the same species—Indraloris himalayensis. They listedSivanasua palaeindica as a secondIndraloris species,I. palaeindica, and continued to regardIndraloris as a lorisid.[9] Gingerich and Sahni published in more detail onSivaladapis in 1984. They then placed the two genera in a separate subfamily of Adapidae, called Sivaladapinae because that name was published two months before Indralorisini.[10] In 1985, Vasishat continued to classifyIndraloris andSivaladapis in a single genus, andIndraloris himalayensis andSivaladapis nagrii in a single species, but other authors have not followed this classification.[11]
In a 1998 review, primatologistMarc Godinot recognized Sivaladapidae as a separate family within theAdapiformes,[12] and this classification has been followed since then. Several genera in addition toIndraloris andSivaladapis are now allocated to Sivaladapidae, which is known from theEocene through the Miocene of China, Thailand, Myanmar, India, and Pakistan.[13] Sivaladapids are notable for including by far the youngest adapiforms; members of this group are otherwise known mostly from the Eocene, but several sivaladapids occurred during the Miocene.[14]
Despite thesetaxonomic changes,Indraloris remained known from only two specimens (theholotypes ofIndraloris lulli andSivanasua palaeindica) until 2005. Both of those specimens—an isolated first lowermolar (m1) and amandible (lower jaw) fragment with m1, respectively—come from Haritalyangar in theNagri Formation.[15] In 2005, however, American paleontologists Lawrence Flynn and Michèle Morgan described five teeth ofIndraloris from fossil sites in the olderKamlial Formation as a second species in the genus,Indraloris kamlialensis. The species was named after the Kamlial Formation.[16] In addition, they suggested that two lower jaw fragments from the Kamlial Formation represented a third, larger species ofIndraloris.[17]
| Specimen[table 1] | Organ[table 2] | Locality | Species | Measurements[table 3] |
|---|---|---|---|---|
| GSI D237[18] | Mandible fragment with m1 | Haritalyangar | I. himalayensis (holotype) | Lm1: 7.0; Wm1: 5.5 |
| YPM 13802[19] | m1 or m2 | Haritalyangar | I. himalayensis (holotype ofIndraloris lulli) | L: 5.5; W: 4.3 |
| YGSP 24338[20] | p4 | Y642 | I. kamlialensis | L: 4.68; W: 2.71 |
| YGSP 32151[20] | dp4 | Y642 | I. kamlialensis | L: 4.38; W: 2.99 |
| YGSP 33157[20] | p3 | Y682 | I. kamlialensis | L: 3.67; W: 2.21 |
| YGSP 44443[20] | m1 or m2 | Y682 | I. kamlialensis (holotype) | L: >4.00; W: 3.34 |
| YGSP 46099[20] | M3 | Y682 | I. kamlialensis | L: >3.86; W: 4.35 |
| YGSP 32152[21] | Mandible fragment with m1 | Y642 | Indraloris, large sp. | Lm1: 5.78; Wm1: 4.91 |
| YGSP 32727[21] | Mandible fragment with left p3 and erupting right p2 | Y801 | Indraloris, large sp. | Lp3: 4.47; Wp3: 2.05 |
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Indraloris is known only from isolated teeth and fragments of the mandible. These show thatIndraloris was a medium-sized sivaladapid, somewhat smaller thanSivaladapis.[22] In 1982, Gingerich and colleagues estimated thatIndraloris himalayensis may have weighed 3.7 to 4.3 kg (8.2 to 9.5 lb) on the basis of allometric scaling of tooth size;[23] Flynn and Morgan estimated a body size of about 2 kg (4.4 lb) forI. kamlialensis.[24] In general, thecingula (shelves) on the margins of the cheekteeth are weak inIndraloris.[16] Among the two named species,I. kamlialensis is about 20% smaller thanI. himalayensis.[17] The unnamed largeIndraloris is similar in size toI. himalayensis.[25]
The mandible is best represented by YGSP 32727, one of two specimens of the unnamed large species ofIndraloris. It preserves both the right and left sides of the dentary, back to the level of the fourth lowerpremolars (p4), but is also damaged at the front. The jaw is deep below p4, but rapidly becomes shallower further to the front. The roots of two lowerincisors and a much largercanine are preserved; the three roots cluster together, with the canine root above the incisor roots, suggesting that these teeth shared some function. Themental foramen, an opening in the jawbone, is below p4. A root for the deciduous second premolar (dp2) is preserved on both the left and right sides, but the tooth itself is not and it is not possible to determine whether dp2 had one or two roots. The right permanent second premolar (p2) is unerupted, but partially visible; it is a blade-shaped cutting tooth. The p3 bears a single cusp, somewhat anterior to the middle of the tooth, with crests descending from it towards the front and back, and weak cingula on the inner and outer sides. It is supported by two roots, which are close together.[17]
Isolated lower premolars are known fromI. kamlialensis. A p3, YGSP 33157, resembles that of YGSP 32727 in possessing a single large cusp connected to crests at the front and back. A heel is present at the back, part of a smalltalonid. The tooth has two roots.[17] The p4, represented by YGSP 24338, is an elongate, two-rooted tooth with a distincttrigonid at the front and talonid at the back. Theprotoconid is the highest cusp of the trigonid. Two crests descend from it at right angles in a lingual direction (towards the inner side of the tooth): the protolophid towards the front, ending at the lowparaconid, and the metalophid towards the back, reaching the elongatemetaconid. The talonid basin is open lingually; on the labial side, thehypoconid cusp is present. A crest, thecristid obliqua, reaches from the hypoconid forward towards the trigonid. No other cusps are visible in the talonid, but the specimen is worn and poorly preserved; theposterolophid, a crest descending from the hypoconid, may end in a smallhypoconulid. A weak cingulum is present on the labial side of the tooth between the protoconid and hypoconid.[26] Another tooth, YGSP 32151, is interpreted as a dp4. It has a more closed trigonid (with the protolophid and metalophid making a more acute angle), the protolophid is shorter, and the paraconid is indistinct. In the talonid, the hypoconulid andentoconid are distinct. The labial cingulum is strong.[17]
The lower molar ofIndraloris is known from four specimens. GSI D237, an m1 in a piece of jaw, is theholotype ofI. himalayensis.[10] YPM 13802, the holotype ofI. lulli (=I. himalayensis) was originally identified as an m1, but Flynn and Morgan suggested in 2005 that it may be an m2 instead.[27] YGSP 44443, the holotype ofI. kamlialensis, is either m1 or m2, but more likely the former.[28] Part of the trigonid is broken off.[29] YGSP 32152, a very worn m1 in a piece of jaw, represents the unnamed largeIndraloris.[17] Vasishat suggested in 1985 that these teeth were instead p4s corresponding to molars referable toSivaladapis, but this hypothesis has been disproven by the discovery of p4s referable toIndraloris.[17]
Indraloris molars are short and organized in two main lophs (lobes).[16] They differ fromSivaladapis teeth in being shorter and broader, with a shorter talonid and a smaller hypoconulid.[30] InIndraloris himalayensis lower molars, there are four main cusps (protoconid and metaconid in the trigonid, hypoconid and entoconid in the talonid), which give the crown a rectangular aspect, although the labial cusps (protoconid and hypoconid) are placed somewhat anterior to their lingual counterparts. InI. kamlialensis, the entoconid is distinct from the hypoconulid, which is large, but the tooth is otherwise similar. The cusps are high relative to those of extant lorises and approximately equal in height. Thecristid obliqua, a crest, descends from the hypoconid to a point on the lingual side of the protoconid. On the hypoconid, this crest forms a right angle with the posterolophid, which runs towards the hypoconulid in the back lingual corner of the tooth. Between the metaconid and entoconid, the talonid basin is open. InI. himalayensis at least (the structure is damaged in the only known lower molar ofI. kamlialensis) there is a well-developed hollow in the trigonid in front of the protoconid and metaconid. There is a labial cingulum between the protoconid and hypoconid.[31] YGSP 32152 is so worn that little of its structure remains visible. It shows a short trigonid and a distinct entoconid. A small hypoconulid, close to the entoconid, is suggested by an enamel swelling.[17] This specimen is fragmentary enough that it could also represent acatarrhine primate or a carnivoran.[25]
The only known upper tooth ofIndraloris is an M3, YGSP 46009. It is broken at the back labial corner. The main cusp is protocone; among the other two cusps, the paracone is higher but the metacone larger. There is a spur at the back of the protocone, suggesting a rudimentaryhypocone. The protocone is connected to the paracone by aprotoloph, which lacks a small cusp (theparaconule). No crest connects the protocone to the metacone, but there is a cingulum at the back margin of the tooth. The tooth bears a strongparastyle (accessory cusp at the front labial corner) and has three roots.[17]
Fossils ofIndraloris have been found only in the MioceneSiwalik fossil beds of India and Pakistan.I. himalayensis is known only fromHaritalyangar,[10] a Late Miocene site in the Indian state ofHimachal Pradesh. This site has been dated to about 9 million years ago.[32] This site has also yieldedSivaladapis nagrii.[10]Indraloris kamlialensis is known from two sites in the province ofPunjab, Pakistan, that are both dated to 15.2 million years ago: Y642 and Y682.Sivaladapis palaendicus has also been recorded at both sites, and two lorisids are known from Y682. The unnamed largeIndraloris is known from Y642 and an older site, Y801 (16.8 million years old).[33] All are in thePotwar Plateau region.[34]
Little is known about sivaladapid ecology. Gingerich and Sahni suggested thatIndraloris was probably arboreal and that it may have been more frugivorous (eating fruit) thanSivaladapis, which they interpreted as a folivore (leaf-eater).[35] Flynn and Morgan interpretedI. kamlialensis as a mixed feeder.[24] The Late Miocene extinction of Indian sivaladapids may be related to a decline in forest cover in Asia and to competition by immigratingcolobine monkeys.[35]
