| Lavanify Temporal range:Late Cretaceous (?Maastrichtian) | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Family: | †Sudamericidae |
| Genus: | †Lavanify Krause et al., 1997 |
| Species: | †L. miolaka |
| Binomial name | |
| †Lavanify miolaka Krause et al., 1997 | |
Lavanify is a mammalian genus from thelate Cretaceous (probablyMaastrichtian, about 71 to 66 million years ago) ofMadagascar. The only species,L. miolaka, is known from two isolated teeth, one of which is damaged. The teeth were collected in 1995–1996 and described in 1997. The animal is classified as a member ofGondwanatheria, an enigmatic extinct group with unclearphylogenetic relationships, and within Gondwanatheria as a member of the familySudamericidae.Lavanify is most closely related to the IndianBharattherium; the South AmericanSudamerica andGondwanatherium are more distantly related. Gondwanatheres probably ate hard plant material.
Lavanify had high-crowned, curved teeth. One of the two teeth is 11.2 mm high and shows a deep furrow and, is centered laterally in the crown, a V-shaped area that consists ofdentine. The other, damaged, tooth is 9.8 mm high and has at least one deep cavity (infundibulum). Characters shared by the teeth ofLavanify andBharattherium include the presence of an infundibulum and a furrow; they both also have large, continuous bands of matrix (unbundledhydroxyapatite crystals) between the prisms (bundles of hydroxyapatite crystals) of theenamel, andperikymata—wave-like ridges and grooves in the enamel surface.
Two teeth ofLavanify were discovered in 1995–1996 during joint expeditions of theState University of New York,Stony Brook University, and theUniversity of Antananarivo to thelate Cretaceous (mostlyMaastrichtian, about 71 to 66 million years ago [mya])Maevarano Formation of northwestern Madagascar.[1] The two teeth were found in different sites in a whitesandstone unit of the Maevarano Formation near the village ofBerivotra and have been deposited in the collections of the University of Antananarivo (specimen UA 8653) andField Museum of Natural History (specimen FMNH PM 59520).David W. Krause and colleagues describedLavanify and asudamericid from India, which they did not name, in a 1997 paper inNature. These were the firstgondwanathere mammals to be found outside of Argentina and provided evidence that the mammal faunas of the differentGondwanan (southern) continents were similar to each other. Thegeneric name,Lavanify, means "long tooth" and thespecific name,miolaka, means "curved" inMalagasy; both refer to the teeth's shape.[2]
Gondwanatheres are a small group of mammals of uncertainphylogenetic affinities known from the late Cretaceous to theEocene (~56–34 mya) of the Gondwanan continents, known only from teeth and a few lower jaws. Upon their discovery in the 1980s, gondwanatheres were initially thought to bexenarthrans—part of the same group as livingsloths,armadillos, andanteaters—but later workers have favored affinities withmultituberculates (a diverse group of fossil mammals) or left the relationships of the gondwanatheres open. The group comprises twofamilies. The familyFerugliotheriidae, whose members had low-crowned teeth, occurs in theCampanian (~84–71 mya) to Maastrichtian of Argentina. All other gondwanatheres, includingLavanify, are placed in the Sudamericidae, which have high-crowned (hypsodont) teeth. These includeGondwanatherium from the Campanian and Maastrichtian of Argentina;Sudamerica from thePaleocene (~66–56 mya) of Argentina;Lavanify; at least one species from the Maastrichtian of India; an unnamed species related toSudamerica from the Eocene of Antarctica; and an unnamed possible gondwanathere,TNM 02067, from the Cretaceous of Tanzania.[3] In 2007, teams led by G.P. Wilson and G.V.R. Prasad independently described this animal asDakshina andBharattherium respectively; as the latter name was published first, it is the correct name for this genus according to thePrinciple of Priority.[4] Gondwanatheres have been interpreted as feeding on roots, bark, and abrasive vegetation or as the earliestgrass-eating mammals.[5]
Several other mammals have been recorded from the late Cretaceous of Madagascar, mostly on the basis of isolated teeth. A possible second gondwanathere is represented by a tooth that is larger and lower-crowned than those ofLavanify, and a yet lower-crowned tooth may also be of a gondwanathere. A lowermolar,UA 8699, may be of amarsupial or aplacental and a molar fragment is referable toMultituberculata. Finally, an as-yet-undescribed mammal is known from a fairly complete skeleton. None of these mammals is related to the living mammals of the island, many of which belong to unique groups (seeList of mammals of Madagascar).[6] The fauna also containscrocodyliforms,dinosaurs, and other animals.[7]
Lavanify is known from the complete cheektooth UA 8653 and the broken tooth FMNH PM 59520. Krause and colleagues could not determine whether the teeth were from the lower or upper jaw and whether they were molars or molariform (molar-like)premolars, but suggested that they represented two different tooth positions.[2] However, Wilson and colleagues in 2007 tentatively identified UA 8653 as a left fourth (last) lower molariform (mf4); because molars and premolars of gondwanatheres cannot be reliably distinguished, the term "molariform" is used instead.[8] FMNH PM 59520 resembles theGondwanatherium fossil MACN Pv-RN 1027,[9] a broken tooth that may be an upper molariform.[10] In bothLavanify teeth, the enamel surface featuresperikymata (ridges and grooves arranged in a transverse, wave-like pattern).[11]
UA 8653, theholotype, is hypsodont and curved. It is 11.2 mm high, of which the crown makes up about 85%, and the dimensions of its crown are 3.4 x 3.2 mm. Theocclusal (chewing) surface is worn flat and contains a V-shaped island ofdentine surrounded byenamel. One side of the crown lacks enamel.[2] Between the two arms of the V, at the lingual (inner) side of the tooth,[11] is a furrow filled withcementum, which extends all the way through the tooth; the presence of such a long furrow distinguishes it fromGondwanatherium. The enamel is made up of small, round prisms (bundles ofhydroxyapatite crystals) that are separated by large, continuous bands ofinterprismatic matrix (IPM; the material between the enamel prisms).[2]
FMNH PM 59520 is 9.8 mm high. It is similar in many respects to UA 8653, but is less curved and its occlusal surface contains a largeinfundibulum (funnel-shaped cavity), filled with cementum and surrounded by enamel that penetrates deeply into the tooth. There is also either a second infundibulum or a cementum-filled furrow. The differences in degree of curvature and occlusal morphology suggest that this tooth represents a different tooth position than UA 8653. Krause and colleagues tentatively placed this tooth inLavanify in view of the considerable variation among other gondwanathere teeth of a single species and in the absence of evidence to the contrary.[12]
| Relationships among gondwanatheres[13] |
In their original description, Krause and colleagues suggested thatLavanify was most closely related to the then-unnamed Indian sudamericid. They based this proposed relationship on the shared presence of prominent, continuous bands of IPM.[14] The teams who named the Indian gondwanathere in 2007 both agreed with this proposed relationship.[15] In their description ofDakshina, Wilson and colleagues added the presence of an infundibulum and of perikymata to the evidence for the relationship between the two. These three characters aresynapomorphies (shared derived traits) for theBharattherium-Lavanifyclade. They also share the presence of furrows on the lingual side of the teeth only, but whether this is a derived feature is uncertain. Wilson and colleagues list twoautapomorphies (unique derived traits) ofLavanify: presence of a V-shaped dentine island and absence of enamel on one side of the crown.[11] Prasad and colleagues who namedBharattherium, noted the absence of enamel on part of the crown of aBharattherium tooth and interpreted this trait as a synapomorphy ofBharattherium andLavanify.[16] They also mentioned the presence of a furrow and infundibulum as shared traits.[17]
