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Lavanify

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Lavanify
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Family: Sudamericidae
Genus: Lavanify
Krauseet al., 1997
Species:
L. miolaka
Binomial name
Lavanify miolaka
Krauseet al., 1997

Lavanifyis 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 Enigma tic extinct group with unclearphylogeneticrelationships, and within Gondwanatheria as a member of the familySudamericidae.Lavanifyis most closely related to the IndianBharattherium;the South AmericanSudamericaandGondwanatheriumare more distantly related. Gondwanatheres probably ate hard plant material.

Lavanifyhad 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 ofLavanifyandBharattheriuminclude the presence of an infundibulum and a furrow; they both also have large, continuous bands of matrix (unbundledhydroxyapatitecrystals) between the prisms (bundles of hydroxyapatite crystals) of theenamel,andperikymata—wave-like ridges and grooves in the enamel surface.

Discovery and context

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Two teeth ofLavanifywere discovered in 1995–1996 during joint expeditions of theState University of New York,Stony Brook University,and theUniversity of Antananarivoto thelate Cretaceous(mostlyMaastrichtian,about 71 to 66 million years ago [mya])Maevarano Formationof northwestern Madagascar.[1]The two teeth were found in different sites in a whitesandstoneunit of the Maevarano Formation near the village ofBerivotraand 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. Krauseand colleagues describedLavanifyand asudamericidfrom India, which they did not name, in a 1997 paper inNature.These were the firstgondwanatheremammals 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 uncertainphylogeneticaffinities 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 includeGondwanatheriumfrom the Campanian and Maastrichtian of Argentina;Sudamericafrom thePaleocene(~66–56 mya) of Argentina;Lavanify;at least one species from the Maastrichtian of India; an unnamed species related toSudamericafrom 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 asDakshinaandBharattheriumrespectively; 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-eatingmammals.[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 amarsupialor aplacentaland 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]

Description

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Lavanifyis 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 theGondwanatheriumfossil MACN Pv-RN 1027,[9]a broken tooth that may be an upper molariform.[10]In bothLavanifyteeth, 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 ofdentinesurrounded 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 ofhydroxyapatitecrystals) 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 inLavanifyin view of the considerable variation among other gondwanathere teeth of a single species and in the absence of evidence to the contrary.[12]

Relationships

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Relationships among gondwanatheres[13]

In their original description, Krause and colleagues suggested thatLavanifywas 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 aBharattheriumtooth and interpreted this trait as a synapomorphy ofBharattheriumandLavanify.[16]They also mentioned the presence of a furrow and infundibulum as shared traits.[17]

References

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  1. ^Krause et al., 1997, p. 504; 2006, p. 179
  2. ^abcdKrause et al., 1997, p. 504
  3. ^Wilson et al., 2007, p. 521
  4. ^Prasad, 2008, p. 91
  5. ^Gurovich and Beck, 2009, p. 37; Wilson et al., 2007, p. 521
  6. ^Krause et al., 2006, pp. 186–188
  7. ^Krause et al., 2006, p. 178
  8. ^Wilson et al., 2007, pp. 522, 526
  9. ^Gurovich, 2005, p. 383
  10. ^Gurovich, 2005, p. 359
  11. ^abcWilson et al., 2007, p. 526
  12. ^Krause et al., 1997, p. 505
  13. ^Krause et al., 1997, fig. 3; Wilson et al., 2007, p. 527; Prasad et al., 2007, p. 23
  14. ^Krause et al., 1997, fig. 3
  15. ^Prasad et al., 2007, p. 23; Wilson et al., 2007, p. 526
  16. ^Prasad et al., 2007, p. 21
  17. ^Prasad et al., 2007, pp. 21–22

Literature cited

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  • Gurovich, Y. 2005.Bio-evolutionary aspects of Mesozoic mammals: description, phylogenetic relationships and evolution of the Gondwanatheria (Late Cretaceous and Paleocene of Gondwana).Ph.D. thesis, Universidad de Buenos Aires, xiii + 546 pp.
  • Gurovich, Y. and Beck, R. 2009.The phylogenetic affinities of the Enigma tic mammalian clade Gondwanatheria(subscription required). Journal of Mammalian Evolution 16:25–49.
  • Krause, D.W., Prasad, G.V.R., von Koenigswald, W., Sahni, A. and Grine, F.E. 1997.Cosmopolitanism among gondwanan Late Cretaceous mammals(subscription required). Nature 390:504–507.
  • Krause, D.W., O'Connor, P.M., Rogers, K.C., Sampson, S.D., Buckley, G.A. and Rogers, R.R. 2006.Late Cretaceous terrestrial vertebrates from Madagascar: Implications for Latin American biogeography(subscription required). Annals of the Missouri Botanical Garden 93(2):178–208.
  • Prasad, G.V.R. 2008."Sedimentary basins & fossil records"(PDF).Archived fromthe original(PDF)on 26 July 2011.Pp. 90–96 in Singhvi, A.K. and Bhattacharya, A. (eds.). Glimpses of Geoscience Research in India: The Indian Report to IUGS 2004–2008. New Delhi: The Indian National Science Academy (INSA).
  • Prasad, G.V.R., Verma, O., Sahni, A., Krause, D.W., Khosla, A. and Parmar, V. 2007. A new late Cretaceous gondwanatherian mammal from central India. Proceedings of the Indian National Science Academy 73(1):17–24.
  • Wilson, G.P., Das Sarma, D.C. and Anantharaman, S. 2007.Late Cretaceous sudamericid gondwanatherians from India with paleobiogeographic considerations of Gondwanan mammals(subscription required). Journal of Vertebrate Paleontology 27(2):521–531.