Afrotherian affinities for endemic South American “ungulates”

Agnolín, Federico; Chimento, Nicolás Roberto

doi:10.1016/j.mambio.2010.12.001

Cited by 38 publications

(38 citation statements)

References 58 publications

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“…3), reflecting the large range in values for astrapotheres (range 5 2.05), which is almost comparable to that of Notoungulata (range 5 2.10). Patterson and Pascual (1972) noted convergences between astrapotheres and amynodont rhinoceroses in terms of their skull and dentition, and more recently the astrapotheres have been united with Afrotheria on the basis of some sharedderived dental and postcranial characters (Agnolin and Chimento 2011), though these hypotheses require further validation (Billet and Martin 2011).…”

Section: Discussionmentioning

confidence: 99%

Testing a developmental model in the fossil record: molar proportions in South American ungulates

Wilson¹,

Sánchez‐Villagra²,

Madden³

et al. 2012

Paleobiology

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Abstract.-A developmental model, based upon murine rodents, has been proposed by Kavanagh et al. (2007) to explain lower molar proportions in mammals. We produce a clade-wide macroevolutionary test of the model using the dental evolutionary trends in a unique radiation of extinct mammals endemic to South America (''Meridiungulata'') that comprise a diverse array of molar morphologies. All of the South American ungulate groups examined follow the inhibitory cascade model with the exception of two groups: Interatheriidae (Notoungulata) and Astrapotheria. For most taxa studied, ratios between lower molar areas are greater than 1.0, indicating a weak inhibition by m1 on the subsequent molars in the tooth row, and a trend to greater absolute size of the posterior molars. Comparisons of mean ratios between clades indicate that a significant phylogenetic signal can be detected, particularly between the two groups within Notoungulata-Typotheria and Toxodontia. Body mass estimates were found to be significantly correlated with both m3/m1 and m2/m1 ratios, suggesting that the larger body size achieved the weaker inhibition between the lower molars. Molar ratio patterns are examined and discussed in relation to the independent and numerous acquisitions of hypsodonty that are characteristic of dental evolution in ''Meridiungulata.''

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Section: Discussionmentioning

confidence: 99%

Testing a developmental model in the fossil record: molar proportions in South American ungulates

Wilson¹,

Sánchez‐Villagra²,

Madden³

et al. 2012

Paleobiology

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“…The relationship of notoungulates to other placental mammals is debated (see Cifelli, 1993;Horovitz, 2004;Billet, 2010;Agnolin & Chimento, 2011;Billet & Martin, 2011;O'Leary et al 2013), as are many of the higher-level relationships within the group. Previous analyses of notoun-gulate interrelationships have relied primarily on dental, external cranial and limited postcranial characters (e.g.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of notoungulate (Placentalia, Mammalia) bony labyrinths and new phylogenetically informative inner ear characters

Macrini

Flynn

et al. 2013

Journal of Anatomy

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The phylogenetic relationships of notoungulates, an extinct group of predominantly South American herbivores, remain poorly resolved with respect to both other placental mammals and among one another. Most previous phylogenetic analyses of notoungulates have not included characters of the internal cranium, not least because few such features, including the bony labyrinth, have been described for members of the group. Here we describe the inner ears of the notoungulates Altitypotherium chucalensis (Mesotheriidae), Pachyrukhos moyani (Hegetotheriidae) and Cochilius sp. (Interatheriidae) based on reconstructions of bony labyrinths obtained from computed tomography imagery. Comparisons of the bony labyrinths of these taxa with the basally diverging notoungulate Notostylops murinus (Notostylopidae), an isolated petrosal from Itabora ı, Brazil, referred to Notoungulata, and six therian outgroups, yielded an inner ear character matrix of 25 potentially phylogenetically informative characters, 14 of them novel to this study. Two equivocally optimized character states potentially support a pairing of Mesotheriidae and Hegetotheriidae, whereas four others may be diagnostic of Notoungulata. Three additional characters are potentially informative for diagnosing more inclusive clades: one for crown Placentalia; another for a clade containing Kulbeckia, Zalambdalestes, and Placentalia; and a third for Eutheria (crown Placentalia plus stem taxa). Several other characters are apomorphic for at least one notoungulate in our study and are of potential interest for broader taxonomic sampling within Notoungulata to clarify currently enigmatic interrelationships. Measures of the semicircular canals were used to infer agility (e.g. capable of quick movements vs. lethargic movements) of these taxa. Agility scores calculated from these data generally corroborate interpretations based on postcranial remains of these or closely related species. We provide estimates of the lowfrequency hearing limits in notoungulates based on the ratio of radii of the apical and basal turns of the cochlea. These limits range from 15 Hz in Notostylops to 149 Hz in Pachyrukhos, values comparable to the Asian elephant (Elephas maximus) and the California sea lion (Zalophus californianus) when hearing in air, respectively.

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“…Given renewed interest in the wider relationships of meridiungulates (e.g., Agnolin and chimento, 2011;o'leary et al, 2013; but see Bond et al, 2011;Billet and martin, 2011;Billet and de muizon, 2013), this is an opportune time to critically review the evidence for novel or unexpected elements in notoungulates, as well as to provide new observations on the caudal cranium of this group that may help in framing future character analyses. methoDs, sPecimens, terminoloGy, AnD AGenDA methods and comparative set…”

mentioning

confidence: 99%

The Serrialis Bone, Interparietals, “X” Elements, Entotympanics, and the Composition of the Notoungulate Caudal Cranium

MacPhee

2014

Bulletin of the American Museum of Natural History

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Afrotherian affinities for endemic South American “ungulates”

Cited by 38 publications

References 58 publications

Testing a developmental model in the fossil record: molar proportions in South American ungulates

Testing a developmental model in the fossil record: molar proportions in South American ungulates

Comparative study of notoungulate (Placentalia, Mammalia) bony labyrinths and new phylogenetically informative inner ear characters

The Serrialis Bone, Interparietals, “X” Elements, Entotympanics, and the Composition of the Notoungulate Caudal Cranium

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