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Diversity and evolution of Hunter-Schreger Band configuration in tooth enamel of perissodactyl mammals

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Koenigswald W., Holbrook L., Rose K.

Acta Palaeontologica Polonica

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2011

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tom 56

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nr 1

Four different Hunter−Schreger Band (HSB) configurations were observed in the teeth of fossil and extant Perissodactyla. This variability exceeds that observed in Artiodactyla or Proboscidea. The four HSB configurations represent two different evolutionary pathways. Transverse HSB found in many mammalian taxa outside the Perissodactyla represents the most primitive HSB configuration. It occurs in several primitive perissodactyl families and is retained in Palaeotheriidae and extant Equidae. Curved HSB evolved from transverse HSB and occurs in Tapiridae, Helaletidae, and Lophiodontidae, as well as in Ancylopoda and Titanotheriomorpha. This likely indicates independent evolution of curved HSB in two or more lineages, but the number of instances of parallelism of this configuration is obscured by uncertainty in the relationships among these taxa and by a lack of data for some important basal taxa. A second evolutionary pathway leads from transverse HSB via compound HSB to vertical HSB. Compound HSB were detected in Hyrachyidae, Deperetellidae, and the early rhinocerotid Uintaceras. Vertical HSB configuration characterizes the molar dentition of other Rhinocerotidae, Hyracodontidae, Indricotheriidae, and Amynodontidae. Often, the incisors of rhinocerotids retain traces of compound HSB. Thus the HSB configuration reflects phylogenetic relationships to some degree. The selective value of the modified HSB configurations is interpreted functionally as a mechanism to reduce abrasion during mastication, assuming that the perpendicular intersection of prisms with the actual grinding surfaces resists wear better than prisms running parallel to the occlusal surface.

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Hypsodonty and enamel microstructure in the Paleocene gondwanatherian mammal Sudamerica ameghinoi

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Koenigswald W., Goin F., Pascual R.

Acta Palaeontologica Polonica

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1999

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tom 44

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nr 3

263-300

Gondwanatherians were the earliest mammals to develop hypsodont cheek-teeth with thick cementum, already by the Late Cretaceous. Hypsodonty occurred independently in Gondwanatheria and Theria; however, very similar biomechanical strategies are observed. The hypsodont molariform cheek-teeth of the early Paleocene Sudamerica ameghinoi, the youngest member of the Gondwanatheria, are described. Sudamerica had in the lower jaw a continuously growing incisor and, separated by a large diastema, four cheek-teeth which cannot be homologized with premolars or molars, therefore they are regarded as molariforms. The analysis of one fragmentary mandible and 30 isolated molariforms led to the recognition of 8 different morphological categories among them, corresponding to four upper and four lower molariforms. The height of the teeth indicates a relatively high shape of the skull. The molariforms are characterized by transverse lophs; when only slightly worn, they show central enamel islets in the anterior/posterior caps and in the transverse valleys. When the first quarter of the tooth is worn down, these islets disappear and the synclines expand leaving only a narrow central longitudinal ridge. The enamel of the molariforms of Sudamerica is one-layered and formed by radial enamel; it resembles the enamel of Gondwanatherium. Compared to the enamel of the Gondwanatheria from Madagascar and India, the South American gondwanatherians are distinctly less derived. In turn, the incisor enamel is less derived in Sudamerica, although younger, than in Gondwanatherium; both show a combination of radial and tangential enamel. The evolution of hypsodonty in gondwanatherians during the Late Cretaceous and early Paleocene cannot be correlated with a grass diet, since grasses were not present during that time. Various lines of evidence including the dental morphology and the inferred habitat for Sudamerica ameghinoi, suggest semiaquatic and perhaps a burrowing way of life, similar to that of living beavers.

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The Upper Pleistocene Tracksite Bottrop-Welheim [Germany]

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Koenigswald W., Sander P. M., Walders M.

Acta Zoologica Cracoviensia

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1996

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tom 39

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nr 1

Ograniczanie wyników

2 Acta Palaeontologica Polonica

1 Acta Zoologica Cracoviensia

3 Koenigswald W.

1 Goin F.

1 Holbrook L.

1 Pascual R.

1 Rose K.

1 Sander P. M.

1 Walders M.

1 2011

1 1999

1 1996

Diversity and evolution of Hunter-Schreger Band configuration in tooth enamel of perissodactyl mammals

Hypsodonty and enamel microstructure in the Paleocene gondwanatherian mammal Sudamerica ameghinoi

The Upper Pleistocene Tracksite Bottrop-Welheim [Germany]