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Home / Equine Research Bank / J Exp Zool B Mol Dev Evol / Teeth out of proportion: Smaller horse and cattle breeds hav...
Journal of experimental zoology. Part B, Molecular and developmental evolution2022; 338(8); 561-574; doi: 10.1002/jez.b.23128

Teeth out of proportion: Smaller horse and cattle breeds have comparatively larger teeth.

Abstract: There are different descriptions of allometric relationships between important components of the mammalian skull. Craniofacial evolutionary allometry describes a pattern of increasing facial cranium in larger skulls. Another body of literature describes disproportionately larger teeth in smaller species or specimens, matching anecdotal observations with dental problems in dwarf breeds whose teeth appear "too large for their skulls." We test the scaling of tooth row length with body size and skull length in a data set comprising 114 domestic horses (representing 40 breeds) and in another data set of 316 domestic cattle (of >60 breeds). We demonstrate that smaller skulls have a relatively longer tooth row in both horses and cattle; larger specimens have relatively shorter tooth rows. Whereas in horses, larger skulls have a relatively longer diastema, the distance of the mesial maxillary premolar to the premaxilla was proportional to cranium length in cattle. While the reasons for these patterns remain to be detected, they support the hypothesis that tooth size might be less "evolvable," in terms of time required for changes, than body size. The pattern may affect (i) the selective breeding for dwarf breeds by setting minimum constraints for skull size, as described previously for domestic horses with the same data set; (ii) the susceptibility of small breeds for dental problems; and (iii) differences in chewing efficiency between breeds of different sizes. The findings support the existing concept that scaling of tooth to body size across taxa becomes more isometric the longer these taxa are separated in evolutionary time.
© 2022 The Authors. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution published by Wiley Periodicals LLC.
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Publication Date: 2022-03-14 PubMed ID: 35286773PubMed Central: PMC9790632DOI: 10.1002/jez.b.23128Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article explores the hypothesis that smaller horse and cattle breeds have disproportionately larger teeth, where the tooth size doesn’t reduce in proportion with the overall body size or skull. This idea is explored using samples from 40 horse breeds and over 60 cattle breeds.

Understanding Allometry and Craniofacial Evolution

  • Allometry is a term used in the study of size and shape transformations in organisms. It’s often applied to describe how characteristics of creatures, such as body size or shape, change disproportionately during the growth of an organism.
  • The research refers to a widely recognized pattern in craniofacial evolution, the science investigating how the skull and face of organisms change over time. This pattern shows that larger mammalian skulls tend to have a more extended facial cranium.

Investigating Oversize Teeth in Smaller Breeds

  • There have been anecdotal observations of dental problems in smaller or dwarf breeds which appear to have oversized teeth for their skulls. The researchers sought to scientifically substantiate these observations.
  • The research tested the proportion of tooth row length to body size and skull length using a large sample size of over 100 domestic horses from 40 breeds, and over 300 domestic cattle from more than 60 breeds.

Findings: Disproportionate Tooth Size in Smaller Breeds

  • The researchers found supporting evidence for their hypothesis: smaller skulls in both horses and cattle tend to have more extended tooth rows, while larger specimens presented shorter tooth rows.
  • In horses, the longer the skull size, the larger the diastema, or gap between teeth. However, in cattle, the distance from the mesial maxillary premolar to the premaxilla was proportional to the cranial length.
  • The reasons behind these patterns remain undetermined, but these findings do support the idea that tooth size is less “evolvable,” or slower to change, than body size. The researchers theorize that these patterns could explain issues in breed selection – for instance, there may be a minimum skull size constraint for dwarf breeds – susceptibility to dental issues in smaller breeds, and variations in chewing efficiency amongst breeds of different sizes.

Broader Implications for Evolutionary Taxonomy

  • This study supports the broader concept in evolutionary taxonomy that the ratio of tooth-to-body size tends to become more isometric, or maintains its scale, the longer these taxa are separated in evolutionary time.
  • This means that the longer two species have been separated from a shared ancestor, the more “in proportion” the teeth become to the overall body size.

Cite This Article

APA
Clauss M, Heck L, Veitschegger K, Geiger M. (2022). Teeth out of proportion: Smaller horse and cattle breeds have comparatively larger teeth. J Exp Zool B Mol Dev Evol, 338(8), 561-574. https://doi.org/10.1002/jez.b.23128

Publication

Journal of experimental zoology. Part B, Molecular and developmental evolution
ISSN: 1552-5015
NlmUniqueID: 101168228
Country: United States
Language: English
Volume: 338
Issue: 8
Pages: 561-574

Researcher Affiliations

Clauss, Marcus
  • Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
Heck, Laura
  • Palaeontological Institute and Museum, University of Zurich, Zurich, Switzerland.
Veitschegger, Kristof
  • Palaeontological Institute and Museum, University of Zurich, Zurich, Switzerland.
Geiger, Madeleine
  • Palaeontological Institute and Museum, University of Zurich, Zurich, Switzerland.
  • SWILD, Urban Ecology & Wildlife Research, Zurich, Switzerland.
  • Naturmuseum St. Gallen, Rorschacher Strasse 263, 9016, St.Gallen, Switzerland.

MeSH Terms

  • Horses
  • Animals
  • Cattle
  • Tooth
  • Skull
  • Head
  • Biological Evolution
  • Body Size
  • Mammals

Conflict of Interest Statement

The authors declare no conflicts of interest.

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Citations

This article has been cited 7 times.
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