Phenetic classification of Kimmeridgian ammonites from the eastern Kachchh Basin, India

Abstract

Thirty Kimmeridgian (Upper Jurassic) ammonite specimens of the genera Torquatisphinctes, Pachysphinctes, Katroliceras, and Indodichotomoceras collected from two horizons in the eastern part of the Kachchh Basin were phenetically classified. First, 23 morphological characters were selected for the analysis. The difference matrix was generated by treating the characters as a binary system (0 or 1) and giving scores between 0 and 2. The dendrogram, prepared using the R program, shows perfect groupings of the different taxa identified earlier through a traditional taxonomic approach. The percentage of shared characters has helped choosing significant characters to be used in distinguishing three major groups and one subgroup, which also validates the visual identification of the ammonite taxa. Categorization of the ammonites was also subjected to a Mann-Whitney U test to verify the results. Overall, the dendrogram depicted three distinct clusters, the Torquatisphinctes, Pachysphinctes, and Katroliceras groups. The specimens of Indodichotomoceras (designated the Indodichotomoceras subgroup) were clustered within the Torquatisphinctes group potentially because of their biplicate ornamentation and presence of constrictions. However, the Indodichotomoceras subgroup maintained its identity because of the thickness of the primary and secondary ribs.

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Acknowledgements

DKP, RD, and Prajna are grateful to the Manipal Center for Natural Sciences, Manipal Academy of Higher Education for providing the facilities to work on the project and manuscript. The authors sincerely thank the reviewers Federico Olóriz and Alexandr Alifirov for their critical review of the manuscript and useful suggestions. DKP and RSS acknowledge the Department of Science and Technology (project no. EMR/2015/001574) for financial support to carry out the field work to collect the samples. MA gratefully acknowledges financial support from the Alexander von Humboldt Foundation.

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Correspondence to Dhirendra K. Pandey.

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Handling editor: Christian Klug.

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Pandey, D.K., Das, R., Alberti, M. et al. Phenetic classification of Kimmeridgian ammonites from the eastern Kachchh Basin, India. PalZ 93, 255–263 (2019). https://doi.org/10.1007/s12542-018-0429-1

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Keywords

  • Jurassic
  • India
  • Ammonites
  • Taxonomy
  • Phenetic classification