Comparative morphotaxonomical affinities, palaeoecological implications and cladistic analyses of ornithoid eggshells (oofamily Laevisoolithidae) from the Late Cretaceous intertrappean beds of Anjar, District Kachchh, Gujarat, India

ABSTRACT

We re-evaluate fragmentary eggshells of avian affinities (ratite morphotype) from the Late Cretaceous Intertrappean beds of Anjar (District Kachchh, Gujarat), India in view of additional material and cladistic analysis. Previously, Anjar eggshells were encompassed in the oofamily Subtiliolithidae; however, now the oofamily Subtiliolithidae has been re-examined as a junior synonym of the oofamily Laevisoolithidae. External surface of the eggshells is smooth to rugose, with unevenly distributed, sub-rounded tubercles; average eggshell thickness (467–491 µm) characterised by two layers: (1) a well-differentiated mammillary layer (196.1 µm), comprising conical, crystalline aggregates with petaloid wedges, and (2) a continuous spongy layer (274.58 µm, CL:ML, 1.3:1) divulges a squamatic zone. The eggshells have been compared with three oofamilies (Elongatoolithidae, Prismatoolithidae and Laevisoolithidae) and their palaeoecological implications have been discussed in detail. Shell microstructure is comparable with oofamily Laevisoolithidae, an ootaxon usually related with enantiornithid birds. Cladistic analysis performed on the eggshells are consistent with the avian kinships recognised based on macro, micro and ultrastructural features.

KEYWORDS:

• Cladistic analyses
• Indian
• Late Cretaceous
• Laevisoolithidae
• ornithoid eggshells
• Subtiliolithus kachchhensis
• palaeoecology

Acknowledgements

Ashu Khosla acknowledges financial support from the Department of Science and Technology (DST), New Delhi (project grant no. SR/S4/ES-382/2008 and DST PURSE project, (grant no. 753/Dean Research dated 29.09.2010 Panjab University, Chandigarh, India). Ashu Khosla is thankful to Manpinder for helping in SEM photography at Freie Universitat, Berlin (Germany). Mariela Soledad Fernández want to thanks CONICET and PICT 2017-0905 (FONCyT) for financial support on this research. We sincerely acknowledge the critical and constructive comments, linguistic improvements and insightful remarks of Professor Spencer Lucas that helped us in improving the manuscript and four anonymous reviewers, which have significantly enhanced the quality of the manuscript during the peer review process.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by DST PURSE project (Panjab University, Chandigarh) and the Department of Science and Technology (DST), Government of India, New Delhi [grant number SR/S4/ES-382/2008] and CONICET and PICT 2017-0905 (FONCyT).