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

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.