Palaeoenvironmental and palaeoecological inferences from inclusions in vertebrate omnivore coprolites from the Upper Cretaceous Lameta Formation of central India

Abstract

Fossil faeces, or coprolites, offer unique insights into prehistoric food webs and ecosystems as well as direct evidence of the diet of faecal producers. We collected hundreds of coprolites from the Upper Cretaceous Pisdura site of Central India. Type A morphotype coprolites from the Lameta Formation of Pisdura, Maharashtra, India, have been found to have a rich microbiota with unique plant fossils. When macerated fractions were analysed using scanning electron microscopy, seven ostracod taxa were found, together with diatoms (Aulacoseira sp.), a charophyte (Microchara sp.), and sponge spicules. Thin sections of one of the coprolites also revealed a large number of likely chrysophytes. One of the cut slab specimens of the coprolite contains an insect body part with a partially intact wing. In addition, a review of previous studies reveals that spores, fungal remnants, thecamoebians, testate amoebae, and plant remains are also present in the Type A coprolites. For the Lameta Formation in Pisdura, the microbiota provide evidence for a Maastrichtian age and fluvio-lacustrine depositional conditions and other varied environments. Much of the plant detritus is not identifiable, but some tissues can be recognised, such as Poaceae cuticle, spores, wood, cones, seeds, phytoliths, and silica-replaced leaf laminae. Chemical analyses show that the coprolites have a phosphorus content of between 12.2 and 16.2 weight% which suggests a carnivorous habit. Thus, these Type A coprolites reveal that the ancient faecal producers not only consumed aquatic microbiota and abundant plant tissues but also likely ingested soft animal tissues as well. Although water input may have been the source of testate amoebae, diatoms, sponge spicules, and algae remnants, the peculiar pairing of a phosphatic composition with dietary residues from plants and microbiota suggests that the ancient faecal producers were omnivores. This feeding habit implied by the Type A coprolites indicates that previous attributions to herbivorous titanosaurs are not well-supported.