First record of Mesozoic scroll coprolites: classification, characteristics, elemental composition and probable producers

Abstract

Multiple, small, cylindrical scroll coprolites having rounded and tapering ends and pertaining to a new ichnotaxon have been recovered from the Upper Triassic Tiki Formation of India. This is the first record of scroll coprolites from the Mesozoic. Based on cross‐sectional geometry, external surface textures, and internal morphology, these coprolites are subdivided into three morphotypes. The coprolites contain several kinds of undigested food material in the form of ganoid fish scales, teeth, lower jaw and skeletal remains of various osteichthyans, chondrichthyans, archosauriforms and indeterminate reptiles. These inclusions are embedded in the groundmass separated by thin mucosal layers. The groundmass contains abundant gas vesicles, and secondarily‐filled shrinkage cracks. EDS analysis shows that the overall composition of the coprolites reflects Ca, P, C and O, suggesting calcium phosphate mineralogy, though other elements such as Fe, Mn, Al, Si are present in lesser proportions. Based on their similarity with the scrolled faeces of extant euryhaline hammerhead sharks, it is deduced that these coprolites were produced by euryhaline hybodontid sharks. At least two hybodontid taxa, Lonchidion and Pristrisodus, show high prevalence in the Tiki vertebrate fauna, suggesting that these were the possible producers. As the coprolite inclusions contain remains of other aquatic animals, these carnivorous hybodonts constituted the dominant predators of the Tiki aquatic ecosystem.

Coprolites from shallow marine deposits of the Nanjemoy Formation, Lower Eocene of Virginia, USA

“…The longitudinal valves ( valvula voluta ) described by Parker (1885) are present in extant carcharhiniform sharks and are related to scrolled scat (Friedman 2012; Stringer & King 2012; Leigh et al 2017). Recently, scroll coprolites were also assigned to Hybodontiformes (Rakshit et al 2018; Bajdek et al 2019). Although Hybodontiformes have been completely extinct since the Late Cretaceous, Carcharhiniformes are common in the Eocene Nanjemoy Formation (Ward & Weist, 1990), suggesting that the scroll morphotype is more likely attributable to this group of neoselachians.…”

“…Cracks occur only on the surface of one sinuous morphotype in the sample studied and only can be visualized by SEM. These cracks could be formed due to shrinkage or when gas escapes from the faecal mass, deforming the faeces (Rakshit et al 2018), or during post‐exposure stage breakage (Hollocher et al 2010). None of the Nanjemoy coprolites have any features that indicate sub‐aerial exposure before the final burial or the production of a large amount of gas (such as gas vesicles in the coprolite matrix), so it is likely that these cracks were formed during the breakage of the coprolite.…”

“…Coprolites are fossilized faeces and contain unique palaeobiological information that has mostly been understudied until recently. Study of food chains in ancient environments is only possible with the analysis of incompletely digested food within coprolites (Chin et al 2008; Zatoń & Rakociński 2014; Schwimmer et al 2015; Zatoń et al 2015, 2017; Bajdek et al 2016; Hansen et al 2016; Niedźwiedzki et al 2016a, 2016b; Luo et al 2018; Loinaze et al 2018; Rakshit et al 2018; Qvarnström et al 2019). Fossil intestinal parasites are also known from coprolites from different strata (Poinar & Boucot 2006; Dentzien‐Dias et al 2013; Wood et al 2013; Silva et al 2014; Hugot et al 2014; Bajdek et al 2016; Francischini et al 2018), indicating that the study of coprolites should be undertaken to gain a better understanding of parasite–host interactions.…”

The first record of exceptionally-preserved spiral coprolites from the Tsagan-Tsab formation (lower cretaceous), Tatal, western Mongolia

“…Generally, the records of scroll coprolite are scarce 7 , 17 , as they are more commonly known from the Palaeozoic and Cenozoic periods. The first recorded Mesozoic scroll coprolites were known from the Tiki Formation, India 18 .…”

New cynodonts (Therapsida, Eucynodontia) from the Late Triassic of India and their significances

“…The second biostratinomic mode is by mass-death assemblage, formed from breaching of banks during flooding, and burial of fishes and unionid bivalves in high-energy deposition of sediments. The macrofossils included disarticulated skeletal remains of an undescribed metoposaurid (Rakshit and Ray, 2020), a derived phytosaur (Datta et al, 2019b), the rhynchosaur Hyperodapedon tikiensis Mukherjee and Ray, 2014, along with numerous, large unionid bivalves, and the scroll coprolite Tikicopros triassicus Rakshit et al, 2019. The vertebrate microfossils, on the other hand, included isolated teeth and skeletal remains of hybodontids, xenacanthids, dipnoans, actinopterygians, various archosauriforms including basal saurischians, and non-mammalian cynodonts (Ray et al, 2016, 2019; Bhat, 2018; Bhat et al, 2018a, b; Rakshit et al, 2018; Bhat and Ray, 2020).…”