Distinguishing Regurgitalites and Coprolites: A Case Study Using a Triassic Bromalite With Soft Tissue of the Pseudosuchian Archosaur Revueltosaurus

Abstract

Regurgitalites (fossilized regurgitates) can provide insight into the behavioral ecology and physiology of extinct species but they are rarely reported because they are difficult to identify and distinguish from coprolites. A compact mass of skeletal material from the Owl Rock Member of the Upper Triassic Chinle Formation of Arizona reveals features that identify it as a regurgitalite. Characteristics of the teeth and osteoderms in the specimen indicate that these remains belong to the pseudosuchian archosaur Revueltosaurus. Chemical and microstructural analysis revealed a dearth of gastric etching, the preservation of muscle fibers, and the absence of a phosphatic matrix, indicating that this bone mass is a regurgitalite and not a coprolite. It was probably produced by a phytosaur, rauisuchid, or temnospondyl, all of which occur in the Owl Rock Member. We offer an identification key to assist in distinguishing between different types of digestive remains produced by vertebrate carnivores.

Exceptional avian pellet from the Paleocene of Patagonia and description of its content: a new species of calyptocephalellid (Neobatrachia) anuran

“…The features above are among the indicators listed by Myhrvold (2012) for recognizing an isolated gastric pellet (see also Gordon et al . 2020). Most of the elements are also cracked in a way usual for fossils, attributed not to the pellet formation but to diagenetic processes.…”

“…2015; O'Connor & Zhou 2020; Gordon et al . 2020). However, several microvertebrate fossil assemblages, mainly of Cenozoic age, have been regarded as originating mostly from the disaggregation of avian gastric pellets (Dodson & Wexlar 1979; Kusmer 1990; Fernández‐Jalvo et al .…”

“…Another record of comparable age comes from the Upper Triassic Owl Rock Member of the Chinle Formation of Arizona, USA (Gordon et al . 2020). It was regarded as a more generalized regurgitalite (i.e.…”

“…egested gastric pellets or occasionally egested items, as contaminated prey; Hunt & Lucas 2010), which was probably produced by phytosaur or rauisuchid archosaurs, or temnospondyl amphibians (Gordon et al . 2020). Focusing on the avian lineage, the oldest gastric pellets were assigned to Anchiornis , a basal paravian from the Middle–Late Jurassic Yanliao biota, China (Zheng et al .…”

Bromalites from the Upper Triassic Polzberg section (Austria); insights into trophic interactions and food chains of the Polzberg palaeobiota

“…Distinguishing between different types of bromalites is not always easy to draw. However, a number of diagnostic criteria have been recently proposed [36][37][38][39][40] . More specifically, regurgitalites are thin, and commonly composed of randomly grouped and intermingled angular skeletal fragments of different size, revealing low degree of roundness and distortion of individual crystal fibers at the shell edges.…”