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

Abstract

The Eocene Nanjemoy Formation crops out on the Maryland and Virginia Coastal Plain, along the eastern coast of the United States. This formation is composed of sands, silts and clays and is divided into the Potapaco and Woodstock members. Remains of fishes, reptiles, birds, mammals, molluscs, fruits and seeds are common in the Potapaco Member, in addition to vertebrate coprolites. Here, we present an analysis of more than 2000 coprolites from the Fisher/Sullivan Site in Virginia. The chemical composition (phosphatic) and the type of inclusions (fish bones) indicate that only scats of carnivorous animals were preserved. The analysed specimens were grouped into six morphotypes: (1) the cylindrical morphotype is a cylinder with rounded ends; (2) the segmented morphotype is a cylinder segmented with rounded ends, and occasionally one end is concave; (3) the oval morphotype represents a bean-shaped coprolite; (4) the scroll morphotype is cylindrical to conical in lateral view and has coils seen only at the ends; (5) the folded morphotype is a spiral that is concentrically folded; and (6) the sinuous morphotype is serpentine, with rounded ends. Coprophagy-related scrape traces occur in different morphotypes and represent both invertebrate burrows and bite traces made by fishes. The mineralogical and chemical analyses indicate an early precipitation of phosphate and pyrite minerals, probably induced by the microbial community. All coprolites at the Fisher/Sullivan Site were produced by fishes: carcharhiniform sharks for the scroll morphotype and lamniform sharks, probably the genus Carcharias, for the folded morphotype; the oval, cylindrical and segmented morphotypes were likely produced by actinopterygian fishes. □ coprolites, dentalites, fish scat, Fisher/Sullivan Site, ichnology, Potapaco Member.

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

“…Among them, one of the most important criteria includes the content and composition of the fecal matter, and those of carnivorous diets tend to form coprolites than those who consumed an herbivorous diet 75 . As mentioned in Dentzien-Dias et al 111 , there are three main stages involved in a coprolite taphonomy history, which include stages before final burial, after the final burial and after exposure. In accordance to this, we introduced the usage of phases to discuss the spiral coprolites morphologies in this study (see material and methods).…”

“…It has been frequently reported in records that almost all spiral coprolite fossilization from various Phenerozoic ages have occurred in low-energy shallow marine environments 54 . Feces that are being excreted in this humid environment have a higher chance of preservation due to the rapid burial, as well as on the acidity level of the water bodies 5 , 7 , 109 – 111 . There are also several crucial factors that are involved in fecal fossilization.…”

The first record of exceptionally-preserved spiral coprolites from the Tsagan-Tsab Formation (Lower Cretaceous), Tatal, western Mongolia

“…Among them, one of the most important criteria includes the content and composition of the fecal matter, and those of carnivorous diets tend to form coprolites than those who consumed an herbivorous diet 104 . As mentioned in Dentzien-Dias et al 103 , there are three main stages involved in a coprolite taphonomy history, which includes stages before nal burial, after the nal burial and after exposure. In accordance to this, we introduced the usage of phases to discuss the spiral coprolites morphologies in this study (see material and methods).…”

“…It has been frequently reported in records that almost all spiral coprolite fossilization from various Phenerozoic ages have occurred in low-energy shallow marine environments 46 . Feces that are being excreted in this humid environment have a higher chance of preservation due to the rapid burial, as well as on the acidity of the water bodies 5,7,101,102,103 .…”

Exceptionally well-preserved crocodilian coprolites from the Late Eocene of Northern Vietnam (Na Duong Formation) and their coproecological implications

“…Most of the known coprolite fossilization from various Phenerozoic ages have occurred in low-energy shallow marine or lake environments 18 , where feces that are being excreted in this humid environment have a higher chance of preservation due to the rapid burial, as well as on the acidity level of the water bodies 51,96,97,98,99 . Besides these trophic factors, several crucial factors contributed to the succession rate of fecal fossilization.…”