176-4 Gut morphology and preservation in trilobites from the Fezouata Shale

Session: Laws of the Grave: Advances in Taphonomy Across the Paleontologic Record

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Abstract:

With more than 22,000 trilobite species described, they were an important component of the early Paleozoic marine ecosystems. During the Ordovician, several trilobite clades underwent a significant diversification, increasing their number of species and exploring new ecological niches. Preserved digestive systems provide information about feeding behavior, paleobiology and the taxa’s role within the marine ecosystem. Despite the diverse fossil record of trilobites, information about their digestive system has been reported in only ca. 50 of them. The trilobite gut record is mainly based on reports of the digestive tract, an elongated axial tube-like structure that runs sagittally from the cephalon to the terminal piece of the pygidium. In some species, paired diverticulae adjacent to the anterior half of the digestive tract have been described. 

Here we present new information about the trilobite digestive system of seven species from the Fezouata Biota (Tremadocian, Early Ordovician) of Morocco. The seven species with gut remains from different genera (Anacheirurus, Pilekiinae nov. gen., Prionocheilus, Parabathycheilus, Selenopeltis, Symphysurus and Niobe). Most of the specimens reported only preserve the digestive tract but specimens from the two cheirurid genera show exquisite preservation of paired diverticulae. The digestive tracts are preserved as a two-dimensional film of framboidal iron oxides or as a three-dimensional sediment infilled or secondarily replaced structures. Meanwhile, the diverticulae are usually preserved as three-dimensional phosphatized or sediment infilled structures with rims of iron oxides. 

In Anacheirurus the digestive tract is accompanied four cephalic paired diverticulae and four thoracic diverticulae associated with the anterior four thoracic segments. In the Pilekiinae nov. gen. the digestive tract and four paired diverticulae in the cephalon are reported. Despite both genera being phylogenetically closely related, the shape and size of their paired diverticulae are different. In the new pilekiine genus, the cephalic diverticulae are strikingly large and robust, extending across the totality of the glabellar width (tr.) and length (sag.), while in Anacheirurus the digestive caeca are usually restricted to the most sagittal part of the glabella and substantially smaller.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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