NOT ENTIRELY ICHTHYOSAUR: A MYSTERIOUS LAMNIFORM AND ICHTHYOPTERYGIAN-FALL ASSOCIATION FROM THE ABYSSAL UPPER CRETACEOUS OF THE NORTHERN APENNINES (ITALY)
Author:
SERAFINI GIOVANNI1, AMALFITANO JACOPO2, DANISE SILVIA3, MAXWELL ERIN E.4, RONDELLI RICCARDO1, PAPAZZONI CESARE A.1
Affiliation:
1. 1 Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 103, I-41125 Modena, Italy 2. 2 Centro di Ateneo per i Musei, Università degli Studi di Padova, Via Giotto, 1, I–35131 Padova, Italy 3. 3 Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via La Pira, 4, 50121, Firenze, Italy 4. 4 Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany
Abstract
ABSTRACT
Axial remains of a large ichthyosaur and a medium-sized anacoracid shark from the deep-water sediments of the Cenomanian of the Northern Apennines (Northern Italy) are described in detail. The specimens were found closely associated (less than 0.3 m apart), and offer an invaluable window into the taphonomy and dead-fall stages of pelagic vertebrates in a Mesozoic abyssal plain. The anacoracid shark remains, initially misinterpreted as an ichthyosaur, consist of eight articulated vertebrae embedded in a block of dark arenaceous matrix, and represent the first occurrence of an articulated shark from the Northern Apennines. The ichthyosaur remains consist of seven discoidal vertebrae and several unidentified fragments. Due to the absence of diagnostic skeletal elements, both specimens are assigned only at higher taxonomic levels. The two fossils, which come from the same outcrop and possibly from the same stratigraphic horizon, share a common taphonomic history, in terms of both their preservation and diagenesis. Mineralogy of the matrices of both is dominated by manganese micro-nodules, consistent with the deposition of polymetallic nodules in bathyal-abyssal settings. Biostratinomic processes that impacted the two specimens also provide insight on the development of Mesozoic marine vertebrate-falls in the deep-sea. Localized pyrite framboids inside the bone spongiosa are possible evidence of the sulfophilic stage (microbially mediated sulfur mobilization during lipid decay) in the ichthyosaur fall. Burrows assigned to Taenidium on the surface of the shark block, interpreted as worm-like feeding burrows or arthropod locomotion and feeding trails, might represent evidence of the enrichment opportunistic stage. Although intriguing, we have no evidence to support the hypothesis that this peculiar association of two pelagic predators is due to ecological interaction between the two animals.
Publisher
Society for Sedimentary Geology
Subject
Paleontology,Ecology, Evolution, Behavior and Systematics
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