Thomas Clements

The fossils of the Lebanese Upper Cretaceous Lagerstätten, especially the articulated fish, are world renowned. Famous for their soft tissue preservation and highly sought after by fossil collectors, Lebanese fossils provide key information concerning the evolution of several major extant and extinct groups of Mesozoic organisms including cephalopods, crustaceans, hagfish, sharks, marine reptiles, pterosaurs, etc. In fact, fossils from Lebanon are so exceptional that historical documentation describing them extends back to the Roman Empire. However, despite over 1600 years of knowledge of these fossils, a thorough understanding of the depositional environments, taphonomy, and palaeoecology of the four main sites: Haqel, Hjoula, Nammoura (each Cenomanian in age), and Sahel Aalma (Santonian) is lacking. Here we compile a review of the palaeoenvironments, fauna, and flora of these four Lebanese Lagerstätten. Our synthesis outlines the history of fossil discovery, describes the current understanding of the geology, ages, mode of preservation, and organisms found at these four sites. We also undertake a bibliometric and holotype analysis to investigate the impact that scientific colonialism has had on Lebanon. Our data confirms that local Lebanese researchers are typically not included on publications pertaining to Lebanese fossils and that the majority of Lebanese type material is stored in large historical collections outside of Lebanon, predominantly in institutions within the northern hemisphere. Here, we recommend some basic practices for researchers utilising historical collections that can help develop local Lebanese fossil collections and establish more research opportunities for local palaeontologists. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7191547

Replacement of soft tissues by calcium phosphate can yield spectacular fossils. However, in the fossil record, the phosphatization of internal organs is highly selective; some internal organs, such as muscles, stomachs, and intestines, appear to preferentially phosphatize while other organs seldom phosphatize. The reasons for this are unclear but one hypothesis is that, during decay, organs create distinct chemical microenvironments and only some fall below the critical pH threshold for mineralization to occur (i.e. below the carbonic acid dissociation constant: pH 6.38). Here, we present a novel investigation using microelectrodes that record dynamic spatial and temporal pH gradients inside organs within a fish carcass in real time. Our experiments demonstrate that within a decaying fish carcass, organ‐specific microenvironments are not generated. Rather, a pervasive pH environment forms within the body cavity which persists until integumentary failure. With no evidence to support the development of organ‐specific microenvironments during decay our data suggest other factors must control differential organ phosphatization. We propose, that when conditions are amenable, it is tissue biochemistry that plays an important role in selective phosphatization. Tissues with high phosphate content (and those rich in collagen) are most likely to phosphatize. Internal organs that typically have lower tissue‐bound phosphate, including the integuments of the stomach and intestine, may require other sources of phosphate such as ingested phosphate‐rich organic matter. If tissue biochemistry is the driver behind selective phosphatization, this may provide insights into other highly selective modes of soft‐tissue preservation (e.g. pyritization).