A silicified bird from Quaternary hot spring deposits

Abstract

The first avian fossil recovered from high-temperature hot spring deposits is a three-dimensional external body mould of an American coot (Fulica americana) from Holocene sinters of Yellowstone National Park, Wyoming, USA. Silica encrustation of the carcass, feathers and colonizing microbial communities occurred within days of death and before substantial soft tissue degradation, allowing preservation of gross body morphology, which is usually lost under other fossilization regimes. We hypothesize that the increased rate and extent of opal-A deposition, facilitated by either passive or active microbial mediation following carcass colonization, is required for exceptional preservation of relatively large, fleshy carcasses or softbodied organisms by mineral precipitate mould formation. We suggest physico-chemical parameters conducive to similar preservation in other vertebrate specimens, plus distinctive sinter macrofabric markers of hot spring subenvironments where these parameters are met.

Exceptionally preserved ostracodes from a Middle Miocene palaeolake, California, USA

“…Though silica frequently pseudomorphs shelly fossils (Schubert et al 1997) and preserves a range of ancient bacteria (see Westall et al 2001), fungi (Taylor et al 2004) and plants (Edwards 2004), it is rarely associated with soft-tissue preservation in animals (Carson 1991). Most documented examples are from hydrothermal sinters (though see Voigt 1988;Lin et al 2006) such as the Devonian Rhynie chert complex where a variety of arthropods, including crustaceans, is encased within silica deposited from supersaturated fluids (Anderson & Trewin 2003); a bird is known from a comparable sub-Recent setting (Channing et al 2005). The Barstow ostracods may have occupied a lake with a hydrothermal or volcanic influence, but their preservation style differs markedly from that of sinter fossils: crucially, the ostracod soft anatomy is predominately replaced, rather than encrusted and/or permineralized as is typical of sinter fossils.…”

Preservation potential of keratin in deep time

“…We build on previous work examining the molecular and microstructural characteristics of modern feathers exposed to degradation under varying conditions for seventeen years (ten years of experimental conditions, including constant high heat, then seven additional years, where samples were stored in burial sediments or in sterile, 1.5 ml tubes, at room temperature until collected for the current analysis [10]). We then apply these methods to relatively recent ‘fossil’ feathers, recovered from a previously described, approximately 10 Ka coot ( Fulica americana ), preserved in siliceous hot spring deposits [47].…”

Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in Fossil Vertebrates Part I: Reptiles—the taphonomy of the bipedal dinosaurs Compsognathus longipes and Juravenator starki from the Solnhofen Archipelago (Jurassic, Germany)

“…In this, it is immaterial whether, or to what extent, sediments of volcanic origin in a lake or opalprecipitation induced by microorganisms in a terraced pool, for example, are involved in embedding (e.g. Beardmore et al 2009Beardmore et al , 2011Benton et al 2008;Chaffee 1952;Channing et al 2005). The commonly accepted present-day state of knowledge about the sedimentary environments of the fossil sites actually referred to or discussed by Faux and Padian (2007) is, in our opinion, also not touched on in their conclusion, whereby: "These and other examples suggest that re-evaluation may be in order for an untold number of palaeoenvironments whose story has been at least partly explained on the basis of the death positions of many of their fossil vertebrates."…”

“…specific gravity and shape characteristics), physiology and thus their centre of gravity (Chanin 1985;Dilen 1984;Haberda 1895;Haglund and Sorg 2002;Rietchel and Storch 1974;Schoener and Schoener 1984;Slijper 1962;Rapp 1988, 1989;Tarasoff and Kooyman 1973a, b), it is to be expected that their fresh carcasses will exhibit differences in sinking behaviour and in the death posture assumed on the bed of the water body (e.g. Burnham 2007;Kielan-Jaworowska and Hurum 2006;Parker 1925;Rietchel and Storch 1974).…”

“…In fact, all examples of fossil air-breathing vertebrates in Faux and Padian (2007) do indeed come from aquatic sediments and are thus to be classified as allochthonous faunal elements of an aquatic taphocoenosis. The majority of these embedding locations are marine, lacustrine and fluvial sediment environments, with only one (a terrace pool environment of the hot springs of Yellowstone National Park) being a small and shallow aquatic depositional environment (Channing et al 2005).…”