Molecular fingerprints resolve affinities of Rhynie chert organic fossils

The affinities of extinct organisms are often difficult to resolve using morphological data alone. Chemical analysis of carbonaceous specimens can complement traditional approaches, but the search for taxon-specific signals in ancient, thermally altered organic matter is challenging and controversial, partly because suitable positive controls are lacking. Here, we show that non-destructive Fourier Transform Infrared Spectroscopy (FTIR) resolves in-situ molecular fingerprints in the famous 407 Ma Rhynie chert fossil assemblage of Aberdeenshire, Scotland, an important early terrestrial Lagerstätte. Remarkably, unsupervised clustering methods (principal components analysis and K-mean) separate the fossil spectra naturally into eukaryotes and prokaryotes (cyanobacteria). Additional multivariate statistics and machine-learning approaches also differentiate prokaryotes from eukaryotes, and discriminate eukaryotic tissue types, despite the overwhelming influence of silica. We find that these methods can clarify the affinities of morphologically ambiguous taxa; in the Rhynie chert for example, we show that the problematic "nematophytes" have a plant-like composition. Overall, we demonstrate that the famously exquisite preservation of cells, tissues and organisms in the Rhynie chert accompanies similarly impressive preservation of molecular information. These results provide a compelling positive control that validates the use of infrared spectroscopy to investigate the affinity of organic fossils in chert.

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

Fossils are a key source of data on the evolution of feather structure and function through deep time, but their ability to resolve macroevolutionary questions is compromised by an incomplete understanding of their taphonomy. Critically, the relative preservation potential of two key feather components, melanosomes and keratinous tissue, is not fully resolved. Recent studies suggesting that melanosomes are preferentially preserved conflict with observations that melanosomes preserve in fossil feathers as external moulds in an organic matrix. To date, there is no model to explain the latter mode of melanosome preservation. We addressed these issues by degrading feathers in systematic taphonomic experiments incorporating decay, maturation and oxidation in isolation and combination. Our results reveal that the production of mouldic melanosomes requires interactions with an oxidant and is most likely to occur prior to substantial maturation. This constrains the taphonomic conditions under which melanosomes are likely to be fossilized. Critically, our experiments also confirm that keratinous feather structures have a higher preservation potential than melanosomes under a range of diagenetic conditions, supporting hitherto controversial hypotheses that fossil feathers can retain degraded keratinous structures.

Fossilization of melanosomes via sulfurization

Fossil melanin granules (melanosomes) are an important resource for inferring the evolutionary history of colour and its functions in animals. The taphonomy of melanin and melanosomes, however, is incompletely understood. In particular, the chemical processes responsible for melanosome preservation have not been investigated. As a result, the origins of sulfur-bearing compounds in fossil melanosomes are difficult to resolve. This has implications for interpretations of original colour in fossils based on potential sulfur-rich phaeomelanosomes. Here we use pyrolysis gas chromatography mass spectrometry (Py-GCMS), fourier transform infrared spectroscopy (FTIR) and time of flight secondary ion mass spectrometry (ToF-SIMS) to assess the mode of preservation of fossil microstructures, confirmed as melanosomes based on the presence of melanin, preserved in frogs from the Late Miocene Libros biota (NE Spain). Our results reveal a high abundance of organosulfur compounds and non-sulfurized fatty acid methyl esters in both the fossil tissues and host sediment; chemical signatures in the fossil tissues are inconsistent with preservation of phaeomelanin. Our results reflect preservation via the diagenetic incorporation of sulfur, i.e. sulfurization (natural vulcanization), and other polymerization processes. Organosulfur compounds and/or elevated concentrations of sulfur have been reported from melanosomes preserved in various invertebrate and vertebrate fossils and depositional settings, suggesting that preservation through sulfurization is likely to be widespread. Future studies of sulfur-rich fossil melanosomes require that the geochemistry of the host sediment is tested for evidence of sulfurization in order to constrain interpretations of potential phaeomelanosomes and thus of original integumentary colour in fossils.

Reconstructing Carotenoid-Based and Structural Coloration in Fossil Skin

Evidence of original coloration in fossils provides insights into the visual communication strategies used by ancient animals and the functional evolution of coloration over time [1-7]. Hitherto, all reconstructions of the colors of reptile integument and the plumage of fossil birds and feathered dinosaurs have been of melanin-based coloration [1-6]. Extant animals also use other mechanisms for producing color [8], but these have not been identified in fossils. Here we report the first examples of carotenoid-based coloration in the fossil record, and of structural coloration in fossil integument. The fossil skin, from a 10 million-year-old colubrid snake from the Late Miocene Libros Lagerstätte (Teruel, Spain) [9, 10], preserves dermal pigment cells (chromatophores)-xanthophores, iridophores, and melanophores-in calcium phosphate. Comparison with chromatophore abundance and position in extant reptiles [11-15] indicates that the fossil snake was pale-colored in ventral regions; dorsal and lateral regions were green with brown-black and yellow-green transverse blotches. Such coloration most likely functioned in substrate matching and intraspecific signaling. Skin replicated in authigenic minerals is not uncommon in exceptionally preserved fossils [16, 17], and dermal pigment cells generate coloration in numerous reptile, amphibian, and fish taxa today [18]. Our discovery thus represents a new means by which to reconstruct the original coloration of exceptionally preserved fossil vertebrates.

Cryptic iridescence in a fossil weevil generated by single diamond photonic crystals

Nature's most spectacular colours originate in integumentary tissue architectures that scatter light via nanoscale modulations of the refractive index. The most intricate biophotonic nanostructures are three-dimensional crystals with opal, single diamond or single gyroid lattices. Despite intense interest in their optical and structural properties, the evolution of such nanostructures is poorly understood, due in part to a lack of data from the fossil record. Here, we report preservation of single diamond (Fd-3m) three-dimensional photonic crystals in scales of a 735,000 year old specimen of the brown Nearctic weevil Hypera diversipunctata from Gold Run, Canada, and in extant conspecifics. The preserved red to green structural colours exhibit near-field brilliancy yet are inconspicuous from afar; they most likely had cryptic functions in substrate matching. The discovery of pristine fossil examples indicates that the fossil record is likely to yield further data on the evolution of three-dimensional photonic nanostructures and their biological functions.

Experimental maturation of feathers: implications for reconstructions of fossil feather colour

Fossil feathers often preserve evidence of melanosomes-micrometre-scale melanin-bearing organelles that have been used to infer original colours and patterns of the plumage of dinosaurs. Such reconstructions acknowledge that evidence from other colour-producing mechanisms is presently elusive and assume that melanosome geometry is not altered during fossilization. Here, we provide the first test of this assumption, using high pressure-high temperature autoclave experiments on modern feathers to simulate the effects of burial on feather colour. Our experiments show that melanosomes are retained despite loss of visual evidence of colour and complete degradation of other colour-producing structures (e.g. quasi-ordered arrays in barbs and the keratin cortex in barbules). Significantly, however, melanosome geometry and spatial distribution are altered by the effects of pressure and temperature. These results demonstrate that reconstructions of original plumage coloration in fossils where preserved features of melanosomes are affected by diagenesis should be treated with caution. Reconstructions of fossil feather colour require assessment of the extent of preservation of various colour-producing mechanisms, and, critically, the extent of alteration of melanosome geometry.

The original colours of fossil beetles

Structural colours, the most intense, reflective and pure colours in nature, are generated when light is scattered by complex nanostructures. Metallic structural colours are widespread among modern insects and can be preserved in their fossil counterparts, but it is unclear whether the colours have been altered during fossilization, and whether the absence of colours is always real. To resolve these issues, we investigated fossil beetles from five Cenozoic biotas. Metallic colours in these specimens are generated by an epicuticular multi-layer reflector; the fidelity of its preservation correlates with that of other key cuticular ultrastructures. Where these other ultrastructures are well preserved in non-metallic fossil specimens, we can infer that the original cuticle lacked a multi-layer reflector; its absence in the fossil is not a preservational artefact. Reconstructions of the original colours of the fossils based on the structure of the multi-layer reflector show that the preserved colours are offset systematically to longer wavelengths; this probably reflects alteration of the refractive index of the epicuticle during fossilization. These findings will allow the former presence, and original hue, of metallic structural colours to be identified in diverse fossil insects, thus providing critical evidence of the evolution of structural colour in this group.

Organic preservation of fossil musculature with ultracellular detail

The very labile (decay-prone), non-biomineralized, tissues of organisms are rarely fossilized. Occurrences thereof are invaluable supplements to a body fossil record dominated by biomineralized tissues, which alone are extremely unrepresentative of diversity in modern and ancient ecosystems. Fossil examples of extremely labile tissues (e.g. muscle) that exhibit a high degree of morphological fidelity are almost invariably replicated by inorganic compounds such as calcium phosphate. There is no consensus as to whether such tissues can be preserved with similar morphological fidelity as organic remains, except when enclosed inside amber. Here, we report fossilized musculature from an approximately 18 Myr old salamander from lacustrine sediments of Ribesalbes, Spain. The muscle is preserved organically, in three dimensions, and with the highest fidelity of morphological preservation yet documented from the fossil record. Preserved ultrastructural details include myofilaments, endomysium, layering within the sarcolemma, and endomysial circulatory vessels infilled with blood. Slight differences between the fossil tissues and their counterparts in extant amphibians reflect limited degradation during fossilization. Our results provide unequivocal evidence that high-fidelity organic preservation of extremely labile tissues is not only feasible, but likely to be common. This is supported by the discovery of similarly preserved tissues in the Eocene Grube Messel biota.

The arthropod Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities

The small, non-biomineralized, three-dimensionally preserved arthropod Offacolus kingi Orr et al. from the Wenlock Series (Silurian) of Herefordshire, England, is re-evaluated, and the new family Offacolidae erected. This new study is based on specimens which have been serially ground, reconstructed by computer and rendered in the round as coloured models. Offacolus possesses a prosomal appendage array similar to that of Limulus, but also bears robust and setose exopods on appendages II-V which are unlike those found in any other arthropods. Opisthosomal appendages are similar in number and morphology to the book-gills of Limulus. Cladistic analysis places Offacolus basally within the Chelicerata, as a sister taxon to the eurypterids and extant chelicerates, but more derived than the Devonian Weinbergina.

Subspecialty training: does it affect the outcome of women treated for a gynecologic malignancy?

A review of available direct and indirect scientific reports strongly suggests that subspecialty training increases the likelihood that the appropriate surgical procedure will be completed in women operated on for gynecologic cancer. It is likely that specialty care lessens the costs associated with diagnosis, treatment and surveillance, and frequently improves survival.

A new arthropod from the Silurian Konservat-Lagerstätte of Herefordshire, UK

A small, non-biomineralized, macrophagous arthropod with chelicerate affinities, Offacolus kingi gen. et sp. nov., from the Silurian (Wenlock Series) of Herefordshire, UK, is described. The dorsal exoskeleton comprises an arch-like cephalic shield, a thorax of three free tergites and a triangular posterior tagma of five fused tergites, the last with a stout postero-dorsally directed medial spine. Seven pairs of appendages beneath the cephalic shield surround a postero-medially sited oral cavity on the ventral surface of the head. Appendages I and, probably II are uniramous and project antero-ventrally; I was sensory and II sensory and/or ambulatory. Appendages III-VI are biramous, each with an antero-ventrally projecting ramus and a robust, highly geniculate, horizontally oriented ramus that projects through an anterior gape. The former rami were ambulatory and the latter have spinose terminal podomeres and functioned as a unit for trapping food and transferring it towards the oral cavity. Appendage VII, which is probably uniramous, is posteroventrally directed and flap like. Each tergite of the thorax and posterior tagma covers at least a pair (probably two pairs) of probably biramous appendages with each ramus flap like and setose.

Cambrian burgess shale animals replicated in clay minerals

Although the evolutionary importance of the Burgess Shale is universally acknowledged, there is disagreement on the mode of preservation of the fossils after burial. Elemental mapping demonstrates that the relative abundance of elements varies between different anatomical features of the specimens. These differences reflect the compositions of the minerals that replicated the decaying organism, which were controlled by contrasts in tissue chemistry. Delicate morphological details are replicated in the elemental maps, showing that authigenic mineralization was fundamental to preserving these fossils, even though some organic remains are also present.

Radical hysterectomy: does the type of incision matter?

OBJECTIVE

Our purpose was to evaluate and compare aspects of operative accessibility and perioperative outcome after radical hysterectomy and pelvic lymphadenectomy performed through a vertical, Pfannenstiel, or Maylard abdominal incision.

STUDY DESIGN

During an 8-year interval, 236 patients underwent radical hysterectomy and pelvic lymphadenectomy as primary treatment for cervical cancer at the Watson Clinic. Patients were admitted under a standard perioperative protocol, and all procedures were performed by a gynecologic oncologist. All clinical data was recorded prospectively and updated regularly.

RESULTS

Radical hysterectomy and pelvic lymphadenectomy was completed through a vertical (n = 113), Pfannenstiel (n = 78), or Maylard (n = 45) incision. Although lesion size and depth of stromal invasion was not different between incision types, patients with a Pfannenstiel incision were younger (p < 0.001) and weighed less than those with a vertical (p = 0.001) or Maylard (p < 0.025) incision. The Pfannenstiel was associated with a shorter operative time (Pfannenstiel vs Maylard, p < 0.05; Pfannenstiel vs vertical, p < 0.001), less blood loss (Pfannenstiel vs Maylard, p < 0.025; Pfannenstiel vs vertical, p < 0.001), a lower risk of transfusion, and a shorter hospital stay (Pfannenstiel vs Maylard, p < 0.025; Pfannenstiel vs vertical, p < 0.001). These differences persisted when controlled for patient weight and surgical experience. There was no significant difference in the total number of nodes evaluated. No patient had a positive vaginal margin.

CONCLUSION

Radical hysterectomy and pelvic lymphadenectomy can be safely performed through a vertical, Maylard, or Pfannenstiel incision. In a selected population a Pfannenstiel incision offers the potential benefit of less abdominal wall trauma without compromising surgical exposure or increasing the risk of surgical complications.