[dinosaur] Amniote paleocolor + preservation of melanosomes + reptile photopigments

Ben Creisler
[email protected]

Some recent paper with free pdfs:

Free pdf:

Arindam Roy, Michael Pittman, Evan T. Saitta, Thomas G. Kaye & Xing Xu
(2019)
Recent advances in amniote palaeocolour reconstruction and a framework for
future research
Biological Reviews (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_brv.12552&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=dJIy7CChU1Dm96XVDize-tl_mkdEnb_7R_G7gKxn6_8&s=eyLwe6iSmCAZYoZXB5y_MMN5xFDf4UG7fB6coi--UQE&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_brv.12552&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=dJIy7CChU1Dm96XVDize-tl_mkdEnb_7R_G7gKxn6_8&s=haZZb2ACwUUE5X_UAj5GZ5WaQidqCUuM8IYo9RhgjMY&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_pdf_10.1111_brv.12552&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=dJIy7CChU1Dm96XVDize-tl_mkdEnb_7R_G7gKxn6_8&s=sn4i8t0BuxLrJTwWF1xhsxb6uBaU2mIrUmgvE9WxDDg&e= 


Preserved melanin pigments have been discovered in fossilised integumentary
appendages of several amniote lineages (fishes, frogs, snakes, marine
reptiles, non‐avialan dinosaurs, birds, and mammals) excavated from
lagerstätten across the globe. Melanisation is a leading factor in organic
integument preservation in these fossils. Melanin in extant vertebrates is
typically stored in rod‐ to sphere‐shaped, lysosome‐derived, membrane‐bound
vesicles called melanosomes. Black, dark brown, and grey colours are
produced by eumelanin, and reddish‐brown colours are produced by
phaeomelanin. Specific morphotypes and nanostructural arrangements of
melanosomes and their relation to the keratin matrix in integumentary
appendages create the so‐called 'structural colours'. Reconstruction of
colour patterns in ancient animals has opened an exciting new avenue for
studying their life, behaviour and ecology. Modern relationships between
the shape, arrangement, and size of avian melanosomes, melanin chemistry,
and feather colour have been applied to reconstruct the hues and colour
patterns of isolated feathers and plumages of the dinosaurs Anchiornis,
Sinosauropteryx, and Microraptor in seminal papers that initiated the field
of palaeocolour reconstruction. Since then, further research has identified
countershading camouflage patterns, and informed subsequent predictions on
the ecology and behaviour of these extinct animals. However, palaeocolour
reconstruction remains a nascent field, and current approaches have
considerable potential for further refinement, standardisation, and
expansion. This includes detailed study of non‐melanic pigments that might
be preserved in fossilised integuments. A common issue among existing
palaeocolour studies is the lack of contextualisation of different lines of
evidence and the wide variety of techniques currently employed. To that
end, this review focused on fossil amniotes: (i) produces an overarching
framework that appropriately reconstructs palaeocolour by accounting for
the chemical signatures of various pigments, morphology and local
arrangement of pigment‐bearing vesicles, pigment concentration, macroscopic
colour patterns, and taphonomy; (ii) provides background context for the
evolution of colour‐producing mechanisms; and (iii) encourages future
efforts in palaeocolour reconstructions particularly of less‐studied groups
such as non‐dinosaur archosaurs and non‐archosaur amniotes.

==============

Free pdf:

Tiffany S. Slater, Maria E. McNamara, Patrick J. Orr, Tara B. Foley,
Shosuke Ito & Kazumasa Wakamatsu (2019)
Taphonomic experiments resolve controls on the preservation of melanosomes
and keratinous tissues in feathers.
Palaeontology (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_pala.12445&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=dJIy7CChU1Dm96XVDize-tl_mkdEnb_7R_G7gKxn6_8&s=EIb4RxdTQJ1GmGve9n6t1MC8cRfA4WSgQn5zly68imA&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_full_10.1111_pala.12445&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=dJIy7CChU1Dm96XVDize-tl_mkdEnb_7R_G7gKxn6_8&s=2okjfyW2w4_kKgDxMTuNlrYl7f63io02SnIbz-44Z94&e= 


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.

================

Free pdf:

Christiana Katti Micaela Stacey-Solis, Nicole Anahí Coronel-Rojas and Wayne
Iwan Lee Davies (2019)
The Diversity and Adaptive Evolution of Visual Photopigments in Reptiles
Frontiers in Ecology and Evolution 7:352
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.3389_fevo.2019.00352&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=dJIy7CChU1Dm96XVDize-tl_mkdEnb_7R_G7gKxn6_8&s=oc8342XM_B4TVrz0XDSZiPxBRzZ5dHDj2OoWVkz80bc&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.frontiersin.org_articles_10.3389_fevo.2019.00352_full&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=dJIy7CChU1Dm96XVDize-tl_mkdEnb_7R_G7gKxn6_8&s=Lu4mhIHcsxAwHNBoDQ8B5UQm2ah3HDpLhDTrrWV_LSc&e= 


Reptiles are a highly diverse class that consists of snakes, geckos,
iguanid lizards, and chameleons among others. Given their unique
phylogenetic position in relation to both birds and mammals, reptiles are
interesting animal models with which to decipher the evolution of
vertebrate photopigments (opsin protein plus a light-sensitive retinal
chromophore) and their contribution to vision. Reptiles possess different
types of retinae that are defined primarily by variations in photoreceptor
morphology, which range from pure-cone to rod-dominated retinae with many
species possessing duplex (rods and cones) retinae. In most cases, the type
of retina is thought to reflect both the lifestyle and the behavior of the
animal, which can vary between diurnal, nocturnal, or crepuscular
behavioral activities. Reptiles, and in particular geckos and snakes, have
been used as prime examples for the "transmutation" hypothesis proposed by
Walls in the 1930s-1940s, which postulates that some reptilian species have
migrated from diurnality to nocturnality, before subsequently returning to
diurnal activities once again. This theory further states that these
behavioral changes are reflected in subsequent changes in photoreceptor
morphology and function from cones to rods, with a return to cone-like
photoreceptors once again. Modern sequencing techniques have further
investigated the "transmutation" hypothesis by using molecular biology to
study the phototransduction cascades of rod- and cone-like photoreceptors
in the reptilian retina. This review will discuss what is currently known
about the evolution of opsin-based photopigments in reptiles, relating
habitat to photoreceptor morphology, as well as opsin and phototransduction
cascade gene expression.

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