Melanosomes or Microbes: Testing an Alternative Hypothesis for the Origin of
Microbodies in Fossil Feathers
Authors: Alison E. Moyer1*, Wenxia Zheng, Elizabeth A. Johnson, Matthew C. Lamanna, DaQing Li, Kenneth J. Lacovara, Mary H. Schweitzer
Supplementary Information:
Figures S1-S4 and Methods
Supplementary Materials:
Figures
Supplementary Figure S1. SEM images of untreated and Bacillus cereus treated extant chicken
feathers. Low (a) and high (b) magnification of untreated feathers. Feathers incubated with
Bacillus cereus (c) for three days, then dried and imaged as described. Columns (1), (2), and (3)
are white feather, brown feather, and black feather respectively. (c1-c3) show feather surfaces
with microbial overgrowth. (c2) shows that B. cereus cells (arrow) are capable of strong
alignment on feather surfaces, a feature ascribed only to melanosomes in the literature. Images
b1, b3, c2 and c3 were captured after the specimens were gold coated (see Methods).
1
Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695.
*Correspondence to [email protected].
a
b
Supplementary Figure S2. FESEM image of environmental biofilm grown on extant feather.
Low magnification (a) shows overgrowth draping individual barbs. High (b) magnification of
closely packed bacterial cells that cover and follow the contours of a guineafowl (N. meleagris)
feather.
Supplementary Figure S3. FESEM images of untreated, fresh-fractured guineafowl feather. (a)
Low magnification of the fractured feather. (b) Higher magnification of the boxed area in (a).
Melanosomes (arrows) are sparse and embedded deep within the interior of the feather.
Supplementary Figure S4. SEM images of the Gansus yumenensis feather (ANSP 23403). The
distal, black region, (a,b) and the brown proximal, or basal part (c,d) visualized using SEM. In
back scatter mode, atomic differences distinguish the feather from the surrounding sediments
(a,c) in lower magnifications. At higher magnifications, textural differences are observed. The
black region (b) exhibits a smooth film-like appearance with ~8µm sized sediment grains. EDS
data identify principle element composition of these grains to be sediment, distinct from the
feather itself. See Fig. 7 and 8. A grainer texture with smaller sediment grains are observed in
the brown region of the fossil (d).
Methods:
Geologic context of fossil feather ascribed to Gansus yumenensis (ANSP 23403)
Location—The study area is located on provincial land in the Changma Basin, on the
northern flank of the Qilian Mountains (the northernmost extent of the Tibetan-Qinghai Plateau)
in far northwestern Gansu Province, China.
Sedimentology—The basin is ringed by near-vertically tilted exposures of sedimentary rocks
of the Lower Cretaceous Xiagou Formation, providing extensive fossiliferous outcrops. The
formation consists of lacustrine shales1 and sandy lakeshore deposits. All known fossils come
from the shale units. At its base, the local section contains about 45 m of deep-water lacustrine
sediment. Fine grain size and thin laminae at this level indicate a quiescent environment in which
plants, insects, and fishes were often preserved. From 45 m to 50 m above the base, depositional
conditions alternated between deep-water and shallower lacustrine environments, as evidenced
by layers of disturbance ripples. This lake margin facies contains the lower of the two known
Gansus-producing quarries, as well as fossil plants, insects, and turtles. Above 50 m, sediments
record a number of expansions and contractions of the lake margin, during which conditions
rapidly fluctuated between shallow water and nearshore states. Matrix-rich conglomerates,
graded sandstones, and symmetrically rippled cross-laminated sandstones represent the latter
condition. The upper Gansus-producing quarry, from 51 m to 54 m above the base, contains
layers of shallow lacustrine shale alternating with massive to rippled sandstones deposited along
the lakeshore. The abrupt facies changes at 60 m and 63 m, from shale to matrix-rich
conglomerate, are typical of lakes with steep margins2 and record the delivery of coarse clastics
via fluvial or mass-wasting processes to the lake margin. The lakeshore sandstones also contain
oscillatory ripples characteristic of wave-dominated lakes. The substantial fetch required to
generate an active littoral zone indicates the presence of a sizable lake. Thus, the sedimentology
of this section shows a deep lake, shallowing at this location, with steep margins set widely apart
leading down to sandy beaches. This depositional setting corresponds well with the interpretation
of Gansus yumenensis as an amphibious bird3.
Geochronology—The Xiagou Formation is Early Cretaceous in age4, 5. Suarez et al.
(2013) have refined the age of the Xiagou Formation lacustrine beds to the early Aptian stage
based on carbon isotope chemostratigraphy.
6
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