Study area map within the Otway Basin (grey box) off the coast of Victoria, Australia (inset).

<p>White dots indicate amber-bearing well locations including well names. Dark grey shading represents modern land; light grey represents continental crust.</p

Examples of other inclusions from Otway amber.

<p>(A) Spherical inclusions (Type A pseudoinclusions) with internal vesiculation, Sample Minerva-1 1836.9. (B) Concentration of ovoid inclusions (Type B pseudoinclusions) on the left side (dark orange) and no inclusions of the right side (lighter orange), Sample THA01 2451.4. (C) Mutually aligned fusiform inclusions (Type B pseudoinclusions), Sample THA01 2451.7. (D) Ovoid inclusion (Type B pseudoinclusion) with single vesicle; Sample THA01 2466.89 2D2-2. (E) Ovoid inclusions (black arrows; Type B pseudoinclusions); lower ovoid inclusion (Type B pseudoinclusions) is stacked on top of an irregular filamentous inclusion (grey arrow; Type D pseudoinclusion); pictured with filamentous microorganisms, Sample THA01 2466.89 2D2-2. (F) Vesicular ovoid inclusion (Type B pseudoinclusion) with projection, Sample THA01 2466.89 2D2-1. (G) Irregular filamentous inclusion (grey arrow; Type D pseudoinclusion) surrounded by mutually aligned filamentous microorganisms and ovoid inclusions (Type B pseudoinclusions), Sample THA01 2466.89 005. (H) Amorphous inclusion (Type E pseudoinclusion), Sample THA01 2466.89 2D2-2. (I) Amorphous inclusions (Type E pseudoinclusion) surrounded by mutually aligned ovoid inclusions, Sample THA01 2466.89 2D2-2. Scale bars: 50 μm (A, F); 200 μm (B); 100 μm (C–E, G–I).</p

Types and interpretations of inclusions found in the Otway amber.

<p>Upper bold box indicates bioinclusions; lower bold box indicates pseudoinclusions. Relative abundances are based visual assessments of inclusion types in the entire sample set. For a breakdown of relative abundances per amber colour, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121307#pone.0121307.t003" target="_blank">Table 3</a>.</p><p>*Interpretations based on the pseudo-protist classification scheme of Girard et al. [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121307#pone.0121307.ref030" target="_blank">30</a>].</p><p>Types and interpretations of inclusions found in the Otway amber.</p

Colours of Australian amber.

<p>A) burst piece of yellow amber, some still embedded in matrix, sample THA01 2529.43; B) Top: Partial nodule of orange amber embedded in matrix, sample THA01 2451.7; Bottom left: cross-section through orange amber nodule containing organic matter, sample Minerva 2a 1857.43; Bottom right: cross-section through orange amber droplet, (not collected) Minerva 2a 1923.5; C) fragments from burst piece of dark orange amber sample Minerva-1 1837.5; D) fragments from burst piece of red amber, sample Minerva 2a 1843.2; E) fragments from burst piece of dark brown amber sample Minerva 2a- 1945.2; F) fragments from burst piece of milky brown amber, sample Minerva 2a 1956.7. Scale bar: 4 mm.</p

Examples of bioinclusions from Otway amber.

<p>(A) Probable specimen of <i>Kraeuselisporites</i> Raine, 2008, Sample THA01 2466.89 2D2-1. (B) <i>Cyathidites minor</i> Couper, 1953, Sample THA01 2466.89 2D2-1. (C) Randomly oriented network of filamentous microorganisms, Sample THA01 2466.89 2D2-2. (D) Mutually aligned filamentous microorganisms pictured with ovoid and fusiform inclusions, Sample THA01 2466.89 2D2-1. (E) Degraded organic matter exhibiting cracks along outer margin, Sample THA01 2466.89 009–1. (F) Degraded organic matter with attached filamentous microorganisms, Sample THA01 2531.07–007. Scale Bars: 100 μm (A–D); 50 μm (E); 200 μm (F).</p

Determining the history of resin exudation and solidification based on the relationship between the relative abundances of pseudoinclusion types and amber colour.

<p>–: not present; +: uncommon; ++: common; +++: abundant, n.o.: not observed (due to opacity), n.d.: not described. Mobility (of resin); inferred from the pseudoinclusion assemblage preserved in each colour of amber (I: immobile; M: mobile). Environment (of solidification); inferred from inclusion assemblage and/or amber morphology. (B: upper tree branches; T; tree trunk; G: ground surface; R: underground (root resin); P: pond). Inclusions were not observed in milky brown amber (sample ID: Minerva-2a 1956.7); therefore, it is not included in the table. Modified from [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0121307#pone.0121307.ref030" target="_blank">30</a>].</p><p>*Most common interpretation based on pseudoinclusion abundances</p><p>Determining the history of resin exudation and solidification based on the relationship between the relative abundances of pseudoinclusion types and amber colour.</p

Sample accession numbers.

<p>Sample numbers (given as well location, depth of collection (m)-sample number) and associated accession numbers. All samples are housed at the Melbourne Museum, part of Museum Victoria (MV).</p><p>Sample accession numbers.</p