Table 1.
List of fossil calibrations that were used in BEAST analyses.
| Calibration no. | MRCA | Description | Reference |
|---|---|---|---|
| Calibration 1 | Lamprotula | Hard minimum age: 34 Ma, †Lamprotula hungi Schneider, Böhme & Prieto, 2013. Diagnosis and phylogenetic placement: Medium large, sub-circular Lamprotula with relatively thin shell; ornamentation of irregular wrinkles on umbo; posterior area and posterior part of flank optionally ornamented with outward-bent flabellae and densely spaced, drop-shaped knobs; lateral teeth strongly arcuate, keel-like, without serration53. Stratigraphic horizon and locality: Na Duong Formation, Palaeogene, Cao Bang brickyard, Cao Bang Province, northern Vietnam53. Absolute age estimate: Eocene/Oligocene boundary, 34 Ma, based on stratigraphy; 95% soft upper bound 68 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 9.3, MRCA: Lamprotula caveata – L. leaii. | Present study: New stem calibration |
| Calibration 2 | Cristaria | Hard minimum age: 34 Ma, †Cristaria mothanica Schneider, Böhme & Prieto, 2013. Diagnosis and phylogenetic placement: Oblique-oval Cristaria with markedly anterior positioned, slightly prosogyrous umbones, posterior half markedly higher than anterior part, and low posterior wing53. Stratigraphic horizon and locality: Na Duong and Rinh Chua formations, Palaeogene, Na Duong coalmine, Lang Son Province, northern Vietnam53. Absolute age estimate: Eocene/Oligocene boundary, 34 Ma, based on stratigraphy; 95% soft upper bound 68 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 9.3, MRCA: Cristaria plicata – Cristaria sp. | Present study: New stem calibration |
| Calibration 3 | Cuneopsis | Hard minimum age: 34 Ma, †Cuneopsis quangi Schneider, Böhme & Prieto, 2013. Diagnosis and phylogenetic placement: Elongate, sub-rectangular, markedly inflated Cuneopsis with strongly prosogyrous umbones and slightly truncated posterior end53. Stratigraphic horizon and locality: Na Duong Formation, Palaeogene, Cao Bang brickyard, Cao Bang Province, northern Vietnam53. Absolute age estimate: Eocene/Oligocene boundary, 34 Ma, based on stratigraphy; 95% soft upper bound 68 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 9.3, MRCA: Cuneopsis pisciculus – C. rufescens. | Present study: New stem calibration |
| Calibration 4 | Margaritifera falcata – M. laevis | Absolute age estimate: 46 Ma; 95% soft upper bound 92 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 12.5, MRCA: Margaritifera falcata – M. laevis. | Ref. 36: Crown calibration |
| Calibration 5 | Margaritifera margaritifera – M. dahurica | Absolute age estimate: 34 Ma; 95% soft upper bound 68 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 9.3, MRCA: Margaritifera margaritifera – M. dahurica. | Ref. 36: Crown calibration |
| Calibration 6 | Margaritiferidae | Hard minimum age: 129.4 Ma, †Margaritifera idubedae (Palacios & Sánchez, 1885). Diagnosis and phylogenetic placement: The assignation of this species to the genus is based on the shell shape, notable mantle attachment scars on the inner side of the valve and the arborescent rugosity of the muscle adductor scars89; it may however be a stem lineage of extant margaritiferids36. Stratigraphic horizon and locality: Hauterivian-Barremian Urbión Group, Valdehierro and Valdemadera sites, La Rioja Province, Cameros Basin, Spain89. Absolute age estimate: Hauterivian/Barremian boundary, 129.4 Ma, based on stratigraphy; 95% soft upper bound 259 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 35.1, MRCA: M. auricularia – M. monodonta. | Present study: New stem calibration |
| Calibration 7 | Unionidae | Absolute age estimate: 155 Ma; 95% soft upper bound 310 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 42, MRCA: Anodonta anatina – Parreysia olivacea. | Ref. 47: Stem calibration |
| Calibration 8 | ‘The core Velesunioninae’ (Velesunio + Alathyria + Lortiella + Microdontia) | Absolute age estimate: 99.6 Ma; 95% soft upper bound 199 Ma (twice the age of the fossil). Prior setting: exponential distribution, mean (lambda) = 27, MRCA: Alathyria pertexta – Velesunio ambiguus. | Ref. 47: Stem calibration |