A new large mound dwelling chiton (Mollusca), from the Late Ordovician Boda Limestone of central Sweden

Figures & data

Figure 1. Map of the Siljan ring structure with the location of the older Kullsberg and the younger Boda carbonate mounds and Jutjärn quarry (WGS 84 60°58ʹ57.7”N 15°15ʹ3.3”E). The stratigraphical column to the right shows the global standard for stages, graptolite, and conodont biozones, in addition to the regional stratigraphy of the Siljan district, Stage Slices based on Bergström et al. (2009). Stratigraphy based on Ebbestad et al. (2015) and Kröger et al. (2016)

Table 1. Upper Ordovician – lower Silurian (Sandbian–Telychian) palaeoloricate taxa. Ordovician Stage Slices follow those defined by Bergström et al. (2009)

Taxon	Occurrence	Local stage	Stage Slice
Helminthochiton griffithi Salter in M’Coy, 1846	Kilbride Fm., Ireland	-	Telychian
Thairoplax birhombivalvis Bergenhayn, 1955	Lower Visby Fm., Sweden	-	Telychian
Septemchiton vermiformis Bergenhayn, 1955	South Threave Fm., Lady Burn Starfish Bed, Scotland	Rawtheyan	Ka4
Crassaplax collicola gen. et sp. nov.	Boda Limestone, Sweden	Pirgu	Ka4
Spicuchelodes? sp. Högström et al. (2009)	Boda Limestone, Sweden	Pirgu	Ka4
Phthipodochiton thraivensis (Reed, 1911)	South Threave Fm., Lady Burn Starfish Bed, Scotland	Rawtheyan	Ka4
Septemchiton iowensis (Rhoads, 1962)	Maquoketa Fm., USA	Richmondian	Ka2
Chelodes sp. sensu Dzik, (1994)	Upper Mójcza Lst., Poland	Nabala	Ka2
Bursata santacrucensis (Dzik, 1994)	Upper Mójcza Lst., Poland	Haljala–Nabala	Sa2–Ka2
Sarkachiton kielcensis Dzik, 1994	Upper Mójcza Lst., Poland	Haljala–Nabala	Sa2–Ka2
Priscochiton? sp. sensu Dzik (1994)	Upper Mójcza Lst., Poland	Haljala-Nabala	Sa2–Ka2
Paleoloricate gen et sp. nov. sensu Candela et al. (2014)	Kirkcolm Fm., Scotland	Cheneyan	Ka1
Helminthochiton blacki Hoare & Pojeta, 2006	Lexington Lst., Curdsville Lst. & Grier Lst. Mbrs, USA	Chatfieldian	Ka1
Listrochiton weiri Hoare & Pojeta, 2006	Lexington Lst., Perryville Lst., Grier Lst. & Devils Hollow mbrs, USA	Chatfieldian	Ka1
Alastega martini Hoare & Pojeta, 2006	Lexington Lst., Perryville Lst. Mbr., USA	Chatfieldian	Ka1
Preacanthochiton baueri Hoare & Pojeta, 2006	Grand Detour Fm., Forreston Mbr., USA	Turinian	Sa2
Echinochiton dufoei Pojeta et al., 2003	Grand Detour Fm., Forreston Mbr., USA	Turinian	Sa2
Helminthochiton marginatus Hoare & Pojeta. 2006	Grand Detour Fm., Forreston Mbr., USA	Turinian	Sa2
Septemchiton grayiae (Woodward, 1885)	Balclatchie Fm., Laggan Mbr., Scotland	Burellian	Sa2
Solenocaris solenoides Young & Young, 1868	Balclatchie Fm., Bellmore & Pumphouse mbrs., Scotland	Burellian	Sa2

Table 2. Measurements for the three described plates of Crassaplax collicola gen. et sp. nov., terminology and measurements after Cherns (1998a). The apical angle in specimen PMU 26954 is an estimate, as the posterior-lateral margins are not well preserved

	PMU 26954	PMU 26955	PMU 25141
Length mm	>15	>12	>19.5
Median length mm	14.6	>11.5	>17.3
Width mm	–	–	~20
Height mm	–	0.4	10
Central valve area mm	–	–	12.5
Lateral valve area mm	–	–	7.3
Apical angle	~66°	–	105°
Jugal angle	103°	106°	98°
Median length/Length	>0.97	~0.96	~0.89

Figure 2. A–L. Crassaplax collicola n. gen, n. sp. A–C, E. PMU 26954, dorsal, detail of lateral valve area, dorsal oblique, and lateral views respectively. The lateral margins are largely missing D, F–H, J. PMU 26955, dorsal, lateral, anterior and cross section of anterior margin respectively. The lateral margins are largely missing I, K–L. PMU 25141, Holotype and most complete specimen. All specimens from Jutjärn quarry. PMU 25141, coll., J.O.R. Ebbestad, 2005; PMU 26954, 26955, coll. J. Suzuki, 2009. Scale bar in A–F, I–L = 0.5 cm; scale bar in G, H = 0.1 cm

Figure 3. Schematic illustration of Crassaplax collicola, head and tail valves are unknown, and in this illustration represented by stippled markings. The outline of the body is conjectural, and the presence/absence of a foot is unknown. Scale bar = 1 cm

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