Supporting Information

Harvey et al. 10.1073/pnas.1115244109 SI Text previous use; bracketed by Late conodont assemb- Details of Sample Distributions and Age. Ceepee Riley Lake (3-4-39- lages (3). 13W3, 52°32′N, 107°82′W, SW Saskatchewan): Seven mudstone/ Ceepee Reward (4-28-38-24W3, 52°29′N, 109°38′W, SW Sas- siltstone samples from within a mixed-lithology interval (∼5,369– katchewan): A single thin (∼5 mm) mudstone seam from within 5,391.5 feet); Middle or Late Cambrian, according to regional a sandstone bed (∼6,044.5 feet) from the “Earlie Formation” of correlation (1, 2). alternative use (4); Middle Cambrian in age, based on regional Rio Bravo Ronald (1-6-38-15W4, 52°23′N, 112°13′W, SE correlation (1, 2) and the presence of Late Cambrian conodonts ): A single mudstone horizon (∼6,542 feet) from within and brachiopods in an overlying interval some 825–1050 feet the carbonate/conglomerate-rich “Finnegan Formation” of higher in the core (5, 6).

1. Binda PL, et al. (1996) Preliminary observations on the acid-resistant microfossils from 4. Greggs DH, Hein FJ (2000) The sedimentology and structure of the Lower Paleozoic the Lower Paleozoic of southern Saskatchewan. Summary of Investigations 1996, of Saskatchewan. Summary of Investigations 2000, Saskatchewan Geological Survey, Sask Energy Mines, Misc Rep 96-4:157–165. Saskatchewan Geological Survey, Sask Energy Mines, Misc Rep 2000-4.1:7–13. 2. Dixon J (2008) and facies of Cambrian to Lower strata in 5. Nowlan GS (1999) Report on 21 samples from Cambrian (Deadwood Formation) and Saskatchewan. Bull Can Pet Geol 56:93–117. Ordovician (Red River Formation) strata in the Ceepee Keppel Forest Well 8-3-40-14W3 3. Hein FJ, Nowlan GS (1998) Regional sedimentology, conodont biostratigraphy and and the Ceepee Reward Well 4-28-38-24W3 in the subsurface of Saskatchewan. correlation of Middle Cambrian - Lower Ordovician(?) strata of the “Finnegan” and Geological Survey of Paleontological Report No. 11-GSN-1999, 1–13. Deadwood formations, Alberta subsurface, Western Canada Sedimentary Basin. Bull 6. Robson SP, Nowlan GS, Pratt BR (2003) Middle to Upper Cambrian linguliformean Can Pet Geol 46:166–188. brachiopods from the Deadwood Formation of subsurface Alberta and Saskatchewan, Canada. J Paleontol 77:201–211.

Fig. S1. Branchiopod-type mandibles from the Deadwood Formation (Riley Lake assemblage), interpreted as the right (A) and left mandibles (B and C)of a single taxon displaying mandibular asymmetry (see also Fig. 1 A, E, and F). The pattern of continuous transverse scale rows on the right molar surface (A) contrasts with the partial rows and dorsal marginal nodes (arrowed) on the left molar surface (B and C). A matching pattern is present in Lepidocaris and certain modern anostracan branchiopods (compare Fig. 2 A and B). See Table S2 for specimen numbers.

Harvey et al. www.pnas.org/cgi/content/short/1115244109 1of4 Fig. S2. Mandibular gnathal edges (“Type 4 mandibles”) from the Rio Bravo Ronald assemblage. The combination of a toothed incisor process and a narrow, finely ornamented molar process defines a fourth distinct type of mandible from the Deadwood Formation. Note that one specimen (Left) is partly folded over on itself. See Table S2 for specimen numbers.

Fig. S3. A branchiopod-type limb from the Deadwood Formation (Reward assemblage) that bears a diversity of setal armatures. (A) Overview. (B) Detail of filter plate. (C) Field of stout pappose setae. (D) Field of slender bifurcating setae. (E) Field of saw-toothed setae. (Scale bar in D also applies also to B, C, and E.) See Table S2 for specimen number.

Harvey et al. www.pnas.org/cgi/content/short/1115244109 2of4 Fig. S4. A comparison of filter plates and saw-toothed armatures from the Mount Cap Formation [O-35 assemblage; see Harvey and Butterfield (1)] (A and C) and the Deadwood Formation (Reward assemblage) (B and D). The detailed similarities between the Mount Cap and Deadwood fossils in the types and ar- rangements of setae within filter armatures (A and B), and the shared presence of unusual, distally branching saw-toothed setae (C and D) (which are de- monstrably articulated with filter plates in 10 Deadwood specimens; see, for example, Fig. S3) point to a close phylogenetic relationship. Accordingly, the Mount Cap taxon is likely to share with the Deadwood taxon a position among total-group branchiopods. See Table S2 for Deadwood specimen numbers.

1. Harvey THP, Butterfield NJ (2008) Sophisticated particle-feeding in a large Early Cambrian crustacean. Nature 452:868–871.

Table S1. Distributions of crustaceans within microfossil assemblages from Ceepee Riley Lake, Rio Bravo Ronald, and Ceepee Reward Approximate Sample Sample no. depth (ft) mass (g) BM CM OM T4M BL

RL13-1-120 5,369 >17 1 RL13-4-15 5,380.5 13.5 5 4 RL13-4-50 5,381.5 12.5 2 RL13-4-60 5,382 >413 RL13-4-90 5,383 >18 4 RL13-4-110 5,383.5 39.7 7 21 RL13-5∼50 5,391.5 21.9 1 RBR21-3-65 6,542 40.7 1 2 RW16-6-45 6,044.5 >40 150

Fossil categories: BL, Branchiopod-type limbs; BM, Branchiopod-type mandi- bles; CM, Copepod-type mandibles; OM, Ostracod-type mandibles; T4M, “Type 4” mandibles. Sample localities: RL, Ceepee Riley Lake; RBR, Rio Bravo Ronald; RW, Ceepee Reward.

Harvey et al. www.pnas.org/cgi/content/short/1115244109 3of4 Table S2. Specimen numbers for figured material Figure no. Slide no. and England Finder coordinates Repository specimen no.

Fig. 1A/S1A NJBRL13-4-90a-P32 135369 Fig. 1B NJBRL13-4-90e-Q25 135370 Fig. 1C RL13-4-110-29-V43 135371 Fig. 1D RL13-4-90-02-S33 135372 Fig. 1E/S1B RL13-4-60-03-W4 135373 Fig. 1F/S1C RL13-4-15-01-G33 135374 Fig. 1G RL13-4-110-09-V15 135375 Fig. 1H RL13-4-110-24-G22 135376 Fig. 1I RL13-4-60-01-J48 135377 Fig. 1J RL13-4-60-07-U34 135378 Fig. 1K RL13-4-110-04-K49 135379 Fig. 1L RL13-4-110-04-H18 135380 Fig. 1M RL13-4-110-17-J42 135381 Fig. 1N RL13-4-110-J39 135382 Fig. 1O RL13-4-60-03-N27 135383 Fig. 1P RBR-21-3-65-01-T10 135384 Fig. 3A RW16-6-45-34-F34 135385 Fig. 3B RW16-6-45-29-L41 135386 Fig. 3C RW-16-6-45-24-R29 135387 Fig. 3D RW16-6-45-22-O20 135388 Fig. S2, Left RBR21-3-65-10-T45 135389 Fig. S2, Right RBR21-3-65-04-N45 135390 Fig. S3 RW16-6-45-12-G30 135391 Fig. S4B NJBRW16-6-45-d-V20 135392 Fig. S4D RW16-6-45-33-W42 135393

Specimens are stored at the Geological Survey of Canada (GSC), 601 Booth Street, Ottawa, ON, Canada.

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