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Table 1 Average dimensions and ratios of ventral and dorsal valves of Eohadrotreta zhenbaensis from the Cambrian (Series 2) Shuijingtuo Formation of the Three Gorges area, South China

From: Earliest ontogeny of early Cambrian acrotretoid brachiopods — first evidence for metamorphosis and its implications

Ventral valve Lpr Wpr Lms Wms Lf Wf Lpr/Wpr Lms/Wms Lpr/Lms Wpr/Wms
 N 23 23 61 67 23 24 23 59 21 23
 Mean 47 71 173 206 53 65 66.94% 84.76% 25.95% 32.27%
 Min 40 58 125 146 25 52 53.25% 68.15% 20.48% 25.88%
 Max 55 79 213 282 77 83 77.59% 97.52% 34.87% 42.53%
 Median 48 70 173 203 52 65 66.23% 85.71% 25.81% 32.46%
 SD 4 5 24 29 14 8 7.13% 6.80% 3.52% 3.61%
Dorsal valve Lpr Wpr Lms Wms Lpr/Wpr Lms/Wms Lpr/Lms Wpr/Wms
 N 19 7 32 34 6 31 17 6
 Mean 53 71 166 220 74.25% 74.96% 29.57% 33.77%
 Min 40 60 114 186 60.00% 55.38% 21.14% 27.76%
 Max 65 78 246 274 82.35% 93.90% 38.56% 41.94%
 Median 53 74 159 214 74.55% 77.25% 28.82% 33.17%
 SD 7 6 32 25 8.15% 10.89% 4.28% 5.24%
  1. All measurements are in μm. Abbreviations: L pr , W pr length and width of protegulum, L ms , W ms length and width of metamorphic shell, L f , W f –length and width of pedicle foramen