sentence: Not all plant species could be identified because most plants were very small and lacked reproductive structures , but those that could be identified were Valeriana sp. ( either Valeriana pycnantha or Valeriana nivalis ) , Arenaria sp. ( likely Arenaria digyna ) , and Deyeuxia sp. ( likely Deyeuxia hackelii ; visible in Fig. 2C ) .