Extended Data Fig. 2: TN content of fossil over matrix.
From: Nitrogen isotopes reveal independent origins of N2-fixing symbiosis in extant cycad lineages
(A) Soma flora, (B) Most Formation, (C) Gatuncillo Formation, (D) Chuckanut Formation, (E) Macquarie Habor Formation, (F) Castle Rock flora, Denver Formation, (G) Comox Formation, Nanaimo Group, (H) Yorkshire flora, Cloughton Formation, (I) Primulaelv Formation, Kap Stewart Group, (J) Lunz flora, Lunz Formation, (K) Thale flora, Lower Keuper, (L) Fremouw Formation. Fremouw Formation samples were permineralized and thus did not allow a separate characterization of carbonaceous compression fossil versus matrix. Cycad data shown as blue circles; non-cycad data as red crosses. Dashed lines denote range of δ15N values observed in modern cycads23. Isotopic trends within and between units are not correlated with the N concentration of recovered foliage. Recovered fossil material has on average an order of magnitude more nitrogen than the background matrix, indicating that the isotopic signatures derive from the foliage and not soil organic matter.
