Too many Ginkgo leaves!!!

The morphological diversity of Ginkgoales leaves!!!

Hi all,

This is just a super quick post* basically for me to show off a diagram I've been working on for the past few months. For about two or three years I've been wanting to make a comparative diagram showing the diversity of Ginkgoales leaves through geological time, so that people might have a good reference of what shaped ginkgo leaves are appropriate in different times and places. While Ginkgo and ginkgo-like plants are a staple in palaeoart, the leaves of such plants are often not appropriate for the time period they're depicted in; unlobed or bilobed flabellate leaves like those of modern Ginkgo biloba are often used as a 'safe bet' within palaeoart, but this has often felt off to me (and in some cases I knew it was just plain wrong) and definitely doesn't represent the diversity of fossil leaves available for people to use.

So that's why I started creating this diagram, so see how widespread unlobed/bilobed flabellate leaves were prior to the Maastrichtian, but also to give an idea of what the past morphological diversity of Ginkgoales was like, and also to show how much intraspecific variation was present in past Ginkgoales species (since modern Ginkgo biloba has insanely variable leaves... even if some of that diversity comes from selective breeding). Another reason was kind of just to see whether past species were actually very distinct from each other, and if they fell into distinct shape categories or not. I also just like drawing leaves and ginkgoes are extremely aesthetically pleasing to me.

The results of this project have been interesting, and while the diagram is nowhere near comprehensive, and will obviously suffer from biases from both me and the published literature, I'm pretty happy with the results and I hope that they are somewhat representative.

I could talk a lot about this diagram, and I have comments on almost all of the species included within it, but that would take far too long to write. Thus, this post is basically just to show them off and provide a key to all the species included. I'll add a few notes at the end about general trends and cool details I've noticed, but for the most part, I hope you enjoy these diagrams!!!

*Future me from 4 hours later.... that was a lie.

The morphological diversity of Ginkgoales leaves through time

So, just a few notes to help you understand the diagram better: it is in three separate images which can be combined to make a since continuous piece. The first (top) image includes Ginkgoales from the Cretaceous until modern day, the second (middle) image contains Ginkgoales from the Jurassic, and the third (bottom) image contains Ginkgoales from the Permian and Triassic, with a few from the Triassic-Jurassic boundary. The leaves are arranged roughly so that the oldest leaves are at the bottom and the youngest leaves are at the top, and they are coloured roughly to match the colours ginkgo leaves may be throughout the year, with fresh spring green for the oldest leaves, and autumn yellows for the most recent. There is also a ginkgo-leaf mimicking imposter hidden somewhere in the images. In the key, I have included the age and location of the specimen illustrated, mostly I have been precise, but in some cases I have been unable to find precise information. I won't include a reference list for now, but most of these taxa are pretty easy to find by googling them, and if you can't find one just contact me directly (or add a comment to this post) and I can either send you the paper or let you know what I used for reference. Anyway, on with the main event!

And here's a key to all of the leaves.... all 136 of them.

(p.s. I'm not sure how clear this is, so any comment on this would be helpful!)

1. Ginkgoites patagonica (Eocene, Paleogene, Argentina)

2. Ginkgoites patagonica (Eocene, Paleogene, Argentina)

3. Ginkgoites patagonica (Eocene, Paleogene, Argentina)

4. Ginkgoites patagonica (Eocene, Paleogene, Argentina)

5. Ginkgoites patagonica (Eocene, Paleogene, Argentina)

6. Ginkgoites patagonica (Eocene, Paleogene, Argentina)

7. Ginkgoites patagonica (Eocene, Paleogene, Argentina)

8. Ginkgo biloba (modern, England)

9. Ginkgo biloba (modern, England)

10. Ginkgo biloba (modern, England)

11. Ginkgo biloba (modern, England)

12. Ginkgo biloba (modern, England)

13. Ginkgo adiantoides (Miocene, Neogene)

14. Ginkgo adiantoides (Paleocene, Paleogene, Svalbard)

15. Ginkgo adiantoides (Paleocene, Paleogene, Svalbard)

16. Ginkgo adiantoides (Maastrichtian, Up. Cretaceous, USA)

17. Ginkgo dissecta (Eocene, USA)

18. Ginkgo dissecta (Eocene, USA)

19. Ginkgo dissecta (Eocene, USA)

20. Ginkgo dissecta (Eocene, USA)

21. Ginkgo dissecta (Eocene, USA)

22. Ginkgoites waarensis (Cenomanian, Up. Cretaceous, New Zealand)

23. Ginkgoites waarensis (Cenomanian, Up. Cretaceous, New Zealand)

24. Ginkgoites waarensis (Cenomanian, Up. Cretaceous, New Zealand)

25. Ginkgoites waarensis (Cenomanian, Up. Cretaceous, New Zealand)

26. Ginkgoites waarensis (Cenomanian, Up. Cretaceous, New Zealand)

27. Nehvizdyella bipartita, leaf taxon Eretmophyllum obtusum (Cenomanian, Up. Cretaceous, Czech Republic)

28. Eretmophyllum (Nehvizdya) penalveri (Albian, Low. Cretaceous, Spain)

29. Sphenobaiera vitimica (Low. Cretaceous, Russia)

30. Baiera aquilonia (Barremian-Aptian, Low. Cretaceous, Svalbard)

31. Ginkgoites villardeseoanii (Maastrichtian, Up. Cretaceous, Argentina)

32. Ginkgoites villardeseoanii (Maastrichtian, Up. Cretaceous, Argentina)

33. Ginkgoites villardeseoanii (Maastrichtian, Up. Cretaceous, Argentina)

34. Ginkgo huolinhensis (late Barremian-earliest Aptian, Low. Cretaceous, Inner Mongolia)

35. Ginkgo huolinhensis (late Barremian-earliest Aptian, Low. Cretaceous, Inner Mongolia)

36. Ginkgo apodes (Aptian, Low. Cretaceous, China)

37. Ginkgo apodes (Aptian, Low. Cretaceous, China)

38. Ginkgo apodes (Aptian, Low. Cretaceous, China)

39. Ginkgoites pluripartita (Low. Cretaceous, Germany)

40. Ginkgoites pluripartita (Low. Cretaceous, Canada)

41. Ginkgoites pluripartita (Low. Cretaceous, Germany)

42. Ginkgoites pluripartita (Low. Cretaceous, Germany)

43. Ginkgoites pluripartita (Low. Cretaceous, Germany)

44. Ginkgoites pluripartita (Low. Cretaceous, Germany)

45. Ginkgoites pluripartita (Low. Cretaceous, Germany)

46. Karkenia incurva, leaf taxon Ginkgoites tigrensis (Aptian, Low. Cretaceous, Argentina)

47. Karkenia incurva, leaf taxon Ginkgoites tigrensis (Aptian, Low. Cretaceous, Argentina)

48. Karkenia incurva, leaf taxon Ginkgoites tigrensis (Aptian, Low. Cretaceous, Argentina)

49. Karkenia incurva, leaf taxon Ginkgoites tigrensis (Aptian, Low. Cretaceous, Argentina)

50. Ginkgoites myrioneurus (Low. Cretaceous, China)

51. Ginkgoites myrioneurus (Low. Cretaceous, China)

52. Ginkgoites myrioneurus (Low. Cretaceous, China)

53. Ginkgoites myrioneurus (Low. Cretaceous, China)

54. Ginkgoites myrioneurus (Low. Cretaceous, China)

55. Ginkgoites myrioneurus (Low. Cretaceous, China)

56. Ginkgoites brauniana (Low. Cretaceous, Germany)

57. Ginkgoites brauniana (Low. Cretaceous, Germany)

58. Sphenobaiera cf. pectin (Albian, Low. Cretaceous, Spain)

59. Sphenobaiera longifolia (Barremian-Aptian, Low. Cretaceous, Svalbard)

60. Pseudotorellia nordenskioeldii (Barremian-Aptian, Low. Cretaceous, Svalbard)

61. Pseudotorellia nordenskioeldii (Barremian-Aptian, Low. Cretaceous, Svalbard)

62. Pseudotorellia nordenskioeldii (Barremian-Aptian, Low. Cretaceous, Svalbard)

63. Umaltolepis mongoliensis, leaf taxon Pseudotorellia resinosa (Aptian-Albian, Low. Cretaceous, Mongolia)

64. Pseudotorellia sp. cf. Pseudotorellia longifolia (Barremian-Aptian, Low. Cretaceous, Svalbard)

65. Eretmophyllum hamiensis (Mid. Jurassic, China)

66. Eretmophyllum hamiensis (Mid. Jurassic, China)

67. Eretmophyllum hamiensis (Mid. Jurassic, China)

68. cf. Eretmophyllum sp. (Kimmeridgian-Tithonian, Up. Jurassic, USA)

69. Eretmophyllum neimengguensis (?Toarcian-?Bajocian, ?Low.-?Mid. Jurassic, Inner Mongolia)

70. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 1 (Callovian, Mid. Jurassic, China)

71. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 1 (Callovian, Mid. Jurassic, China)

72. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 1 (Callovian, Mid. Jurassic, China)

73. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 1 (Callovian, Mid. Jurassic, China)

74. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 1 (Callovian, Mid. Jurassic, China)

75. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 1 (Callovian, Mid. Jurassic, China)

76. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 2 (Callovian, Mid. Jurassic, China)

77. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 2 (Callovian, Mid. Jurassic, China)

78. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 3 (Callovian, Mid. Jurassic, China)

79. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 3 (Callovian, Mid. Jurassic, China)

80. Yimaia capituliformis, leaf taxon Ginkgoites sp. Morphotype 3 (Callovian, Mid. Jurassic, China)

81. Ginkgoites cascadensis (Kimmeridgian-Tithonian, Up. Jurassic, USA)

82. The Imposter, Juracimbrophlebia ginkgofolia (Callovian, Mid. Jurassic, China)

83. Baiera gracilis (Aalenian–Bathonian, Mid. Jurassic, England)

84. Baiera gracilis (Aalenian–Bathonian, Mid. Jurassic, England)

85. Baiera gracilis (Aalenian–Bathonian, Mid. Jurassic, England)

86. Baiera gracilis (Aalenian–Bathonian, Mid. Jurassic, England)

87. Baiera furcata (Aalenian–Bathonian, Mid. Jurassic, England)

88. Baiera furcata (Aalenian–Bathonian, Mid. Jurassic, England)

89. Umaltolepis zhoui, leaf taxon Pseudotorellia zhoui (Callovian, Mid. Jurassic, China)

90. Sphenobaiera  huangii (Low. Jurassic, China)

91. Sphenobaiera  huangii (Low. Jurassic, China)

92. Sphenobaiera  huangii (Low. Jurassic, China)

93. Ginkgo cordilobata (Mid. Jurassic, Afghanistan)

94. Ginkgo cordilobata (Mid. Jurassic, Afghanistan)

95. Ginkgo cordilobata (Mid. Jurassic, Afghanistan)

96. Ginkgo cordilobata (Mid. Jurassic, Afghanistan)

97. Ginkgo cordilobata (Mid. Jurassic, Afghanistan)

98. Ginkgo yimaensis (Mid. Jurassic, China)

99. Ginkgo yimaensis (Mid. Jurassic, China)

100. Ginkgo yimaensis (Mid. Jurassic, China)

101. Ginkgo yimaensis (Mid. Jurassic, China)

102. Ginkgo yimaensis (Mid. Jurassic, China)

103. Ginkgo yimaensis (Mid. Jurassic, China)

104. Ginkgo yimaensis (Mid. Jurassic, China)

105. Ginkgo yimaensis (Mid. Jurassic, China)

106. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

107. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

108. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

109. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

110. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

111. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

112. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

113. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

114. Ginkgo ginkgoidea, leaf taxon Ginkgoites regnellii (Bajocian, Mid. Jurassic, Sweden)

115. Arberophyllum substrictum (Carnian, Up. Triassic, Svalbard)

116. Arberophyllum spetsbergensis (Carnian, Up. Triassic, Svalbard)

117. Sphenobaiera (Baiera) spectabilis (Hettangian, Low. Jurassic, Greenland)

118. Sphenobaiera (Baiera) spectabilis (Hettangian, Low. Jurassic, Greenland)

119. Sphenobaiera (Baiera) spectabilis (Rhaetian, Up. Triassic, Sweden)

120. Baiera muensteriana (Up. Triassic, Low. Jurassic, China)

121. Ginkgoites sp. (Carnian, Up. Triassic, Svalbard)

122. Ginkgoites obovata (Rhaetian, Up. Triassic, Greenland)

123. Ginkgoites obovata (Rhaetian, Up. Triassic, Greenland)

124. Ginkgoites (Baiera) simmondsi (?Carnian, Up. Triassic, Australia)

125. Sphenobaiera steinmannii (Carnian-Norian, Up. Triassic, Brazil)

126. Sphenobaiera schenkii (Anisian-Carnian, Mid.-Up. Triassic, Brazil)

127. Esterella gracilis (Wuchiapingian, Lopingian, Permian, Germany)

128. Sphenobaiera kungurica (Kungurian, Cisuralian, Permian)

129. Baiera mansfeldensis (Wuchiapingian, Lopingian, Permian, Germany)

130. Baiera mansfeldensis (Wuchiapingian, Lopingian, Permian, Germany)

131. Baiera mansfeldensis (Wuchiapingian, Lopingian, Permian, Germany)

132. Baiera digitata (Wuchiapingian, Lopingian, Permian, Germany)

133. Baiera digitata (Wuchiapingian, Lopingian, Permian, Germany)

134. Baiera digitata (Wuchiapingian, Lopingian, Permian, Germany)

135. Ginkgoites huraensis (?Kungurian, Cisuralian, Permian, Indian)

136. Ginkgoites semirotunda (Anisian, Mid. Triassic, Australia)

Random notes and wild thoughts

There were a few interesting things I came across while doing this diagram which I think are worth pointing out. These notes aren't in any particular order, and in many cases I'd like to explore them further, but for now I thought they'd be worth mentioning as you may find them interesting.

Trends through time

This is just a trend I noticed when arranging the leaves I've drawn; however, I would like to point out that any trends we might see in my diagram MAY NOT ACTUALLY EXIST, and more extensive statistical studies would be required to properly assess any trends we might think we see in the fossil record. So anyway, the trend I think I see: older leaves were biiiiggg: there seems to be a general trend towards smaller leaves over time, with many of the largest leaves being present in the Triassic and Early Jurassic. Smaller leaves have always been present, but in the Cretaceous almost all species seemed to have small leaves. The sizes of Cenozoic leaves seem to be larger on average than Cretaceous ones, although as always there is a LOT of both inter and intraspecific variation. 

Spikes in diversity and biased distributions

There are several distinct spikes in diversity, most notably in the Middle Jurassic, Early Cretaceous, and around the Triassic-Jurassic boundary. This is probably NOT representative of the true diversity which existed throughout time, and is likely due to the presence of Lagerstätten at these time intervals. The majority of taxa here are also from the northern hemisphere, which is caused by a bias in where the majority of studies occur. Some authors have suggested in the past that Ginkgoales (particularly those directly related to Ginkgo) were less common in the southern hemisphere, but this may not actually be the case and I suspect is due mostly to human bias. I also did not include any Ginkgoales from the Triassic Molteno Formation of South Africa, mainly because the taxonomy presented by Anderson and Anderson , 2003, needs reviewing, and the affinities of some leaves are uncertain. In general I avoided taxa (particularly taxa named 100 years ago or more) which may be in need of taxonomic review, even if they are known from good figures/ specimens and would be interesting to include. 

Just a general note on taxonomy

Yeah, so, as you might have expected, the taxonomy of extinct Ginkgoales is sh*t. The assignment of many taxa to a specific genera is often blurry, as many genera have poor or inconsistent definitions. The main inconsistencies I came across which you should look out for are: Sphenobaiera and Baiera species are often shifted between the two genera (this caused me such a headache with Sphenobaiera spectabilis); Baiera and highly divided, many lobed Ginkgoites species often shift between the two genera (tbh these two morphogenera probably do not represent true, distinct biological taxa, and the line between the two is arbitrary and almost blurred); and isolated ginkgo-like leaves are sometimes assigned to Ginkgo instead of Ginkgoites (I personally think that all isolated 'Ginkgo' leaves should be assigned to Ginkgoites, unless an association to Ginkgo reproductive organs can be made; under this, species such as Ginkgo dissecta, Ginkgo huolinhensis, and Ginkgo cordilobata should be reclassified into Ginkgoites).

Dichotomies often form a pattern

The way in which basically all of the leaves I've illustrated dichotomise is almost always consistent within each species, but in each species is is subtly different (although of couse some species will share similar styles of branching). This is worth paying attention to as it can be useful in reconstructing leaves from partial fossils.

Splits within the leaf lamina can be predicted from venation

I would like to look at more specimens to definitively confirm this, but I think that there may be a way to predict were a leaf will divide when only part of the leaf is preserved: there is often an absence of venation, forming a long narrow wedge between the veins, leading up to a split in the leaf. I first noticed this when looking at Ginkgoites waarensis in Mays et al., (2015).

Modified diagram from Mays et al., 2015, showing the absence of veins prior to the lamina splitting, and how this can be used to infer a split which is not preserved in a fossil.

The 3D shape of ginkgoes

If you look at modern Ginkgo biloba leaves you will notice that they're not flat and planar, but usually curve up towards the adaxial side (the curve in the lamina is perpendicular to the main axis of the leaf), so that in profile they create a triangular shape. To see how this might affect the look of fossil ginkgoes I cut a couple of modern leaves into shapes similar to fossil taxa. This was interesting, but also got me wondering.... would all extinct Ginkgoales leaves have curved up like this? I want to look into this more, but my suspicion is 'no', and that the curvature of extinct Ginkgoales leaves in 3D space would have been very variable. I don't know what is specifically responsible for the curvature in modern leaves, but my suspicion is that it's either a product of the leaf's development (which starts off being inwardly curved, and unfurls as it develops), or that the raised curve is maintained by the tension of the basal edge of the leaf lamina, which is thickened and composed of a single vein, which branches into the rest of the leaf lamina; when I cut this thick basal edge off a modern Ginkgo leaf the lamina was more easily flattened, but it did maintain some curvature (probably from the turgor pressure of the cells). Many fossil Ginkgoales do not posses this basal vein, instead dichotomising near the base and continuing to dichotomise into the rest of the lamina more or less symmetrically. This is particularly common in deeply lobed species, where the incisions between the lobes extent to near the lamina base. Would these veins have supported the leaf enough to maintain an upwardly curved 3D shape, or would these leaves have been more planar or drooping? We basically don't know at the moment. Speaking of drooping PLEASE check out this study by Marlene Hill Donnelly, it's great, and I'd like to replicate it with more leaf shapes at some point. To wrap this all up I just want to say that all the leaves in my diagram are drawn as if flattened into a single plane (even the modern ginkgo leaves, which are based on scanned specimens I collected).

A) Three Ginkgo biloba leaves cut into shapes similar to extinct Ginkgoites species. B) Profile view of unaltered modern Ginkgo biloba leaf, showing the triangular profile and upward curve. C) Profile view of a less curved Ginkgo biloba leaf (not all modern leaves are curved upwards, some are flat) cut into thin lobes. D) Front view of a Ginkgo biloba leaf cut into deep dichotomies (top leaf in A). E) Profile view of same leaf. F) About 45o view of same leaf. G) Modified diagram from Mustoe, (2002), showing the difference between modern and (many) extinct Ginkgo/Ginkgoites species, and how this might affect their 3d shape (note, this is speculative and I wanna look into it more).

Different leaves for different trees

Let me begin with a disclaimer: small leaves can grow on BIG trees, and BIG leaves can grow on small trees. Leaf size DOES NOT correlate to the size of the overall plant. However, the shear diversity of leaf sizes in fossil Ginkgoales means that there must have been a diversity of growth forms present in extinct Ginkgoales, so don't feel like you always need to restore such plants as big towering Ginkgo-like trees. Almost certainly many extinct species were large, but some probably also grew as small trees or perhaps even as shrubs. While leaf size does not correlate to tree size, I have wondered whether petiole base diameter might roughly correlate to the size of the overall plant? I don't recall having ever seen a tree with petioles as narrow as those seen in Ginkgoites regnellii, for example; might this particular plant, Ginkgo ginkgoidea, have grown as a smaller plant than modern Ginkgo? Just some food for thought.

So to wrap it all up...

There's not much else I really have to say at this time. Just a quick note (because I forgot to say elsewhere) leaves attributed to Pseudotorellia, which belong to the Umaltolepis-plant, may not be part of Ginkgoales and are of uncertain taxonomic affinity. However, I included it here as it has historically been grouped with the Ginkgoales and is likely still closely related to them.

Right then, I think that's everything. I hope that this has been useful, especially the main diagram (the rest is basically just unproven personal thoughts, so please please PLEASE take my thoughts with a pinch of salt and a critical mind). Once again If you want any specific references just ask me and I can send you a paper or link to my references (it's just turned 1 in the morning and I'm too tired to format 50+ references right now).

Please let me know if you have any questions or comments.

And...

That's all folk!

Toodles!

Jules Kiely