Detailed Seeds Found in Early Cretaceous Rock
Hundreds of flowering plant seeds from early Cretaceous strata on two continents show exceptional preservation; how can they be 125 million years old?
A paper in Nature reports another example of “exceptional preservation” of biological material, this time of plant seeds. The seeds were found in Portugal and in the eastern United States. They contain embryos and nutritive material, the paper says, yet are thought to be 125 to 110 million years old, the time in the evolutionary story when angiosperms (flowering plants) were rapidly diversifying. Here are some quotes from the paper:
- Here we report the discovery of embryos and their associated nutrient storage tissues in exceptionally well-preserved angiosperm seeds from the Early Cretaceous.
- …we analysed the internal structure of mature seeds from about 75 different angiosperm taxa recovered from rich assemblages of angiosperm flowers, fruits and seeds in 11 mesofossil floras from eastern North America and Portugal, ranging in age from Barremian-Aptian to early or middle Albian, about 125–110 million years ago.
- SRXTM revealed exquisite preservation of three-dimensional cellular structure, often including traces of nuclei and subcellular nutritive bodies.
- In mature fossil fruits and seeds, the seed coat is generally well-developed and cellular preservation is usually excellent. Softer tissues such as embryo and nutrient storage tissues may be degraded or distorted, but of the roughly 250 Early Cretaceous mature seeds examined about half show cellular structure inside the seed coat.
- In about 50 seeds, complete or partly preserved embryos occur along with remains of the surrounding nutrient storage tissue. Minimal shrinkage of the seeds during preservation is indicated by the typically straight cell walls and the fact that the nutrient storage tissue often fills out the whole seed volume inside the seed coat.
- Cellular preservation of the embryos in all six taxa [i.e., those shown in a figure] is excellent.
- [Figure 4 caption]: …Surface rendering of embryo showing the two small cotyledon primordia. c, Detail of endosperm with nutritive bodies (protein and lipids).
- Mesofossils preserved in these floras are often exquisitely preserved in three dimensions as charcoalified or lignitic specimens and include complete and fragmentary flowers, as well as abundant fruits and seeds.
The authors make a big deal of the fact that the seeds are tiny, as if this represents a primitive condition before the evolution of modern flowering plants. Other statements, however, make it hard to imagine 130 million years going by. Some aspects of these seeds compare well with those found in modern plants:
- Cells in the nutritive storage tissue often contain small rounded structures (Figs 2a, c and 3) that are most probably remains of the protein and lipid bodies that occur in the equivalent seed tissues of many extant angiosperms.
- In each cell there is typically a central body about 4–6 μm in diameter (Fig. 2b) that is similar in size and position to the nuclei seen in the embryo cells of extant early diverging angiosperm lineages.
- Very similar cellular differentiation occurs in the endosperm of modern Sarcandra (Fig. 4a, c) and other extant early diverging angiosperm lineages.
- As in extant taxa, the contents of the cells immediately around the embryo were apparently consumed very early in the development of the young plant.
- The distinctive exotestal seeds of taxon 1 and taxon 3 are also indicative of a relationship to Schisandraceae or Nymphaeaceae, and the broad embryo of taxon 3 is very similar to the embryos in seeds of extant Nymphaeaceae.
- Canrightiopsis is phylogenetically close to the common ancestor of extant Ascarina, Sarcandra and Chloranthus (Chloranthaceae). Comparison of the almost spherical Canrightiopsis embryo with that of extant Sarcandra shows strong similarities and the same cellular features. However, the seeds and embryos of Canrightiopsis are much smaller.
The differences between fossil and extant seeds appear slight. The authors confess the “limitations of inferring ancestral characteristics solely by extrapolation from the features of extant taxa.”
Again, the authors are frustratingly equivocal about whether the remains are composed of original biological material or lithified remains. It would be helpful if they would state clearly whether the “proteins and lipids” are just that—proteins and lipids—or if they are minerals that replaced them. It seems reasonable to infer, though, that these structures are the original material. The authors say that some of them are “decomposed” but do not say they are lithified. For instance, they say, “The nutrient storage tissue immediately around the embryo is often partly or fully decomposed, but in seeds with particularly good preservation these cells are usually distinguished by their smaller size, thinner walls and lack of nutritive bodies.” Even decomposed biological material is still biological. Given the hubbub over original soft tissue found in dinosaur bones and fossils older than 100 million Darwin years, it would seem they would brag that the fossils are fully replaced by rock if they could. Also, it seems unreasonable to expect that structures as small as subcellular units and nuclei could be lithified. The clearest reference to original biological material is that “Mesofossils preserved in these floras are often exquisitely preserved in three dimensions as charcoalified or lignitic specimens and include complete and fragmentary flowers, as well as abundant fruits and seeds.” (See Field Museum discussion of mesofossils.) The Methods section suggests the specimens are not mineralized: “Fossils were isolated from the sediments by sieving in water, remaining mineral matrix was removed using hydrofluoric and hydrochloric acids, and the fossils were then rinsed in water and air-dried.“
Assuming, then, that the fossils are composed of original biological material, is it reasonable to expect it would be preserved for 110 million years or more? Even if it were permineralized, how could such detail be preserved that long? Remember, evolutionists believe that a major catastrophe struck the Earth just 65 million years ago. Undoubtedly there were smaller catastrophes across the eastern US and Portugal from the time those seeds were laid down till now. A lot of geological change can happen in even 1 million years, or 100,000, or 10,000 years. The logical conclusion is that the “Cretaceous” strata containing these fossils are young, not millions of years old. Until that sinks in to open-minded scientists, we can add this paper to the pile of evidence for exceptional preservation of original biological material that cannot be anywhere near as old as claimed.