Paleobotany is the study of fossil plants and their relationship to modern plants. Early angiosperms first appeared in the fossil record during the Lower Cretaceous period, around 130 million years ago. However, they diversified and dominated plant communities only later in the Cretaceous. Transitional fossils like Archaefructus provide evidence of early flowering plants, but their exact position is unclear. During the Lower and Mid-Cretaceous, there was an increase in the diversity of angiosperm leaves, pollen, and plant families, indicating the rapid radiation and rise of flowering plants.

1. SREERAJ E
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2. Introduction
• A branch of botany dealing with fossil plants.
• Includes the study and classification of plants of the
geological past as well as the study of their relationship
with each other and with extant plants.
• Palynology : the study of pollen
• Paleobotany and paleozoology are usually joined in the
science of paleontology.

3. The Geological Time
scale
Geological Time scale describes the timing and relationships
between events that have occurred throughout Earth’s
history.

4. How is a fossil
formed?
1. Sediment
An animal/plant is
buried by sediment,
such as volcanic ash
or silt, shortly after it
dies. It is protected
from rotting by the
layer of sediment.
4. Erosion
Erosion from rain,
rivers, and wind wears
away the remaining
rock layers.
Eventually, erosion or
people digging for
fossils will expose the
preserved remains.
2. Layers
More sediment layers
accumulate above
the animal’s/plant’s
remains.
3. Movement
Movement of
tectonic plates, or
rock slabs lifts up the
sediments and pushes
the fossil closer to the
surface.
Remains of organisms that lived a very long
time ago

5. Five main types of fossils
Petrified
Fossils
Molds and
Casts
Carbon
Films
Trace
Fossils
Preserved
Remains

6. • All living things contain an
element called carbon.
• When an organism dies and is
buried in sediment, the
materials that make up the
organism break down.
• Eventually, only carbon
remains.
• The thin layer of carbon left
behind can show an
organism’s delicate parts, like
leaves on a plant.
Carbon film
FERN FOSSIL
This carbon-film
fossil of a
fern is more than 300
million years old.

7. Angiosperm origin: fossil record
• Darwin with reference to the origin of flowering plants,used the phrase the
"Abominable Mystery".
• Angiosperms appear suddenly in the fossil record with no obvious ancestors for a
period of 80-90 million years before their appearance.
• Clarifying the origin and diversification of angiosperms poses fascinating challenges
to evolutionary biologists
• The lack of fossils has been attributed to the idea that angiosperms arose in dry,
upland areas that were not optimal for fossilization.
• The earliest definite angiosperm fossils are from the Cretaceous, approximately 130
MYA. Angiosperms dominated the flora by 90 MYA, and most existing families were
present by 75 MYA.
• During the late Mesozoic, the major branches of the clade diverged from their
common ancestor.

8. The Pre-Cretaceous record of presumed angiosperms
• There is no good evidence in the fossil record of presumed
angiosperm remains that suggests that they had a pre-cretaceous
origin.
• The first valid evidence does not appear until the Lower Cretaceous.
• Furcula granulifera (upper triassic) provides an excellent example of
fossil leaf remains that combine characteristics of angiosperms.

9. • Leaf
Bifurcated lamina
A forked midrib from which dichotomizing secondary veins arising.
The intercostal veins between the secondary veins joins to form a
reticulam.
Stomata is syndetocheilic with surface of the guars cells thinly cutinized.
The stomata are oval and only slightly sunken.
The charecterestics of venation and stomata are those of angiosperms.
But the forking lamina is like that of certain cycadophytes,for this reason
it still not completely classified as an angiosperms.
Furcula granulifera (upper Triassic)

10. The Lower and Mid Cretaceous
record
• The origin and rapid diversification of angiosperms occurred in the
lower cretaceous.
• This conclusion is based in part on comprehensive studies of leaf
compression-impression and dispersed pollen types from the Potomac
group of the Lower Cretaceous in the US.

11. Archaefructus liaoningensis 1998 Archaefructus sinensis 2002
Non-Angiosperm Seed Plant? Early Angiosperms?
Or Specialized Early Angiosperm?

12. Archaefructus liaoningensis
1998

13. Archaefructus liaoningensis
It is a 125 MY old fossil angiosperm
•fruiting axes and remains of two subtending
leaves.
•Enlarged view of the carpels showing
remains of the
adaxial (top) crest, abaxial(bottom) venation,
seeds in each “carpel”, and finger-like
prominences.
•SEM of Portion of a seed removed from a
carpel
.

14. Archaefructus sinensis
May, 2002

15. Carpel
Stamen
5 cm
Archaefructus sinensis, a
125-million-year-old fossil
Artist’s reconstruction
of
Archaefructus sinensis
Archaefructus sinensis An aquatic
herb?!

16. • Archaefructus lacks petals and sepals-- both found in most
Angiosperms.
• It shares features with some non-angiosperm seed plants-- making its
position equivocal.
• There is no data on ovule structure or evidence that the “carpels” are
derived from modified leaves.
• Archaefructus may be a non-angiosperm seed plant group, a basal
angiosperm, or a specialized angiosperm.
• It may also hint at the importance of an herbaceous, aquatic habitat,
early in the evolution of angiosperms.
Archaefructus

17. Leaves (Cretaceous
period)
There is rapid increase in diversity of angiosperm leaf types higher in the
cretaceous.
The percentage of angiosperm leaf remains increase dramatically to as much as
25%
in the lower cretaceous.
These tend to be dominated by members of the palmately lobed
Araliaephyllum,Araliopsoides etc.
Pinnately compound leaves of Sapindopsis and leaves exhibiting a diversification
of monocot and dicot types also make their appearance.

18. Angiosperm
Pollen• Vascular plant pollen and spore walls contain one of the most stable and decay-
resistant biopolymers known to man.
• Palynologists can extract pollen from rocks using some of the strongest acids
know, without damaging the pollen.
• Spores and pollen get trapped in fine-grained rocks, usually when they settle
out of a column of lake or ocean water into bottom muds.
• which later become compressed into rock as more layers of sediment
accumulate above them.

19. Pollen (The Lower and Mid Cretaceous period)
Monocolpate pollen
The earliest acceptable record of angiosperm is from lower cretaceous,Hautervian
strata of England.
Early Angiosperms had pollen grains with one aperture (slit or pore, termed
monocolpate), as do cycads and Ginkgo.
Found here are grains with an angiospermous sporoderm comprising a tectum that
covers columellae and continueous inner layer of the exine.
Some of the grains are boat-shaped monocolpate type that could belong to either
monocots or some magnoliaceous dicots.
The occurrence of these pollen types correlates well with the presence of monocot and
dicot leaf types in this era.

20. Monocolpate pollen
Tricolpate
pollen
Tricolpate pollen goes back approximately 127
MYA. The diversification of pollen closely follows
the
diversification of leaf types.
Pollen
Colpi are any thinning, thickening or other modification of the wall of pollen or spores that serve as an exit
for
its contents or to allow shrinking and swelling of the grain in response to changes in moisture content

21. First angiosperm fossils --- sequence of diversification
The diversification of pollen closely follows the diversification of leaf
types.

22. Evolution of the angiosperm flower
• (a) cone of the Jurassic bennettitalean Williamsoniella, showing the female fertile structure, the
ovule, contained in a central receptacle, and surrounded by the male fertile structures, the
microsporophylls;
• flower of the gnetale Welwitschia, showing the central ovule, and surrounding male elements;
and
• flower of the angiosperm Berberis, showing the same pattern, but with the seed enclosed in a
carpel.

23. Bevhalstia pebja - the worl d ’s ol de st fl ower ( 130
MYA)
Carpels in primitive angiosperms were imperfectly fused, and make a
physical intermediate between a folded leaf and fused pistil.

24. Protonemestrius jurassicus
(A) drawing of specimen(B) photo of fly fossil (C) photo of proboscis
These fossil Brachycera flies were found in the same late rocks as Archaefructus! They
suggest the link between flies and flowers is old and also may suggest an earlier origin for
the angiosperms.
(Ren, D. 1998. Flower-associated Brachycera flies as fossil evidence for Jurassic angiosperm origins. Science 280: 85-88.)

25. (A) Drawing of specimen (B) Photograph of body (C) Photograph of
proboscis
Palaepangonius eupterus-- another long tongued fly!
From Ren, D. 1998. Flower-associated Brachycera flies as fossil evidence for Jurassic angiosperm origins. Science 280: 85-
88.
Initially the thought was that they were Jurassic-- but they are also early to mid-
cretaceous. Supporting and early Cretaceous origin for flowers.

26. Rapid radiation of the angiosperms during the
Cretaceous
Rapid radiation of the angiosperms during the Cretaceous, shown by the rise in
the number of angiosperm families, from none at the beginning of the Cretaceous
to more than 35 by the end of the period. Neocom, Neocomian;
B, Barremian; Ce, Cenomanian; T, Turonian.

27. Basal Angiosperms:Amborella
• Analysis of DNA reveals this genus is the most primitive flowering plant.
• Found only on island of New Caledonia in the South Pacific.
• Understory shrub; plants dioecious
• Flowers with moderate number of petals.
• Flowers are imperfect (separate male and female gametophytes).
• Leaves simple, evergreenFlowers small, unisexual: ♀ apocarpous, with stigmatic crests;
♂
with laminar stamens
• No vessels in wood
New CaledoniaFlower

28. Flowers of Amborella - carpels incompletely fused, no
vessels