Fossil angiosperms

for graduates

1. Fossil angiosperms Geological time scale Dr. Jasmine Brar E-mail: [email protected]

2. Geological time scale

3. Abominable mystery Writing to his friend Joseph Hooker in 1879, Charles Darwin famously referred to the origin of  flowering plants  — the angiosperms — as an ' abominable mystery '. Even today, botanists argue about what the first angiosperms must have been like. Fossil evidence  indicates that flowering plants first appeared in the Lower Cretaceous, about 125 million years ago, and were rapidly diversifying by the Middle Cretaceous, about 100 million years ago. Earlier traces of  angiosperms  are scarce.

4. Furcula granulifera (upper Triassic) Bifurcated lamina Discovered by Harris in rocks of Eastern Greenland   7-15 cm 6-8 cm Acute apex

5. Furcula granulifera Leaf : Bifurcated lamina A forked midrib from which dichotomizing secondary veins arising. The intercostal veins between the secondary veins joins to form a reticulum. Stomata is syndetocheilic with surface of the guars cells thinly cutinized. The stomata are oval and only slightly sunken. The characteristics 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.

6. Archaefructus liaoningensis Archaefructus eoflora :  bisexual flower present in the region between staminate and pistillate organs. If this interpretation is correct,  Archaefructus  may not be basal within the angiosperms, rather it may be close to the  Nymphaeales  or the basal  eudicots . Geological time scale: late  Jurassic or or early  Cretaceous period  ; Origin: China

7. Archaefructus sinensis

8. Homoxylon rajmahalense ( Jurassic) It is a piece of secondary wood, a fossil from the Rajmahal Hills in Bengal to the northwest of Calcutta (India) and described by the Indian botanist Birbal Sahni (1932). The wood resembles to that of a gymnosperm in having no vessels, but the tracheid walls bear a mixture of scalariform and circular pits as found in the family Winteraceae .

9. pre-Cretaceous angiosperms The most positive evidence of the existence of pre-Cretaceous angiosperms is pollen found in coal of Jurassic age in Scotland (Arnold 1947). The pollengrains bear three longitudinal grooves similar to those of the genus Nelumbo (family Nymphaeaceae ).

10. Pluricarpellatia peltate: Early Cretaceous  Origin: Brazil It is a fruiting structure preserved in organic connection with peltate nymphaealean leaves ( Mohr  et al . 2007 ). Fruiting body

11. Bevhalstia pebja : Lower Cretaceous Bevhalstia pebja - the world’s oldest flower (130 MYA) Carpels in primitive angiosperms were imperfectly fused, and make a physical intermediate between a folded leaf and fused pistil.

12. Sapindopsis : Cretaceous Period Pinnately compound leaves of Sapindopsis and leaves exhibiting a diversification of monocot and dicot types also make their appearance. Associated reproductive structures now suggest it was more closely related to planes and sycamores of the family Platanaceae .

13. Fossil Monocotyledons The record of monocots can be considered in the three headings (Chamberlin):  I. Families represented during the Cretaceous.  II. Families whose earliest representatives are in the Tertiary.  III. Families only known since the Tertiary. Our knowledge of the monocotyledones is based mainly on leaves that are often fragmentary and hardly identifiable, on petrified stems and on several large specimens of palm leaves. If the parallel venation of leaves is taken as the distinctive character of the Monocotyledones their presence is claimed in the Carboniferous period.

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