Darwin called the evolution of the Angiosperms a

“ Perplexing phenomenon”

…and in a letter to Joseph Hooker he called them …

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www.jdhooker.org.uk

an “Abominable Mystery”

—Charles Darwin in a letter to Sir Joseph Hooker, 1879.

90 million year old fossil flowers (Fig. A- Clusiaceae and B- related to the Heath Family) already are highly developed suggesting an earlier origin for flowering plants.

(C) Phylogeny of living seed plants based on morphological characters. Note Gnetales and Angiosperms clustered as the Anthophytes..

(D) A contrasting phylogeny of living seed plants based on cpITS sequences. Note support for the Gnetifer theory.

Crepet, William L. 1998. The Abominable Mystery. Science 282: 1653-1654

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Paleoclusia

Microvictoria (related to water lilies)

Mabelia (monocot)

Reconstructions of three fossil flowers (Crepet et al., 1998. Am. J. Bot.91:1666-1682)

Location of fossil finds of Archaefructus and Brachycera flies

This has changed our view of early angiosperms

Paleogeographic Map showing Positions of Modern Countries in the Early Cretaceous

J=Japan, K=Korea, Mon=Mongolia NCB=North China, SCB=South China, etc.

Current Geography

Archaefructus liaoningensis 1998 Archaefructus sinensis 2002

Non-Angiosperm Seed Plant? Early Angiosperms? Or Specialized Early Angiosperm?

Archaefructus liaoningensis

1998

Archaefructus liaoningensis Is a fossil angiosperm from the Jurassic (190-136mya)-- the late Jurassic. It predates the presumed Cretaceous (136-65 mya) origin for the angiosperms. (A) fruiting axes and remains of two subtending leaves. (Scale bar, 5 mm).

(B) Enlarged view of the carpels showing remains of the

adaxial (top) crest, abaxial(bottom) venation, seeds in each “carpel”, and finger-like prominences. (Scale bar, 5 mm).

(C) SEM of Portion of a seed removed from a carpel (Scale bar, 25 µm).

Sun et al.1998 Science 282: 1692-1695.

Archaefructus sinensis

May, 2002

Archaefructus sinensis An aquatic herb!! No petals or sepals! Protandrous?

Archaefructus sinensis

A. Whole specimen

B & C. Multiseed stalked carpels and paired stamens.

D &I. Leaves (with swollen leaf base).

Archaefructus liaoningensis

E. Two young fruits with stamens below.

F & G Pollen (monosulcate)

J, K&L. Mature Fruits

Archaefructus sinensis

Fossil Reproductive Branch

Controversies:

Are they flowering plants?

Most likely- though this is not definitive.

Are they the earliest angiosperms to date?

Could be but seems unlikely.

Are they dated accurately?

Initial dates were too old.Stamens

Carpels

Ovules

First 2 alternatives for Archaefructus placement:

1. Basal to all other Angiosperms.

2. Specialized genus in a clade with aquatic plants.

1 2

Evidence:

1. Earlier dates (Late Jurassic >144mya) for this Yixian formation (which includes the Jehol biota) were based on flawed data. Recent data suggest this formation is about 125my old (early to mid Cretaceous). Other fossils of early angiosperms date to this time.

2. Archaefructus lacks petals and sepals-- both found in most bona fide Angiosperms. It shares features with some non-angiosperm seed plants-- making its position equivocal. We have no data on ovule structure or evidence that the “carpels” are derived from modified leaves.

3. 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.

1. Early estimates of age (Late Jurassic >144mya) for the Yixian formation (including the Jehol biota) were flawed. New estimates suggest this formation is about 125my old (early to mid Cretaceous). Other fossils of early angiosperms date to this time.

Mammal diversity was high. Plants were also diverse.

2. Archaefructus lacks petals and sepals-- both found in most bona fide Angiosperms. It shares features with some non-angiosperm seed plants-- making its position equivocal. We have no data on ovule structure or evidence that the “carpels” are derived from modified leaves.

Archaefructus may be 1. a non-angiosperm seed plant group, a 2. basal angiosperm, or 3. a specialized angiosperm. It may also hint at the importance of an herbaceous, aquatic habitat, early in the evolution of angiosperms.

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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.)

(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.

The Archaefructaceae were at one point considered basal with in the angiosperms. But that view is being questioned and the search for the earliest flowering plants continue.

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