EARLIST FLOWERS

EARLIEST FLOWERS ARE GEOLOGICALLY OLDER THAN MANY DINOSAURS

                                  Earliest Known Fossil Flowers

Angiosperms are plants that have male and female reproductive parts and also bear their seeds in fruit. The earliest known angiosperm fossil is Montesechia vidalii, approximately 130 mya [i.e., million years ago] (= Early Cretaceous time) from Spain (Gomez et al, 2015). Today, angiosperms are the most diverse group within Kingdom Plantae and represent 80% of all living green plants.

Figure 1. Early Cretaceous fossil of Montesechia vidalii, 60 mm long. This weed-like plant had no roots and was probably an ancient aquatic angiosperm plant.

The next evolutionary “step” in flower evolution was Archaefructus liaonigensis, approximately 125-130 mya (Early Cretaceous) from northeastern China. This  angiosperm plant, which is one of three species of this genus, probably lived in a lacustrine environment (i.e., lake or pond).

Figure 2. Early Cretaceous fossil of Archaefructus, less than 50 cm (20 inches) tall) with simple roots. It was most probably an aquatic angiosperm species with two types of flowers: one bearing pollen (yellowish in the figure shown here) and one bearing reproductive structures (grayish in the figure shown here). This plant most likely lived in lacustrine (lake) or pond environments.

                                                  Water lilies

Water lilies (family Nymphaeceae) are perennials that live in fresh water at depths between 6 and 15 feet. Although these plants are rooted in soil in the bodies of water, their leaves and flowers float or rise above the surface. The leaves are oval to heart shaped and are fully circular or can have a slit (short radial notch). The edges of the leaves can be smooth or serrated. 

The leaves have hollow air-filled  channels (tubes) in their stems that provide buoyancy. The flowers, which can be any color—but commonly white) have unspecialized reproductive parts. Recent generic studies confirm that the evolutionary position of water lilies to be basal angiosperms. Only 2% of angiosperms are aquatic today.

The flowering season of water lilies is May through September. These plants propagate via rhizomes that allow the plant to spread into interconnected aquatic habitats. They live in temperate and tropical areas around the world. They are represented by five genera and approximately 70 species. 

Water lilies now provide the critical link in the evolution of flowers. This statement is based on modern genetic studies that have helped confirm that water lilies, with their unspecialized reproductive parts, have a basal position among flowering plants.

Several fossil species of water lilies are known—mainly of Cretaceous age from Brazil.

Figure 3

Figure 4

Figures 3-4. Water lilies in the early part of their “blooming time.” Images kindly provided by Lindsey Groves, Collections Manager at the Natural History Museum of Los Angeles County, southern California.

Note: Although water lilies resemble lotus flowers, they are not the same. Interestingly, botanists are now recognizing the floral and vegetative similarities between the lotus and sycamore trees (see one of my previous posts regarding the latter plant) (Alka, 2007).

                                         Magnolia Tree 

The oldest known flowering tree is Magnolia, which originated approximately 100 Ma to 95 Ma. This tree co-existed with some dinosaurs of that time. Magnolias evolved before bees evolved and, therefore, had to rely on beetles for pollination. The flowers of the magnolia tree are generally now regarded as being primitive, mainly based on the relative positions of the female (pistils) and male parts (anthers) within the flowers. Also, magnolia leaves are relatively unspecialized.

                                               Figure 5

Figures 5-9. The image directly above and the next four images are all from the same Magnolia tree, which is located in northern Los Angeles County, Southern California (note: most Magnolias are most common in the southeastern part of the United States). Although Magnolia trees can be up to 80 feet tall, the tree figured here is only about 45 feet tall. 

                                                                        Figure 6

Close-up view of the previously shown Magnolia grandiflora tree. This kind of tree has rather thick (kind of rubbery), large-sized leaves that can have an orange-tint coloration on their lower surface. Magnolia trees have large flowers that are typically white or pink (as shown here). 

Figure 7. Although flower buds of the tree shown here appeared in mid April, they did not “erupt” into open flowers for a several until late June before the flowers opened up and reveled the central core area (note: it was worth the many repeated trips to photograph these flowers, but it was worth it!).

Figure 8. Exterior view Magnolia grandiflora reproductive area of flower: total length 61 mm. Yellow part 16 mm wide and 30 mm long; lower part (consisting of reddish upper part and brownish lower areas), 31 mm length and 5 mm wide.

Figure 9. Cross-section of main (see yellow part of preceding figure) core area, with seeds in capsules. 

RERERENCES CITED: 

Alka. Floral designs by Alka. https://www.floraldesignsbyalka.com/blog/tag/Waterlilies.

Gomez, B. and four others. 2015. Montsechia, an ancient aquatic angiosperm. Proceeding of the National Academy of Sciences (PNSA). www.pnas.org/cgi/doi/10.1073/pnas. 150292411.