Frondosity (from Latin ''frondōsus'' meaning 'leafy') is the property of an organism that normally flourishes with

fronds A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

or leaf-like structures. Many frondose organisms are

thalloid Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...

and lack the organization of tissues into organs, with the exception of

ferns A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except th ...

. Frondosity is significant mainly for distinguishing particular types of macroscopic algae, and in

paleobotany Paleobotany, which is also spelled as palaeobotany, is the branch of botany dealing with the recovery and identification of plant remains from geological contexts, and their use for the biological reconstruction of past environments (paleogeogr ...

and

paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

, by analyzing features present in fossil biota. Frondose macroalgae are relevant to the ecology of many marine and coastal ecosystems. Large frondose algae play an important role in the creation and functioning of healthy ecosystems from

kelp forests Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on Ea ...

to similar habitats. Yet, in

coral reefs A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of Colony (biology), colonies of coral polyp (zoology), polyps held together by calcium carbonate. Most coral reefs are built from stony corals, wh ...

, frondose seaweed can be recognized as harmful due to the link between excessive blooms and coastal

eutrophication Eutrophication is the process by which an entire body of water, or parts of it, becomes progressively enriched with minerals and nutrients, particularly nitrogen and phosphorus. It has also been defined as "nutrient-induced increase in phytopla ...

Ediacaran biota

The

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

from the

Ediacaran Period The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and th ...

is sparse, as more easily fossilized hard-shelled animals had yet to evolve. Most fossils of the time are only faint impressions, and the shapes of fronds are one of the few identifying traits available. Frondose fossils are the longest studied of any Ediacaran remains, but, despite this, their affinities and biology are amongst the most controversial, ranging from animal to

protist A protist () is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor (the last eukaryotic common ancestor), the exc ...

to plant or stem fungi. The oldest members of the

Ediacaran biota The Ediacaran (; formerly Vendian) biota is a Taxonomy (biology), taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-sh ...

include discoid (disk-shaped) and frondose forms. Discoidal fossils had been classified as cnidarian

medusae Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

before being redefined as holdfasts of frondose organisms, that is, the roots or stalks that held them to the sea bed.

Rangeomorphs The rangeomorphs are a form taxon of frondose Ediacaran fossils that are united by a similarity to ''Rangea''. Some researchers, such as Pflug and Narbonne, suggest that a natural taxon Rangeomorpha may include all similar-looking fossils. Ra ...

consist of branching "frond" elements, each a few centimeters long, each of which is itself composed of many smaller branching tubes held up by a semi-rigid organic skeleton. This self-similar structure proceeds over four levels of

fractal In mathematics, a fractal is a geometric shape containing detailed structure at arbitrarily small scales, usually having a fractal dimension strictly exceeding the topological dimension. Many fractals appear similar at various scales, as illu ...

ity, and could have been formed using fairly simple developmental patterns. Rangeomorphs were radially symmetrical and likely

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

Bryozoans

Bryozoans Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...

, marine invertebrates, grow in colonial structures. The patterns of growth may be used for identification. One of the identifiable forms of bryozoan colonies, is frondose. Frondose colonies are erect and have branches that are flattened like leaves. These frond-bearing bryozoans existed in both ancient and modern times. Large tree-like forms flourished in the

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...

and

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

, although frondose forms saw a decline in the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

. A notable modern bryozoan with seaweed-like fronds is ''

Flustra foliacea ''Flustra foliacea'' is a species of bryozoans found in the northern Atlantic Ocean. It is a colonial animal that is frequently mistaken for a seaweed. Colonies begin as encrusting mats, and only produce loose fronds after their first year of g ...

''.

References

Botany Plant morphology Animal morphology {{Biology-stub