Evolution and Life of Coral Reefs – Key Vocabulary

This set of vocabulary flashcards reviews major organisms, structures, geologic periods, and ecological concepts covered in the lecture on coral-reef evolution.

Algal Reef

A reef primarily constructed by algae; in the Precambrian they were far more common than today.

Stromatolite

Layered, mound-like structure built by cyanobacteria that represents the oldest known reef-building organism.

Microbialite

Calcareous organo-sedimentary deposit produced by benthic microbial communities, appearing ~3.5 billion years ago.

Cyanobacteria

Photosynthesising ‘blue-green’ bacteria that precipitate calcium carbonate and helped oxygenate Earth’s early atmosphere.

Precambrian Era

Geologic time before 541 Ma; dominated by stromatolites and early microbial reefs.

Archaeocyatha

Extinct sponge-like organisms of the Cambrian, considered the first major animal reef builders.

Porifera

The sponge phylum; Archaeocyatha are now treated as an extinct class within this group.

Stromatoporoid

Sponge-related Ordovician reef builder that secreted a reticulate skeleton of laminae supported by pillars.

Ordovician Period

Geologic period (485–444 Ma) noted for diverse microbial and stromatoporoid reefs.

Thrombolitic Fabric

Clotted macro-fabric seen in some Ordovician mud-mound reefs.

Laminar Fabric

Layered or sheet-like structure, common in stromatolitic reefs.

Digitate Structure

Finger-like projections in certain stromatolitic reef forms.

Laminae

Horizontal skeletal layers in stromatoporoids.

Pillars (Stromatoporoids)

Upright rod-like supports between laminae in stromatoporoid skeletons.

Tabulata

Extinct colonial corals with honeycomb-like hexagonal cells and horizontal partitions called tabulae.

Rugosa

Extinct ‘horn corals’; solitary or colonial tetracorals prevalent from Ordovician to Permian.

Heliolitida

Smallest of the three main Paleozoic coral orders, forming massive reefs; extinct by late Devonian.

Horn Coral

Characteristic solitary, conical rugose coral that could reach nearly a meter in length.

Calice

The cup-shaped upper surface of a coral corallite where the polyp resides.

Corallite

The skeletal tube or chamber secreted by an individual coral polyp.

Corallum

The entire skeletal structure of a colonial coral, comprising many corallites.

Scleractinian Coral

Modern stony corals that first appeared in the Triassic and dominated Jurassic reef building.

Phaceloid Growth Form

Scleractinian arrangement with long, separate tubular corallites, each with its own wall.

Jurassic Period

Time (201–145 Ma) when scleractinian corals reached their peak diversity.

Permo-Triassic Mass Extinction

Event ~245 Ma that eliminated Tabulata and Rugosa corals.

Rudist

Unusual bivalve mollusc that became an important reef builder during the Mesozoic.

Bryozoan

Colonial, filter-feeding invertebrate that, with algae and corals, dominated certain late Paleozoic reefs.

Tubiphytes

Tubular, calcareous organisms common in late Paleozoic reef assemblages.

Foraminifera

Single-celled protists with calcareous shells that have persisted as reef dwellers since the Paleozoic.

Hypersaline Environment

Water body with exceptionally high salinity; crucial for modern stromatolite survival (e.g., Hamelin Pool).

Hamelin Pool

Shark Bay, Western Australia site famous for extensive living marine stromatolites.

Bahama Banks

Region in the Bahamas (e.g., Lee Stocking Island) hosting modern stromatolitic reefs.

Reef Discontinuity

Long interruptions in reef development due to events such as climate change, sea-level shifts, or extinctions.

Mass Extinction

Global event causing abrupt, widespread loss of biodiversity; five major events punctuated reef evolution.

Algae–Coral Symbiosis

Mutualistic relationship, established early in scleractinian history, between coral polyps and photosynthetic algae.