Final answer:
Scleractinia, or stony corals, are key reef-building organisms with skeletons made of aragonite, often forming colonial structures known as corallum. Fossil records, such as those from the Paleontological Research Institution, highlight their diversity and importance in marine ecosystems since the Middle Triassic. Their structural features like septa and columella within the corallites are critical for understanding past paleoenvironments.
Step-by-step explanation:
The order Scleractinia, commonly known as stony corals, exhibits certain key characteristics that can be recognized in both fossil and living forms. These organisms are paramount to reef-building processes and have contributed significantly to marine biodiversity over millions of years. The skeletons of Scleractinia are composed of aragonite, which is a crystalline form of calcium carbonate. As colonial organisms, their structure is known as a corallum, an assembly of individual members called polyps, which occupy spaces known as corallites. Each polyp secretes a hard exoskeleton that contributes to the overall structure of the coral.
Through paleontological research, such as that from the Paleontological Research Institution, we understand that the Scleractinia corals have been integral to the structure of marine ecosystems since the Middle Triassic Period. The diversity of genera within Scleractinia, as seen in the variety of fossil specimens, reveals the adaptive nature of these corals to various paleoenvironments. Typical examples include the colonial scleractinian corals Siderastrea pliocenica and Oculina sarasotana from the Plio-Pleistocene of Lee County, Florida. These specimens showcase the intricate framework of septa and columella found within the corallites of each coral, demonstrating fundamental features that have persisted throughout their evolutionary history. Understanding these characteristics is crucial for interpreting the paleoenvironmental conditions in which these organisms thrived.