Trimestritidae

Note: Trimestritidae is a fictional taxonomic family created for illustrative purposes in this article. In the imagined biota, Trimestritidae comprises marine invertebrates known from fossil records and is used to explore patterns of morphology and evolution in a temperate-sea ecosystem.

Members of Trimestritidae are described as having a calcified exoskeleton divided into three regional plates and a life cycle that appears to follow quarterly, or trimester, phases. These phases are interpreted from growth rings in the shell and from seasonal microstructures preserved in some specimens. The group is treated as having a relatively simple internal organization compared with more derived modern taxa, with feeding and locomotion inferred from associated trace fossils.

Within the fictional taxonomy, Trimestritidae is placed in the order Trimerida, within a hypothetical class and phylum used for world-building purposes. The precise boundaries of the family have varied with new discoveries in the narrative, and some authors have proposed merging it with adjacent lineages while others retain it as a distinct clade.

Fossils attributed to Trimestritidae have been found in mid-latitude shelf and delta deposits across several fictional continents. They appear in stratigraphic horizons corresponding to a broad temporal window in the late Paleozoic to early Mesozoic in the imagined setting. The diversity of the family is imagined as comprising several genera, differentiated by plate arrangement and ornament patterns, though the specifics are intentionally fluid to illustrate taxonomic revision in a fictional context.

Etymology: The name combines Latin trimestris meaning “three months” with the standard -idae suffix for animal families, reflecting the proposed trimester-based life cycle. See also: Trilobitiformes (fictional), Fossil invertebrates.