Estartidae

Estartidae is a hypothetical taxonomic family that has been proposed within the order Artiodactyla, though it is not currently recognized by the International Commission on Zoological Nomenclature (ICZN) or widely accepted in mainstream scientific literature. The concept of Estartidae arose from attempts to classify certain extinct ungulates exhibiting unique skeletal characteristics that did not neatly fit into established families. Researchers who proposed this family suggested it would encompass a group of early ruminants or closely related taxa that diverged from the main evolutionary lineage of artiodactyls during the Paleogene period.

The primary evidence for Estartidae's existence, as put forth by its proponents, comes from fossilized remains found in specific geological formations. These fossils exhibit a mosaic of primitive and derived traits, including features of the skull, dentition, and limb bones. The proposed members of Estartidae are generally depicted as small to medium-sized herbivores with adaptations for browsing or grazing. However, due to the fragmentary nature of many of the fossils and the debated interpretation of their phylogenetic relationships, the validity of Estartidae as a distinct family remains a subject of ongoing scientific discussion and investigation. Further discoveries and detailed comparative anatomical studies are needed to definitively establish its taxonomic status.