Morphological and ontogenetic criteria for defining a trilobite species: The example of Siluro-Devonian Phacopidae

Siluro-Devonian phacopid morphology and ontogeny provide an explicit worked sample for diagnosing species within Phacopida. The study samples Phacopidae and neither revises every phacopid lineage nor fixes order-wide temporal endpoints.

Crônier et al. use morphological and ontogenetic characters to delimit Siluro-Devonian Phacopidae species; these observations are a bounded family sample, not universal phacopid anatomy.

The former 488-359 Ma Phacopida display is withheld because the available primary study treats Siluro-Devonian Phacopidae rather than an order-wide first and last occurrence synthesis; no numerical global range is assigned here.

Crônier et al. document Siluro-Devonian Phacopidae material and ontogenetic series, while Fortey reviews sampled trilobite systematics; these records are regional and taxon-sampled rather than a complete geographic distribution of Phacopida.

The cited phacopid taxonomy studies focus on morphology, ontogeny and classification, not diet, habitat use, locomotor performance, body size or ecological guild; those fields remain unassigned for Phacopida here.