A quantitative analysis of conodont distributional patterns in the Middle Pennsylvanian (Atokan and Desmoinesian) Morgan Formation of northeastern Utah and northwestern Colorado supports previous empirically derived Pennsylvanian conodont biofacies models. R-mode factor analysis and stepwise discriminant analysis both demonstrate strong facies-dependence for the platform conodonts Adetognathus and Idiognathodus . The Adetognathus biofacies, which may also include Hindeodus and Diplognathodus , characterizes nearshore marine deposits in which salinity and/or temperature fluctuated considerably. The Idiognathodus biofacies, which also includes Neognathodus , characterizes slightly offshore, normal-marine deposits. The environmental significance of Idioprioniodus is uncertain because of its sporadic distribution; Gondolella , its normal faunal associate, was not observed, because its habitat is probably far offshore from those in which Morgan limestones were deposited. Even at the generic level, Pennsylvanian conodonts are environmentally sensitive; hence, they are useful for both sedimentologists and paleontologists. Sedimentologists can use conodont distributional data as an independent test of their paleoenvironmental interpretations. Paleontologists can identify conodonts that are strongly facies-dependent, and differentiate conodonts best suited for biostratigraphy.

Relative abundances of conodonts stem from abiotic or biotic causes. High frequencies can result from: 1) biotic positive = high standing crop; 2) biotic negative = lethality (mass mortality); 3) abiotic positive = lag concentrates; 4) abiotic negative = starved sedimentation. Neither abiotic cause should substantially affect the taxonomic composition of the fauna, although either biotic cause—good or bad environmental responses—can and must. Pennsylvanian conodont biofacies are clearly established and evidence of their interrelationships and complexity has continued to mount. We currently recognize no fewer than five levels of conodont biofacies: Ia - Primary generic-level biofacies (examples: Cavusgnathus, Aethotaxis) Ib - Secondary generic-level (“nested”) biofacies (examples: Ellisonia with Cavusgnathus, Hindeodus with Aethotaxis) II - Species-level microbiofacies (examples: Idiognathodus delicatus with Missourian Idioprioniodus / Gondolella , Streptognathodus elegantulus with Missourian Aethotaxis ) III - Apparatus-level biofacies (examples: scottognathoid apparatuses least complete with Cavusgnathus, intermediate with Aethotaxis, most with Idioprioniodus in the Missourian) IV - Ecophenotype variant-level biofacies (examples: perhaps two “species” of Ellisonia with contrasting apparatus plans and morphologies in the Desmoinesian, possible Cavusgnathus morphotypes from the Cavusgnathus- to the Streptognathodus -biofacies).