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− THE ROLE OF FOSSILIZATION AND WEATHERING IN THE SYSTEMATICS OF PHACOPIDA (CALMONIIDAE AND HOMALONOTIDAE) TRILOBITES, FROM THE DEVONIAN OF THE PARANÁ BASIN, BRAZIL. Until now, nearly 17 names were applied to the calmoniid trilobites of the Ponta Grossa Formation, Paraná Basin suggesting a high diversity Based on the taphonomic analysis of 516 specimens of calmoniid (n= 412) and homalonotid (n= 104) trilobites it is now clear that some species are artificial, since the morphological features that diagnose them are the product of fossilization and weathering (post-fossilization). This is particularly true to those “species” that are preserved in different lithofacies, since they are submitted to distinct diagenetic (e.g., compression) and weathering (e.g., obliteration/ effacement) processes. To the studied calmoniid trilobites, three are the main morphological characters that are susceptible to modifications via taphonomy and weathering: (i) variation in inflation of glabelar lobe, (ii) variation in lobe shape, depth of axial and glabelar furrows, and (iii) presence/absence of external ornamentation. To the homalonotids, the following morphological characters are susceptible to modifications: (i) variation in glabelar lobe shape, and (ii) presence/absence of external ornamentation. Based on this, the status of some species of calmoniid (Paracalmonia paranaensis, P. cuspidata, Calmonia signifier, C. subseciva) and homalonotid (Burmeisteria herschelii and Digonus noticus) trilobites is discussed. Data presented here reinforces the idea that the erection of new trilobite species should be based on large scientific collections, enabling the detection of the patterns of morphologic variation both biologic and taphonomic. This procedure reduces the possibility to erect invalid taxa.

O papel da fossilização e do intemperismo na sistemática de trilobites Phacopida (Calmoniidae e Homalonotidae) do Devoniano da bacia do Paraná, Brasil