Systematics, taphonomy, and paleoecology of homalonotid trilobites (Phacopida) from the Ponta Grossa Formation

Abstract

Homalonotid trilobites (Phacopida) from the Ponta Grossa Formation (Lower Devonian), Paraná State are revised. A total of 156 specimens recovered from rocks that belong to the Jaguariaíva Member (or Sequence B), of the Ponta Grossa Formation cropping out at Ponta Grossa, Tibagi and Jaguariaíva counties, were examined. Data gathered indicate that at least two species are present (Burmeisteria noticus and B. herscheli). B. noticus is a conspicuous species of the Devonian rocks of South Africa (Bokkeveld Group), Argentina (Lipéon Formation), Bolivia (Icla and Bélen Formations), and Brazil (Pimenteiras and Ponta Grossa formations). B. herscheli is common in Devonian strata on the Falkland Islands (Fox Bay Formation), South Africa (Bokkeveld Group), and Bolivia (Icla and Tarija formations), and is a newly recognized member of the trilobite fauna of the Ponta Grossa Formation. Hence, the homalonotid fauna of the Ponta Grossa Formation is not monospecific, as previously assumed. Finally, homalonotids are not randomly distributed throughout the succession of the Ponta Grossa Formation. B. herscheli shows a more restricted bathymetric distribution, preferentially occurring in sandstones and siltstones deposited just at the storm wave base. B. noticus lived and/or were preserved in sedimentary deposits varying from sandy facies, generated just in and/or above the fair weather wave base, and in muddy facies deposited below storm wave base. Despite the differences in the distribution of both species, homalonotid remains are rather abundant in the shallow water facies, deposited jus at or above storm wave base, being potentially important paleoenvironmental (neritic facies) indicators. Key words: Homalonotidae, Systematics, Devonian, Ponta Grossa Formation, Paraná Basin.