Análises morfométrica, icnológica e revisão histórica sobre equinoides irregulares da formação Jandaíra, Bacia Potiguar

Abstract

The study of the Potiguar Basin fossil echinoderms has little less than 100 years. Since then, the studies published focused on the group’s taxonomy, that is classifying to which groups or species these organisms were included. The present work aimed to make a historical survey on the taxonomic status of species described for the Potiguar Basin marine sequence taxa. Additionally, this manuscript contains the taxonomic identification, a review on the morphometric diversity, and ichnofossil identification and classification of the Potiguar Basin irregular echinoids deposited in Laboratório de Paleontologia of Departamento de Geologia (DG) of the Universidade Federal do Rio Grande do Norte (UFRN) collection. The historical survey revealed that there are currently three irregular echinoid genera and three regular echinoid genera valid in the Jandaíra Formation. Among the 220 irregular echinoids analyzed in the collection of the Laboratório de Paleontologia do DG-UFRN, 150 specimens were identified as Petalobrissus Lambert, 1916 and 70 individuals were identified as Mecaster Pomel, 1883. Not a single specimen of Coenholectypus Pomel, 1883 has been found. Among all specimens analyzed, only 101 had information on the fossil site locality. Professor Leon Diniz collected all the specimens studied before the 1990s, in eight different outcrops in the surroundings of the Governador Dix-sept Rosado municipality, RN. For the morphometric study, 70 better-preserved individuals were selected. Length, width, and height of the test were measured, contributing to the knowledge of the species descriptive measures, specially Petalobrissus cubensis Weisbord, 1934 e P. setifensis Cotteau, 1866. Ichnofossil analysis revealed linear, circular, and irregular traces, similar to the ones classified by Farrar (2020). However, other morphotypes that do not fit in previous classifications were also found: zigzag, concave, and reticulate. All of them were probably produced by other invertebrate groups, such as annelids and mollusks. Finally, the paleoichnological analysis brings new paleoecological information and the first described ichnofossils in echinoid tests from the Potiguar Basin.