New Finding of Regular Echinoid Elements and Microfossils from the Pilmatué Member, Agrio Formation (Early Cretaceous), Neuquén Basin, Argentina.

CONCHEYRO, A.; CARAMÉS, ANDREA; ADAMONIS, S.

Advances in South American Micropaleontology, Selected Papers of the 11th Argentine Paleontological Congress,

Springer

Lugar: Berlín; Año: 2019; p. 1 - 20

This contribution presents new findings of regular echinoid elementsfrom Upper Valanginian claystones, marlstones, and mudstones recovered nearthe base of the Pilmatué Member, Agrio Formation, in the Puerta Curaco andÁrea 3000 sections, Province of Neuquén. The recovered material includesisolated elements of Aristotle?s lantern, spines, ambulacral and interambulacralplates obtained from washed residues of micropaleontological samples. Theirtaxonomy covers several possible regular echinoids included within theAcroechinoidea. Considering the tubercles, pore-pairs, type of plates, andambulacral plating style, these fragments could be assigned to the ?diademataceans?.The spines and the rotulae cannot be attributed to a specific taxonbecause they are found in several different regular echinoid clades. The morphology of the hemi-pyramids is common to different regulars; this fact coupledwith their poor preservation prevents a confident assignment to a higher taxonomic level. Wedge-shaped teeth, typical of irregular echinoids, cannot belinked to any of the other recovered remains. These fossiliferous horizons alsocontain a rare to very abundant assemblage of benthic foraminifera dominatedby Epistomina loncochensis Ballent, few ostracods, and resistant calcareousnannofossils. The presence of E. loncochensis indicates quiet marine environmentsand scarcity of oxygen in the water/bottom interface. Claystone compositionof the level rich in echinoid remains suggests a detrital input fromshallower environments by means of currents, explaining the disarticulation ofthe echinoids.