VERTEBRATE MICRO"REMAINS FROM THE LOWER CRETACEOUS AGRIO FORMATION NEUQUEN BASIN, ARGENTINA

PAOLO CITTON; MARTINA CARATELLI; JOHANNES PIGNATTI; FERNANDO ARCHUBY

Virtual

Congreso; 3rd Palaeontological Virtual Congress Palaeontology in the virtual era; 2021

Fish skeletal debris, composed of minute-sized teeth and dermalscales highly resistant to dissolution, occurs in marine and nonmarinepalaeoenvironments, especially in the deep-sea. Althoughparataxonomically classi!ed and generally rare, ichthyolithshave been used to interpret abundance and diversity of !shcommunities, and as biostratigraphic markers in otherwise barren,muddy sediments. Here we describe three teleost teeth from marlyshales (Crioceratites schlagintweiti Zone) and calcareous shales(Crioceratites diamantensis and Paraspiticeras groeberi zones) ofthe Lower Cretaceous (Hauterivian) Agua de la Mula Member (AgrioFormation), which formed in a mixed siliciclastic-carbonate marinehomoclinal ramp system, under low energy and dysoxic conditions.Specimens were picked from three washing residues (90 g totalweight) that yield foraminiferal assemblages with low abundanceand species richness. The specimens are between 0.5 and 1.5 mmlong, triangular in outline, and have a smooth external surface withstraight margins. Adopting the system of morphological descriptorsfor ichthyoliths, the specimen with "attened cusp and circular sectionin occlusal view can be referred to type a8/b1/c1/d1, while two teethshowing acute cusps and with sub-oval and acute laterally section canbe referred to types a9/b1/c5/d2/e1/f1/g1/h0 and a9/b2/c5/d2/e4/f3/g1/h0, respectively. The new material enriches the poor vertebratefossil record of the marine members of the Agrio Formation, to datecomposed of scattered remains of marine ?reptiles?, pycnodontiform!shes, hybodont and lamniform sharks, and adds further faunalcomponents exploiting di#erent, as yet unrecorded, niches.