MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
Huncalotis, an enigmatic new pectinoid genus (Bivalvia, Late Jurassic) from South America
LEANZA, H.A.; DAMBORENEA, S.E.
Lugar: HEIDELBERG; Año: 2016 vol. 90 p. 449 - 449
The extensive outcropsof the Late Jurassic-Early Cretaceous Vaca Muerta Formation black shales andmarls in the Neuquén Basin have yielded very few bivalves, and these are notwell-known. The material described here was collected in central Neuquén, from lateTithonian calcareous levels within the black shales, between beds with Substeueroceras sp. and with Argentiniceras noduliferum (Steuer). Thematerial is referred to the new genus Huncalotisand to the new species H. millaini. Thestrongly inequivalve shells, the ligamental area with a triangular slightlyprosocline resilifer, the right valve with ctenolium and a very deep byssalnotch, and the lack of radial ornamentation, make the shell of this new genus strikinglysimilar to the Triassic pectinid Pleuronectites.This resemblance may be due to either phylogenetic relationships or convergence.Obliquipecten peruanum Riverafrom central Peru is tentatively referred to Huncalotis. The Neuquén specimensare found in two main preservation types. Most of the material occurs in shellpavements, with equally abundant right and left valves and a wide size range, within?beef? or ?sandwich concretions?. These specimens are commonly complete butdisarticulated, and show radial fractures orientated at right angles to theshell margins. A few specimens were found on the outside of large calcareousconcretions within black shales; these are often articulated, complete shells,which preserve the original convexity of the valves. In some cases these articulatedshells seem to be associated with large ammonite shells, suggesting anepibyssate (possibly also pseudoplanktonic) life style.