INSIDE PSEUDOSEISUROPSIS NEHUEN’S SKULL: DETAILS OF THE NEUROANATOMY OF A PLEISTOCENE FURNARIIDAE (AVES, PASSERIFORMES) FROM ARGENTINA

DEMMEL FERREIRA, MARÍA MANUELA; DEGRANGE, FEDERICO JAVIER

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Congreso; XXXV Jornadas Argentina de Paleontología de Vertebrados; 2022

The South America fossil record of Passeriformes is scarce, hence the available information abouttheir characteristics and phylogenetic relations is limited and challenging, especially regarding theirskull and endocast (a proxy of the brain morphology). Pseudoseisuropsis nehuen is a fossil species from the Miramar Formation (early-middle Pleistocene) of Miramar, Buenos Aires province, Argentina. This taxon is included in Furnariidae, one of the most diverse Neotropical passerines, although its relation with other furnariids is still discussed. We aim to describe the endocranial anatomy of this species and compare it with other Furnariidae in order to infer ecological and phylogenetic aspects. Brain 3D modelling was performed based on micro-CT scans obtained from the holotype specimen (MLP-69- XII-3-9) in a Bruker Skyscan 1272 available at the “Facultad de Odontología” of the “Universidad de Buenos Aires”. The endocast agrees with an airencephalic type of brain. The telencephalon is wider than longer and dorsoventrally compressed, as is typical of furnariids. The olfactory bulb is wide and short, although its boundaries are not well anatomically demarcate thus they are not easy to identify in the 3D image. The eminentiae sagittales (wulsts) are wide and subtriangular. There are two small but conspicuous protuberances caudally to the wulsts, disposed at each side of the fissura interhemispherica, as observed only in Lepidocolaptes angustirostris. The cerebellum’s overall shape is similar to that of Pseudoseisura lophotes. It is longer than wider and there are seven visible folds, like in Furnarius rufus. The contact with the telencephalon has an “U” shape, as in L. angustirostris, Coryphistera alaudina, P. lophotes and F. rufus. The flocculi are short, stout, rostrally curved, as in most Furnariidae. The elliptical and rostrally projected optic lobes are dorsally overlapped by the telencephalic hemispheres. Their contact with the telencephalon draws a curved line, similar to L. angustirostris. Cranial nerve I is small and each branch has an independent origin. Regarding the vasculature, there is no intercarotid anastomosis as in all Furnariidae. Of all the endocasts here compared, the endocast of L. angustirostris, a scansorial Dendrocolaptine (Furnariidae) that feeds mainly on insects, is the one that resembles the most to P. nehuen. This allow us to think that P. nehuen is phylogenetically related to the subfamily Dendrocolaptinae, as mentioned in previous phylogenetic hypothesis, and that it may share its locomotion and feeding behaviour.