INVESTIGADORES
NICOLI Laura
congresos y reuniones científicas
Título:
A new Eocene broad-headed frog from Patagonia: testing the effect of hyperossification on the reconstruction of Anuran phylogeny.
Autor/es:
GÓMEZ, R.O.; BÁEZ, A. M.; NICOLI, L.; MUZZOPAPPA, P
Lugar:
Londres
Reunión:
Congreso; 69th Annual Meeting Society of Vertebrate Paleontology; 2009
Resumen:
We report on the discovery of anuran remains in the lacustrine layers of the Ventana Formation that have yielded the highly diverse flora of Río Pichileufú (RP), Rio Negro Province, northwestern Patagonia, Argentina. Radiometric ages of tuff beds from this succession indicate a depositional age of 47.46 ± 0.05 Ma (middle Eocene, Lutetian). A single specimen that consists of an incomplete articulated skeleton (SVL ca 110 mm) is considered to represent a new taxon. One of the most conspicuous features of this frog is its wide, heavily ossified skull whose roofing bones have a pit-and-ridge sculpture. The combined presence of eight presacral vertebrae bearing equally developed transverse processes, bicondylar articulation between the sacrum and urostyle, slightly dilated sacral diapophyses, and a long scapular shaft precludes referral to an “archeobatrachian” taxon and, conversely, is consistent with neobatrachian affinity. The overall morphology of the skull recalls that of other broad-headed hyperossified frogs, such as the extant ceratophryines, Calyptocephalella, and Pyxicephalus, and several fossil taxa including the Late Cretaceous Baurubatrachus from Brazil and Beelzebufo from Madagascar, and the Paleogene Thaumastosaurus from Europe. However, the ornamentation pattern and different cranial and postcranial characters readily differentiate the anuran from RP from the aforementioned taxa. These taxa share many features, such as cranial exostosis and squamosal with extensive otic plate and zygomatic ramus, which have been widely used in morphology-based phylogenetic analyses. Notwithstanding, results of recent molecular analyses have made evident that this suite of characters may produce a misleading phylogenetic signal, calling for a more critical use of such characters; some of them may have developed in association with a broad, highly ossified skull. In order to assess the systematic position of the new taxon from Patagonia, we conducted several parsimony analyses based on available matrices based on morphology, and preliminarily explored the impact of some of the characters that a priori might reflect hyperossification rather than phylogeny.