Juvenile pterosaurs (Pterodactyloidea: Pterodaustro guinazui) from the Lower Cretaceous of central Argentina

CODORNIÚ, L. AND L. M. CHIAPPE

CANADIAN JOURNAL OF EARTH SCIENCES

NRC Research Press

Lugar: Canadá; Año: 2004 vol. 41 p. 9 - 18

0008-4077

We report on two juvenile specimens of Pterodaustro guinazui, a medium-sized, filter-feeding pterodactyloid pterosaur from the Lower Cretaceous (Albian) lacustrine deposits of the Lagarcito Formation of central Argentina (Sierra de Las Quijadas, San Luis Province). Both specimens lack the skull but one is otherwise nearly complete and articulated; the other is more fragmentary. Their small size (~ 300 mm of wingspan), the lack of fusion of several postcranial bones, the minimal epiphyseal ossification, and the porous appearance of the periosteal surfaces, indicate the specimens died at a very early stage of postnatal development. The presence of derived characters unique, within Pterodactyloidea, to Pterodaustro guinazui (e.g., caudal vertebrae exceeding 16 elements) supports the proposed specific identification of the specimens. The new material provides anatomical information previously unknown for Pterodaustro guinazui and sheds light on allometric transformations during the growth of this pterosaur. Comparisons with more mature and much larger individuals support two major allometric trends: (1) the negative allometric growth of the proximal portion of the forelimb and (2) the positive allometric growth of the metacarpal IV.