Argentinian unhatched pterosaur fossil.

CHIAPPE, L.M., L. CODORNIÚ, G. GRELLET-TINNER AND D. RIVAROLA

NATURE

Nature Publishing Group

Lugar: Inglaterra; Año: 2004 vol. 432 p. 571 - 572

0028-0836

Our knowledge of the eggs and embryos of pterosaurs, the Mesozoic flying reptiles, is sparse. Until now, the recent discovery of an ornithocheirid embryo from 121-million-year-old rocks in China constituted the only reliable evidence of an unhatched pterosaur. Here we describe an embryonic fossil of a different pterosaur from the Early Cretaceous lacustrine deposits of Loma del Pterodaustro (the Lagarcito Formation, which is about 100 million years old) in central Argentina. The new fossil provides insight into the eggshell morphology, early growth and nesting environments of pterosaurs. The specimen (MHIN-UNSL-GEO-V 246) is split into two slabs, with its articulated bones preserved as an aggregate in an oval shape. The relatives sizes of limb elements of the specimen, which give an estimated wingspan of 27 cm, are similar to those of early juvenile specimens of Pterodaustro and agree well with allometric observations based on a growth series of this taxon indicating negative and positive allometry for the proximal (humerus and ulna) and distal (metacarpal IV) portions of the wing, respectively. No information on egg morphology was recovered with the previously reported pterosaurian embryo from China. Our specimen, however, shows that pterosaurs shared with extant archosaurs and chelonians an eggshell composed of an single layer of juxtaposed carbonatic crystals, but they differed from chelonians in that they laid calcitic eggs with blade-shaped crystals. The association of the specimen with remains of early juveniles, subadults and adults of Pterodaustro agrees with previous inferences of parental care in pterosaurs.