Abstract
Studies of fossil nests and nesting sites provide information on the reproductive biology of
the egg-laying taxon that, otherwise, could not be evaluated by the study of skeletal remains.
However, only dinosaur and turtle nests and nesting sites have been described to date.
Here we report a hitherto unknown crocodylomorph nesting site in the Upper Cretaceous
Adamantina Formation at Jales, Southeastern Brazil. At least twenty egg clutches were found
in four distinct stratigraphic layers within an area of ≈0.15 km2. Morphological analyses
of the eggs and eggshells showed that all eggs can be assigned to the same egg type. Most
of the egg clutches were collected from the same layer, whereas few were collected from
three other layers, respectively 1.09 m under and 0.71 and 0.99 m above the main egg
layer. The minimum distance among egg clutches in the same layer is 1.8 m. The terrestrial
mesoeucrocodylian Baurusuchus was the only vertebrate recovered from the outcrop, with
three partially articulated specimens and several scattered remains found in close association
with the egg clutches. The maximum number of preserved eggs per clutch is five, and all
have been found with the main axis parallel to the ground. Eggshell fragments are frequent
inside the nests, randomly distributed within the egg clutches (concave up and concave
down percentages of 59% and 41%, respectively). Within the most complete eggs several
stacked eggshell fragments where found. These are interpreted as hatched eggs in which the
opening hole made by the hatchling also cracked the eggshell, producing additional eggshell
fragments that fell within the egg as the shell membrane detached from the inner surface of the egg. These data suggest that: a) most of the egg clutches were preserved in situ, without
any transport; b) this crocodylomorph species nested in colonies, returning to the same
nesting site periodically, and; c) nest fidelity in crocodylomorphs may have been present as
far back as the Late Cretaceous.
| Translated title of the contribution | A crocodylomorph nesting site from the Upper Cretaceous Adamantina Formation of Brazil |
|---|---|
| Original language | English |
| Title of host publication | Society of Vertebrate Paleontology 69th Annual Meeting, Bristol |
| Pages | 159A |
| Number of pages | 1 |
| Publication status | Published - 2009 |
Bibliographical note
Conference Proceedings/Title of Journal: Journal of Vertebrate Paleontology v29(3)Conference Organiser: Society of Vertebrate Paleontology / University of Bristol