Deinonychus(?) egg description

[bh480@scn.org]

From: Ben Creisler bh480@scn.org

In case this paper has not been mentioned yet:

Gerald Grellet-Tinner and Peter Makovicky, 2006. A 
possible egg of the dromaeosaur Deinonychus antirrhopus: 
phylogenetic and biological implications

Canadian Journal of Earth Sciences  43(6): 705-719 (2006) 


Abstract: A unique find of a partial egg in contact with 
articulated gastralia from a known specimen of the 
dromaeosaurid Deinonychus antirrhopus (AMNH 3015) is 
described. Much of the original taphonomic context of the 
specimen was lost during the 1931 excavation and 
preparation, but enough information is preserved to 
provide strong evidence for a parental association between 
the adult skeleton and egg. The articulated nature of the 
gastralia suggests that the adult skeleton was at least 
partially articulated and had not suffered from either 
extensive subaerial exposure or postmortem transport, and 
the egg preservation also indicates in situ burial and 
postburial lithogenic crushing. Additional support stems 
from the presence of limey claystone matrix that indicates 
a low-energy depositional event. Phylogenetic 
characteristics of the eggshell microstructure are 
consistent with a theropod origin, and 
skeletochronological analysis suggests that AMNH 3015 was 
an adult and thus of breeding age bolstering the 
interpretation that the egg derives from the skeletal 
specimen. Physiological parameters of D. antirrhopus, such 
as estimated mass and pelvic canal diameter, as well as 
eggshell thickness, are very similar to the similar sized 
and closely related oviraptorid Citipati osmolskae. 
Closely related maniraptoran theropods of several species 
have been found brooding their nests with the gastralia 
close to or in contact with eggs, and such a scenario is 
consistent with the preservation of AMNH 3015. Alternative 
explanations to a parental association, such as random co-
occurrence or feeding, are improbable given the taphonomic 
and biological data of the find. AMNH 3015, therefore, 
probably represents the first identifiable dromaeosaurid 
egg yet discovered. It shares derived characters such as 
two eggshell layers with other theropods. Within 
theropods, the AMNH 3015 eggshell shares derived 
characteristics with oviraptorids and differs from 
troodontid eggshell despite the fact that these taxa are 
often recovered as sister groups in analyses of skeletal 
characters, but this signal is weak.