Dinosaur egg illustration. Credit: University of Tsukuba
Fossilized eggshells from Gifu Prefecture, Japan, dating back to the Early Cretaceous duration, reveal formerly unidentified egg species from a little theropod dinosaur.
Dinosaurs left behind more evidence than just giant skeletons. Tiny eggshell pieces can provide insights into Mesozoic environments that fossils of bones and teeth do not. This is especially important for comprehending the smaller animals that were less most likely to be maintained. Early Cretaceous eggshell fragments, the oldest found in Japan, use a glimpse into the ecosystem of dinosaurs during this time duration.
The research study focused on seven eggshell fragments and six eggshell impressions, which were gathered from the Okurodani Formation in Gifu Prefecture between 1988 and 2009. Two of the eggshell pieces were identified as belonging to the Testudoolithidae household, a family of turtle egg fossils.
2 eggshell impressions belonged to indeterminate egg groups. Many of the egg product, including 5 pieces and 4 impressions, belonged to a new egg genus and species, which the scientists named Ramoprismatoolithus okurai.
The researchers carefully analyzed the physical characteristics of the eggshell fragments and impressions and carried out phylogenetic analysis (which examines the evolutionary development of a species, group of organisms, or a particular characteristic they have) to identify the type of dinosaur more than likely to have laid the eggs. According to study co-author Professor Kohei Tanaka, “The shell fragments of Ramoprismatoolithus are defined by a prismatic microstructure with branching ridges on the outer surface. Our analysis recommends an affinity with the troodontids, a group of little non-avian theropod dinosaurs.”
Fossils of the small raptor that laid the eggs have actually not yet been discovered in the Lower Cretaceous strata that yielded these fossils. As very first author Rina Uematsu explains, “Based on the measurements of the egg fragments, we calculated that the adults of the maniraptoran types that laid them would have weighed about 12 to 17 kgs. The discovery of little maniraptoran eggs of this age in Japan likewise extends the temporal and geographical series of these small, non-avian theropods to the middle of the Early Cretaceous of the eastern margin of Asia.”
The turtle eggshells expose the presence of small-sized non-marine turtles that can be ascribed to previously acknowledged skeletal remains from the strata where they were found.
Together, these findings show the worth of even tiny, fragmentary eggshells in rebuilding ancient communities, specifically the presence of smaller animals that might be underrepresented in the skeletal fossil record.
Referral: “Fossil eggshells from the Early Cretaceous Okurodani Formation, northern main Japan” by Rina Uematsu, Kohei Tanaka, Shohei Kozu, Shinji Isaji and Shizuo Shimojima, 24 November 2022, Historical Biology.DOI: 10.1080/ 08912963.2022.2142910.
The research study was moneyed by the Japan Society for the Promotion of Science..
The study focused on 7 eggshell pieces and 6 eggshell impressions, which were collected from the Okurodani Formation in Gifu Prefecture between 1988 and 2009. Two of the eggshell pieces were determined as belonging to the Testudoolithidae family, a family of turtle egg fossils.
The scientists thoroughly evaluated the physical attributes of the eggshell fragments and impressions and performed phylogenetic analysis (which analyzes the evolutionary advancement of a types, group of organisms, or a particular characteristic they have) to determine the type of dinosaur most likely to have actually laid the eggs. Fossils of the small raptor that laid the eggs have actually not yet been discovered in the Lower Cretaceous strata that yielded these fossils.