NH Notes: Fossil Wasp Cocoons in Dinosaur Eggs – Evidence of a Complex Ecology

What happened to huge dinosaur eggs that were either abandoned or broke prematurely?  You might think that this is a question that is impossible to answer, but dinosaur eggs have been discovered with intriguing evidence of scavenging of various forms.   I recently came across a report from 2011 that I thought was especially interesting because it provides indirect, but compelling, evidence of a complex ecology that existed during the time of the dinosaurs.   Today there are a number of insects and other organisms that specialize in feeding on eggs of reptiles and birds.  These include beetles and spiders that are attracted to old eggs either to feed off the eggs or to predate on other insects attracted to the eggs.   One of the most complex relationships involves parasitic wasps that lay eggs on the back, or inside, of spiders or other insects which hatch and then burrow into the host and consume them from the inside eventually using their carcass for their own cocoons to produce new wasps.

A very interesting fossil was found in Patagonia that suggests these very complex relationships between eggs, insects/spiders and wasps were present at the time of the dinosaurs.   Here is the abstract from the paper by Genise and Sarzette entitled “Fossil cocoons associated with a dinosaur egg from Patagonia, Argentina:”

Several fossilized wasp cocoons visible here in this titanosaurus egg.  Image:  SARZETTI (co-author of the paper describing this finding)
Several fossilized wasp cocoons visible here in this titanosaurus egg. Image: SARZETTI (co-author of the paper describing this finding)

Abstract:  Eight fossil (Cretaceous) insect cocoons were discovered within the infillings of a broken dinosaur egg of a clutch from a Patagonian locality. Cocoons are considered to be in situ based on detailed preservation of thin, delicate walls with surface texture, infillings that are similar to the surrounding rock matrix and the clustered distribution of cocoons in only one egg out of the clutch of five eggs. According to the shape, size, and thin wall with surface texture, the cocoons are interpreted as having been produced by wasps. The wasps may have been attracted to the egg because of the presence of scavenging insects feeding on the decaying organic matter, or they may have been attracted to spiders feeding on the scavenging insects. In either scenario, after attacking the insects or spiders inside the sand infillings of the egg, the wasp larvae produced the cocoons described herein. The presence of wasps, which are at the top of the scavenging food webs, suggests that a complex community of invertebrates would have developed around rotten dinosaur eggs.

So these fossilized cocoons inside preserved broken dinosaur egg provide a glimpse into the ecology of the time when this egg was laid.  That ecology is one in which there are very likely multiple levels of scavenging and predation occurring in this one location.

Yet Another Challenge to Young Earth Creationist’ Flood Geology Models

This fossil caught my eye because it illustrates and supports an observation I made a year ago about preserved dinosaur nests in two posts:  Juvenile Dinosaur Fossils in a Next: Testimony to Rapid Burial but not by a Flood and Fossil Eggs, Nests, Floods and Stressed Pregnant Dinosaurs.  In these I noted that dinosaur nests from Mongolia were found in layers of rock sitting on top of 20,000 feet of layers fossil-bearing rock.  As a result young earth creationists have had to result to some very creative story telling to find a way for dinosaurs to have been roaming the land after 20,000 feet of sediments had already been deposited in global flood. They claim (see prior posts for references) that pregnant dinosaurs which had been treading water and running up mountain to escape the global calamity wandered onto layers or newly deposited sediments and being so stressed out found any place they could to simply lay their eggs.  Hours or days later, those locations would have been covered by the continuing global events that eventually even killed the parents and covered over the nests with fresh sediments quickly preserving them for us today.

As implausible as that might sound it makes even less sense when dinosaur nests are studied in detail such as the one above.  Young earth creationists paint a picture of half-crazed dinosaurs running around to escape the next giant wave washing new layers of sediments over the world and laying nests in barren sand layers and then running off to try to find higher ground.  What we find in this nest contradicts everything about this explanation.   Here we find that a well-organized preserved nest in which one of the broken eggs has these cocoons preserved in it. How did the cocoons get there?  Most likely from wasps living on organisms that were scavenging the eggs.  How did these scavenging insects find this nest during this crazy flooding event in this barren environment?  On top of that, how does a tiny parasitic wasp survive the harrowing rains storms and water covering the earth and find itself where not only a dinosaur has laid its eggs but there is also a collection of insects it can infect? I might also add that today most parasitic wasps specialize on a particular species of insect or spider as its host and if this is the case in the past then what we have here is an incredible set of coincidences that all these members of this ecological unit are found together in one location in the middle of a chaotic world-wide catastrophe.  One would not expect the maintenance of complex ecological relationships to be maintained in the middle of a disaster and yet we see evidence of that in these eggs.

Fossil cocoons associated with a dinosaur egg from Patagonia, Argentina.  JORGE F. GENISE and LAURA C. SARZETTI,
13 JUN 2011 | DOI: 10.1111/j.1475-4983.2011.01064.x

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