MICRORAPTOR WITH INGESTED LIZARD PRESERVED IN SITU AND PRELIMINARY RECONSTRUCTION OF THE JEHOL FOOD WEB

Direct indicators of diet and predator-prey relationships are exceedingly rare in the fossil record. However, it is through such traces that we can best understand trophic interactions in ancient ecosystems, confirm dietary inferences derived from skeletal morphologies, and clarify behavioral and ecological interpretations. A previously unrecognized species of lizard was found in the abdomen of a specimen of Microraptor. The lizard is largely complete and articulated confirming the current perception of Microraptor as an agile opportunistic predator that, like extant reptiles including raptorial birds, ingested small prey whole and head first. The lizard can be readily distinguished from previously recognized Early Cretaceous species based on its unusual widely spaced and brachydont dentition. Phylogenetic analysis suggests Indrasaurus wangyuani gen. et sp. nov. is a basal scleroglossan closely related to the slightly older Liushusaurus. Comparison of ingested remains preserved across Paraves suggests that dromaeosaurids retained the plesiomorphic condition in which ingested prey were fully digested, rather than egested, as has recently been demonstrated was the case in the probable troodontid Anchiornis. This supports a closer relationship between Aves and Anchiornis but also suggests that flight did not precipitate the evolution of pellet egestion in Paraves. This specimen represents the 20th trophic link known from direct evidence in the Jehol Biota. We reconstruct a preliminary food web of this ecosystem, representing the first step towards a greater ecological understanding of this important Biota.