Lizard Forefoot Found Preserved in Dominican Amber
The left forelimb of an anole lizard (genus Anolis) has been found perfectly preserved in a piece of Miocene-Epoch amber from the Dominican Republic.
“Vertebrate inclusions in amber are very rare, the majority are insect fossils,” said Jonas Barthel, a doctoral student in the Institute for Geosciences at the University of Bonn.
Barthel and colleagues found the left forelimb of the Anolis lizard in a 2-cm piece of 15-20-million-year old Dominican amber.
“The claws and toes are very clearly visible in the honey-brown amber mass, almost as if the tree resin had only recently dripped onto them — yet the tiny foot is about 15 to 20 million years old,” they said.
The researchers examined the specimen by micro-Raman spectroscopy, electron microprobe, and time-of-flight secondary ion mass spectroscopy.
The analyses revealed that the forefoot is broken in two places and that one of the fractures is surrounded by a slight swelling.
“We propose the following model for our observations,” the scientists said.
“While climbing the tree, the lizard got into contact with a flow of resin and could not escape its sticky trap.”
“After some time, it attracted the attention of a predator that ripped off the lizard, leaving solely the fore limb in the resin. Later on, the resin hardened and became deposited within the surrounding soil which represents the starting point of its diagenesis.”
“The presence of ‘Schlauben’ (a succession of flows), the splintered humerus, the edema, the peeled off parts of the skin, and lastly the numerous air bubbles strongly support this model.”
The Raman spectroscopy revealed that mineral hydroxyapatite in the bone had been transformed into fluoroapatite by the penetration of fluorine.
“This is surprising, because we assumed that the surrounding amber largely protects the fossil from environmental influences,” Barthel said.
“However, the small crack may have encouraged chemical transformation by allowing mineral-rich solutions to find their way in.”
The Raman spectroscopy also showed that collagen — the bone’s elastic component — had largely degraded. Despite the seemingly very good state of preservation, there was actually very little left of the original tissue structure.
“We have to expect that at least in amber from the Dominican Republic, macromolecules are no longer detectable,” said Professor Jes Rust, also from the Institute for Geosciences at the University of Bonn.
“It was not possible to detect more complex molecules such as proteins, but the final analyses are still pending.”
“The degradation processes in this amber deposit are therefore very advanced, and there is very little left of the original substance.”
The findings were published in the journal PLoS ONE.
H.J. Barthel et al. 2020. Fluoridation of a lizard bone embedded in Dominican amber suggests open-system behavior. PLoS ONE 15 (2): e0228843; doi: 10.1371/journal.pone.0228843