Our knowledge of the evolution of anoles comes primarily from studying living forms and using information about how species are related (phylogenetic trees) to predict how traits such as their head shape have changed over time. Scientists often use this approach because there may be few (or no) actual fossils representing those stages in the evolutionary past. For anoles, this is no exception; the fossil history of our favourite lizards is sparsely recorded. Here I shall give you, Anole Annals readers, a brief overview of what we do know about anole ancestors and what we can learn from studying these fossils.
Fossil hunting history
In the box below I summarise the five papers that have published upon fossils of the genus Anolis.
Three of the specimens are lizards preserved (embedded) in amber from mines in the Dominican Republic – which according to George Poinar in his book is around 25 million years old. These specimens, therefore, are much older than the cave deposits Etheridge discussed, and so are even more important for our understanding of anole evolution.
(Keen anole annals readers will remember reading about amber before, although these papers present genuine Oligocene/Miocene lizards in amber!).
Recall that across the Greater Antilles Islands, anoles inhabit a variety of ecological niches (identified as ecomorphs; e.g. trunk-crown, crown-giant, twig, etc.). From these published papers we see that in the Pleistocene, Etheridge reported finding evidence of three ecomorphs, while the older Dominican Republic amber reveals only trunk-crown-like forms. One thing we intend to learn from studying fossil anoles is when the apparent modern diversity came about. Does the fossil evidence support hypotheses made from comparing living species? How are fossil and modern forms related? To do this we must study in detail the anatomy of these fossil lizards and compare them to modern species.
The most recent paper mentioned above is pivotal for this research because they CT scanned the fossil and showed this non-destructive imaging technique revealed a great deal of information about the anatomy of the lizard’s skeleton. Read more about that here.
I have been fortunate enough to track down a number of yet unpublished fossils (anoles preserved in amber). The future in studying anole fossil history will be in trying to solve what species these fossils are, to what (if any) ecomorph they belong, so as to help answer the question of when anoles ecologically diversified and better understand the evolution of the group. More to come on this in the near future….!
- 20-Million-Year-Old Fossils Reveal Ecomorph Diversity in Hispaniola - July 27, 2015
- Anolis proboscis: Ugly and Famous - September 5, 2014
- The Fossil Species Anolis electrum Gets an X-ray Makeover - August 14, 2014
Jean-Michel D
Wow, what a great post! Your work will certainly make some waves. Have any anole fossils been uncovered in the Lesser Antilles or South America?
Emma Sherratt
Thank you, yes I am very much enjoy this jaunt into anole paleo. To my knowledge, no they haven’t. The fossils so far are from Mexico and Dominican Republic only. South America is exporting copal, a non-fossilised tree resin (amber is fossilised), and invertebrate and vertebrate inclusions are known from copal. No anoles have yet been described from this, but let’s never say never!