NOT Just Another Lizard!

Spent the morning writing a test and the afternoon giving it. Since it was partly on evolution, here's a favorite bit of that topic:

Tuatara (Sphenodon punctatus), St. Louis Zoo, St. Louis, MO 3/2/2012

This little guy lives in a nice enclosure in the corner of the St. Louis Zoo's reptile house, where I heard someone dismiss him as "just another lizard." (Although  I don't quite get why you would go into a reptile house if you don't like lizards.) But he isn't a lizard at all! In fact, the vipers in another part of the house have a better claim to the title lizard, as they actually split off from one of the two branches of lizards at least 50 million years more recently than the last common ancestor of this guy and all of the lizards and snakes.

So what is he? A Tuatara (Sphenodon punctatus). He belongs to one of two species of Rhynchocephalians left, the other being the congener Sphenodon guntheri. During the early Mesozoic era, however, Rhynchocephalians were a diverse, wide ranging (1) and very successful group, filling niches similar to many of our modern lizards, and even including a marine form, Pleurosaurus.

Modern Tuatara are limited to New Zealand, where they were widespread before human settlement. By the time Europeans arrived, they were limited to a few offshore islands. There is some evidence that the Maori used them for food, but they also brought rats to the islands, and recent evidence from islands with Tuatara suggests that while rats don't eat adult Tuatara, they do eat eggs and juveniles. (2,3) Over a long enough time, this could easily cause the extinction of a species. Fortunately for modern conservation efforts, Tuatara live a long time and can reproduce for decades. So we have time to deal with rats on those islands they've colonized.

On the other hand, S. guntheri was only described as a separate species in 2008, and it's only known from one island (North Brother Island). Since 4 islands have lost their Tuatara completely in recent years, we could easily have lost this species before we knew we had it. (4)

In 2005, an attempt was made to introduce them back onto the North Island. In 2009 the first mainland hatchling in over 200 years was found - a bit of very good news for one of our last reminders of the age of the dinosaurs!

(1) Reynoso, V. H. (1996). A Middle Jurassic Sphenodon-like sphenodontian (Diapsida: Lepidosauria) from Huizachal Canyon, Tamaulipas, Mexico. Journal of Vertebrate Paleontology, 16(2), 210-221.

(2) Cree, A., Daugherty, C. H., & Hay, J. M. (1995). Reproduction of a rare New Zealand reptile, the tuatara Sphenodon punctatus, on rat‐free and rat‐inhabited islands. Conservation Biology, 9(2), 373-383.

(3) Newman, D. G. (1988). Evidence of predation on a young tuatara, Sphenodon punctatus, by kiore, Rattus exulans, on Lady Alice Island. New Zealand journal of zoology, 15(3), 443-446.

(4) Daugherty, C. H., Cree, A., Hay, J. M., & Thompson, M. B. (1990). Neglected taxonomy and continuing extinctions of tuatara (Sphenodon).