Guest Post: 150 Years Not a Lizard

This month marks 150 years since the iconic New Zealand tuatara was recognised to be the only living member of a distinct reptile lineage entirely separate from lizards and snakes.

Albert Günther, a zoologist was the first to recognise that the tuatara could not be grouped under the classification of “lizard”. His detailed anatomical description in 1867 revealed several features of the skeleton that set it apart such as the presence of a second row of upper teeth located parallel and just inside to the outer row. He placed it into a new group (Rhynchocephalia) which he regarded to have equal rank to lizards, snakes, crocodiles, and turtles.

The tuatara had been first described in 1931 and received its full name in 1842 but it wasn’t examined very closely and was simply considered a type of lizard. Genetics and fossils have confirmed Günther’s insightful conclusion, and we now recognise that the tuatara as the sole survivor of a once diverse lineage that shared a common ancestor with the group that includes lizards and snakes (Squamata) over 240 million years ago.

As the only living evolutionary cousin to over 10,000 species of snakes and lizards (Squamata), the tuatara has played a pivotal role for understanding the evolution and development of vertebrates. Often tagged with the misleading and unhelpful phrase “living fossil”, or “basal lepidsoarus”, the tuatara has attracted an enormous body of research and is a keystone organism for many evolutionary studies of vertebrate anatomy, development, and function.

For example, despite startling variation amongst the external genitals of amniotes, embryonic tuatara were critical for showing that all amniotes share developmental traits indicative of a single origin for this anatomical component. Similarly, a recent survey of tuatara specimens using X-ray micro Computed Tomography recently clarified which of the bony structures associated with joints (such as the knee cap) in lizards and tuatara were inherited from a common ancestor and which are relatively new. Its frame-like skull has led the tuatara becoming a model organism for biomechanics showing for example that the connective tissue between bones is important for redirecting stresses sustained during biting.

The tuatara also has an unusual, for reptile, cold-adapted physiology, and it is remarkable too for its impressive lifespan; tuatara can breed when over 100 years old! The tuatara is considered to be very reliant on its large eyes but increasing evidence suggests that scent may also be important to their life sensory tool kit. The unique heritage of the tuatara make it a key component of extant biodiversity and in turn the subject of intensive and innovative conservation research in New Zealand. It is also of special cultural importance to the Maori and the nation as a whole.

 

 

Writing in Nature, Marc Jones and Mark Hutchinson wish to draw attention to the 150 year anniversary. In Alison Cree’s recent book on the tuatara – a genuine tour de force – she describes 1867 as a “momentous” year for tuatara classification.

The anniversary is also recognised by an article in the Conversation by Marc. The article was featured in a daily email round up of the Conversation under Science and Technology.

There will be a dedicated celebration event hosted by the Royal Society of South Australia later this month.

Follow hashtag #150NotALizard to celebrate the anniversary online.

Marc Jones and Mark Hutchinson are currently working on a variety of projects together including measuring bite force and aspects of skull anatomy amongst Australian agamid lizards.