Indonesia's Living Fossils

By Donald L. Blanchard
Editor: The Cold Blooded News

This article was originally published in The Cold Blooded News, the newsletter of the Colorado Herpetological Society, Vol 26, #2, February, 1999.

Just as I was becoming desperate to find a lead article for an issue of the Cold Blooded News, I chanced upon two interesting articles about unusual and largely unknown reptiles. Both articles were too long to reprint, and one was copyrighted so I couldn't use it anyway.

The first article was in the January, 1999 issue of The Tortuga Gazette, the newsletter of the California Turtle and Tortoise Club, and concerned the Papua, or Pig-nose Turtle (Carettochelys insculpta) of Papua New Guinea. This article was written by Thomas Schultze-Westrum, was originally published in German, and translated by Paul Gritis at Lehigh University, PA. The other article, by Robert G. Sprackland, was in the March, 1999, issue of Reptiles Magazine, and was on the Earless Monitor Lizard (Lanthanotus borneensis) from the Sarawak region of northern Borneo. Both reptiles are the sole living representatives of their respective families.

The Pig-nose turtle is classified in the Family Carettochelyidae, which is known to have occurred back in the Early Cenozoic through Eurasia and North America. Its closest living relatives are the soft-shelled turtles of the Family Trionychidae. Like soft-shelleds, it has a soft dorsal skin over its carapace, and in the case of the Pig-nose, the skin is very tender and full of blood vessels, which may aid in respiration. Unlike soft-shelled turtles, Carettochelys has flippers instead of feet! A strong swimmer, the turtle's primary habitat is the Fly River of Southern New Guinea. [An editor's note in the CTTC article states that its range has been extended to include a small area in Northern Territory, Australia.] Like sea turtles, to which it is not closely related, the Pig-nose turtle apparently only leaves the water to lay eggs. They range from the salt water in the tidal zone at the mouth of the Fly, through the brackish waters of its delta, and into fresh water far upstream.

The Pig-nose is not as strong a swimmer as sea turtles, but better than other aquatic turtles. The article's author speculated that it may dwell primarily in the calmer, murky waters at the bottom of the river. It's flippers are softer and more flexible than those of marine turtles, and the first two digits bear strong, broad claws. These claws are used by the turtle to hold food while chunks are bitten off with its strong jaws, or torn off by laterally shaking the forelimbs. The author offered captives green, leafy vegetables, fruit, chunks of meat, worms, snails, and young mice, but observed that they showed little interest in live fish.

Carettochelys is described as a muddy brownish gray above, with wrinkled skin, and lighter on its underside. The record length for the species is reported to be 18 inches.

The Earless Monitor of Borneo is the sole member of Family Lanthanotidae, although for a long time it was included with the Gila Monster and the Mexican Beaded Lizard in the Family Helodermatidae, because of its beaded skin. It is now considered to be more closely related to Monitors, although lying somewhere between the two. Lanthanotus borneensis was first discovered in 1878, and the type specimen still remains well preserved in a museum in Vienna. Although considered to be quite rare, a surprising number of them can be found in museums around the world.

Little is known of the Earless Monitor's life history, nor is it known whether they are truly rare in their native habitat. Although primarily a land dweller, most known specimens were captured in fishing nets while swimming. Too small to be considered a food source (the type specimen is 17 inches, the record, 20), the lizard is of little interest to the Borneo natives. Orange-brown on top, without any spots or bands, and a mottled rusty orange and ochre underside, it is, as the author puts it, "not what one would consider an impressive animal." Unusual features include earlessness, a flat head, small beady eyes, translucent white windows in the eyelids, recurved teeth, short, stocky legs with well developed claws on all feet, and a slender, sinuous body covered with a mixture of large and small tubercles. The larger of these scales form rows that run from the neck down the back and to the tip of the tail.

If the attributes above suggest to you that this animal may be adapted for a fossorial (burrowing) lifestyle, you can pat yourself on the back. In fact, this can easily account for their perceived scarcity. The article's author speculates that they may spend most of their time deep underground, for they are rarely found when tilling gardens. If their habits are anything like their Helodermatid relatives, they could spend only a small percentage of their time above ground in search of food. (Also see the article on Savanna Monitors in the November, 1998, Cold Blooded News, wherein it was observed that Savanna Monitors only feed during about four months out of the year.)

If the same attributes suggest that this might be related somehow to snakes, this too has been proposed. So far, however, there is little evidence that Lanthanotids might be ancestral to snakes. The only known fossil relative was recently discovered from 75 million year old (Late Cretaceous) deposits in the Gobi desert of Mongolia. The remains indicate that Lanthanotus has changed little in that span of time, thus making the Earless Monitor truly a living fossil. (Snakes are also known from the Late Cretaceous, but snakes don't preserve well, and the remains found so far shed little light on the question of snake origins.)