Lindworms, also know as "Chinese dragons" and "lungs" are medium to large-sized creatures with short, powerful forearms but lack hindlimbs entirely. Although secretive and rarely seen, it's clear that lindworms are totally flightless, having no wings to speak of. At first glance, that fact may imply their relationship with dragons, rather than wyverns, as dragons have both forelimbs and wings. However, preliminary genetic comparisons between a dead lindworm recovered from China (in press) and a living wyvern and dragon show that, in fact, lindworms are genetically closer to wyverns than dragons. The obvious taxonomic implications are that lindworms are stem wyverns, sitting somewhere below true wyverns on the archosaur family tree, branching off before wyverns developed wings.
Given their rarity, lindworms are rarely studied. In fact, the first named wyvern is Lindwyrmus nychognathus from Argentina, and it was described only recently (Farke, 2005). Although it features plenty of its own peculiar anatomical features, Lindwyrmus is generally viewed as diagnostic of the entire group. Most impressively, Lindwyrmus is semi-arboreal, rather than semi-aquatic as lindworms are usually thought to be. Farke noted that the bright-green lindworm curls its serpentine body on a branch as would an anaconda or constrictor. The arms are used to help pull the animal up through the trees and clamber across the canopy. While the body is bright green, Lindwyrmus has bright orange flaps of skin on the arms and along the spine. These structures are usually draped across the body or arms, but when aggravated, the lindworm can "flare them up" and create a striking threat display. In fact, the flaps are structured by thin muscular rods akin to the actinofibrils of pterosaur wings.
The skull of Lindwyrmus is very distinctive. There are two pairs of cranial horns which point posteriorally behind the eyes. Two small nasal horns rise from the tip of the snout. The skull is dorsoventrally flattened. Unlike most dragons and wyverns, there is no "lip" around the teeth. Instead, the teeth erupt from the underlying skin as in crocodilians. Most interestingly, however, is the pair of laterally-placed, spike-like mandibles that boarder the mouth. These mandibles are mobile in two places: at the point of articulation with the skull itself and immediately behind the spike-like process. This novel structure seems to serve two purposes: first, it greatly increases the effect of the animal's threat display, and second, the mandibles actually impale prey while the mouth grips it. Bizarrely, the main articulation of the mandibles is a cup-like depression in the jaw just above the mandibular joint, and the proximal surface of the mandible is a ball joint. However, in life, the mandibles are limited to fore and aft movement. Exactly what environmental forces combined to create the need for such a strange structure is not understood. Incidentally, while the mouth is closed, the mandibles are held forward, overlying the exposed teeth and framing the face.
Lindwyrmus subsists on small vertebrates almost exclusively, though Harrison (2007), on a trip to Argentina's jungles, witnessed a pair of lindworms feasting on a dead hog. He was unable to determine whether the lindworms actually killed the hog or were simply scavenging on it. Both he and Farke were unable to tell males from females, and Harrison commented that, generally, lindworms seemed to be solitary animals. Neither man saw juvenile animals, which is unfortunate. It would interesting to see whether juveniles and subadults also posess the strange mandibular array that adults do. Farke estimated the total length of an adult Lindwyrmus at "about twenty feet," though he left open the possibility that larger individuals existed.
Farke said a recent draconology conference that he intends to travel back to Argentina to further observe Lindwyrmus and hopefully find some juvenile animals. Other workers, perhaps inspired by Farke's work with Lindwyrmus, are traveling to Asia to track down other species of lindworm. Hopefully, this little-known branch of the wyvern family tree will soon be better understood!
Farke, A. (2005). The first description of a "lindworm," from the jungles of Argentina. European Journal of Draconology 106(2): 245-258.
Harrison, M. A. (2007). Observations on Lindwyrmus nychognathus (Farke 2005). Draconium 48(3): 402-405.