Close Surface Cousin: Rhamphorhynchus
At The Earth’s Core , Chapter 4, Chapter 5, Chapter 8
Environment: Primarily dwells in their own underground cities.
She described the Mahars largely by comparisons. In this way they were like unto thipdars, in that to the hairless lidi.
About all I gleaned of them was that they were quite hideous, had wings, and webbed feet; lived in cities built beneath the ground; could swim under water for great distances, and were very, very wise.
Involuntarily I shrank back as one of the creatures approached to inspect us. A more hideous thing it would be impossible to imagine. The all-powerful Mahars of Pellucidar are great reptiles, some six or eight feet in length, with long narrow heads and great round eyes. Their beak-like mouths are lined with sharp, white fangs, and the backs of their huge, lizard bodies are serrated into bony ridges from their necks to the end of their long tails. Their feet are equipped with three webbed toes, while from the fore feet membranous wings, which are attached to their bodies just in front of the hind legs, protrude at an angle of 45 degrees toward the rear, ending in sharp points several feet above their bodies.
“A rhamphorhynchus of the Middle Olitic, David,” he said, “but, gad, how enormous! The largest remains we ever have discovered have never indicated a size greater than that attained by an ordinary crow.”
The method of communication between these two was remarkable in that no spoken words were exchanged. They employed a species of sign language. As I was to learn later, the Mahars have no ears, not any spoken language. Among themselves they communicate by means of what Perry says must be a sixth sense which is cognizant of a fourth dimension.
I never did quite grasp him, though he endeavored to explain it to me upon numerous occasions. I suggested telepathy, but he said no, that it was not telepathy since they could only communicate when in each others’ presence, nor could they talk with the Sagoths or the other inhabitants of Pellucidar by the same method they used to converse with one another.
“What they do,” said Perry, “is to project their thoughts into the fourth dimension, when they become appreciable to the sixth sense of their listener. Do I make myself quite clear?”
“You do not, Perry,” I replied. He shook his head in despair, and returned to his work.
“Life within Pellucidar is far younger than upon the outer crust. Here man has but reached a stage analogous to the Stone Age of our own world’s history, but for countless millions of years these reptiles have been progressing. Possibly it is the sixth sense which I am sure they possess that has given them an advantage over the other and more frightfully armed of their fellows; but this we may never know. They look upon us as we look upon the beasts of our fields, and I learn from their written records that other races of Mahars feed upon men—they keep them in great droves, as we keep cattle. They breed them most carefully, and when they are quite fat, they kill and eat them.”
The dominant race of Pellucidar, David, have not yet learned that men converse among themselves, or reason. Because we do not converse as they do it is beyond them to imagine that we converse at all. It is thus that we reason in relation to the brutes of our own world. They know that the Sagoths have a spoken language, but they cannot comprehend it, or how it manifests itself, since they have no auditory apparatus. They believe that the motions of the lips alone convey the meaning. That the Sagoths can communicate with us is incomprehensible to them.
“Once the males were all-powerful, but ages ago the females, little by little, assumed the mastery. For other ages no noticeable change took place in the race of Mahars. It continued to progress under the intelligent and beneficent rule of the ladies. Science took vast strides. This was especially true of the sciences which we know as biology and eugenics. Finally a certain female scientist announced the fact that she had discovered a method whereby eggs might be fertilized by chemical means after they were laid—all true reptiles, you know, are hatched from eggs.
“What happened? Immediately the necessity for males ceased to exist—the race was no longer dependent upon them. More ages elapsed until at the present time we find a race consisting exclusively of females…"
Edit: towards the end of Chapter 8 (“At the Earth’s Core”) we get pretty good description of them swimming and hypnosis powers. Hypnotizing victims into following them under water, where they nibble whole limbs off.