Source : Webster's Revised Unabridged Dictionary (1913)

Pentail \Pen"tail`\, n. (Zo["o]l.)
   A peculiar insectivore ({Ptilocercus Lowii}) of Borneo; -- so
   called from its very long, quill-shaped tail, which is scaly
   at the base and plumose at the tip.

Source : WordNet®

pentail
     n : brown tree shrew having a naked tail bilaterally fringed
         with long stiff hairs on the distal third; of Malaysia
         [syn: {pen-tail}, {pen-tailed tree shrew}]