 Reference Base  Palpebral vibrissae in the Sumatran rhinoceros (Didermoce... |
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World |
| Subject: |
Anatomy - Head |
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All Rhino Species |
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The erroneous notion that palpebral vibrissae (eyelashes) are wanting from the lower eyelid of the Rhinocerotidae is attributable to Pocock (1914), whose observations were apparently made on museum skins and mounted specimens only. Examination of living and of freshly dead specimens shows such vibrissae to be present upon both eyelids in three of the five extant rhinoceros forms, viz. Rhinoceros unicornis, Diceros bicornis, Ceratotherium simum (Cave, 1969; Van den Bergh, 1970). Reviewing the subject of rhinoceros epidermal appendages Cave (1969) referred to lower eyelid vibrissae as ?doubtless present' in the two remaining (and rarer) rhinoceros forms - Didermocerus sumatrensis and Rhinoceros sondaicus, no example of either having been specifically examined to date.
Now, however, the presence of both upper and lower eyelid vibrissae is established for Didermocerus sumatrensis, since these structures are plainly observable in the fresh carcase of an adult female Sumatran rhinoceros (?Subur') which died recently in the Copenhagen Zoo, as the then sole specimen of its kind in captivity. The animal was captured as an adult by the Copenhagen Expedition of 1959, near the Siak River, Central Sumatra and for over 12 years (December 1959 to February 1972) lived in the Copenhagen Zoo: at death it was probably at least 15 years old.
The upper eyelid vibrissae of this animal are thick, fairly stiff hairs, about 10 mm long, implanted without particular density upon the lid margin; the lower eyelid vibrissae are much less prominent, and are generally much shorter and thinner hairs, though some attain 10 mm in length. Thus eyelid vibrissa arrangement in Didermocerus is essentially similar to that recorded (Cave, 1969) for Rhinoceros unicornis, Diceros bicornis and Ceratotherium simum, the lower eyelid, in all four forms, manifesting a distinct complement of vibrissae. The presumption is, therefore, that lower eyelid vibrissae are likewise present in the fifth extant rhinoceros form - the now vanishing Rhinoceros sondaicus.
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