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< > APPEARANCE/ MORPHOLOGY: HEAD AND NECK with literature reports for the Bonobo - Pan paniscus: Use sub-contents list below, or simply scroll down the page to view findings.

Face of a Pan paniscus - Bonobo First tooth appearing in an infant bonobo. Click here for full page view with caption

HEAD AND NECK - Editorial Comment

Editorial Comment

(Editorial Overview Text Replicated on Overall Species page - Pan paniscus - Bonobo

GENERAL HEAD STRUCTURE:
Adult:
Bonobos have a relatively high and rounded forehead with a small brow ridge, relatively small ears, and long hair on the sides of the head. The skull is longer than it is broad, but the skull is more rounded and globular than in Pan troglodytes; cranial capacity is slightly lower.
Newborn: --

DENTITION:
Adult:
Dental formula i 2/2, c 1/1, pm 2/2, m 3/3 (x 2, total 32 teeth). There is no sexual dimorphism in tooth size except for slightly longer, broader canine teeth in males. 
Newborn:
 The deciduous dental formula is i2/2, c 1/1, dm 2/2. 

EYES:
Adult:
Bonobos have brown eyes.
Newborn:
--

(References are available in detailed literature reports below)

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General Head Structure

Adult

SUMMARY: Bonobos have a relatively high and rounded forehead with a small brow ridge, relatively small, rounded, hairless ears, and long hair on the sides of the head. The skull is longer than it is broad, but the skull is more rounded and globular than in Pan troglodytes; cranial capacity is slightly lower.
  • The skull is longer than it is broad. (B147)
  • Brain capacity averages 364 cubic cm in Pan spp. (B147)
  • The forehead is relatively high. (B147)
  • The ears are relatively small. As in the other great apes the ears are rounded and hairless.(B147)
  • For seven individuals, ear height was 55-72 mm and ear width, 38-42 mm. (J576.23.w1)
  • There is long hair on the sides of the head. (B147)
  • "Calvarium rounded, facial skeleton moderately prognathic, orbits frontally directed and surmounted by prominent and confluent supraorbital crests. Small sagittal crest very occasionally seen in large [males] and [females]; nuchal crest absent. Cranial capacity 290-500cc (94 adults). Foramen magnum situated well posteriorly on basis cranii." (B578.w1)
  • Bonobos have a relatively high and rounded forehead with a small brow ridge; in chimpanzees the forehead is relatively lower and the brow ridge more massive. The vault length, vault height, postorbital breadth and cranial capacity are slightly lower than in Pan troglodytes. Mandibular length and maximum palatal length are lower than in Pan troglodytes, giving a relatively rounded, globular cranium. (B577.1.w1) Dimensions include (B577.1.w1)
    • Vault length 122.8 mm
    • Vault breadth 105.8 mm
    • Vault height 85.4 mm
    • Interorbital breadth 14.5 mm
    • Postorbital breadth 65.6 mm
    • Palatal breadth 51.5 mm
    • Palatal length 58.1 mm
    • Mandibular breadth 93.4 mm
    • Mandibular length 102.4 mm
    • Mandibular height 55.4 mm
    • Cranial capacity 350 cm³. 

Neonate / Young

SUMMARY: --
  • --

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Dentition

Adult

SUMMARY: Dental formula i 2/2, c 1/1, pm 2/2, m 3/3 (x 2, total 32 teeth). There is no sexual dimorphism in tooth size except for slightly longer, broader canine teeth in males. Deciduous dental formula is i2/2, c 1/1, dm 2/2. 
  • Dental formula i 2/2, c 1/1, pm 2/2, m 3/3 (x 2, total 32 teeth). (B147, B578.w1)
  • Dental formula of apes (and humans and Old World monkeys) is I 2/2, C 1/1, P 2/2, M 3/2 = 32. (B52)
  • The incisors are approximately equal in size to one another while the canines are larger. The premolars are similar to the molars, with these being wide-crowned and having tubercles. (B147)
  • The central upper incisors are broad and spatulate, the canines are long, powerful and conical in males but in females are shorter. There is a diastema between the upper lateral incisor and the upper canine in adults. The upper premolars are homodont and bicuspid while the lower are heterodont; the anterior premolar is unicuspid and sectorial and the posterior premolar is bicuspid. The molars decrease in size from 1 to 3 with conical cusps; the upper molars are quadricuspid while the lower molars have five cusps in a "Y" or "Dryopithecus" pattern - there is a hypoconulid but, unlike catarrhine monkeys, no talonid heel. (B578.w1)
  • The incisors are spatulate (shovel-shaped) and the cheek teeth are squared-off and have relatively low cusps. (B52)
  • Dental formula: (B596.5.w5)
    • Deciduous - i2/2, c 1/1, dm 2/2. (B596.5.w5)
      • There is no sexual dimorphism in the size of the deciduous teeth. specifically, there is no difference in the crown height of the canines. The teeth are significantly (P<0.01) smaller than in Pan troglodytes for all except one measurement (buccolingual diameter of the first deciduous premolar). (B596.5.w5)
    • Permanent: I2/2C 1/1, P2/2 M3/3. (B596.5.w5)
      • In adults, with the exception of the canines, there are no sexual differences in the size of teeth (unlike in Pan troglodytes, in which all teeth of males generally are larger than those of females. The canines are larger in males: maxillary canines 23% longer and 25% broader; mandibular canines 17% longer and 21% broader. (B596.5.w5)
    • Usually, the premolars have two roots (three in the upper anterior premolar) while most of the upper molars have three roots (sometimes reduced to two or even one, particularly in M3) and the lower molars have two roots. (B596.5.w5)
    • Order of eruption of the permanent dentition is usually M1, I1, M2, I2, P3, P4, C, M3. Sometimes I2 erupts before M2, but sometimes eruption of I2 is delayed such that M3, and even M4, sometimes erupt before I2. The last deciduous tooth to erupt is the deciduous canine; this usually erupts before the first permanent molar has erupted. (B596.5.w5)
    • The incisors appear to receive more wear than in Pan troglodytes; this may be associated with eating more foliage and with biting through the fibrous sheaths of plants such as Haumania liebrechtsiana to reach pith. (B596.5.w5)

Neonate / Young

 First tooth appearing in an infant bonobo. Click here for full page view with caption

  • First deciduous teeth visible at four to six weeks of age, with temporary dentition complete at 10 months old. (J23.20.w1)

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Eyes

Adult

SUMMARY: Bonobos have brown eyes.
  • Brown eyes; both the iris and the sclera are brown, although the sclera is paler. (B580.5.w5)

Neonate / Young

SUMMARY: --
  • --

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Authors & Referees

Authors

Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)

Referees

--

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