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Anatomical Contributions to Hylobatid Taxonomy and Adaptation.

Zihlman AL, Mootnick AR, Underwood CE - Int. J. Primatol. (2011)

Bottom Line: Previous morphological studies based on relative bone lengths, e.g., intermembral indices; molar tooth sizes; and body masses did not distinguish the 4 genera from each other.Although Symphalangus has been treated as a scaled up version of Hylobates, its forelimb exceeds its hind limb mass, an unusual primate pattern otherwise found only in orangutans.The research also underscores the important contribution of studies on rare species in captivity.

View Article: PubMed Central - PubMed

ABSTRACT
Compared with the great apes, the small-bodied hylobatids were treated historically as a relatively uniform group with 2 genera, Hylobates and the larger-bodied Symphalangus. Four genera are now recognized, each with a different chromosome number: Hoolock (hoolock) (38), Hylobates (44), Nomascus (crested gibbon) (52), and Symphalangus (siamang) (50). Previous morphological studies based on relative bone lengths, e.g., intermembral indices; molar tooth sizes; and body masses did not distinguish the 4 genera from each other. We applied quantitative anatomical methods to test the hypothesis that each genus can be differentiated from the others using the relative distribution of body mass to the forelimbs and hind limbs. Based on dissections of 13 hylobatids from captive facilities, our findings demonstrate that each of the 4 genera has a distinct pattern of body mass distribution. For example, the adult Hoolock has limb proportions of nearly equal mass, a pattern that differentiates it from species in the genus Hylobates, e.g., H. lar (lar gibbon), H. moloch (Javan gibbon), H. pileatus (pileated gibbon), Nomascus, and Symphalangus. Hylobates is distinct in having heavy hind limbs. Although Symphalangus has been treated as a scaled up version of Hylobates, its forelimb exceeds its hind limb mass, an unusual primate pattern otherwise found only in orangutans. This research provides new information on whole body anatomy and adds to the genetic, ecological, and behavioral evidence for clarifying the taxonomy of the hylobatids. The research also underscores the important contribution of studies on rare species in captivity.

No MeSH data available.


Related in: MedlinePlus

Means of head/trunk, forelimb, and hind limb mass distribution as percent of total body mass.
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Fig1: Means of head/trunk, forelimb, and hind limb mass distribution as percent of total body mass.

Mentions: At the whole body level, each genus shows a distinct pattern in limb proportions relative to total body mass. Hylobates differ from the other 3 genera in having heavy hind limbs relative to body mass: mean 20.3%, range 19.0–21.8%. The forelimbs average 19.1% and show more variation than hind limbs (range 16.3–21.9%, Table II). Hoolock has nearly equal mass in the forelimbs (16.5%) and hind limbs (16.0%), a pattern distinct from that of the other genera. With the least mass in the limbs, its head/trunk segment is the heaviest among the hylobatids. Nomascus has close to equal mass in the forelimbs (16.6%) and hind limbs, though with slightly heavier hind limbs (17.9%). Symphalangus combines heavy forelimbs (21.2%, range 20.2–22.2%) with light hind limbs (16.8%, range 15.1–17.7%, Fig. 1).Table II


Anatomical Contributions to Hylobatid Taxonomy and Adaptation.

Zihlman AL, Mootnick AR, Underwood CE - Int. J. Primatol. (2011)

Means of head/trunk, forelimb, and hind limb mass distribution as percent of total body mass.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3139862&req=5

Fig1: Means of head/trunk, forelimb, and hind limb mass distribution as percent of total body mass.
Mentions: At the whole body level, each genus shows a distinct pattern in limb proportions relative to total body mass. Hylobates differ from the other 3 genera in having heavy hind limbs relative to body mass: mean 20.3%, range 19.0–21.8%. The forelimbs average 19.1% and show more variation than hind limbs (range 16.3–21.9%, Table II). Hoolock has nearly equal mass in the forelimbs (16.5%) and hind limbs (16.0%), a pattern distinct from that of the other genera. With the least mass in the limbs, its head/trunk segment is the heaviest among the hylobatids. Nomascus has close to equal mass in the forelimbs (16.6%) and hind limbs, though with slightly heavier hind limbs (17.9%). Symphalangus combines heavy forelimbs (21.2%, range 20.2–22.2%) with light hind limbs (16.8%, range 15.1–17.7%, Fig. 1).Table II

Bottom Line: Previous morphological studies based on relative bone lengths, e.g., intermembral indices; molar tooth sizes; and body masses did not distinguish the 4 genera from each other.Although Symphalangus has been treated as a scaled up version of Hylobates, its forelimb exceeds its hind limb mass, an unusual primate pattern otherwise found only in orangutans.The research also underscores the important contribution of studies on rare species in captivity.

View Article: PubMed Central - PubMed

ABSTRACT
Compared with the great apes, the small-bodied hylobatids were treated historically as a relatively uniform group with 2 genera, Hylobates and the larger-bodied Symphalangus. Four genera are now recognized, each with a different chromosome number: Hoolock (hoolock) (38), Hylobates (44), Nomascus (crested gibbon) (52), and Symphalangus (siamang) (50). Previous morphological studies based on relative bone lengths, e.g., intermembral indices; molar tooth sizes; and body masses did not distinguish the 4 genera from each other. We applied quantitative anatomical methods to test the hypothesis that each genus can be differentiated from the others using the relative distribution of body mass to the forelimbs and hind limbs. Based on dissections of 13 hylobatids from captive facilities, our findings demonstrate that each of the 4 genera has a distinct pattern of body mass distribution. For example, the adult Hoolock has limb proportions of nearly equal mass, a pattern that differentiates it from species in the genus Hylobates, e.g., H. lar (lar gibbon), H. moloch (Javan gibbon), H. pileatus (pileated gibbon), Nomascus, and Symphalangus. Hylobates is distinct in having heavy hind limbs. Although Symphalangus has been treated as a scaled up version of Hylobates, its forelimb exceeds its hind limb mass, an unusual primate pattern otherwise found only in orangutans. This research provides new information on whole body anatomy and adds to the genetic, ecological, and behavioral evidence for clarifying the taxonomy of the hylobatids. The research also underscores the important contribution of studies on rare species in captivity.

No MeSH data available.


Related in: MedlinePlus