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A Novel Objective Method of Estimating the Age of Mandibles from African Elephants (Loxodonta africana Africana).

Stansfield FJ - PLoS ONE (2015)

Bottom Line: The importance of assigning an accurate estimate of age and sex to elephant carcasses found in the wild has increased in recent years with the escalation in levels of poaching throughout Africa.These 'Age Reference Lines' were then associated with an age scale based on previous studies and Zimbabwean mandibles of known age.The new ranking produced a single age scale that proved useful for both male and female mandibles up to the maximum lifespan age of 70-75 years.

View Article: PubMed Central - PubMed

Affiliation: The Elephant Research and Conservation Unit, Savé Valley Conservancy, Chiredzi, Zimbabwe.

ABSTRACT
The importance of assigning an accurate estimate of age and sex to elephant carcasses found in the wild has increased in recent years with the escalation in levels of poaching throughout Africa. Irregularities identified in current ageing techniques prompted the development of a new method to describe molar progression throughout life. Elephant mandibles (n = 323) were studied and a point near the distal dental alveolus was identified as being most useful in ranking each jaw according to molar progression. These 'Age Reference Lines' were then associated with an age scale based on previous studies and Zimbabwean mandibles of known age. The new ranking produced a single age scale that proved useful for both male and female mandibles up to the maximum lifespan age of 70-75 years. Methods to aid in molar identification and the sexing of found jaws were also identified.

No MeSH data available.


Related in: MedlinePlus

Demonstrates age estimation in the African elephant using the Age Reference Line.A straight line is drawn from Point A at the base of the mandibular foramen to Point B at the most distal point of molar occlusal wear. A line is drawn or vizualised along the ridge of the medial mandible (Line C). The two lines intersect at the red dot, Point D, which has been termed the Age Reference Point (ARP). A measurement of 10 cm is made from this point passing centrally through the distal molar. In this example 10 cm is marked as the distance from ARP (Point D) to the yellow line at E. This yellow line at E is termed the Age Reference Line (ARL). In this example the ARL falls on the 7th lamella (L) of the 4th molar. By reference to this ARL in Table 1 the elephant’s age can be estimated as 11.5 years. The green arrow at the mesial end of the mandible marks the mesial end of the dental alveolus, named the ‘crest’.
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pone.0124980.g002: Demonstrates age estimation in the African elephant using the Age Reference Line.A straight line is drawn from Point A at the base of the mandibular foramen to Point B at the most distal point of molar occlusal wear. A line is drawn or vizualised along the ridge of the medial mandible (Line C). The two lines intersect at the red dot, Point D, which has been termed the Age Reference Point (ARP). A measurement of 10 cm is made from this point passing centrally through the distal molar. In this example 10 cm is marked as the distance from ARP (Point D) to the yellow line at E. This yellow line at E is termed the Age Reference Line (ARL). In this example the ARL falls on the 7th lamella (L) of the 4th molar. By reference to this ARL in Table 1 the elephant’s age can be estimated as 11.5 years. The green arrow at the mesial end of the mandible marks the mesial end of the dental alveolus, named the ‘crest’.

Mentions: A stable reference point situated close to the alveolar apex (Fig 2), proximal to the occlusal surface on either side of the jaw, was identified and termed the ‘age reference point’ (ARP; Fig 2). To determine this point, a straight line from the distal occlusal surface to the base of the mandibular foramen (MF) and continuing to the back of the ramus, was selected as a starting reference (see Fig 2; In this study, this was performed on each side of the mandible in order to gauge any possible difference between left and right). As a reference point was required, a line of intersection was provided using the arc formed by the ridge of the medial ramus surface (medial ramus ridge), which merges mesially into the alveolar crestal plane (see Fig 2). After many observations and measurements, it became evident that this point of intersection occurred just above the opening of the dental alveolus proximal to the occlusal surface, and it varied very little throughout life or between sexes. In order to gauge molar progression on jaws of all ages, a distance of 10 cm from the ARP was chosen to represent the Age Reference Line (ARL) beneath which the lamella of the tooth in question would be studied and described as, for example, M6L3 (third lamella of the sixth molar). An ARL at 10 cm from the ARP in a perinatal mandible fell at 1.6 cm mesial to the M1 (Fig 3A). The same mark placement fell 3.8 cm distal to the 2 cm long remnant of the M6 in a >70 year old female (Fig 4). From this rank of all the molars and their constituent lamellae Table 1 was created.


A Novel Objective Method of Estimating the Age of Mandibles from African Elephants (Loxodonta africana Africana).

Stansfield FJ - PLoS ONE (2015)

Demonstrates age estimation in the African elephant using the Age Reference Line.A straight line is drawn from Point A at the base of the mandibular foramen to Point B at the most distal point of molar occlusal wear. A line is drawn or vizualised along the ridge of the medial mandible (Line C). The two lines intersect at the red dot, Point D, which has been termed the Age Reference Point (ARP). A measurement of 10 cm is made from this point passing centrally through the distal molar. In this example 10 cm is marked as the distance from ARP (Point D) to the yellow line at E. This yellow line at E is termed the Age Reference Line (ARL). In this example the ARL falls on the 7th lamella (L) of the 4th molar. By reference to this ARL in Table 1 the elephant’s age can be estimated as 11.5 years. The green arrow at the mesial end of the mandible marks the mesial end of the dental alveolus, named the ‘crest’.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4430523&req=5

pone.0124980.g002: Demonstrates age estimation in the African elephant using the Age Reference Line.A straight line is drawn from Point A at the base of the mandibular foramen to Point B at the most distal point of molar occlusal wear. A line is drawn or vizualised along the ridge of the medial mandible (Line C). The two lines intersect at the red dot, Point D, which has been termed the Age Reference Point (ARP). A measurement of 10 cm is made from this point passing centrally through the distal molar. In this example 10 cm is marked as the distance from ARP (Point D) to the yellow line at E. This yellow line at E is termed the Age Reference Line (ARL). In this example the ARL falls on the 7th lamella (L) of the 4th molar. By reference to this ARL in Table 1 the elephant’s age can be estimated as 11.5 years. The green arrow at the mesial end of the mandible marks the mesial end of the dental alveolus, named the ‘crest’.
Mentions: A stable reference point situated close to the alveolar apex (Fig 2), proximal to the occlusal surface on either side of the jaw, was identified and termed the ‘age reference point’ (ARP; Fig 2). To determine this point, a straight line from the distal occlusal surface to the base of the mandibular foramen (MF) and continuing to the back of the ramus, was selected as a starting reference (see Fig 2; In this study, this was performed on each side of the mandible in order to gauge any possible difference between left and right). As a reference point was required, a line of intersection was provided using the arc formed by the ridge of the medial ramus surface (medial ramus ridge), which merges mesially into the alveolar crestal plane (see Fig 2). After many observations and measurements, it became evident that this point of intersection occurred just above the opening of the dental alveolus proximal to the occlusal surface, and it varied very little throughout life or between sexes. In order to gauge molar progression on jaws of all ages, a distance of 10 cm from the ARP was chosen to represent the Age Reference Line (ARL) beneath which the lamella of the tooth in question would be studied and described as, for example, M6L3 (third lamella of the sixth molar). An ARL at 10 cm from the ARP in a perinatal mandible fell at 1.6 cm mesial to the M1 (Fig 3A). The same mark placement fell 3.8 cm distal to the 2 cm long remnant of the M6 in a >70 year old female (Fig 4). From this rank of all the molars and their constituent lamellae Table 1 was created.

Bottom Line: The importance of assigning an accurate estimate of age and sex to elephant carcasses found in the wild has increased in recent years with the escalation in levels of poaching throughout Africa.These 'Age Reference Lines' were then associated with an age scale based on previous studies and Zimbabwean mandibles of known age.The new ranking produced a single age scale that proved useful for both male and female mandibles up to the maximum lifespan age of 70-75 years.

View Article: PubMed Central - PubMed

Affiliation: The Elephant Research and Conservation Unit, Savé Valley Conservancy, Chiredzi, Zimbabwe.

ABSTRACT
The importance of assigning an accurate estimate of age and sex to elephant carcasses found in the wild has increased in recent years with the escalation in levels of poaching throughout Africa. Irregularities identified in current ageing techniques prompted the development of a new method to describe molar progression throughout life. Elephant mandibles (n = 323) were studied and a point near the distal dental alveolus was identified as being most useful in ranking each jaw according to molar progression. These 'Age Reference Lines' were then associated with an age scale based on previous studies and Zimbabwean mandibles of known age. The new ranking produced a single age scale that proved useful for both male and female mandibles up to the maximum lifespan age of 70-75 years. Methods to aid in molar identification and the sexing of found jaws were also identified.

No MeSH data available.


Related in: MedlinePlus