Abstract
Intraspecific variation (e.g., ontogenetic, individual, sexual dimorphic) is rarely examined among cranial endocasts (infillings of the braincase cavity) because of the difficulty in obtaining multiple specimens of a species, particularly fossil taxa. We extracted digital cranial endocasts from CT scans of a growth series of skulls of Monodelphis domestica, the gray short-tailed opossum, as a preliminary assessment of the amount of intraspecific variation in mammalian endocranial morphology. The goals of this study were 1) to provide an anatomical description to document developmental changes in endocranial morphology of M. domestica and 2) to examine ontogenetic and individual variation with respect to phylogenetic characters of endocranial cavities that are known to be variable between different mammalian taxa. In this study, "ontogenetic variation" refers to variation between specimens of different ages whereas "individual variation" (i.e., polymorphism) is restricted to variation between specimens of comparable age. Aside from size, changes in shape account for the greatest amount of morphological variation between the endocasts of different ages. Endocast length, width, and volume increase with age for the growth series. Relative olfactory bulb cast size increases with age in the growth series, but the relative size of the parafloccular casts shows a slight negative allometric trend through ontogeny. More than one-third of the phylogenetic characters of the endocranial cavity we examined showed some sort of variation (ontogenetic, individual, or both). This suggests that although endocasts are potentially informative for systematics, both ontogenetic and individual variation affect how endocranial characters are scored for phylogenetic analysis. Further studies such as this are necessary to determine the taxonomic extent of significant intraspecific variation of these endocranial characters.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 844-865 |
| Number of pages | 22 |
| Journal | Journal of Morphology |
| Volume | 268 |
| Issue number | 10 |
| DOIs | |
| State | Published - Oct 2007 |
| Externally published | Yes |
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Keywords
- Computed tomography
- Cranial endocast
- Intraspecific variation
- Opossum
- Polymorphism
ASJC Scopus subject areas
- Agricultural and Biological Sciences (miscellaneous)
- Developmental Biology
- Anatomy
Cite this
Cranial endocasts from a growth series of Monodelphis domestica (Didelphidae, Marsupialia) : A study of individual and ontogenetic variation. / Macrini, Thomas E.; Rowe, Timothy; VandeBerg, John L.
In: Journal of Morphology, Vol. 268, No. 10, 10.2007, p. 844-865.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Cranial endocasts from a growth series of Monodelphis domestica (Didelphidae, Marsupialia)
T2 - A study of individual and ontogenetic variation
AU - Macrini, Thomas E.
AU - Rowe, Timothy
AU - VandeBerg, John L.
PY - 2007/10
Y1 - 2007/10
N2 - Intraspecific variation (e.g., ontogenetic, individual, sexual dimorphic) is rarely examined among cranial endocasts (infillings of the braincase cavity) because of the difficulty in obtaining multiple specimens of a species, particularly fossil taxa. We extracted digital cranial endocasts from CT scans of a growth series of skulls of Monodelphis domestica, the gray short-tailed opossum, as a preliminary assessment of the amount of intraspecific variation in mammalian endocranial morphology. The goals of this study were 1) to provide an anatomical description to document developmental changes in endocranial morphology of M. domestica and 2) to examine ontogenetic and individual variation with respect to phylogenetic characters of endocranial cavities that are known to be variable between different mammalian taxa. In this study, "ontogenetic variation" refers to variation between specimens of different ages whereas "individual variation" (i.e., polymorphism) is restricted to variation between specimens of comparable age. Aside from size, changes in shape account for the greatest amount of morphological variation between the endocasts of different ages. Endocast length, width, and volume increase with age for the growth series. Relative olfactory bulb cast size increases with age in the growth series, but the relative size of the parafloccular casts shows a slight negative allometric trend through ontogeny. More than one-third of the phylogenetic characters of the endocranial cavity we examined showed some sort of variation (ontogenetic, individual, or both). This suggests that although endocasts are potentially informative for systematics, both ontogenetic and individual variation affect how endocranial characters are scored for phylogenetic analysis. Further studies such as this are necessary to determine the taxonomic extent of significant intraspecific variation of these endocranial characters.
AB - Intraspecific variation (e.g., ontogenetic, individual, sexual dimorphic) is rarely examined among cranial endocasts (infillings of the braincase cavity) because of the difficulty in obtaining multiple specimens of a species, particularly fossil taxa. We extracted digital cranial endocasts from CT scans of a growth series of skulls of Monodelphis domestica, the gray short-tailed opossum, as a preliminary assessment of the amount of intraspecific variation in mammalian endocranial morphology. The goals of this study were 1) to provide an anatomical description to document developmental changes in endocranial morphology of M. domestica and 2) to examine ontogenetic and individual variation with respect to phylogenetic characters of endocranial cavities that are known to be variable between different mammalian taxa. In this study, "ontogenetic variation" refers to variation between specimens of different ages whereas "individual variation" (i.e., polymorphism) is restricted to variation between specimens of comparable age. Aside from size, changes in shape account for the greatest amount of morphological variation between the endocasts of different ages. Endocast length, width, and volume increase with age for the growth series. Relative olfactory bulb cast size increases with age in the growth series, but the relative size of the parafloccular casts shows a slight negative allometric trend through ontogeny. More than one-third of the phylogenetic characters of the endocranial cavity we examined showed some sort of variation (ontogenetic, individual, or both). This suggests that although endocasts are potentially informative for systematics, both ontogenetic and individual variation affect how endocranial characters are scored for phylogenetic analysis. Further studies such as this are necessary to determine the taxonomic extent of significant intraspecific variation of these endocranial characters.
KW - Computed tomography
KW - Cranial endocast
KW - Intraspecific variation
KW - Opossum
KW - Polymorphism
UR - http://www.scopus.com/inward/record.url?scp=34848813811&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34848813811&partnerID=8YFLogxK
U2 - 10.1002/jmor.10556
DO - 10.1002/jmor.10556
M3 - Article
VL - 268
SP - 844
EP - 865
JO - Journal of Morphology
JF - Journal of Morphology
SN - 0362-2525
IS - 10
ER -