In the August 27, 2003 Annals of Carnegie Museum , Curator John R. Wible describes and illustrates in detail the exterior bones of the skull of this small South American opossum, close relative of the now popular laboratory mammal Monodelphis domestica .
He also standardizes terminology for the numerous cranial foramina that transmits nervous and vascular structures to and from the skull. This study represents one of the few such resources for scientists and students other than veterinary textbooks on domesticated mammals.
This Web page includes an alphabetical listing of the bones of the skull and some of the illustrations from this paper, all by Gina Scanlon. The figured specimen is one of 55 examples of the genus Monodelphis in the collections of the Section of Mammals. For more information, see the original reference. Direct queries to wiblej@carnegiemuseums.org
Wible, J. R. 2003. On the cranial osteology of the short-tailed opossum
Monodelphis brevicaudata (Didelphidae, Marsupialia). Annals of Carnegie
Museum 72 (3): 1-66.
Alisphenoid – (figs. 1, 2, 3, 4: as ) paired, endochondral bone in the skull base and braincase wall.
Basioccipital – (fig. 2, 3: bo ) unpaired, endochondral bone in the skull base.
Basisphenoid – (figs. 2, 3, 5: bs ) unpaired, endochondral bone in the skull base.
Ectotympanic – (figs. 2, 3, 4, 5: ec ) paired, intramembranous bone in the skull base (ear region).
Exoccipital – (figs. 2, 3, 4, 6: eo ) paired, endochondral bone in the skull base and occiput.
Frontal – (figs. 1, 4, 5: fr ) paired, intramembranous bone in the skull roof and orbit.
Incus – (figs. 3, 5: i ) paired, endochondral bone in the ear region.
Interparietal – (figs. 1, 4: ip ) unpaired, intramembranous bone in the skull roof.
Jugal – (figs. 1, 2, 3, 4, 5: ju ) paired, intramembranous bone in the zygomatic arch.
Lacrimal – (figs. 1, 2, 4, 5: lac ) paired, intramembranous bone in the face and orbit.
Malleus – (figs. 3, 5: m ) paired, endochondral bone in the ear region.
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Mandible – (fig. 4, unlabelled) paired, intramembranous bone of the lower jaw containing four incisors, one canine, three premolars, and four molars.
Maxilla – (figs. 1, 2, 4, 5: mx ) paired, intramembranous bone in the palate and face containing the canine, three premolars, and four molars.
Nasal – (figs. 1, 4, 5: na ) paired, intramembranous bone in the roof of the nasal cavity.
Orbitosphenoid – (fig. 5: os ) paired, endochondral bone in the orbit.
Palatine – (figs. 2, 4, 5: pal ) paired, intramembranous bone in the palate and orbit.
Parietal – (figs. 1, 4, 5: pa ) paired, intramembranous bone in the skull roof.
Petrosal – (figs. 2, 3 [not labelled], 4, 6: pe ) paired, endochondral bone in the skull base
(ear region) and occiput.
Premaxilla – (figs. 1, 2, 4: pmx ) paired, intramembranous bone in the palate and face containing five incisors.
Presphenoid – (figs. 2, 5: ps ) unpaired, endochondral bone in the skull base and nasal cavity.
Pterygoid – (figs. 2, 3, 4, 5: pt ) paired, intramembranous bone in the skull base.
Squamosal – (figs. 1, 2, 3, 4, 5, 6: sq ) paired, intramembranous bone in the skull base and braincase wall.
Supraoccpital – (figs. 4, 6: so ) unpaired, endochondral bone in the occiput.
Stapes – (fig. 3: s ) paired, endochondral bone in the ear region.
Vomer – (not figured) unpaired, intramembranous bone in the nasal cavity.
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Figure 1. Monodelphis brevicaudata CM 52729, dorsal view of skull. Abbreviations: as , alisphenoid; fr , frontal; iof , infraorbital foramen; ip , interparietal; ju , jugal; lac , lacrimal; lacf , lacrimal foramen; mx , maxilla; na , nasal; pa , parietal; pmx , premaxilla; ptp , posttympanic process; sq , squamosal; tl , temporal line.
Figure 2. Monodelphis brevicaudata CM 52729, skull in ventral view excluding mandibles. Abbreviations: as , alisphenoid; bo , basioccipital; bs , basisphenoid; ec , ectotympanic; eo , exoccipital; fr , frontal; ham , pterygoid hamulus; inf , incisive foramen; ju , jugal; mapf , major palatine foramen; mpf , minor palatine foramen; mx , maxilla; pal , palatine; pe , petrosal; pmx , premaxilla; ppt , postpalatine torus; ps , presphenoid; pt , pterygoid; sq , squamosal.
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Figure 3. Monodelphis brevicaudata CM 52729, line drawing of left ear region in ventral view.
Abbreviations: apm , anterior process of the malleus; as , alisphenoid; ashs , alisphenoid hypotympanic sinus; astp , alisphenoid tympanic process; at , groove for the auditory tube; bo , basioccipital; bs , basisphenoid; cf , carotid foramen; ctpp , caudal tympanic process of the petrosal; ec , ectotympanic; eo , exoccipital; eP , element of Paaw; fc , fenestra cochleae; fgpn , foramen for greater petrosal nerve; fo , foramen ovale; gf , glenoid fossa; glf , glaserian fissure; gpas , glenoid process of the alisphenoid; gpju , glenoid process of the jugal; hf , hypoglossal foramen; i , incus; ips , foramen for the inferior petrosal sinus; jf , jugular foramen; ju , jugal; m , malleus; mp , mastoid process; oc , occipital condyle; pap , paracondylar process of the exoccipital; pgf , postglenoid foramen; pgp , postglenoid process; pr , promontorium; pt , pterygoid; ptc , pterygoid canal; ptcr ; posttympanic crest; ptn , posttemporal notch; ptp , posttympanic process; rtpp , rostral tympanic process of the petrosal; s , stapes; sq , squamosal; tc , transverse sinus canal; th , tympanohyal.
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Figure 4. Monodelphis brevicaudata CM 52729, left lateral view of skull including mandible ( A ) with accompanying line drawing ( B ). Abbreviations: an , angular process; as , alisphenoid; astp , alisphenoid tympanic process; coc , coronoid crest; con , mandibular condyle; cor , coronoid process; ec , ectotympanic; eo , exoccipital; fc , fenestra cochleae; fr , frontal; frp , frontal process of the jugal; iof , infraorbital foramen; ip , interparietal; ju , jugal; lac , lacrimal; maf , masseteric fossa; mf , mental foramen; mx , maxilla; na , nasal; oc , occipital condyle; pa , parietal; pal , palatine; pcp , paracondylar process of the exoccipital; pe , petrosal; pmx , premaxilla; pt , pterygoid; ptp , posttympanic process; rtpp , rostral tympanic process of the petrosal; so , supraoccipital; sq , squamosal.
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Figure 5. Monodelphis brevicaudata CM 52729, line drawing of left orbitotemporal region without zygoma
(parallel lines represent cut surfaces). Abbreviations: ap , anterior process of the alisphenoid; as , alisphenoid; astp , alisphenoid tympanic process; bs , basisphenoid; ec , ectotympanic; ef , ethmoidal foramen; fdv , foramen for the frontal diploic vein; fr ; frontal; fro , foramen rotundum; fo , foramen ovale; i , incus; ju , jugal; lac , lacrimal; lacf , lacrimal foramen; m, malleus; mpf , minor palatine foramen; mx , maxilla; na , nasal; os , orbitosphenoid; pa , parietal; pal , palatine; pgp , postglenoid process; ps , presphenoid; pt , pterygoid; smf , suprameatal foramen; sof , sphenorbital fissure; spf , sphenopalatine foramen; sq , squamosal.
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Figure 6. Monodelphis brevicaudata CM 52729, skull in occipital view excluding mandibles.
Abbreviations: astp , alisphenoid tympanic process; ctpp , caudal tympanic process of the petrosal; ec , ectotympanic; eo , exoccipital; fm , foramen magnum; ham , pterygoid hamulus; jf , jugular foramen; M 4 , upper fourth molar; m , malleus; oc , occipital condyle; pcp , paracondylar process of the exoccipital; pe , petrosal; pgp , postglenoid process; pptf , foramen in the postpalatine torus; ptn , posttemporal foramen; rtpp , rostral tympanic process of the petrosal; so , supraoccipital; sq , squamosal.
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