New skull of «Lystrosaurus curvatus» from the Fremouw Formation
Survey of salt minerals collected
Area
Number of samples
Nussbaum Riegel
14
Darwin Mountains
12
Bull Pass
12
Walcott Glacier
11
Haskell Ridge
7
Roadend Nunatak Turnstile Ridge
2 2
Olympus Range
5
McMurdo
1
Main salt minerals Calcite (CaCO3) Gypsum (CaSO 4 ' 21-120) Thenardite (Na2SO4) Gypsum Mirabilite (Na 2SO4 • 10 H20) Thenardite Calcite Gypsum Halite (NaC1) Calcite Thenardite Gypsum Calcite Calcite Gypsum Thenardite Gypsum Calcite Gypsum Gypsum Halite Nitronatrite (NaNO3) Gypsum Mirabilite Thenardite
Other minerals Bassanite (CaSO4 • 1/21-120) Na-Jarosite (NaFe3[(OH)6 ( SO4) 21)
Bassan ite
Hexahyd rite (MgSO 4 ' 6H20) Astrakanite (Na 2Mg(SO4) 2 . 4H20) Darapskite (Na 3 [SO4NO3]. H2O)
Source. Miotke and Hodenberg (1980).
New skull of Lystrosaurus curvatus from the Fremouw Formation \\ ( . :
1
I\'\i
Wayne State Universitt Detroit, t4ic!i içan 482L
During the 1977-78 field season, a cranium of Lystrtuirii curvatus was collected in the Fremouw Formation of the
Cumulus Hills (Collinson, Stanley, and Varva 1978; Cosgrif I and Hammer 1979; Cosgriff et al. 1978). The entire cranial specimen (wsu0977) is shown photographed in its prepared state in figure 1; the skull portion is shown in reconstructed lateral view by the line drawing in figure 2. The skull represents the most complete cranium of Lystrosaurus curvatus collected to date from this formation. Portions preserved include most of the skull, the nearly complete left lower jaw ramus and the anterior part of the right ramus. Distortion is severe and seems to have resulted from postmortem pressure exerted obliquely against the upper left side of the cranium. This has laterally compressed the entire specimen, flattened the left side, and folded under the right side. *presen t address: Department of Geology, Augustana College, Rock Island, IL 61201.
52
Figure 1. Lystrosaurus curvatus (wsu0977) skull and lower Jaws, dorsolateral view.
ANTARCTIC JOURNAL
fir
a primitive species while L. murrayi and L. maccaigi are derived. t.f
or p.b
IJ
^cm
Figure 2. Lystrosaurus curvatus (wsu0977). Restoration of the left lateral aspect of the skull. Abbreviations: e.n = external narls; or = orbit; p.b = postorbital bar; s.f = squamosal flange; t = tusk; t.f = temporal fenestra; z.a = zygomatic arch.
The cranium was found in a gray siltstone, 43 meters above the base of the section at Collinson Ridge, which lies east of the Shackleton Glacier just to the south of its junction with the McGregor Glacier in the Cumulus Hills (85 008'S 174°50'W) of the Queen Maud Mountains. The level from 42-43 meters at this locality was highly fossiliferous; it also produced the only specimens of Myosaurus gracilis known from the Fremouw Formation (Hammer and Cosgriff 1981). Three species of Lystrosaurus are presently known from the Fremouw Formation. Colbert (1974) described cranial material of L. curvatus and L. murrayi, and Cosgriff, Hammer, and Ryan (in press) described cranial material of L. maccaigi. Principal skull features of wsu0977, which is best preserved on the left side, include the entire snout with canine tusk, the external naris, the orbit, the constricted parietal region, the zygomatic arch, and the flared squamosal region. Preservation of surface bone is poor and, hence, the sutures separating the various skull bones cannot be discerned. The skull, small compared against the total size range for Lystrosaurus, measures (in its distorted state) about 135 millimeters in a straight line from ventral snout edge to posterior edge of skull table between the parietals. The chief resource for morphologic and taxonomic work on the genus Lystrosaurus is the extensively studied and documented complex of species from the Lystrosaurus Zone (basal Triassic) of the Beaufort Series of South Africa. Brink (1951) provided the first modern review of these, recognizing eleven species. Cluver (1971) reduced the number to nine. Kitching (1968) and Colbert (1974) recognize only six, namely, L. curvatus, L. murrayi, L. maccaigi, L. platyceps, L. oviceps, and L. declivus. Cosgriff and associates (in press) tentatively accept these six as valid but suggest that further analysis may reduce the set to the three known to be shared with the fauna from the Fremouw Formation. Of these three, L. curvatus is clearly
1981 REVIEW
WSU0977 fits the description of L. curvatus (see Cluver 1971; Colbert 1974; Cosgriff et al. in press) through the following primitive features: (1) skull roof a smooth curve in profile; (2) no vertical ridges on the premaxillary surface; (3) no frontonasal ridges; and (4) no surface ornament on the frontal region. L. murrayi, L. maccaigi, and L. declivus contrast with L. curvatus and show the derived conditions in all four features. L. platyceps contrasts in feature 1, and L. oviceps in features 2-4. The L. curvatus specimen described by Colbert (1974), AMNH9515, is a natural longitudinal section of a skull. It can be compared to L. curvatus primarily on feature 1. WSU0977 further substantiates the presence of L. curvatus in the Fremouw Formation through demonstration of features 2-4. It serves to emphasize again the remarkable fact that three species of a single genus are shared by the fossil vertebrate faunas of the Fremouw Formation of Antarctica and the Lystrosaurus Zone of South Africa. This information, together with other taxonomic data, establishes these units as closely synchronous within the earliest phase of the Triassic. In addition to its occurrences in Antarctica and South Africa, L. curvatus is also known from Lower Triassic deposits of Sinkiang, China (by L. youngi; Sun 1964, placed in synonymy by Colbert 1974). This research was supported by National Science Foundation grants DPP 76-23435 and 79-26279.
References Brink, A. S. 1951. On the genus Lystrosaurus Cope. Transactions of the Royal Society of South Africa, 33(1), 107-120. Cluver, M. A. 1971. The cranial morphology of the dicynodont genus Lystrosaurus. Annals of the South African Museum, 56(5), 155-274. Colbert, E. H. 1974. Lystrosaurus from Antarctica. American Museum Novitates, 2535, 1-44. Collinson, J . W., Stanley, K. 0., and Varva, C. L. 1978. Stratigraphy and sedimentary petrology of the Fremouw Formation (Lower Triassic), Cumulus Hills, Central Transantarctic Mountains. Antarctic Journal of the U.S., 13(4), 21-22. Cosgriff, J . W., and Hammer, W. R. 1979. New species of the Dicynodontia from the Fremouw Formation. Antarctic Journal of the U.S., 14(5), 30-32. Cosgriff, J. W., Hammer, W. R., and Ryan, W. J. In press. The Pangaean reptile, Lystrosaurus maccaigi, in the Lower Triassic of Antarctica. Journal of Paleontology. Cosgriff, J . W., Hammer, W. R., Zawiski, J. M., and Kemp, N. R. 1978. New Triassic vertebrates from the Fremouw Formation of the Queen Maud Mountains. Antarctic Journal of the U.S., 13(4), 23-24. Hammer, W. R., and Cosgriff, J . W. 1981. Myosaurus gracilis, an anomodont reptile from the Lower Triassic of Antarctica and South Africa. Journal of Paleontology, 55(2), 410-424. Kitching, J. W. 1968. On the Lystrosaurus zone and its fauna with special reference to some immature Lystrosauridae. Paleontologica Africana, 11, 61-76. Sun, A. -L. 1964. Preliminary report on a new species of Lystrosaurus of Sinkiang. Vertebrate Palasisatica, 8, 216-217.
53
Area
Number of samples
Nussbaum Riegel
14
Darwin Mountains
12
Bull Pass
12
Walcott Glacier
11
Haskell Ridge
7
Roadend Nunatak Turnstile Ridge
2 2
Olympus Range
5
McMurdo
1
Main salt minerals Calcite (CaCO3) Gypsum (CaSO 4 ' 21-120) Thenardite (Na2SO4) Gypsum Mirabilite (Na 2SO4 • 10 H20) Thenardite Calcite Gypsum Halite (NaC1) Calcite Thenardite Gypsum Calcite Calcite Gypsum Thenardite Gypsum Calcite Gypsum Gypsum Halite Nitronatrite (NaNO3) Gypsum Mirabilite Thenardite
Other minerals Bassanite (CaSO4 • 1/21-120) Na-Jarosite (NaFe3[(OH)6 ( SO4) 21)
Bassan ite
Hexahyd rite (MgSO 4 ' 6H20) Astrakanite (Na 2Mg(SO4) 2 . 4H20) Darapskite (Na 3 [SO4NO3]. H2O)
Source. Miotke and Hodenberg (1980).
New skull of Lystrosaurus curvatus from the Fremouw Formation \\ ( . :
1
I\'\i
Wayne State Universitt Detroit, t4ic!i içan 482L
During the 1977-78 field season, a cranium of Lystrtuirii curvatus was collected in the Fremouw Formation of the
Cumulus Hills (Collinson, Stanley, and Varva 1978; Cosgrif I and Hammer 1979; Cosgriff et al. 1978). The entire cranial specimen (wsu0977) is shown photographed in its prepared state in figure 1; the skull portion is shown in reconstructed lateral view by the line drawing in figure 2. The skull represents the most complete cranium of Lystrosaurus curvatus collected to date from this formation. Portions preserved include most of the skull, the nearly complete left lower jaw ramus and the anterior part of the right ramus. Distortion is severe and seems to have resulted from postmortem pressure exerted obliquely against the upper left side of the cranium. This has laterally compressed the entire specimen, flattened the left side, and folded under the right side. *presen t address: Department of Geology, Augustana College, Rock Island, IL 61201.
52
Figure 1. Lystrosaurus curvatus (wsu0977) skull and lower Jaws, dorsolateral view.
ANTARCTIC JOURNAL
fir
a primitive species while L. murrayi and L. maccaigi are derived. t.f
or p.b
IJ
^cm
Figure 2. Lystrosaurus curvatus (wsu0977). Restoration of the left lateral aspect of the skull. Abbreviations: e.n = external narls; or = orbit; p.b = postorbital bar; s.f = squamosal flange; t = tusk; t.f = temporal fenestra; z.a = zygomatic arch.
The cranium was found in a gray siltstone, 43 meters above the base of the section at Collinson Ridge, which lies east of the Shackleton Glacier just to the south of its junction with the McGregor Glacier in the Cumulus Hills (85 008'S 174°50'W) of the Queen Maud Mountains. The level from 42-43 meters at this locality was highly fossiliferous; it also produced the only specimens of Myosaurus gracilis known from the Fremouw Formation (Hammer and Cosgriff 1981). Three species of Lystrosaurus are presently known from the Fremouw Formation. Colbert (1974) described cranial material of L. curvatus and L. murrayi, and Cosgriff, Hammer, and Ryan (in press) described cranial material of L. maccaigi. Principal skull features of wsu0977, which is best preserved on the left side, include the entire snout with canine tusk, the external naris, the orbit, the constricted parietal region, the zygomatic arch, and the flared squamosal region. Preservation of surface bone is poor and, hence, the sutures separating the various skull bones cannot be discerned. The skull, small compared against the total size range for Lystrosaurus, measures (in its distorted state) about 135 millimeters in a straight line from ventral snout edge to posterior edge of skull table between the parietals. The chief resource for morphologic and taxonomic work on the genus Lystrosaurus is the extensively studied and documented complex of species from the Lystrosaurus Zone (basal Triassic) of the Beaufort Series of South Africa. Brink (1951) provided the first modern review of these, recognizing eleven species. Cluver (1971) reduced the number to nine. Kitching (1968) and Colbert (1974) recognize only six, namely, L. curvatus, L. murrayi, L. maccaigi, L. platyceps, L. oviceps, and L. declivus. Cosgriff and associates (in press) tentatively accept these six as valid but suggest that further analysis may reduce the set to the three known to be shared with the fauna from the Fremouw Formation. Of these three, L. curvatus is clearly
1981 REVIEW
WSU0977 fits the description of L. curvatus (see Cluver 1971; Colbert 1974; Cosgriff et al. in press) through the following primitive features: (1) skull roof a smooth curve in profile; (2) no vertical ridges on the premaxillary surface; (3) no frontonasal ridges; and (4) no surface ornament on the frontal region. L. murrayi, L. maccaigi, and L. declivus contrast with L. curvatus and show the derived conditions in all four features. L. platyceps contrasts in feature 1, and L. oviceps in features 2-4. The L. curvatus specimen described by Colbert (1974), AMNH9515, is a natural longitudinal section of a skull. It can be compared to L. curvatus primarily on feature 1. WSU0977 further substantiates the presence of L. curvatus in the Fremouw Formation through demonstration of features 2-4. It serves to emphasize again the remarkable fact that three species of a single genus are shared by the fossil vertebrate faunas of the Fremouw Formation of Antarctica and the Lystrosaurus Zone of South Africa. This information, together with other taxonomic data, establishes these units as closely synchronous within the earliest phase of the Triassic. In addition to its occurrences in Antarctica and South Africa, L. curvatus is also known from Lower Triassic deposits of Sinkiang, China (by L. youngi; Sun 1964, placed in synonymy by Colbert 1974). This research was supported by National Science Foundation grants DPP 76-23435 and 79-26279.
References Brink, A. S. 1951. On the genus Lystrosaurus Cope. Transactions of the Royal Society of South Africa, 33(1), 107-120. Cluver, M. A. 1971. The cranial morphology of the dicynodont genus Lystrosaurus. Annals of the South African Museum, 56(5), 155-274. Colbert, E. H. 1974. Lystrosaurus from Antarctica. American Museum Novitates, 2535, 1-44. Collinson, J . W., Stanley, K. 0., and Varva, C. L. 1978. Stratigraphy and sedimentary petrology of the Fremouw Formation (Lower Triassic), Cumulus Hills, Central Transantarctic Mountains. Antarctic Journal of the U.S., 13(4), 21-22. Cosgriff, J . W., and Hammer, W. R. 1979. New species of the Dicynodontia from the Fremouw Formation. Antarctic Journal of the U.S., 14(5), 30-32. Cosgriff, J. W., Hammer, W. R., and Ryan, W. J. In press. The Pangaean reptile, Lystrosaurus maccaigi, in the Lower Triassic of Antarctica. Journal of Paleontology. Cosgriff, J . W., Hammer, W. R., Zawiski, J. M., and Kemp, N. R. 1978. New Triassic vertebrates from the Fremouw Formation of the Queen Maud Mountains. Antarctic Journal of the U.S., 13(4), 23-24. Hammer, W. R., and Cosgriff, J . W. 1981. Myosaurus gracilis, an anomodont reptile from the Lower Triassic of Antarctica and South Africa. Journal of Paleontology, 55(2), 410-424. Kitching, J. W. 1968. On the Lystrosaurus zone and its fauna with special reference to some immature Lystrosauridae. Paleontologica Africana, 11, 61-76. Sun, A. -L. 1964. Preliminary report on a new species of Lystrosaurus of Sinkiang. Vertebrate Palasisatica, 8, 216-217.
53
