Lystrosaurus (dicynodont) embryo from Triassic of South Africa + multituberculates from Upper Cretaceous Nemegt Formation of Mongolia
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Ben Creisler
Apr 9, 2026, 2:14:09 PMApr 9
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Ben Creisler
New papers:
Julien Benoit, Vincent Fernandez & Jennifer Botha (2026)
The first non-mammalian synapsid embryo from the Triassic of South Africa.
PLoS One 21(4): e0345016.
doi: https://doi.org/10.1371/journal.pone.0345016
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0345016
Oviparity was likely the plesiomorphic reproductive condition for non-mammalian Synapsida, the stem-mammal group. Yet, despite nearly two centuries of research, no definitive fossil eggs of late Palaeozoic or early Mesozoic synapsids have been discovered. Here, three perinate specimens of the dicynodont genus Lystrosaurus from the Early Triassic of the South African Karoo Basin are examined using high-resolution CT and synchrotron scanning. One specimen, NMQR 3636, displays a tightly curled posture suggestive of an in ovo position and completely lacks tusks. Crucially, the lower jaw symphysis remains unfused—a developmental trait found only in pre-hatching embryos of modern birds and turtles. No calcified eggshell is preserved, so the egg might have been soft and leathery. The large size of the reconstructed egg suggests a precocial, non-milk-feeding developmental strategy. As a non-cynodont synapsid, Lystrosaurus offers a rare and valuable glimpse into reproductive biology far removed from the mammalian crown group. Unlike the more derived, mammal-like cynodont Kayentatherium, whose egg size aligns with lactation, Lystrosaurus anchors the plesiomorphic condition deep within Synapsida. Its reproductive strategy may have played a crucial role in its resilience and ecological dominance following the end-Permian mass extinction.
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Alexey V. Lopatin & Alexander O. Averianov (2026)
Multituberculate mammals from the Upper Cretaceous Nemegt Formation of Mongolia
Cretaceous Research 106407
doi: https://doi.org/10.1016/j.cretres.2026.106407
https://www.sciencedirect.com/science/article/abs/pii/S0195667126000960
Two multituberculate mandible specimens from the Maastrichtian Nemegt Formation at the Gurilin Tsav locality in Mongolia exhibit djadochtatherioid dental features: enamel restricted to the ventrolateral side of the lower incisor, as well as two lower premolars, including a non-functional, single-rooted p3 and a three-rooted p4. These specimens represent the first record of Djadochtatherioidea in the Nemegt Formation, extending the stratigraphic range of this clade to the Maastrichtian. The Gurilin Tsav taxon differs from all other known Djadochtatherioidea in a number of details and apparently represents a new genus and species. The Maastrichtian Nemegt multituberculate assemblage includes Djadochtatherioidea and Taeniolabidoidea (Buginbaatar), as well as possibly Cimolomyidae. In contrast, the Campanian Djadokhta and Barungoyot multituberculate assemblages of the Gobi Desert only include Djadochtatherioidea.
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Free pdf:
Julien Benoit, Vincent Fernandez & Jennifer Botha (2026)
The first non-mammalian synapsid embryo from the Triassic of South Africa.
PLoS One 21(4): e0345016.
doi: https://doi.org/10.1371/journal.pone.0345016
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0345016
Oviparity was likely the plesiomorphic reproductive condition for non-mammalian Synapsida, the stem-mammal group. Yet, despite nearly two centuries of research, no definitive fossil eggs of late Palaeozoic or early Mesozoic synapsids have been discovered. Here, three perinate specimens of the dicynodont genus Lystrosaurus from the Early Triassic of the South African Karoo Basin are examined using high-resolution CT and synchrotron scanning. One specimen, NMQR 3636, displays a tightly curled posture suggestive of an in ovo position and completely lacks tusks. Crucially, the lower jaw symphysis remains unfused—a developmental trait found only in pre-hatching embryos of modern birds and turtles. No calcified eggshell is preserved, so the egg might have been soft and leathery. The large size of the reconstructed egg suggests a precocial, non-milk-feeding developmental strategy. As a non-cynodont synapsid, Lystrosaurus offers a rare and valuable glimpse into reproductive biology far removed from the mammalian crown group. Unlike the more derived, mammal-like cynodont Kayentatherium, whose egg size aligns with lactation, Lystrosaurus anchors the plesiomorphic condition deep within Synapsida. Its reproductive strategy may have played a crucial role in its resilience and ecological dominance following the end-Permian mass extinction.
===
Alexey V. Lopatin & Alexander O. Averianov (2026)
Multituberculate mammals from the Upper Cretaceous Nemegt Formation of Mongolia
Cretaceous Research 106407
doi: https://doi.org/10.1016/j.cretres.2026.106407
https://www.sciencedirect.com/science/article/abs/pii/S0195667126000960
Two multituberculate mandible specimens from the Maastrichtian Nemegt Formation at the Gurilin Tsav locality in Mongolia exhibit djadochtatherioid dental features: enamel restricted to the ventrolateral side of the lower incisor, as well as two lower premolars, including a non-functional, single-rooted p3 and a three-rooted p4. These specimens represent the first record of Djadochtatherioidea in the Nemegt Formation, extending the stratigraphic range of this clade to the Maastrichtian. The Gurilin Tsav taxon differs from all other known Djadochtatherioidea in a number of details and apparently represents a new genus and species. The Maastrichtian Nemegt multituberculate assemblage includes Djadochtatherioidea and Taeniolabidoidea (Buginbaatar), as well as possibly Cimolomyidae. In contrast, the Campanian Djadokhta and Barungoyot multituberculate assemblages of the Gobi Desert only include Djadochtatherioidea.
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