Nujalikodon, new docodontan from Early Jurassic of Greenland + Bienotheroides cranial endocast
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Ben Creisler
Jun 13, 2025, 12:01:52 PMJun 13
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Ben Creisler
New mammaliaforms papers:
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Nujalikodon cassiopeiae gen. et sp. nov.
Sofia Patrocínio, Elsa Panciroli, Filippo Maria Rotatori, Octavio Mateus, Jesper Milàn, Lars B. Clemmensen & Vicente D. Crespo (2025)
The oldest definitive docodontan from central East Greenland sheds light on the origin of the clade
Papers in Palaeontology 11(3): e70022
doi: https://doi.org/10.1002/spp2.70022
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70022
The first mammaliaforms emerged in the Late Triassic, but their exact origins remain unclear due to the scarcity of fossils from this period. One of the earliest diverging mammaliaform groups, the order Docodonta, became unusually ecomorphologically diverse compared with other early mammals, and this may be connected to the possession of complex molar cusp morphology. The specimen described here, found in the Rhætelv Formation of the Kap Stewart Group (Rhaetian–Sinemurian) of central East Greenland, provides novel information on docodontan origins and evolution, as well as key biogeographic insights into early mammal dispersal. Nujalikodon cassiopeiae gen. et sp. nov. is the first mammaliaform found in the Rhætelv Formation, and is likely to be Early Jurassic (Hettangian) in age. Comprising an incomplete dentary with a single preserved molar, it was visualized using micro-computed tomography; the molar bears similarities to the putative early docodontan Delsatia, and docodontan Dobunnodon. Phylogenetic analysis places Nujalikodon cassiopeiae as a basal member of Docodonta or a close sister taxon, making it one of the oldest definitive docodontans and pushing the origin of the group back to at least the Early Jurassic. It provides insights into the development of docodontan dental complexity, a key factor in their ecological diversification during the Middle to Late Jurassic. Its presence in Greenland supports the hypothesis that docodontans originated in the region now comprising Europe and Greenland before dispersing across the rest of Laurasia.
Nujalikodon cassiopeiae gen. et sp. nov.
Sofia Patrocínio, Elsa Panciroli, Filippo Maria Rotatori, Octavio Mateus, Jesper Milàn, Lars B. Clemmensen & Vicente D. Crespo (2025)
The oldest definitive docodontan from central East Greenland sheds light on the origin of the clade
Papers in Palaeontology 11(3): e70022
doi: https://doi.org/10.1002/spp2.70022
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70022
The first mammaliaforms emerged in the Late Triassic, but their exact origins remain unclear due to the scarcity of fossils from this period. One of the earliest diverging mammaliaform groups, the order Docodonta, became unusually ecomorphologically diverse compared with other early mammals, and this may be connected to the possession of complex molar cusp morphology. The specimen described here, found in the Rhætelv Formation of the Kap Stewart Group (Rhaetian–Sinemurian) of central East Greenland, provides novel information on docodontan origins and evolution, as well as key biogeographic insights into early mammal dispersal. Nujalikodon cassiopeiae gen. et sp. nov. is the first mammaliaform found in the Rhætelv Formation, and is likely to be Early Jurassic (Hettangian) in age. Comprising an incomplete dentary with a single preserved molar, it was visualized using micro-computed tomography; the molar bears similarities to the putative early docodontan Delsatia, and docodontan Dobunnodon. Phylogenetic analysis places Nujalikodon cassiopeiae as a basal member of Docodonta or a close sister taxon, making it one of the oldest definitive docodontans and pushing the origin of the group back to at least the Early Jurassic. It provides insights into the development of docodontan dental complexity, a key factor in their ecological diversification during the Middle to Late Jurassic. Its presence in Greenland supports the hypothesis that docodontans originated in the region now comprising Europe and Greenland before dispersing across the rest of Laurasia.
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Jicheng Ren, Ping Wang, Zhaoying Wei, Lu Liu, Jin Meng & Fangyuan Mao (2025)
The cranial endocast of tritylodontid Bienotheroides (Cynodontia, Mammaliamorpha) and its relevance to mammalian neurosensory evolution
Papers in Palaeontology 11(3): e70021
doi: https://doi.org/10.1002/spp2.70021
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70021
Tritylodontidae are a cosmopolitan group of derived cynodonts that thrived during the Mesozoic Era. Among the tritylodontids, the genus Bienotheroides is distinguished by its short snout, reduced maxilla, and deep zygomatic arch. Here we describe the endocranial anatomy (brain endocast, inner ear, blood vessels and cranial nerves) of Bienotheroides sp. collected from the Middle Jurassic Lower Shaximiao Formation and Xintiangou Formation in the Yunyang area of Chongqing, China. The cranial endocast features enlarged olfactory bulbs and a slender hypophysis. It is long and horizontally oriented in the brain cavity. The unossified zone is moderately developed. The paraflocculus is less developed than in most known cynodonts. The brain cast of Bienotheroides is divided into two cerebral hemispheres by a median interhemispheric sulcus, which is present only in the anterior half of the forebrain. The posterior portion of the forebrain remains undifferentiated. This condition appears to be more derived than the completely undifferentiated forebrain found in basal cynodonts. However, it is primitive compared with the fully divided cerebral hemispheres observed in probainognathian cynodonts, as well as in mammaliaforms. The 11 pairs of cranial nerves (excluding CN VI) in Bienotheroides are arranged longitudinally along the brain endocast, and its inner ear labyrinth is characterized by an elongated, uncoiled cochlea. The estimated encephalization quotient of Bienotheroides is similar to that of basal probainognathians or traversodontids, but relatively lower compared with derived probainognathians and mammaliaforms.
The cranial endocast of tritylodontid Bienotheroides (Cynodontia, Mammaliamorpha) and its relevance to mammalian neurosensory evolution
Papers in Palaeontology 11(3): e70021
doi: https://doi.org/10.1002/spp2.70021
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70021
Tritylodontidae are a cosmopolitan group of derived cynodonts that thrived during the Mesozoic Era. Among the tritylodontids, the genus Bienotheroides is distinguished by its short snout, reduced maxilla, and deep zygomatic arch. Here we describe the endocranial anatomy (brain endocast, inner ear, blood vessels and cranial nerves) of Bienotheroides sp. collected from the Middle Jurassic Lower Shaximiao Formation and Xintiangou Formation in the Yunyang area of Chongqing, China. The cranial endocast features enlarged olfactory bulbs and a slender hypophysis. It is long and horizontally oriented in the brain cavity. The unossified zone is moderately developed. The paraflocculus is less developed than in most known cynodonts. The brain cast of Bienotheroides is divided into two cerebral hemispheres by a median interhemispheric sulcus, which is present only in the anterior half of the forebrain. The posterior portion of the forebrain remains undifferentiated. This condition appears to be more derived than the completely undifferentiated forebrain found in basal cynodonts. However, it is primitive compared with the fully divided cerebral hemispheres observed in probainognathian cynodonts, as well as in mammaliaforms. The 11 pairs of cranial nerves (excluding CN VI) in Bienotheroides are arranged longitudinally along the brain endocast, and its inner ear labyrinth is characterized by an elongated, uncoiled cochlea. The estimated encephalization quotient of Bienotheroides is similar to that of basal probainognathians or traversodontids, but relatively lower compared with derived probainognathians and mammaliaforms.
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