Bienotheroides (Jurassic tritylodontid) new specimen described (free pdf)
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Ben Creisler
Oct 13, 2025, 11:34:11 AM (6 days ago) Oct 13
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Ben Creisler
Free pdf:
Jicheng Ren, Lu Liu, Fenglu Han, Xing Xu, James M. Clark, Jun Liu, Jin Meng, and Fangyuan Mao (2025)
A new specimen of the tritylodontid Bienotheroides zigongensis (Cynodontia, Mammaliamorpha) from the Wucaiwan area of Xinjiang, China, and phylogeny of Tritylodontidae
Bulletin of the American Museum of Natural History 477: 117 pp.
doi: https://doi.org/10.5531/sd.sp.77
https://digitallibrary.amnh.org/items/dd8a804a-ee81-4a73-a50b-2911543db08c
Tritylodontidae is a Mesozoic group of small to medium-sized mammaliamorph cynodonts with cosmopolitan geographic distribution and characterized by possessing three mesiodistal rows of cusps in each of their upper postcanine teeth and two rows in the lower postcanines. Abundant tritylodontid materials have been discovered in Sichuan, Xinjiang, Yunnan, and other localities in China since 1938, but detailed description of their morphologies has been wanting. This paper describes a well-preserved tritylodontid skull with both mandibles, complete dentitions, and post-dentary bones. The specimen was collected from the Upper Jurassic Shishugou Formation in the Wucaiwan area of Junggar Basin, Xinjiang, China. It is assigned to Bienotheroides zigongensis because it possesses a typical characteristic combination of B. zigongensis, such as an extremely deep zygomatic arch, a greatly reduced maxilla, upper postcanine cusp formula of 2-3-3 and a quadrate with a mediodorsally directed stapedial process. Using micro-CT scan data, we are able to create three-dimensional digital reconstructions and provide a complete description of the specimen. We also reconstruct the inner ear and the maxillary canal system, which provide considerable craniodental information previously unknown in Bienotheroides. These new morphological data are informative for better diagnosing the genus and reconstructing the phylogeny of tritylodontids. A revised character data matrix with 15 tritylodontid genera and 70 characters is generated based on reevaluated morphological characters, of which 23 characters are new. Our phylogenetic analysis of Tritylodontidae resulted in a better-resolved topology of the phylogenetic relationship of tritylodontids. Using this phylogenetic framework, we postulate an evolutionary pattern of tritylodontid cranial morphology unique among cynodonts, characterized by shortening of the snout and basicranial region and reduction of the maxilla.
A new paper:
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Free pdf:
Jicheng Ren, Lu Liu, Fenglu Han, Xing Xu, James M. Clark, Jun Liu, Jin Meng, and Fangyuan Mao (2025)
A new specimen of the tritylodontid Bienotheroides zigongensis (Cynodontia, Mammaliamorpha) from the Wucaiwan area of Xinjiang, China, and phylogeny of Tritylodontidae
Bulletin of the American Museum of Natural History 477: 117 pp.
doi: https://doi.org/10.5531/sd.sp.77
https://digitallibrary.amnh.org/items/dd8a804a-ee81-4a73-a50b-2911543db08c
Tritylodontidae is a Mesozoic group of small to medium-sized mammaliamorph cynodonts with cosmopolitan geographic distribution and characterized by possessing three mesiodistal rows of cusps in each of their upper postcanine teeth and two rows in the lower postcanines. Abundant tritylodontid materials have been discovered in Sichuan, Xinjiang, Yunnan, and other localities in China since 1938, but detailed description of their morphologies has been wanting. This paper describes a well-preserved tritylodontid skull with both mandibles, complete dentitions, and post-dentary bones. The specimen was collected from the Upper Jurassic Shishugou Formation in the Wucaiwan area of Junggar Basin, Xinjiang, China. It is assigned to Bienotheroides zigongensis because it possesses a typical characteristic combination of B. zigongensis, such as an extremely deep zygomatic arch, a greatly reduced maxilla, upper postcanine cusp formula of 2-3-3 and a quadrate with a mediodorsally directed stapedial process. Using micro-CT scan data, we are able to create three-dimensional digital reconstructions and provide a complete description of the specimen. We also reconstruct the inner ear and the maxillary canal system, which provide considerable craniodental information previously unknown in Bienotheroides. These new morphological data are informative for better diagnosing the genus and reconstructing the phylogeny of tritylodontids. A revised character data matrix with 15 tritylodontid genera and 70 characters is generated based on reevaluated morphological characters, of which 23 characters are new. Our phylogenetic analysis of Tritylodontidae resulted in a better-resolved topology of the phylogenetic relationship of tritylodontids. Using this phylogenetic framework, we postulate an evolutionary pattern of tritylodontid cranial morphology unique among cynodonts, characterized by shortening of the snout and basicranial region and reduction of the maxilla.
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