Huehuecuetzpalli mixtecus is an extinct lizard from the Early Cretaceous (late Albian) Tlayúa Formation in Tepexi de Rodríguez, Central Mexico. Although it is not the oldest known lizard, Huehuecuetzpalli may be amongst the most basal members of Squamata (the group that includes lizards and snakes), making it an important taxon in understanding the origins of squamates.[1]
| Huehuecuetzpalli Temporal range: Late Albian,
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| Artist's reconstruction | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Genus: | †Huehuecuetzpalli Reynoso, 1998 |
| Type species | |
| †Huehuecuetzpalli mixtecus Reynoso 1998
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The generic name comes from the Nahuatl words huehuetl ("the ancient") and cuetzpalli ("lizard"), while the specific name refers to the La Mixteca region.[1]
Description edit
Unique characteristics (autapomorphies) of Huehuecuetzpalli include a long pair of premaxilla bones at the tip of the upper jaw that contributes to an elongated snout and the apparent retraction of the external nares or nostril openings. At the top of the skull, a small rounded postfrontal and a hole called the parietal foramen between the junction of the frontal bone and the parietal bone (the frontoparietal suture) suggest affinities with iguanians, but the retention of divided premaxillae, amphicoelous vertebrae (vertebrae that are concave at both ends), thoracolumbar intercentra (bones between the vertebrae of the back), an entepicondylar foramen in the humerus (upper arm bone), and a second distal tarsal bone in the foot supports the hypothesis that Huehuecuetzpalli is a basal squamate.[1] A 2021 study suggested that Huehuecuetzpalli was bipedal.[2]
Taxonomy edit
Huehuecuetzpalli has been suggested to be either a basal squamate or an iguanian. The most parsimonious tree recovered by Reynoso (1998), seen below, recovers it as the outgroup of crown-group squamates:[1]
| Squamata |
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| (total group) |
Its position as a stem-group squamate has been supported by subsequent studies.[3][4][5]
Cladogram after Talanda et al. 2022[5]
References edit
- ^ a b c d Reynoso, V.-H. (29 March 1998). "Huehuecuetzpalli mixtecus gen. et sp. nov: a basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodríguez, Central México". Philosophical Transactions of the Royal Society B: Biological Sciences. 353 (1367): 477–500. doi:10.1098/rstb.1998.0224. JSTOR 56466. PMC 1692218.
- ^ Villaseñor-Amador, Damián; Suárez, Nut Xanat; Cruz, J. Alberto (August 2021). "Bipedalism in Mexican albian lizard (squamata) and the locomotion type in other cretaceous lizards". Journal of South American Earth Sciences. 109: 103299. Bibcode:2021JSAES.10903299V. doi:10.1016/j.jsames.2021.103299. S2CID 233526155.
- ^ Simões, Tiago R.; Caldwell, Michael W.; Tałanda, Mateusz; Bernardi, Massimo; Palci, Alessandro; Vernygora, Oksana; Bernardini, Federico; Mancini, Lucia; Nydam, Randall L. (May 2018). "The origin of squamates revealed by a Middle Triassic lizard from the Italian Alps". Nature. 557 (7707): 706–709. Bibcode:2018Natur.557..706S. doi:10.1038/s41586-018-0093-3. ISSN 0028-0836. PMID 29849156. S2CID 44108416.
- ^ Bolet, Arnau; Stubbs, Thomas L; Herrera-Flores, Jorge A; Benton, Michael J (2022-05-03). "The Jurassic rise of squamates as supported by lepidosaur disparity and evolutionary rates". eLife. 11: e66511. doi:10.7554/eLife.66511. ISSN 2050-084X. PMC 9064307. PMID 35502582.
- ^ a b Tałanda, Mateusz; Fernandez, Vincent; Panciroli, Elsa; Evans, Susan E.; Benson, Roger J. (2022-10-26). "Synchrotron tomography of a stem lizard elucidates early squamate anatomy". Nature. 611 (7934): 99–104. Bibcode:2022Natur.611...99T. doi:10.1038/s41586-022-05332-6. ISSN 0028-0836. PMID 36289329. S2CID 253160713.
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