Komodo dragon iron-coated teeth + osmoregulation in Alligatoroidea + Early Permian tetrapod tracks from China
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Ben Creisler
Jul 24, 2024, 2:04:18 PM (3 days ago) Jul 24
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Ben Creisler
Aaron R. H. LeBlanc, Alexander P. Morrell, Slobodan Sirovica, Maisoon Al-Jawad, David Labonte, Domenic C. D’Amore, Christofer Clemente, Siyang Wang, Finn Giuliani, Catriona M. McGilvery, Michael Pittman, Thomas G. Kaye, Colin Stevenson, Joe Capon, Benjamin Tapley, Simon Spiro & Owen Addison (2024)
Iron-coated Komodo dragon teeth and the complex dental enamel of carnivorous reptiles
Nature Ecology & Evolution (advance online publication)
doi: https://doi.org/10.1038/s41559-024-02477-7
https://www.nature.com/articles/s41559-024-02477-7
Komodo dragons (Varanus komodoensis) are the largest extant predatory lizards and their ziphodont (serrated, curved and blade-shaped) teeth make them valuable analogues for studying tooth structure, function and comparing with extinct ziphodont taxa, such as theropod dinosaurs. Like other ziphodont reptiles, V. komodoensis teeth possess only a thin coating of enamel that is nevertheless able to cope with the demands of their puncture–pull feeding. Using advanced chemical and structural imaging, we reveal that V. komodoensis teeth possess a unique adaptation for maintaining their cutting edges: orange, iron-enriched coatings on their tooth serrations and tips. Comparisons with other extant varanids and crocodylians revealed that iron sequestration is probably widespread in reptile enamels but it is most striking in V. komodoensis and closely related ziphodont species, suggesting a crucial role in supporting serrated teeth. Unfortunately, fossilization confounds our ability to consistently detect similar iron coatings in fossil teeth, including those of ziphodont dinosaurs. However, unlike V. komodoensis, some theropods possessed specialized enamel along their tooth serrations, resembling the wavy enamel found in herbivorous hadrosaurid dinosaurs. These discoveries illustrate unexpected and disparate specializations for maintaining ziphodont teeth in predatory reptiles.
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Jeremy B. Stout (2024)
Jianye Chen and Jun Liu (2024)
Journey to the east: the oldest tetrapod fauna of east Pangea in Early Permian
National Science Review, nwae249
doi: https://doi.org/10.1093/nsr/nwae249
https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwae249/7718806
Excerpt:
Recently we discovered a new early Permian tetrapod footprint assemblage, the Mentougou Ichno-fauna, from Taiyuan Formation (Asselian, 298 Ma) of Beijing, China (Fig. 1; Supple. Fig. 1-17). These footprints were the earliest record of terrestrial tetrapods in eastern Pangea. A total of six slabs were cataloged (IVPP V31904-31909), each with one or more footprints of variable qualities (Fig. 1a-m, Supple. Fig. 1-16, Supple. Data). Both anamniote and amniote footprints can be identified. Most identifiable footprints belong to Limnopus, probably produced by temnospondyls (Fig. 1a-d, I, j; Suppl. Fig. 1-8). One footprint is probably produced by amniotes such as parareptiles or eureptiles) (Fig. 1e, f, k; Suppl. Fig. 11, 12). Other footprints cannot be confidently attributed to ichno-genus due to poor preservation, but they represent a variety of morphology and sizes (5-17 cm) (Fig. 1j, h, l, m; Suppl. Fig. 13-16).
The footprint combination probably belongs to the Dromopus biochron, which is widely distributed in central and western Pangea during the late Carboniferous-early Permian (Fig. 1n) . For the whole fauna to be also distributed in the far east of Pangea, a free land movement must have existed between [North China Block] NCB and the rest of Pangea by 298 Ma. In other words, it provides strong evidence that NCB was connected with Tarim Block prior to early Permian, supporting the “Early Collision” hypothesis [in the formation of Pangea].
Recent reptile and tetrapod papers:
Free pdf:
Aaron R. H. LeBlanc, Alexander P. Morrell, Slobodan Sirovica, Maisoon Al-Jawad, David Labonte, Domenic C. D’Amore, Christofer Clemente, Siyang Wang, Finn Giuliani, Catriona M. McGilvery, Michael Pittman, Thomas G. Kaye, Colin Stevenson, Joe Capon, Benjamin Tapley, Simon Spiro & Owen Addison (2024)
Iron-coated Komodo dragon teeth and the complex dental enamel of carnivorous reptiles
Nature Ecology & Evolution (advance online publication)
doi: https://doi.org/10.1038/s41559-024-02477-7
https://www.nature.com/articles/s41559-024-02477-7
Komodo dragons (Varanus komodoensis) are the largest extant predatory lizards and their ziphodont (serrated, curved and blade-shaped) teeth make them valuable analogues for studying tooth structure, function and comparing with extinct ziphodont taxa, such as theropod dinosaurs. Like other ziphodont reptiles, V. komodoensis teeth possess only a thin coating of enamel that is nevertheless able to cope with the demands of their puncture–pull feeding. Using advanced chemical and structural imaging, we reveal that V. komodoensis teeth possess a unique adaptation for maintaining their cutting edges: orange, iron-enriched coatings on their tooth serrations and tips. Comparisons with other extant varanids and crocodylians revealed that iron sequestration is probably widespread in reptile enamels but it is most striking in V. komodoensis and closely related ziphodont species, suggesting a crucial role in supporting serrated teeth. Unfortunately, fossilization confounds our ability to consistently detect similar iron coatings in fossil teeth, including those of ziphodont dinosaurs. However, unlike V. komodoensis, some theropods possessed specialized enamel along their tooth serrations, resembling the wavy enamel found in herbivorous hadrosaurid dinosaurs. These discoveries illustrate unexpected and disparate specializations for maintaining ziphodont teeth in predatory reptiles.
***
News:
Komodo dragons have teeth coated in iron to kill prey, study finds
https://www.imperial.ac.uk/news/255014/komodo-dragons-have-iron-coated-teeth-apart/
https://www.iflscience.com/komodo-dragons-teeth-are-iron-tipped-for-extra-bite-raising-questions-about-t-rexes-75244
https://www.theguardian.com/environment/article/2024/jul/24/komodo-dragons-iron-coated-teeth
https://www.iflscience.com/komodo-dragons-teeth-are-iron-tipped-for-extra-bite-raising-questions-about-t-rexes-75244
https://www.theguardian.com/environment/article/2024/jul/24/komodo-dragons-iron-coated-teeth
===
Jeremy B. Stout (2024)
Osmoregulation in Alligatoroidea: shifting the paradigm untethers biogeographic questions
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2379029
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2379029
A pervasive maxim in herpetology is that alligators (Alligatoridae) are poor salinity regulators relative to their taxonomic kin, crocodiles (Crocodylidae), evidenced by the purported lack of osmoregulatory abilities of modern Alligator and caimans, which has led to the assumption that freshwater obligation is synapomorphic across the clade, to include extinct members of Alligatoridae, or even Alligatoroidea. Presented here is a brief review of osmoregulation and the fossil record of alligatoroids and a suggestion that salt-tolerance may have been more widespread in the group than is widely assumed, based upon the observations that 1) modern alligatorids are increasingly reported from brackish and marine environs and possess osmoregulatory abilities attained through different regulatory pathways than their crocodile counterparts, and 2) fossil members of the group are routinely (or exclusively) found in or near marine depositional settings, suggesting plausibility that earlier members of the clade were more ocean-going than their extant descendants. Starting with fewer assumptions about the osmoregulatory abilities of extinct taxa may help solve continuing problems in eusuchian biogeography, namely, the dispersals of alligatoroids into Europe and Asia, and multiple dispersal events to and from pre-Interchange South America. Secondary loss of salinity tolerance in Alligator may be adaptive in continental habitats.
Historical Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2024.2379029
https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2379029
A pervasive maxim in herpetology is that alligators (Alligatoridae) are poor salinity regulators relative to their taxonomic kin, crocodiles (Crocodylidae), evidenced by the purported lack of osmoregulatory abilities of modern Alligator and caimans, which has led to the assumption that freshwater obligation is synapomorphic across the clade, to include extinct members of Alligatoridae, or even Alligatoroidea. Presented here is a brief review of osmoregulation and the fossil record of alligatoroids and a suggestion that salt-tolerance may have been more widespread in the group than is widely assumed, based upon the observations that 1) modern alligatorids are increasingly reported from brackish and marine environs and possess osmoregulatory abilities attained through different regulatory pathways than their crocodile counterparts, and 2) fossil members of the group are routinely (or exclusively) found in or near marine depositional settings, suggesting plausibility that earlier members of the clade were more ocean-going than their extant descendants. Starting with fewer assumptions about the osmoregulatory abilities of extinct taxa may help solve continuing problems in eusuchian biogeography, namely, the dispersals of alligatoroids into Europe and Asia, and multiple dispersal events to and from pre-Interchange South America. Secondary loss of salinity tolerance in Alligator may be adaptive in continental habitats.
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Free pdf:
Free pdf:
Jianye Chen and Jun Liu (2024)
Journey to the east: the oldest tetrapod fauna of east Pangea in Early Permian
National Science Review, nwae249
doi: https://doi.org/10.1093/nsr/nwae249
https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwae249/7718806
Excerpt:
Recently we discovered a new early Permian tetrapod footprint assemblage, the Mentougou Ichno-fauna, from Taiyuan Formation (Asselian, 298 Ma) of Beijing, China (Fig. 1; Supple. Fig. 1-17). These footprints were the earliest record of terrestrial tetrapods in eastern Pangea. A total of six slabs were cataloged (IVPP V31904-31909), each with one or more footprints of variable qualities (Fig. 1a-m, Supple. Fig. 1-16, Supple. Data). Both anamniote and amniote footprints can be identified. Most identifiable footprints belong to Limnopus, probably produced by temnospondyls (Fig. 1a-d, I, j; Suppl. Fig. 1-8). One footprint is probably produced by amniotes such as parareptiles or eureptiles) (Fig. 1e, f, k; Suppl. Fig. 11, 12). Other footprints cannot be confidently attributed to ichno-genus due to poor preservation, but they represent a variety of morphology and sizes (5-17 cm) (Fig. 1j, h, l, m; Suppl. Fig. 13-16).
The footprint combination probably belongs to the Dromopus biochron, which is widely distributed in central and western Pangea during the late Carboniferous-early Permian (Fig. 1n) . For the whole fauna to be also distributed in the far east of Pangea, a free land movement must have existed between [North China Block] NCB and the rest of Pangea by 298 Ma. In other words, it provides strong evidence that NCB was connected with Tarim Block prior to early Permian, supporting the “Early Collision” hypothesis [in the formation of Pangea].
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