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Reconstructing the archosaur radiation using a Middle Triassic archosauriform tooth assemblage from Tanzania.
PeerJ. 2019; 7:e7970.P

Abstract

Following the Permo-Triassic mass extinction, Archosauriformes-the clade that includes crocodylians, birds, and their extinct relatives outside crown Archosauria-rapidly diversified into many distinct lineages, became distributed globally, and, by the Late Triassic, filled a wide array of resource zones. Current scenarios of archosauriform evolution are ambiguous with respect to whether their taxonomic diversification in the Early-Middle Triassic coincided with the initial evolution of dietary specializations that were present by the Late Triassic or if their ecological disparity arose sometime after lineage diversification. Late Triassic archosauriform dietary specialization is recorded by morphological divergence from the plesiomorphic archosauriform tooth condition (laterally-compressed crowns with serrated carinae and a generally triangular lateral profile). Unfortunately, the roots of this diversification are poorly documented, with few known Early--Middle Triassic tooth assemblages, limiting characterizations of morphological diversity during this critical, early period in archosaur evolution. Recent fieldwork (2007-2017) in the Middle Triassic Manda Beds of the Ruhuhu Basin, Tanzania, recovered a tooth assemblage that provides a window into this poorly sampled interval. To investigate the taxonomic composition of that collection, we built a dataset of continuous quantitative and discrete morphological characters based on in situ teeth of known taxonomic status (e.g., Nundasuchus, Parringtonia: N = 65) and a sample of isolated teeth (N = 31). Using crown heights from known taxa to predict tooth base ratio (= base length/width), we created a quantitative morphospace for the tooth assemblage. The majority of isolated, unassigned teeth fall within a region of morphospace shared by several taxa from the Manda Beds (e.g., Nundasuchus, Parringtonia); two isolated teeth fall exclusively within a "Pallisteria" morphospace. A non-metric multidimensional scaling ordination (N = 67) of 11 binary characters reduced overlap between species. The majority of the isolated teeth from the Manda assemblage fall within the Nundasuchus morphospace. This indicates these teeth are plesiomorphic for archosauriforms as Nundasuchus exhibits the predicted plesiomorphic condition of archosauriform teeth. Our model shows that the conservative tooth morphologies of archosauriforms can be differentiated and assigned to species and/or genus, rendering the model useful for identifying isolated teeth. The large overlap in tooth shape among the species present and their overall similarity indicates that dietary specialization lagged behind species diversification in archosauriforms from the Manda Beds, a pattern predicted by Simpson's "adaptive zones" model. Although applied to a single geographic region, our methods offer a promising means to reconstruct ecological radiations and are readily transferable across a broad range of vertebrate taxa throughout Earth history.

Authors+Show Affiliations

Department of Geosciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA.Department of Geosciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA. Department of Geological Sciences, University of Cape Town, Rondebosch, South Africa.Department of Earth Sciences, Natural History Museum, London, UK.Department of Geosciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, USA.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31720109

Citation

Hoffman, Devin K., et al. "Reconstructing the Archosaur Radiation Using a Middle Triassic Archosauriform Tooth Assemblage From Tanzania." PeerJ, vol. 7, 2019, pp. e7970.
Hoffman DK, Edwards HR, Barrett PM, et al. Reconstructing the archosaur radiation using a Middle Triassic archosauriform tooth assemblage from Tanzania. PeerJ. 2019;7:e7970.
Hoffman, D. K., Edwards, H. R., Barrett, P. M., & Nesbitt, S. J. (2019). Reconstructing the archosaur radiation using a Middle Triassic archosauriform tooth assemblage from Tanzania. PeerJ, 7, e7970. https://doi.org/10.7717/peerj.7970
Hoffman DK, et al. Reconstructing the Archosaur Radiation Using a Middle Triassic Archosauriform Tooth Assemblage From Tanzania. PeerJ. 2019;7:e7970. PubMed PMID: 31720109.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Reconstructing the archosaur radiation using a Middle Triassic archosauriform tooth assemblage from Tanzania. AU - Hoffman,Devin K, AU - Edwards,Hunter R, AU - Barrett,Paul M, AU - Nesbitt,Sterling J, Y1 - 2019/11/05/ PY - 2019/07/17/received PY - 2019/10/01/accepted PY - 2019/11/14/entrez PY - 2019/11/14/pubmed PY - 2019/11/14/medline KW - Adaptive zones KW - Archosauria KW - Diversification KW - Macroevolution KW - Morphospace KW - Vertebrate paleontology SP - e7970 EP - e7970 JF - PeerJ JO - PeerJ VL - 7 N2 - Following the Permo-Triassic mass extinction, Archosauriformes-the clade that includes crocodylians, birds, and their extinct relatives outside crown Archosauria-rapidly diversified into many distinct lineages, became distributed globally, and, by the Late Triassic, filled a wide array of resource zones. Current scenarios of archosauriform evolution are ambiguous with respect to whether their taxonomic diversification in the Early-Middle Triassic coincided with the initial evolution of dietary specializations that were present by the Late Triassic or if their ecological disparity arose sometime after lineage diversification. Late Triassic archosauriform dietary specialization is recorded by morphological divergence from the plesiomorphic archosauriform tooth condition (laterally-compressed crowns with serrated carinae and a generally triangular lateral profile). Unfortunately, the roots of this diversification are poorly documented, with few known Early--Middle Triassic tooth assemblages, limiting characterizations of morphological diversity during this critical, early period in archosaur evolution. Recent fieldwork (2007-2017) in the Middle Triassic Manda Beds of the Ruhuhu Basin, Tanzania, recovered a tooth assemblage that provides a window into this poorly sampled interval. To investigate the taxonomic composition of that collection, we built a dataset of continuous quantitative and discrete morphological characters based on in situ teeth of known taxonomic status (e.g., Nundasuchus, Parringtonia: N = 65) and a sample of isolated teeth (N = 31). Using crown heights from known taxa to predict tooth base ratio (= base length/width), we created a quantitative morphospace for the tooth assemblage. The majority of isolated, unassigned teeth fall within a region of morphospace shared by several taxa from the Manda Beds (e.g., Nundasuchus, Parringtonia); two isolated teeth fall exclusively within a "Pallisteria" morphospace. A non-metric multidimensional scaling ordination (N = 67) of 11 binary characters reduced overlap between species. The majority of the isolated teeth from the Manda assemblage fall within the Nundasuchus morphospace. This indicates these teeth are plesiomorphic for archosauriforms as Nundasuchus exhibits the predicted plesiomorphic condition of archosauriform teeth. Our model shows that the conservative tooth morphologies of archosauriforms can be differentiated and assigned to species and/or genus, rendering the model useful for identifying isolated teeth. The large overlap in tooth shape among the species present and their overall similarity indicates that dietary specialization lagged behind species diversification in archosauriforms from the Manda Beds, a pattern predicted by Simpson's "adaptive zones" model. Although applied to a single geographic region, our methods offer a promising means to reconstruct ecological radiations and are readily transferable across a broad range of vertebrate taxa throughout Earth history. SN - 2167-8359 UR - https://www.unboundmedicine.com/medline/citation/31720109/Reconstructing_the_archosaur_radiation_using_a_Middle_Triassic_archosauriform_tooth_assemblage_from_Tanzania_ L2 - https://doi.org/10.7717/peerj.7970 DB - PRIME DP - Unbound Medicine ER -
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