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Dentary morphological variation in Clevosaurus brasiliensis (Rhynchocephalia, Clevosauridae) from the Upper Triassic of Rio Grande do Sul, Brazil.

Romo de Vivar Martínez PR, Soares MB - PLoS ONE (2015)

Bottom Line: This allometric growth is similar to what is observed in other rhynchocephalians and is accompanied by the allometric skull growth, similar to the trend exhibited by clevosaurs.The taphocoenosis is bimodal (juveniles and adults) with a bias towards adult preservation.Some diagenetic influence is reflected in deformed skulls and this is observed in the tangent-plot.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Paleontologia de Vertebrados, Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.

ABSTRACT
Clevosaurus was a cosmopolitan rhynchocephalian genus, known from the Late Triassic to the Early Jurassic. In South America this genus is represented by C. brasiliensis, an important component of the Linha São Luiz taphocoenosis, on the top of the Norian Santa Maria 2 Sequence of Southern Brazil. The best preserved and most abundant bone elements of C. brasiliensis are dentaries, in which variations of shape and size are observed. The aim of this study is to describe and evaluate the variation, using geometric morphometrics methods. Geometric morphometric analysis of 10 specimens highlights variations in relative size of the dentary. Most of the variation observed for PC1 (83.3%) is likely related to ontogeny, and PC2 (10.0%) is likely related to taphonomic signatures. The development patterns observed, such as the growth of the dentary, consists of differential growth in length between the posterior portion of the dentary, that grows at a higher rate, regarding the anterior portion of the element. This allometric growth is similar to what is observed in other rhynchocephalians and is accompanied by the allometric skull growth, similar to the trend exhibited by clevosaurs. The taphocoenosis is bimodal (juveniles and adults) with a bias towards adult preservation. Some diagenetic influence is reflected in deformed skulls and this is observed in the tangent-plot. Finally, a strong correlation was detected between the taphonomic signatures and the PC2, regarding specially disarticulation and degree of fragmentation.

No MeSH data available.


Related in: MedlinePlus

Reconstruction of the dentary growth.A) Juvenile individual; B) Mature individual. The tricolor, bar represents the regions of dentary: Blue = the tooth row; Black = diastema; Green = the posterior region; j = the regions in juvenile individual, and m = regions in mature individual Scale bars 1 cm.
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pone.0119307.g011: Reconstruction of the dentary growth.A) Juvenile individual; B) Mature individual. The tricolor, bar represents the regions of dentary: Blue = the tooth row; Black = diastema; Green = the posterior region; j = the regions in juvenile individual, and m = regions in mature individual Scale bars 1 cm.

Mentions: In Sphenodon, “the dentary increases in length posteriorly, and may continue to do so after the implantation of the last member of the additional series, producing an diastema between the last additional tooth and the coronoid process of the dentary” [17], and the same was inferred for Cynosphenodon huizachalensis [34]. In the thin plate (Fig. 9, and S1 Fig.), we see that the dentary is gracile in the “G shape” (juveniles), and that in the “R shape” (adults) the dentary is more robust. Also, the tooth row is relatively longer in juvenile compared to mature specimens (Fig. 11). Because in Clevosaurus there are no successional teeth, the only reference point are the last additional teeth, and it is not possible to compare the other points of growth in the anterior part with Sphenodon and Cynosphenodon huizachalensis.


Dentary morphological variation in Clevosaurus brasiliensis (Rhynchocephalia, Clevosauridae) from the Upper Triassic of Rio Grande do Sul, Brazil.

Romo de Vivar Martínez PR, Soares MB - PLoS ONE (2015)

Reconstruction of the dentary growth.A) Juvenile individual; B) Mature individual. The tricolor, bar represents the regions of dentary: Blue = the tooth row; Black = diastema; Green = the posterior region; j = the regions in juvenile individual, and m = regions in mature individual Scale bars 1 cm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4368672&req=5

pone.0119307.g011: Reconstruction of the dentary growth.A) Juvenile individual; B) Mature individual. The tricolor, bar represents the regions of dentary: Blue = the tooth row; Black = diastema; Green = the posterior region; j = the regions in juvenile individual, and m = regions in mature individual Scale bars 1 cm.
Mentions: In Sphenodon, “the dentary increases in length posteriorly, and may continue to do so after the implantation of the last member of the additional series, producing an diastema between the last additional tooth and the coronoid process of the dentary” [17], and the same was inferred for Cynosphenodon huizachalensis [34]. In the thin plate (Fig. 9, and S1 Fig.), we see that the dentary is gracile in the “G shape” (juveniles), and that in the “R shape” (adults) the dentary is more robust. Also, the tooth row is relatively longer in juvenile compared to mature specimens (Fig. 11). Because in Clevosaurus there are no successional teeth, the only reference point are the last additional teeth, and it is not possible to compare the other points of growth in the anterior part with Sphenodon and Cynosphenodon huizachalensis.

Bottom Line: This allometric growth is similar to what is observed in other rhynchocephalians and is accompanied by the allometric skull growth, similar to the trend exhibited by clevosaurs.The taphocoenosis is bimodal (juveniles and adults) with a bias towards adult preservation.Some diagenetic influence is reflected in deformed skulls and this is observed in the tangent-plot.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Paleontologia de Vertebrados, Departamento de Paleontologia e Estratigrafia, Instituto de Geociências, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.

ABSTRACT
Clevosaurus was a cosmopolitan rhynchocephalian genus, known from the Late Triassic to the Early Jurassic. In South America this genus is represented by C. brasiliensis, an important component of the Linha São Luiz taphocoenosis, on the top of the Norian Santa Maria 2 Sequence of Southern Brazil. The best preserved and most abundant bone elements of C. brasiliensis are dentaries, in which variations of shape and size are observed. The aim of this study is to describe and evaluate the variation, using geometric morphometrics methods. Geometric morphometric analysis of 10 specimens highlights variations in relative size of the dentary. Most of the variation observed for PC1 (83.3%) is likely related to ontogeny, and PC2 (10.0%) is likely related to taphonomic signatures. The development patterns observed, such as the growth of the dentary, consists of differential growth in length between the posterior portion of the dentary, that grows at a higher rate, regarding the anterior portion of the element. This allometric growth is similar to what is observed in other rhynchocephalians and is accompanied by the allometric skull growth, similar to the trend exhibited by clevosaurs. The taphocoenosis is bimodal (juveniles and adults) with a bias towards adult preservation. Some diagenetic influence is reflected in deformed skulls and this is observed in the tangent-plot. Finally, a strong correlation was detected between the taphonomic signatures and the PC2, regarding specially disarticulation and degree of fragmentation.

No MeSH data available.


Related in: MedlinePlus