Triassic turtle remains from northeastern Thailand

Ingavat, Rucha; Janvier, Philippe; Sattayarak, Nares

doi:10.1080/02724634.1982.10011916

Cited by 22 publications

(9 citation statements)

References 7 publications

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“…A roughly contemporary, but very incomplete taxon was found in Thailand (de Broin et al . ) and later named Proganochelys ruchae de Broin, , and a more complete turtle was reported as cf. Proganochelys , but not described in detail, from Greenland (Jenkins et al .…”

Section: Institutional Abbreviationsmentioning

confidence: 99%

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The early composition and evolution of the turtle shell (Reptilia, Testudinata)

Szczygielski

Sulej

2018

Palaeontology

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The shell of the oldest true turtle (Testudinata) branch (Proterochersidae) from the Late Triassic (Norian) of Poland and Germany was built in its anterior and posterior part from an osteodermal mosaic which developed several million years after the plastron, neurals and costal bones. We provide the most detailed description of the shell composition in proterochersids to date, together with a review of the shell composition in other Triassic pantestudinates. A scenario of early evolution of the turtle shell is proposed based on new data, and the possible adaptive meaning of the observed evolutionary changes is discussed. These observations are consistent with the trend of shell simplification previously reported in turtles. Several aspects of proterochersid shell anatomy are intermediate between Odontochelys semitestacea and more derived turtles, supporting their stem phylogenetic position. Three additional ossifications were sutured to xiphiplastra and pelvis in Proterochersis spp. and at least in some individuals the nuchal bone was paired. The peripherals, suprapygals, and pygal bone are most likely to be of osteodermal origin and homologous to the proterochersid shell mosaic.

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Section: Institutional Abbreviationsmentioning

confidence: 99%

“…semitestacea , after the costals, neurals and plastron developed, and all the Norian turtles already had complete shells (Fraas ; de Broin et al . ; de Broin ; Gaffney , ; Jenkins et al . ; Rougier et al .…”

Section: Institutional Abbreviationsmentioning

confidence: 99%

The early composition and evolution of the turtle shell (Reptilia, Testudinata)

Szczygielski

Sulej

2018

Palaeontology

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“…(e.g., Figs. S8A, S8B and S8E–S8G), are present in numerous Triassic (De Broin et al, 1982; Gaffney, 1990) and Jurassic (De Broin, 1994; Anquetin & Claude, 2008; Anquetin & Joyce, 2014; Anquetin, Püntener & Billon-Bruyat, 2014; Jansen & Klein, 2014; Anquetin, Püntener & Joyce, 2017; Sullivan & Joyce, 2017) turtles. The same superficial characters are also present in K. limendorsa specimen SMNS 17757, including clear striation and growth marks along the cranial and lateral edges of the last vertebral scute, and unlike Proterochersis spp.…”

Section: Variation Of Shell Featuresmentioning

confidence: 99%

Shell variability in the stem turtlesProterochersisspp.

Szczygielski

Słowiak

Dróżdż

2018

PeerJ

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BackgroundTurtle shells tend to exhibit frequent and substantial variability, both in bone and scute layout. Aside from secondary changes, caused by diseases, parasites, and trauma, this variability appears to be inherent and result from stochastic or externally induced flaws of developmental programs. It is, thus, expected to be present in fossil turtle species at least as prominently, as in modern populations. Descriptions of variability and ontogeny are, however, rare for fossil turtles, mainly due to rarity, incompleteness, damage, and post-mortem deformation of their remains. This paper is an attempt at description and interpretation of external shell variability in representatives of the oldest true turtles, Proterochersis robusta and Proterochersis porebensis (Proterochersidae, the sister group to all other known testudinatans) from the Late Triassic (Norian) of Germany and Poland.MethodsAll the available shell remains of Proterochersis robusta (13 specimens) and Proterochersis porebensis (275 specimens) were studied morphologically in order to identify any ontogenetic changes, intraspecific variability, sexual dimorphism, and shell abnormalities. To test the inferred sexual dimorphism, shape analyses were performed for two regions (gular and anal) of the plastron.ResultsProterochersis spp. exhibits large shell variability, and at least some of the observed changes seem to be correlated with ontogeny (growth of gulars, extragulars, caudals, and marginals, disappearance of middorsal keel on the carapace). Several specimens show abnormal layout of scute sulci, several others unusual morphologies of vertebral scute areas, one has an additional pair of plastral scutes, and one extraordinarily pronounced, likely pathological, growth rings on the carapace. Both species are represented in a wide spectrum of sizes, from hatchlings to old, mature individuals. The largest fragmentary specimens of Proterochersis porebensis allow estimation of its maximal carapace length at approximately 80 cm, while Proterochersis robusta appears to have reached lower maximal sizes.DiscussionThis is the second contribution describing variability among numerous specimens of Triassic turtles, and the first to show evidence of unambiguous shell abnormalities. Presented data supplement the sparse knowledge of shell scute development in the earliest turtles and suggest that at least some aspects of the developmental programs governing scute development were already similar in the Late Triassic to these of modern forms.

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“…(e.g., Fig. S8A-B, E-G), are present in numerous Triassic (de Broin et al, 1982;Gaffney, 1990) and Jurassic (Broin, 1994;Anquetin & Claude, 2008;Anquetin & Joyce, 2014;Anquetin, Püntener & Billon-Bruyat, 2014;Jansen & Klein, 2014;Anquetin, Püntener & Joyce, 2017;Sullivan & Joyce, 2017) turtles. The same superficial characters are also present in Keuperotesta limendorsa specimen SMNS 17757, including clear striation and growth marks along the cranial and lateral edges of the last vertebral scute, and unlike Proterochersis spp.…”

Section: Variation Of Shell Featuresmentioning

confidence: 99%

Peer Review #2 of "Shell variability in the stem turtles Proterochersis spp. (v0.1)"

Ferreira¹

2018

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Background. Turtle shells tend to exhibit frequent and substantial variability, both in bone and scute layout. Aside from secondary changes, caused by diseases, parasites, and trauma, this variability appears to be inherent and result from stochastic or externally-induced flaws of developmental programs. It is, thus, expected to be present in fossil turtle species at least as prominently, as in modern populations. Descriptions of variability and ontogeny are, however, rare for fossil turtles, mainly due to rarity, incompleteness, damage, and post-mortem deformation of their remains. This paper is an attempt at description and interpretation of external shell variability in representatives of the oldest true turtles, Proterochersis robusta and P. porebensis (Proterochersidae, the sister group to all other known testudinatans) from the Late Triassic (Norian) of Germany and Poland. Methods. All the available shell remains of Proterochersis robusta (13 specimens) and P. porebensis (275 specimens) were studied morphologically in order to identify any ontogenetic changes, intraspecific variability, sexual dimorphism, and shell abnormalities. To test the inferred sexual dimorphism, shape analyses were performed for two regions (gular and anal) of the plastron. Results. Proterochersis spp. exhibits large shell variability, and at least some of the observed changes seem to be correlated with ontogeny (growth of gulars, extragulars, caudals, and marginals, disappearance of middorsal keel on the carapace). Several specimens show abnormal layout of scute sulci, several others unusual morphologies of vertebral scute areas, one has an additional pair of plastral scutes, and one extraordinarily pronounced, likely pathological, growth rings on the carapace. Both species are represented in a wide spectrum of sizes, from hatchlings to old, mature individuals. The largest fragmentary specimens of P. porebensis allow estimation of its maximal carapace length at approximately 80 cm, while P. robusta appears to have reached lower maximal sizes. Discussion. This is the second contribution describing variability among numerous specimens of Triassic turtles, and the first to show evidence of unambiguous shell abnormalities. Presented data supplement the sparse knowledge of shell scute development in the earliest turtles and suggest that at least some aspects of the developmental programs governing scute development were already similar in the Late Triassic to these of modern forms.

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Triassic turtle remains from northeastern Thailand

Cited by 22 publications

References 7 publications

The early composition and evolution of the turtle shell (Reptilia, Testudinata)

The early composition and evolution of the turtle shell (Reptilia, Testudinata)

Shell variability in the stem turtlesProterochersisspp.

Peer Review #2 of "Shell variability in the stem turtles Proterochersis spp. (v0.1)"

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