A Review of the Fossil Record of Turtles of the Clade<i>Thalassochelydia</i>

Anquetin, Jérémy; Püntener, Christian; Joyce, Walter G.

doi:10.3374/014.058.0205

Cited by 49 publications

(90 citation statements)

References 59 publications

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“…Since both DORCM G.10715 and the shell-based Hylaeochelys belli co-occur in the Purbeck Group and appear to be representatives of Thalassochelydia, a group usually considered to disappear at the end of the Jurassic (e.g., Bardet, 1994;Anquetin et al, 2017), we believe that there is a reasonably good chance that they actually represent the same species. Although we lack more definitive evidence for the moment, it should be noted that the shell corresponding to the cranium DORCM G.10715 can be estimated to be around 38-40 cm in length (supposing the cranium represents about 20% of the carapace length as common in these turtles), which matches fairly well with the size range of Hylaeochelys belli (Milner, 2004;Pérez-García, 2012).…”

Section: Alpha Taxonomymentioning

confidence: 93%

“…Although there is no strong morphological argument to support or discredit this hypothesis, Hylaeochelys belli has been repeatedly suggested to have affinities with Plesiochelyidae (Lydekker, 1889;Nopcsa, 1928;Hirayama et al, 2000;Lapparent de Broin, 2001;Milner, 2004;Karl et al, 2007;Pérez-García, 2012). However, plesiochelyids are usually found in more frankly marine deposits and are believed to go extinct at the Jurassic-Cretaceous transition due to the disappearance of their coastal marine habitat in Europe (e.g., Bardet, 1994;Lapparent de Broin et al, 1996;Anquetin et al, 2017). Therefore, Hylaeochelys belli is usually left out of consideration in studies dealing with plesiochelyids or more generally with Thalassochelydia, the clade uniting plesiochelyids and other Late Jurassic coastal marine turtles .…”

Section: Introductionmentioning

confidence: 99%

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The last surviving Thalassochelydia—A new turtle cranium from the Early Cretaceous of the Purbeck Group (Dorset, UK)

Anquetin¹,

André²

2020

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Background. The mostly Berriasian (Early Cretaceous) Purbeck Group of southern England has produced a rich turtle fauna dominated by the freshwater paracryptodires Pleurosternon bullockii and Dorsetochelys typocardium. Each of these species is known by numerous relatively complete shells and by a single cranium. The two other turtles found in the Purbeck Group (Hylaeochelys belli, a species of uncertain affinities, and the terrestrial helochelydrid "Helochelydra" anglica) are known only from shell remains.Methods. In the present contribution, we describe a new turtle cranium from the Purbeck Group of Swanage, Dorset (southern England). We also explore the phylogenetic relationships of this new cranium and of Hylaeochelys belli in the context of a recently published global turtle matrix.Results. Before complete preparation, the new Purbeck cranium was provisionally referred to Dorsetochelys typocardium, but our analysis clearly contradicts a referral to this species in particular and to paracryptodires in general. In contrast, the new cranium shares a number of features with the Late Jurassic, coastal marine Thalassochelydia, including a posterolaterally open foramen palatinum posterius, a strong ridge on the posterior surface of the processus articularis of the quadrate, a strong posterior orientation of the processus articularis in ventral view, and a processus trochlearis oticum limited to the medial part of the otic chamber and bordered by a deep recess laterally. Our phylogenetic analysis confirms a placement of the new Purbeck cranium within the clade Thalassochelydia.Discussion. In terms of morphology, the new Purbeck cranium does not correspond to any known taxon. However, we refrain from naming a new species based on it because there is a good chance that this cranium actually belongs to the shell-based species Hylaeochelys belli (also recovered as a thalassochelydian in our phylogenetic analysis). Unfortunately, we lack any objective evidence to support this conclusion for the moment. In any case, the new Purbeck cranium confirms what others have previously suggested based on Hylaeochelys belli: thalassochelydian turtles survived the Jurassic-Cretaceous transition.

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Section: Alpha Taxonomymentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

The last surviving Thalassochelydia—A new turtle cranium from the Early Cretaceous of the Purbeck Group (Dorset, UK)

Anquetin¹,

André²

2020

Preprint

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“…Additionally, some extinct marine Jurassic thalassochelydians, such as Solnhofia parsoni or Plesiochelys planiceps, also have welldeveloped antra postotica that extend deeply into the squamosals (e.g. Gaffney, 1975Gaffney, , 1976Anquetin et al 2017;.…”

Section: Middle Ear Cavity Shapementioning

confidence: 99%

Comparative analysis of the shape and size of the middle ear cavity of turtles reveals no correlation with habitat ecology

et al. 2019

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The middle ear of turtles differs from other reptiles in being separated into two distinct compartments. Several ideas have been proposed as to why the middle ear is compartmentalized in turtles, most suggesting a relationship with underwater hearing. Extant turtle species span fully marine to strictly terrestrial habitats, and ecomorphological hypotheses of turtle hearing predict that this should correlate with variation in the structure of the middle ear due to differences in the fluid properties of water and air. We investigate the shape and size of the air-filled middle ear cavity of 56 extant turtles using 3D data and phylogenetic comparative analysis to test for correlations between habitat preferences and the shape and size of the middle ear cavity. Only weak correlations are found between middle ear cavity size and ecology, with aquatic taxa having proportionally smaller cavity volumes. The middle ear cavity of turtles exhibits high shape diversity among species, but we found no relationship between this shape variation and ecology. Surprisingly, the estimated acoustic transformer ratio, a key functional parameter of impedance-matching ears in vertebrates, also shows no relation to habitat preferences (aquatic/terrestrial) in turtles. We suggest that middle ear cavity shape may be controlled by factors unrelated to hearing, such as the spatial demands of surrounding cranial structures. A review of the fossil record suggests that the modern turtle ear evolved during the Early to Middle Jurassic in stem turtles broadly adapted to freshwater and terrestrial settings. This, combined with our finding that evolutionary transitions between habitats caused only weak evolutionary changes in middle ear structure, suggests that tympanic hearing in turtles evolved as a compromise between subaerial and underwater hearing.

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“…Currently, eight species are considered valid within "Eurysternidae" (see Anquetin et al, 2017 for a review). Four of them are characterized by a relatively reduced shell fenestration (costo-peripheral fontanelles small or absent, plastral fontanelles reduced in development in adults): Idiochelys fitzingeri Meyer, 1839b, Palaeomedusa testa Meyer, 1860, Parachelys eichstaettensis Meyer, 1864, and Solnhofia parsonsi Gaffney, 1975b.…”

Section: Introductionmentioning

confidence: 99%

New material of “Eurysternidae” (Thalassochelydia, Pan-Cryptodira) from the Kimmeridgian of the Swiss Jura Mountains

Püntener¹,

Anquetin²,

Billon‐Bruyat³

2019

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The region of Porrentruy (Swiss Jura Mountains) is known for its rich and diverse assemblage of Late Jurassic coastal marine turtles (Thalassochelydia). Dominated by the "Plesiochelyidae", this assemblage also includes representatives of the two other thalassochelydian groups, the "Thalassemydidae" and "Eurysternidae." In this study, we present new shell-based material from Porrentruy referable to eurysternids. One specimen represents a juvenile individual or a relatively small taxon, and is notably characterized by a well fenestrated plastron exhibiting a wider than long central plastral fontanelle. Two other specimens are much larger and possibly represent the largest eurysternids known to date. The fourth specimen is characterized by a unique plastral morphology otherwise only known in very small juveniles. This is the first time this unique plastral morphology is known to persist in an adult or subadult. The new material described herein represents at least three distinct taxa, all of them probably new. However, we refrain from naming new species based on this incomplete material in order to avoid adding confusion to an already complex taxonomical situation. This study provides new insights into the great diversity of eurysternids during the Late Jurassic.

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A Review of the Fossil Record of Turtles of the CladeThalassochelydia

Cited by 49 publications

References 59 publications

The last surviving Thalassochelydia—A new turtle cranium from the Early Cretaceous of the Purbeck Group (Dorset, UK)

The last surviving Thalassochelydia—A new turtle cranium from the Early Cretaceous of the Purbeck Group (Dorset, UK)

Comparative analysis of the shape and size of the middle ear cavity of turtles reveals no correlation with habitat ecology

New material of “Eurysternidae” (Thalassochelydia, Pan-Cryptodira) from the Kimmeridgian of the Swiss Jura Mountains

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