Figure 2 - uploaded by Gabriel Ferreira
Content may be subject to copyright.
Bairdemys thalassica sp. nov. Holotype skull IVIC-P-2908 in (A) dorsal, (B) ventral, (C) rostral, (D) caudal, (E) left, and (F) right lateral views.
Source publication
The extinct Stereogenyina turtles form a relatively diverse Podocnemididae lineage, with twelve described and phylogenetically positioned species. They are characterized by a wide geographic and temporal range, from the Eocene of Africa to the Pleistocene of Southeast Asia, and a peculiar palate morphology, with a secondary palate that is unique am...
Contexts in source publication
Context 1
... holotype and only specimen assigned to Bairdemys thalassica, IVIC-P-2908 ( Figs. 2 and 3), is very well preserved, with almost no taphonomic distortion. It is nearly complete, lacking only the rostral and the right dorsal regions. Only the vomeri, the premaxillae, and the prefrontals are completely absent. The frontal, jugal, quadratojugal, parietal, squamosal, maxilla, and palatine have one of the elements of the pair ...
Context 2
... Bairdemys species, the general shape of the skull of B. thalassica is more similar to that of B. venezuelensis, which is rounded, almost oval in dorsal outline ( Fig. 2A), and relatively high in lateral view (Figs. 2C and 2D). The temporal emargination is not well developed, and rostrocaudally shallower than in B. hartsteini and B. sanchezi (Gaffney et al., 2008). The cheek emargination is as developed as in other Bairdemys, not reaching the dorsal edge of the cavum tympanii (Fig. 2E). As in other ...
Context 3
... oval in dorsal outline ( Fig. 2A), and relatively high in lateral view (Figs. 2C and 2D). The temporal emargination is not well developed, and rostrocaudally shallower than in B. hartsteini and B. sanchezi (Gaffney et al., 2008). The cheek emargination is as developed as in other Bairdemys, not reaching the dorsal edge of the cavum tympanii (Fig. 2E). As in other Bairdemys species, the orbits face laterally and the skull bone surface is smooth, lacking ornamentations except for the dermal scale sulcii. Dermal scales of the skull-The scale sulcii of the skull are well defined in IVIC-P-2908. In comparison to those of Meiolaniformes, the only turtle lineage with a described and ...
Context 4
... and other Bairdemys species (Gaffney & Wood, 2002). It forms the roof and lateral wall of the cavum cranii and, together with the postorbital, the caudal surface of the septum orbitotemporale. The processus contacts the medial and lateral ascending processes of the pterygoid caudomedially, forming the roof of the sulcus palatinopterygoideus (Figs. 2F and 3F). Caudal to this sulcus, the parietal forms the dorsal margin of the foramen nervi trigemini. Jugal-As in all pelomedusoid turtles, the jugal forms the laterocaudal portion of the orbital ridge, between the maxilla and the postorbital (Gaffney & Wood, 2002). The semi-circular dorsal margin of the cheek emargination is formed by the ...
Context 5
... Musculus (M.) adductor mandibulae and the M. depressor mandibulae, respectively. Both of them are more developed in B. thalassica than in any other known Stereogenyina. Postorbital-The postorbital is composed of a dorsal horizontal plate, very thick in Baird- emys spp., and a ventral vertical process that forms most of the septum orbitotemporale (Figs. 2C and 3C). The horizontal plate forms the caudal portion of the orbital ridge and contacts the frontal medially, parietal caudomedially, quadratojugal laterocaudally, and jugal laterally. The ventral process contacts the palatine rostrally and the pterygoid and jugal caudally, as seen in all other Bairdemys species, as well as in Lemurchelys ...
Context 6
... ventral process contacts the palatine rostrally and the pterygoid and jugal caudally, as seen in all other Bairdemys species, as well as in Lemurchelys diasphax and Latentemys plowdeni (Gaffney et al., 2011). Quadrate-The quadrate forms the entire cavum tympani which encloses the incisura columellae auris and the opening of the antrum postoticum (Figs. 2E and 3E). As in other Bairdemys species (Gaffney & Wood, 2002;Gaffney et al., 2008) the fossa precolumellaris is absent in B. thalassica. The incisura columellae auris is completely surrounded by bone and encloses the stapes and the eustachian tube. In B. thalassica this bone forms a very thick caudal bar, as seen in all Stereogenyina that ...
Context 7
... bone. It bears two distinct horizontal plates forming the caudal portions of the primary and secondary palate, and two very thick vertical plates, one separating the fossa orbitalis from the sulcus palatinopterygoideus and another forming the rostromedial wall of the sulcus palatinopterygoideus and the laterorostral wall of the cavum cranii (Figs. 2F and 3F). The horizontal plates are sutured to the maxilla rostrally and to the pterygoid caudally. These form the caudal portion of the midline cleft and the triturating surface, which extends towards the palatine-pterygoid contact, but does not reach it as in Stereogenys cromeri, Shweboemys pilgrimi, Brontochelys gaffneyi, and Lemurchelys ...
Context 8
... the latter on a narrow suture. In B. thalassica it has well developed horizontal plates that extend laterally to the crista supraoccipitalis, a common feature among Stereogenyina (Gaffney et al., 2011). In Bairdemys spp. those plates are even more pronounced and form a bulbous structure on the caudal edge of the crista supraoccipitalis ( Figs. 2A and 3A). The crista supraoccipitalis of B. thalassica is not as expanded as in B. venezuelensis and B. winklerae, and does not reach the line formed by the caudal edges of the squamosals. Exoccipital-The exoccipitals form the lateral and ventral margins of the foramen magnum and meet the supraoccipital dorsally. They also form the laterodorsal ...
Context 9
... to the later foramen, a trough extends laterally towards the fenestra postotica. In B. thalassica, as well as in B. venezuelensis and B. sanchezi, this trough is deep, in contrast to the shallower trough of other Stereogenyina (Gaffney et al., 2008). Basisphenoid-The basisphenoid of B. thalassica is subtriangular and has a rounded rostral edge (Figs. ...
Context 10
... to the later foramen, a trough extends laterally towards the fenestra postotica. In B. thalassica, as well as in B. venezuelensis and B. sanchezi, this trough is deep, in contrast to the shallower trough of other Stereogenyina (Gaffney et al., 2008). Basisphenoid-The basisphenoid of B. thalassica is subtriangular and has a rounded rostral edge (Figs. 2B and 3B), as seen in B. venezuelensis, and in contrast to the angular edge of B. hartsteini and B. sanchezi (Gaffney et al., 2008). The lateral margins of the bone are straight, differing from the curved lateral margins as seen in B. sanchezi. It contacts the pterygoid rostrally, the quadrate laterally, and the basioccipital caudally. The ...
Citations
... Considering that skull height and the proportions/complexity of the triturating surfaces adequately distinguish general feeding categories in turtles [27][28][29][30], the dentary morphology of Pe. maturin suggests a diet akin to that of Pe. dumerilianus. Although extant podocnemidids are all plant-biased omnivorous, Pe. dumerilianus has the highest percentage of animal items in its diet [26], commonly preying on apple snails [31]. ...
Overkill of large mammals is recognized as a key driver of Pleistocene megafaunal extinctions in the Americas and Australia. While this phenomenon primarily affected mega-mammals, its impact on large Quaternary reptiles has been debated. Freshwater turtles, due to the scarcity of giant forms in the Quaternary record, have been largely neglected in such discussions. Here we present a new giant podocnemidid turtle, Peltocephalus maturin sp. nov., from the Late Pleistocene Rio Madeira Formation in the Brazilian Amazon, that challenges this assumption. Morphological and phylogenetic analyses of the holotype, a massive partial lower jaw, reveal close affinities to extant Amazonian species and suggest an omnivorous diet. Body size regressions indicate Pe. maturin possibly reached about 180 cm in carapace length and is among the largest freshwater turtles ever found. This finding presents the latest known occurrence of giant freshwater turtles, hinting at coexistence with early human inhabitants in the Amazon.
... Ecological habitat transitions occurred repeatedly since then. For example, during the marine transitions in extant chelonioid sea turtles, thalassochelydian stem-turtles (Anquetin et al. 2017b;Joyce et al. 2021a) and bothremydid and sterogenyine pleurodires (Gaffney et al. 2006;Gaffney et al. 2011;Ferreira et al. 2015), but also during terrestrial adaptation of extant tortoises, box turtles (Testudinidae, Cuora geomydids, Terrapene emydids; Ernst and Barbour 1989), extinct meiolaniforms (Sterli 2015) and nanhsiungchelyid pantrionychians (Yeh 1966). ...
... Turtles show very diverse skull morphologies, which plausibly reflects adaptation to variation in diets, methods of food acquisition, and other traits (Pritchard 1979;Claude et al. 2004;Ferreira et al. 2015;Foth et al. 2017). Previous geometric morphometric work focused on ecological explanations (e.g., habitat or diet) and on different clade levels, arriving at contrasting ecological signals of skull shape. ...
... Previous geometric morphometric work focused on ecological explanations (e.g., habitat or diet) and on different clade levels, arriving at contrasting ecological signals of skull shape. However, these studies either did not account for phylogenetic structure when testing hypotheses (Claude et al. 2004;Ferreira et al. 2015;Foth et al. 2017), did not include fossils (Claude et al. 2004), or used two-dimensional projections of skulls in different views as a proxy for threedimensional skull morphology (Ferreira et al. 2015;Foth et al. 2017). Furthermore, the association between turtle skull shape and ecology was never analyzed in a broader context that included additional key functional traits (e.g., neck retraction) distinct from the effects of ecological variables. ...
Turtles have a highly modified body plan, including a rigid shell that constrains postcranial anatomy. Skull morphology and neck mobility may therefore be key to ecological specialization in turtles. However, the ecological signal of turtle skull morphologies has not been rigorously evaluated, leaving uncertainties about the roles of ecological adaptation and convergence. We evaluate turtle cranial ecomorphology using three-dimensional geometric morphometrics and phylogenetic comparative methods. Skull shape correlates with allometry, neck retraction capability, and different aquatic feeding ecologies. We find that ecological variables influence skull shape only, whereas a key functional variable (the capacity for neck retraction) influences both shape and size. Ecology and functional predictions from three-dimensional shape are validated by high success rates for extant species, outperforming previous two-dimensional approaches. We use this to infer ecological and functional traits of extinct species. Neck retraction evolved among crownward stem-turtles by the Late Jurassic, signaling functional decoupling of the skull and neck from the shell, possibly linked to a major episode of ecomorphological diversification. We also find strong evidence for convergent ecological adaptations among marine groups. This includes parallel loss of neck retraction, evidence for active hunting, possible grazing, and suction feeding in extinct marine groups. Our large-scale assessment of dietary and functional adaptation throughout turtle evolution reveals the timing and origin of their distinct ecomorphologies, and highlights the potential for ecology and function to have distinct effects on skull form.
... Fully shelled turtles have a rich fossil record (e.g., Cleary et al., 2020), which dates back to the Late Triassic (Joyce, 2017). During their 230 Ma of evolution, turtles experienced several independent ecological transitions, such as the evolution of secondary marine lifestyles (Anquetin et al., 2015;Ferreira et al., 2015;Gaffney et al., 2006), the transition to terrestriality from an aquatic ancestral habitat (e.g., Claude et al., 2004), or the independent evolution of specialized feeding styles, including durophagy (Parham & Pyenson, 2010) and suction feeding (Bardet et al., 2013;Joyce, Rollot, et al., 2021). ...
Turtles are a charismatic reptile group with a peculiar body plan, which most notably includes the shell. Anatomists have often focused descriptive efforts on the shell and other strongly derived body parts, such as the akinetic skull, or the cervical vertebrae. Other parts of turtle osteology, like the girdles, limbs, and mandibles, are documented with less rigor and detail. The mandible is the primary skeletal element involved in food acquisition and initial food processing of turtles, and its features are thus likely linked to feeding ecology. In addition, the mandible of turtles is composed of up to seven bones (sometimes fused to as little as three) and has thus anatomical complexity that may be insightful for systematic purposes and phylogenetic research. Despite apparent complexity and diversity to the mandible of turtles, this anatomical system has not been systematically studied, not even in search of characters that might improve phylogenetic resolution. Here, we describe the mandibular osteology for all major subclades of extant turtles with the help of digitally dissected 3D models derived from high‐resolution computed tomography (μCT) scans of 70 extant species. We provide 31 fully segmented mandibles, as well as 3D models of the mandibular musculature, innervation, and arterial circulation of the cryptodire Dermatemys mawii. We synthesize observed variation into 51 morphological characters, which we optimize onto a molecular phylogeny. This analysis shows some mandibular characters to have high systematic value, whereas others are highly homoplastic and may underlie ecological influences or other factors invoking variation.
... Finally, diversification within the genus Podocnemis began during the Tertiary, approximately 37 million years ago (Vargas-Ramírez et al. 2008). Unfortunately, presently there are no known Peltocephalus fossils that could provide accuracy to time estimates for the origin of this species (for morphological comparisons between P. dumerilianus and fossil species, see Gaffney et al. 1998;De La Fuente 2003;Gaffney and Forster 2003;França and Langer 2006;Matiazzi 2007;Cadena et al. 2010;Gaffney et al. 2011;Cadena et al. 2012;Dumont Júnior 2013;Cadena 2015;Carvalho 2015;Ferreira et al. 2015;Cadena et al. 2020). ...
We review the extent and nature of scientific knowledge of the Big-headed Amazon River Turtle, Peltocephalus dumerilianus, covering distribution, morphology, taxonomy, diet, behaviour, reproduction, and ecology. We discuss the phylogenetic position of the species and its evolutionary relationships with the other podocnemidids, comparing morphological, karyological and molecular information. Also, we describe the importance of this species and its relationship with traditional Amazonian communities, including capture techniques, uses, beliefs and taboos. Finally, we comment on the conservation status of the species and the urgent need for additional studies. Besides discussing and reinterpreting published data, we provide new information from recent genetic studies, field activities and captive observations.
... Over the course of the last 25 years, however, an astounding diversity of fossil forms has been documented from Cretaceous to Palaeocene strata (e.g. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]). These fossils not only expand the range of pelomedusoids to Arabia, the Caribbean, Europe, India and North America but also document an incredible array of diversity and disparity within the group. ...
... These fossils not only expand the range of pelomedusoids to Arabia, the Caribbean, Europe, India and North America but also document an incredible array of diversity and disparity within the group. Although a formal ecomorphological analysis is still outstanding for the entire clade, fossil and extant pelomedusoids generally possess high skulls with well-developed triturating surfaces that suggest herbivorous, omnivorous and durophagous diets [8,22]. ...
The Maevarano Formation in northwestern Madagascar has yielded a series of exceptional fossils over the course of the last three decades that provide important insights into the evolution of insular ecosystems during the latest Cretaceous (Maastrichtian). We here describe a new genus and species of pelomedusoid turtle from this formation, Sahonachelys mailakavava, based on a nearly complete skeleton. A phylogenetic analysis suggests close affinities of Sahonachelys mailakavava with the coeval Madagascan Sokatra antitra. These two taxa are the only known representatives of the newly recognized clade Sahonachelyidae, which is sister to the speciose clade formed by Bothremydidae and Podocnemidoidae. A close relationship with coeval Indian turtles of the clade Kurmademydini is notably absent. A functional assessment suggests that Sahonachelys mailakavava was a specialized suction feeder that preyed upon small-bodied invertebrates and vertebrates. This is a unique feeding strategy among crown pelomedusoids that is convergent upon that documented in numerous other clades of turtles and that highlights the distinct evolutionary pathways taken by Madagascan vertebrates.
... They are also an ancient clade, with stem fossils dating to the Late Permian or Triassic and a crown age estimated at 220 million years ago (mya) (4)(5)(6). Turtles enjoy an essentially global distribution spanning an ecologically diverse set of terrestrial, marine, and freshwater habitats, and have invaded each multiple times during their long history (7,8). ...
Significance
Biodiversity is unevenly distributed across the tree of life. Understanding the factors that led to this unevenness can illuminate how macroevolutionary processes have interacted with changing global environments to shape patterns of biodiversity. By developing a comprehensive phylogeny for extant turtles and analyzing the diversification dynamics of the group, we show that species-level diversity is strongly associated with historical climate shifts. Our findings indicate that newly exposed continental margins created during a period of cooling and drying are important evolutionary cradles for turtle speciation, explain why turtle biodiversity is orders of magnitude more depauperate than the remaining major lineages of amniotes, and reconcile the seemingly contradictory insights that fossils and extant species suggest into a single picture of evolutionary diversification.
... As phylogenetic nomenclature was slowly gaining momentum at the beginning of the twenty-first century, Joyce et al. (2004) explored difficulties associated with converting a large number of traditionally used names to phylogenetically defined ones and provided an internally consistent nomenclature for the most important crown and total groups of turtles that evenly implemented the "crown group rule" (i.e., the application of the most commonly used name to crown groups) in combination with the "pan convention" (i.e., the creation of new names for total clade by combination with the crown group name with the prefix pan-). Although it is difficult to measure the impact of this study, its publication coincides with unprecedented stability in the application of names for the primary clades of turtles (mostly through an adjustment of the paleontological community) while serving as the basis for later studies that expanded upon the proposed nomenclature through the naming of further crown and total clades (Engstrom et al. 2004;Parham et al. 2006b;Lyson et al. 2012;Crawford et al. 2015;Joyce and Bourque 2016;Georgalis and Joyce 2017;Vlachos 2018;Vlachos and Rabi 2018) and the conversion of names pertaining to extinct clades (Joyce and Norell 2005;Danilov and Parham 2006;Joyce and Lyson 2010;Lyson and Joyce 2011;Joyce et al. 2013Joyce et al. , 2016aSterli and de la Fuente 2013;Rabi et al. 2014;Cadena and Joyce 2015;Cadena and Parham 2015;Ferreira et al. 2015Ferreira et al. , 2018Sterli 2015;Anquetin et al. 2017;Joyce 2017;. As an alternative to the system proposed by Joyce et al. (2004), Sereno and ElShafie (2013) suggested systematically tying common names to total clades, but this proposal did not gain traction. ...
Over the last 25 years, researchers, mostly paleontologists, have developed a system of rank-free, phylogenetically defined names for the primary clades of turtles. As these names are not considered established by the PhyloCode, the newly created nomenclatural system that governs the naming of clades, we take the opportunity to convert the vast majority of previously defined clade names for extinct and extant turtles into this new nomenclatural framework. Some previously defined names are converted with minor adjustments. We also define a number of new clade names to close apparent nomenclatural gaps. In total, we establish 113 clade names, of which 79 had already received phylogenetic definitions and 34 are new.
... There have been many studies of cranial disparity within amniote subclades, including lepidosaurs (Da Silva et al., 2018;Watanabe et al., 2019), turtles (Claude, Pritchard, Tong, Paradis, & Auffray, 2004;Ferreira, Rincón, Solórzano, & Langer, 2015;Foth, Rabi, & Joyce, 2016), crocodylians (Morris, Vliet, Abzhanov, & Pierce, 2019;Pierce, Angielczyk, & Rayfield, 2008;Piras et al., 2010;Sadleir, 2009), birds (Bright, Marugán-Lobón, Cobb, & Rayfield, 2016;Felice, Tobias, et al., 2019), mammals (Camacho et al., 2019;Goswami et al., 2011;Lu et al., 2013;Wroe & Milne, 2007), and even those sampling extinct lineages (e.g., Felice et al., 2020;Godoy et al., 2018;Pierce, Angielczyk, & Rayfield, 2009). Often these studies have focused on the relationship between changes in skull shape and ecological diversification (e.g., Felice, Tobias, et al., 2019;Foth et al., 2016), particularly in well-studied adaptive radiations (Campàs, Mallarino, Herrel, Abzhanov, & Brenner, 2010;Hedrick et al., 2020;Sanger et al., 2013;Tokita, Yano, James, & Abzhanov, 2016). ...
... Importantly, similar face shapes are observed in fossorial snakes and "lizards" (e.g., amphisbaenians, annielids, and dibamids), demonstrating that these axes of facial proportions share important ecological correlations across squamates (Da Silva et al., 2018;Watanabe et al., 2019). Habitat and, to a lesser extent, diet have a significant effect on skull shape in turtles (Claude et al., 2004;Foth et al., 2016), but this is predominantly related to modifications to the palate (Ferreira et al., 2015) and post-temporal emargination for jaw muscles (Foth et al., 2016), with much less variation in the distinct facial skeleton. Clearly, the most variable aspects of cranial form for the majority of sauropsid lineages, with the notable exception of turtles, are the length and breadth of the face. ...
... These macroevolutionary trends demonstrate the selective pressures and functional constraints operating on the amniote skull in deep time. However, the more recent radiations of extant amniote clades show clear connections between the anterior of the skull, the face, and ecological diversification (e.g., Da Silva et al., 2018;Felice, Tobias, et al., 2019;Ferreira et al., 2015;Goswami et al., 2011;Pierce et al., 2008;Watanabe et al., 2019). The anatomical, developmental, and evolutionary coherence and distinctiveness of the facial region of the skull have been recovered time and time again (Esteve-Altava et al., 2013;Felice, Tobias, et al., 2019;Lee et al., 2020;Watanabe et al., 2019). ...
Amniotes, a clade of terrestrial vertebrates, which includes all of the descendants of the last common ancestor of the reptiles (including dinosaurs and birds) and mammals, is one of the most successful group of animals on our planet. In addition to having an egg equipped with an amnion, an adaptation to lay eggs on land, amniotes possess a number of other major morphological characteristics. Chief among them is the amniote skull, which can be classified into several major types distinguished by the presence and number of temporal fenestrae (windows) in the posterior part. Amniotes evolved from ancestors who possessed a skull composed of a complex mosaic of small bones separated by sutures. Changes in skull composition underlie much of the large-scale evolution of amniotes with many lineages showing a trend in reduction of cranial elements known as the “Williston's Law.” The skull of amniotes is also arranged into a set of modules of closely co-evolving bones as revealed by modularity and integration tests. One of the most consistently recovered and at the same time most versatile modules is the “face,” anatomically defined as the anterior portion of the head. The faces of amniotes display extraordinary amount of variation, with many adaptive radiations showing parallel tendencies in facial scaling, e.g., changes in length or width. This review explores the natural history of the amniote face and discusses how a better understanding of its anatomy and developmental biology helps to explain the outstanding scale of adaptive facial diversity. We propose a model for facial evolution in the amniotes, based on the differential rate of cranial neural crest cell proliferation and the timing of their skeletal differentiation.
... The youngest possible thalassochelydian cranial and mandibular material from the Lower Cretaceous of Dorset shows only a moderate expansion of the triturating surface (Anquetin and André 2020). Nonetheless, although the expansion of the triturating surface is correlated with a durophagous diet (Claude et al. 2004;Ferreira et al. 2015), this correspondence is not always strict and some species with only a moderate expansion (such as Owadowia borsukbialy nickae and Eurysternum wagleri) may fall within the variability spectrum of non-durophagous forms (Walter Joyce, personal communication 2020). In any case, in light of the lack of any cranial remains referable to turtles from Krzyżanowice, in particular, and Craspedochelys spp., in general, the relative rarity of durophagy in Late Jurassic turtles, and no evidence of such adaptations in the supposedly closely related species (traditionally grouped into "Plesiochelyidae"), the interpretation of MZ VIII Vr-71 as a durophagous form (Tyborowski and Błażejowski 2019a: fig. 3) is unjustified. ...
Marine reptiles from the Upper Jurassic of Central Europe are rare and often fragmentary, which hinders their precise taxonomic identification and their placement in a palaeobiogeographic context. Recent fieldwork in the Kimmeridgian of Krzyżanowice, Poland, a locality known from turtle remains originally discovered in the 1960s, has reportedly provided additional fossils thought to indicate the presence of a more diverse marine reptile assemblage, including giant pliosaurids, plesiosauroids, and thalattosuchians. Based on its taxonomic composition, the marine tetrapod fauna from Krzyżanowice was argued to represent part of the “Matyja-Wierzbowski Line”—a newly proposed palaeobiogeographic belt comprising faunal components transitional between those of the Boreal and Mediterranean marine provinces. Here, we provide a detailed re-description of the marine reptile material from Krzyżanowice and reassess its taxonomy. The turtle remains are proposed to represent a “plesiochelyid” thalassochelydian (Craspedochelys? sp.) and the plesiosauroid vertebral centrum likely belongs to a cryptoclidid. However, qualitative assessment and quantitative analysis of the jaws originally referred to the colossal pliosaurid Pliosaurus clearly demonstrate a metriorhynchid thalattosuchian affinity. Furthermore, these metriorhynchid jaws were likely found at a different, currently indeterminate, locality. A tooth crown previously identified as belonging to the thalattosuchian Machimosaurus is here considered to represent an indeterminate vertebrate. The revised taxonomy of the marine reptiles from Krzyżanowice, as well as the uncertain provenance of the metriorhynchid specimen reported from the locality, cast doubt on the palaeobiogeographic significance of the assemblage.
... pair of medially projecting lateral flanges, each formed jointly by the maxilla and palatine. This partial secondary palate was likely an adaptation to a durophagous diet (Andrews, 1906;Wood, 1971;Ferreira et al., 2015). Stereogenyina has no living members, but extinct species span most of the Cenozoic from both sides of the Atlantic and in Asia. ...
... A Mesozoic occurrence was reported from India (Jain, 1977(Jain, , 1986, but this taxon is of doubtful assignment to Stereogenyina (Gaffney et al., 2011) and has been excluded here. Stereogenyina has been positively identified from the Eocene of Egypt (Andrews, 1901(Andrews, , 1903Wood, 1971;Gaffney et al., 2011); the Oligocene of South Carolina (Weems, 2009;Weems and Knight, 2013); the Miocene of Egypt (Dacqué, 1912;Gaffney et al., 2011), India (Prasad, 1974), Pakistan (Wood, 1970), Puerto Rico (Gaffney and Wood, 2002), and Venezuela (Wood and Diáz de Gamero, 1971;Sánchez-Villagra and Winkler, 2006;Gaffney et al., 2008;Ferreira et al., 2015); and the Pliocene or Pleistocene of Burma (Swinton, 1939) (Fig. 2). Thus, the Fayum deposits of Egypt have produced the two oldest known stereogenyines, Stereogenys (Andrews, 1901) and Cordichelys (Gaffney et al., 2011), which also record the earliest definitive appearance of the partial secondary palate that characterizes the group. ...
... Our emendment of the diagnosis eliminates two important features listed by Gaffney et al. (2011: 49) as diagnostic: the 'cordiform' carapace for which the genus was named and the minimal contact of the pterygoids FIGURE 2 -Global distribution of Stereogenyina. Asterisks designate shell specimens we consider tentatively assigned to Stereogenyina. 1, Collins and Lynn (1936), Weems and Knight (2013); 2, Weems (2009), Weems and Knight (2013); 3, Gaffney and Wood (2002); 4, Wood and Diáz de Gamero (1971), Sánchez-Villagra and Winkler (2006), Gaffney et al. (2008), Ferreira et al. (2015); 5, Zouhri et al. (2018); 6, Broin et al. (2018); 7, Andrews (1901); 8, Andrews (1903), Wood (1971), Gaffney et al. (2011); 9, Pérez-García (2019); 10, Gaffney et al. (2011); 11, Dacqué (1912), Gaffney et al. (2011); 12, Wood (1970), Gaffney et al. (2011); 13, Jain (1977Jain ( , 1986; 14, Prasad (1974), Ferreira et al. (2018); 15, Swinton (1939 at the midline. Three-dimensional reconstruction of the nearly complete shell described below (CGM 42191) suggests that the cordiform or heart-shaped outline of the Yale carapace (YPM 7457) probably resulted from taphonomic crushing of a carapace that was arched more anteriorly than posteriorly, an observation first made by Andrews (1906: 289). ...
