Two turtles with soft tissue preservation from the platy limestones of Germany provide evidence for marine flipper adaptations in Late Jurassic thalassochelydians

Late Jurassic deposits across Europe have yielded a rich fauna of extinct turtles. Although many of these turtles are recovered from marine deposits, it is unclear which of these taxa are habitually marine and which may be riverine species washed into nearby basins, as adaptations to open marine conditions are yet to be found. Two new fossils from the Late Jurassic of Germany provide unusually strong evidence for open marine adaptations. The first specimen is a partial shell and articulated hind limb from the Late Jurassic (early Tithonian) platy limestones of Schernfeld near Eichstätt, which preserves the integument of the hind limb as an imprint. The skin is fully covered by flat, polygonal scales, which stiffen the pes into a paddle. Although taxonomic attribution is not possible, similarities are apparent with Thalassemys. The second specimen is a large, articulated skeleton with hypertrophied limbs referable to Thalassemys bruntrutana from the Late Jurassic (early Late Kimmeridgian) platy limestone of Wattendorf, near Bamberg. Even though the skin is preserved as a phosphatic film, the scales are not preserved. This specimen can nevertheless be inferred to have had paddles stiffened by scales based on the pose in which they are preserved, the presence of epibionts between the digits, and by full morphological correspondence to the specimen from Schernfeld. An analysis of scalation in extant turtles demonstrated that elongate flippers stiffed by scales are a marine adaptation, in contrast to the elongate but flexible flippers of riverine turtles. Phylogenetic analysis suggests that Thalassemys bruntrutana is referable to the mostly Late Jurassic turtle clade Thalassochelydia. The marine adapted flippers of this taxon therefore evolved convergently with those of later clades of marine turtles. Although thalassochelydian fossils are restricted to Europe, with one notable exception from Argentina, their open marine adaptations combined with the interconnectivity of Jurassic oceans predict that the clade must have been even more wide-spread during that time.

An early bothremydid from the Arlington Archosaur Site of Texas

Four turtle taxa are previously documented from the Cenomanian Arlington Archosaur Site (AAS) of the Lewisville Formation (Woodbine Group) in Texas. Herein, we describe a new side-necked turtle (Pleurodira), Pleurochayah appalachius gen. et sp. nov., which is a basal member of the Bothremydidae. Pleurochayah appalachius gen. et sp. nov. shares synapomorphic characters with other bothremydids, including shared traits with Kurmademydini and Cearachelyini, but has a unique combination of skull and shell traits. The new taxon is significant because it is the oldest crown pleurodiran turtle from North America and Laurasia, predating bothremynines Algorachelus peregrinus and Paiutemys tibert from Europe and North America respectively. This discovery also documents the oldest evidence of dispersal of crown Pleurodira from Gondwana to Laurasia. Pleurochayah appalachius gen. et sp. nov. is compared to previously described fossil pleurodires, placed in a modified phylogenetic analysis of pelomedusoid turtles, and discussed in the context of pleurodiran distribution in the mid-Cretaceous. Its unique combination of characters demonstrates marine adaptation and dispersal capability among basal bothremydids.

The genome of Shaw’s sea snake (Hydrophis curtus) reveals secondary adaptation to its marine environment

The transition of terrestrial snakes to marine life approximately 10 million years ago (Ma) is ideal for exploring adaptive evolution. Sea snakes possess phenotype specializations including laterally compressed bodies, paddle-shaped tails, valvular nostrils, cutaneous respiration, elongated lungs and salt glands yet knowledge on the genetic underpinnings of the transition remain limited. Herein, we report the first genome of Shaw’s sea snake (Hydrophis curtus) and use it to investigate sea snake secondary marine adaptation. A hybrid assembly strategy obtains a high quality genome. Gene family analyses date a pulsed coding-gene expansion to about 20 Ma, and these genes associate strongly with adaptations to marine environments. Analyses of selection pressure and convergent evolution discover the rapid evolution of protein-coding genes, and some convergent features. Additionally, 108 conserved non-coding elements appear to have evolved quickly, and these may underpin the phenotypic changes. Transposon elements may contribute to adaptive specializations by inserting into genomic regions around functionally related coding genes. The integration of genomic and transcriptomic analyses indicates independent origins and different components in sea snake and terrestrial snake venom; the venom gland of the sea snake harbours the highest PLA2 (17.23%) expression in selected elapids and these genes may organize tandemly in the genome. These analyses provide insights into the genetic mechanisms that underlay the secondary adaptation to marine and venom production of this sea snake.

Early Paleoindian Potentials on the Continental Shelf in the Southeastern United States

As two researchers with significant credibility in the study of early Florida, James S. Dunbar and David K. Thulman evaluate the potential for Paleoindian research on the Southeastern Continental Shelf (SECS) of the U.S. In this chapter, they discuss ways to explore Clovis and pre-Clovis landscapes (or, as they collectively call them, early Paleoindian sites) in the SECS and how researchers might narrow their search and increase their chances of finding Clovis and pre-Clovis sites offshore. In doing so, they complement Halligan’s chapter in this volume (chapter 3) on exploring Florida’s inland waters for submerged sites. They evaluate the strategies available: thoughtful searching for both analogous natural and manmade landforms and serendipity. Of the two, the second approach has arguably produced the most sites so far. Dunbar and Thulman explore the “thermal enclave hypothesis” of Russell et al (2009) and follow David Webb’s earlier work on his idea for a climatically propitious region that could support animals and plants through the Last Glacial Maximum (LGM). Dunbar and Thulman further suggest the possibility of a shellfish/marine adaptation by early-Paleoindian-period colonists. They posit that finding such sites would open new windows into the study on the behaviors of the early Floridians.

Anatomy ofRhinochelys pulchriceps(Protostegidae) and marine adaptation during the early evolution of chelonioids

Knowledge of the early evolution of sea turtles (Chelonioidea) has been limited by conflicting phylogenetic hypotheses resulting from sparse taxon sampling and a superficial understanding of the morphology of key taxa. This limits our understanding of evolutionary adaptation to marine life in turtles, and in amniotes more broadly. One problematic group are the protostegids, Early–Late Cretaceous marine turtles that have been hypothesised to be either stem-cryptodires, stem-chelonioids, or crown-chelonioids. Different phylogenetic hypotheses for protostegids suggest different answers to key questions, including (1) the number of transitions to marine life in turtles, (2) the age of the chelonioid crown-group, and (3) patterns of skeletal evolution during marine adaptation. We present a detailed anatomical study of one of the earliest protostegids,Rhinochelys pulchricepsfrom the early Late Cretaceous of Europe, using high-resolution μCT. We synonymise all previously named European species and document the variation seen among them. A phylogeny of turtles with increased chelonioid taxon sampling and revised postcranial characters is provided, recovering protostegids as stem-chelonioids. Our results imply a mid Early Cretaceous origin of total-group chelonioids and an early Late Cretaceous age for crown-chelonioids, which may inform molecular clock analyses in future. Specialisations of the chelonioid flipper evolved in a stepwise-fashion, with innovations clustered into pulses at the origin of total-group chelonioids, and subsequently among dermochelyids, crown-cheloniids, and gigantic protostegids from the Late Cretaceous.

New species of the side necked turtle Bothremys (Pleurodira: Podocnemidoidea: Bothremydidae) from the Upper Cretaceous of Morocco

Background. Moroccan phosphates bed includes fossils of Sauropterygia, Testudines and mosasaurs from the latest Cretaceous (Maastrichitian) to Eocene. Family Bothremydidae (Podocnemidoidea), an extinct side-necked turtle group, has broad diversity in cranial morphology as shown by the genus Bothremys (Bothremydini). This genus is known from the Cretaceous and Paleogene of North America, Europe, Africa and middle east Asia, uniquely characterized by a pair of pits on the triturating surface of upper and lower jaws. Hitherto, four species have been recognized in Bothremys; B. cooki, B. kellyi, B. maghrebiana, and B. arabicus. Compared to the diversity of cranial morphology, little difference is known in the shell morphology in bothremydids. Also little is known about the limb morphology of bothremydini turtles, because of poor association of skull and postcranial skeleton. A new excellently preserved specimen of Bothremys is reported from the Upper Cretaceous of Morocco. Methods. The WSILS-RHg519 specimen stored in Waseda University is a large bothremydid skull associated with lower jaw and several postcranial elements including left humerus and peripherals. Results. The pair of pits on the triturating surfaces of upper and lower jaws in WSILSRHg519 specimen is a distinct autoapomorphic characters of the genus Bothremys. With the skull width 171mm, B. arabicus from the Santonian age of Jordan had been the largest species of genus Bothremys. The WSILS-RHg519 reaches the skull width 220mm and would be the largest member of Bothremys. Also, comparing the bone composition of the ventral surface of skull of the WSILS-RHg519 specimen to all other known Bothremys, the palatine-pterygoid contacts and pterygoid-pterygoid contact are quite unique. The left humerus is associated with the skull, partly damaged. The distal end of humerus is wide and the shaft is nearly straight, showing the first morphological evidence of aquatic/marine adaptation different from that of Chedighaii, the sister taxon of Bothremys. Discussion. The marine habitat of bothremydid turtles had been roughly discussed on the basis of the association of shallow marine animals such as shark teeth. Morphological evidence has not suggested yet partly because of the difficulty of bothremydid taxonomy which is just based on the cranial morphology. The WSILS-RHg519 specimen will hopefully shed light on the mysterious habitats of bothremydid turtles.

New species of the side necked turtle Bothremys (Pleurodira: Podocnemidoidea: Bothremydidae) from the Upper Cretaceous of Morocco

Background. Moroccan phosphates bed includes fossils of Sauropterygia, Testudines and mosasaurs from the latest Cretaceous (Maastrichitian) to Eocene. Family Bothremydidae (Podocnemidoidea), an extinct side-necked turtle group, has broad diversity in cranial morphology as shown by the genus Bothremys (Bothremydini). This genus is known from the Cretaceous and Paleogene of North America, Europe, Africa and middle east Asia, uniquely characterized by a pair of pits on the triturating surface of upper and lower jaws. Hitherto, four species have been recognized in Bothremys; B. cooki, B. kellyi, B. maghrebiana, and B. arabicus. Compared to the diversity of cranial morphology, little difference is known in the shell morphology in bothremydids. Also little is known about the limb morphology of bothremydini turtles, because of poor association of skull and postcranial skeleton. A new excellently preserved specimen of Bothremys is reported from the Upper Cretaceous of Morocco. Methods. The WSILS-RHg519 specimen stored in Waseda University is a large bothremydid skull associated with lower jaw and several postcranial elements including left humerus and peripherals. Results. The pair of pits on the triturating surfaces of upper and lower jaws in WSILSRHg519 specimen is a distinct autoapomorphic characters of the genus Bothremys. With the skull width 171mm, B. arabicus from the Santonian age of Jordan had been the largest species of genus Bothremys. The WSILS-RHg519 reaches the skull width 220mm and would be the largest member of Bothremys. Also, comparing the bone composition of the ventral surface of skull of the WSILS-RHg519 specimen to all other known Bothremys, the palatine-pterygoid contacts and pterygoid-pterygoid contact are quite unique. The left humerus is associated with the skull, partly damaged. The distal end of humerus is wide and the shaft is nearly straight, showing the first morphological evidence of aquatic/marine adaptation different from that of Chedighaii, the sister taxon of Bothremys. Discussion. The marine habitat of bothremydid turtles had been roughly discussed on the basis of the association of shallow marine animals such as shark teeth. Morphological evidence has not suggested yet partly because of the difficulty of bothremydid taxonomy which is just based on the cranial morphology. The WSILS-RHg519 specimen will hopefully shed light on the mysterious habitats of bothremydid turtles.