Ren Hirayama

Oldest known sea turtle

Reptiles constitute a primarily terrestrial assemblage, but several groups returned to the marine environment after the first appearance of reptiles in the late Palaeozoic era. Successful diversification of the chelonioid sea turtles, particularly during the Cretaceous period, was perhaps one of the most important events in the history of turtles (and marine reptiles). The fossil record of chelonioids before the Late Cretaceous has been poorly documented. Here I report the discovery of an exceptionally well-preserved skeleton of the oldest known chelonioid, from the Early Cretaceous stage (about 110 million years before the present) of eastern Brazil. This specimen represents a new taxon, extending the history of chelonioids by 10 million years, and it sheds new light on the early evolution of the group. The limb of the specimen is a relatively primitive paddle, which still possesses movable digits as in freshwater turtles. However, the skull is specialized in the manner of later chelonioids, with large interorbital foramina that are indicative of huge lachrymal salt glands surrounding the eyes,. This discovery supports the idea that the establishment of the salt-excreting system, and the occupation of a marine habitat, may have preceded the formation of rigid paddles in the history of chelonioids.

Distribution and Diversity of Cretaceous Chelonioids

Publisher Summary This chapter discusses distribution and diversity of Cretaceous chelonioids. The Cretaceous Chelonioidea, which includes at least 22 valid genera, is divided into the three monophyletic families—Cheloniidae, Protostegidae, and Dermochelyidae. The cheloniids are well diversified and abundant in the Late Cretaceous of North America and Western Europe, whereas they are absent from the Japanese Cretaceous. The Protostegidae and Dermochelyidae are considered to be more closely related to each other than either is to the cheloniids. They possess a very elongated coracoid, a pelvic girdle with a huge lateral process of the pubis, and a very long plastron. The skull of protostegids may be modified to feed on hard-shelled animals, judging from the extensive contact between pterygoid and quadrate, and the strong processus trochlearis oticum as seen in the living batagurid Malayemys, which is a typical molluscivorous freshwater turtle. The protostegids were cosmopolitan as were the dominant chelonioids from the Aptian to the Turonian; however, they drastically declined and became extinct during the Maastrichtian. The Mesozoic dermochelyids were dominant only in the Late Cretaceous of Japan. It has been suggested that most Mesozoic sea turtles are endemic, and, cosmopolitan chelonioid species are quite rare.

Phylogenetic Relationships of the Asian Box Turtles of the Genus Cuora sensu lato (Reptilia: Bataguridae) Inferred from Mitochondrial DNA Sequences

Abstract Phylogenetic relationships of the genus Cuora sensu lato (Cuora sensu stricto and Cistoclemmys) and other testudinoid genera were inferred from variations in 882 base positions of mitochondrial 12S and 16S rRNA genes. Results yielded a robust support to the monophyly of a group (Cuora group) consisting of Cuora sensu lato and the monotypic Pyxidea. Within the Cuora group, the continental Cuora (sensu stricto) and the two subspecies of Ci. flavomarginata constituted two well-supported monophyletic groups. Distinctly small interspecific genetic distances in the former groups suggested that in the continent speciations in Cuora took place much later than the primary divergences in the Cuora group, or speciations in other related genera, such as Mauremys. Our analyses failed to provide a substantial support to the monophyly of any other combinations of taxa within the Cuora group, including Cuora in broad and strict senses, and Cistoclemmys as consisting of Ci. galbinifrons and Ci. flavomarginata. Besides these, our results also suggested the non-monophyly for the Batagurinae and the Geoemydinae, and sister relationships of the Bataguridae with Testudinidae rather than with the Emydidae.

Osteopygis (Testudines: Cheloniidae) from the Lower Tertiary of the Ouled Abdoun phosphate basin, Morocco

Osteopygis emarginatus Cope 1868 is described from the Lower Tertiary of the Ouled Abdoun phosphate basin, Morocco, on the basis of skulls and lower jaws. Osteopygis is a cosmopolitan turtle that had a wide geographical distribution during the Late Cretaceous and Paleocene. Osteopygis emarginatus is a very conservative species which crossed the Cretaceous/Tertiary boundary without major changes.

Cretaceous soft-shelled turtles (Trionychidae) of Mongolia: New diversity, records and a revision

This paper is devoted to the description and revision of material of Cretaceous soft-shelled turtles (Trionychidae) of Mongolia. It includes the description of seven trionychid species, six of which are new, and two new genera: the cyclanorbine Nemegtemys conflata gen. et sp. nov. from the Nemegt Formation (Maastrichtian), and the trionychines Gobiapalone breviplastra gen. et sp. nov. from the Nemegt and Barungoyot (Campanian) formations, G. orlovi from the Baynshire Formation (Cenomanian–Santonian), ‘Trionyx’ baynshirensis sp. nov. from the Baynshire Formation, ‘T.’ gilbentuensis sp. nov. from the Nemegt Formation, ‘T.’ gobiensis sp. nov. from the Nemegt Formation, and ‘T.’ shiluutulensis sp. nov. from an unknown formation (Campanian). In addition, one shell from the ?Baynshire Formation of Khermin Tsav is assigned to Gobiapalone sp. The type material of Amyda menneri is considered to be Trionychidae indet. and Amyda menneri to be a nomen dubium. Finally, we revise other available materials of Cretaceous trionychids from 45 localities in Mongolia. Nemegtemys conflata, if correctly assigned, is the earliest known member of Cyclanorbinae. The two species of the new genus Gobiapalone are included in two phylogenetic analyses of Trionychidae. In both analyses Gobiapalone is monophyletic. In the first analysis, Gobiapalone is placed within Apalonina. In the second analysis, Gobiapalone is sister to Apalonina. Thus, the results of both analyses show that Apalonina, which is a rather advanced and well-supported trionychid clade, or its closest sister taxon (stem-Apalonina), were present in the Late Cretaceous of Asia. These results suggest that most other supra-generic clades of modern trionychids had been established in Asia by the Late Cretaceous. That suggestion is supported by the discovery of a cyclanorbine Nemegtemys conflata in the Late Cretaceous of Mongolia. Finally we summarize the latest data on temporal and geographical distributions of Cretaceous Trionychidae of Asia and North America. http://zoobank.org/urn:lsid:zoobank.org:pub:921DA1C5-C4B2-463D-A49D-608024C6036A

A new species of the genus Manouria (Testudines: Testudinidae) from the Upper Pleistocene of the Ryukyu Islands, Japan

Abstract An extinct tortoise known from the uppermost Pleistocene of the Ryukyu Islands is described as the new species, Manouria oyamai (Testudines: Testudinidae) based on the skull, lower jaw and some postcranial elements. The specimens of M. oyamai were newly collected from the latest Pleistocene fissure deposits on Okinawa and Tokunoshima Islands, Ryukyu Islands, Japan. This is the first fossil record of Manouria sensu stricto. Phylogenetic analysis shows that Manouria sensu stricto, comprising M. emys, M. impressa and M. oyamai, is monophyletic. Manouria oyamai flourished in the Central and South Ryukyus until the Late Pleistocene and became extinct there, along with other endemic terrestrial vertebrates, in the latest Pleistocene.

Kappachelys okurai gen. et sp. nov., a New Stem Soft-Shelled Turtle from the Early Cretaceous of Japan

Kappachelys okurai gen. et sp. nov. is named and described based on two isolated carapacial elements (right seventh costal and left seventh peripheral) from the Lower Cretaceous (?upper Neocomian) Akaiwa Formation of west-central Honshu, Japan. Kappachelys is a small turtle (shell length ~10 cm) that exhibits a unique combination of three features: coarse and deep vermiculate sculpture on carpace; no scute sulci; and well-developed peripherals. The form of the sculpture and lack of scute sulci both suggest affinities with the Trionychidae (soft-shelled turtles), whereas the plesiomorphic retention of well-developed peripherals indicates Kappachelys lies outside the Trionychidae. Given this combination of primitive and derived features, we interpret Kappechelys as a stem trionychid. In the same region of Japan, the overlying Lower Cretaceous (Aptian) Kitadani Formation contains some of the oldest known, unequivocal trionychid fossils. Based on its slightly older age, similar geographical distribution, and more primitive shell morphology, Kappachelys could be ancestral to the trionychids of the Kitadani Formation.

Chelonian eggshells from the Lower Cretaceous Kuwajima Formation of the Tetori Group, Central Japan

ABSTRACT Chelonian eggshell fossils from the Lower Cretaceous Kuwajima Formation of the Tetori Group are described. The eggs were originally spherical or ellipsoidal in shape. The eggshells consist of a single layer of spherulitic shell units composed of needle-like crystallites originating from a nucleation center. This corresponds to modern rigid-shelled chelonian eggs. The eggshell fragments are commonly found buried together and are known from deposits of subaerial environments, such as vegetated swamps. In contrast, the vast majority of turtle remains are known primarily from nearby shallow lake deposits, indicating that they are aquatic; no terrestrial turtles are known from this formation. These taphonomic settings suggest that the eggs were laid on land by lacustrine turtles in a process still apparent today.

Ocadia nipponica, a new species of aquatic turtle (Testudines: Testudinoidea: Geoemydidae) from the Middle Pleistocene of Chiba Prefecture, central Japan

ABSTRACT A new species of the genus Ocadia (Testudines; Testudinoidea; Geoemydidae), O. nipponica, is described on the basis of a nearly complete skeleton from the Middle Pleistocene Kiyokawa Formation of the Shimosa Group at Sodegaura City, Chiba Prefecture, central Japan. O. nipponica is distinguished from O. sinensis (Gray) by its more extensive secondary palate, smoother shell surface, narrower second and third vertebral scutes, and larger size (carapace up to 33 cm long). Considering that the living species O. sinensis is distributed in the coastal area of eastern to southeastern Asia in subtropical to tropical climates, the new fossil species may have been thrived in warmer paleoclimatic conditions for the Japanese Islands in the Pleistocene age than hitherto have been estimated on the basis of floral evidences.

Turtle remains (Testudines, Chelonioidea) from the Middle Turonian of northwest Germany

Turtle remains ascribed to the family Cheloniidae (Testudines, Cryptodira, Chelonioidea), collected from the lamarcki zone (Middle Turonian) at Wullen (NW Germany) are described. The material consists of a right humerus, a scapula, a complete costalia, and costalia fragments of a single individual with the humerus indicating a primitive cheloniid of the ‘toxochelyid grade’. The present material, as well as previously recorded chelonioid humeri from the Cenomanian and Turonian of Germany illustrate a progressive diversification of chelonioids during the early Late Cretaceous.