Topic
Hyphalosaurus
About: Hyphalosaurus is a research topic. Over the lifetime, 6 publications have been published within this topic receiving 98 citations.
Papers
Journal Article•
TL;DR: A cladistic analysis was performed in order to place Japanese and Chinese taxa, including the incompletely described Chinese long-necked Hyphalosaurus lingyanensis, into choristoderan phylogeny, and the results support the monophyly of Neochoristodera and a Sino-Japanese clade of long necked Choristoderes.
Abstract: The choristoderan reptile Monjurosuchus is described from the Lower Cretaceous Tetori Group of Japan on the basis of an associated specimen from the Kuwajima, Formation, Ishikawa Prefecture, and more fragmentary remains from the contemporaneous Okurodani Formation, Gifu Prefecture. This is the first report of Monjurosuchus from Japan, but a long-necked choristodere, Shokawa, has already been recorded from these deposits. Monjurosuchus was first described from the Lower Cretaceous Jehol Biota of China, although it has only recently been recognised as a choristodere. As reconstructed, the Japanese Monjurosuchus differs from the type species, Monjurosuchus splendens, in the structure of the postorbital region, reduction of the quadratojugal, a slenden parietal with a deep groove along the interparietal suture, and elongation of the jugal. As in M. splendens the lowest temporal fenestrae are closed. A cladistic analysis was performed in order to place Japanese and Chinese taxa, including the incompletely described Chinese long-necked Hyphalosaurus lingyanensis, into choristoderan phylogeny. The results support the monophyly of Neochoristodera and a Sino-Japanese clade of long necked choristoderes. The placement of the European Tertiary Lazarussuchus remains problematic, but the analysis supports its placement within Choristodera rather than on the stem. The identification of Monjurosuchus from Japan provides and additional link between the fossil assemblages of the Tetori Group and those of the slightly younger Jehol Biota of China.
34 citations
TL;DR: This exquisitely preserved specimen of the Early Cretaceous Hyphalosaurus baitaigouensis contains up to 18 embryos arranged in pairs, and size comparison with small free-living individuals and the straight posture of the posterior-most pair suggest that those embryos were at term and had probably reached parturition.
Abstract: Viviparity (giving birth to live young) in fossil reptiles has been known only in a few marine groups: ichthyosaurs, pachypleurosaurs, and mosasaurs. Here, we report a pregnant specimen of the Early Cretaceous Hyphalosaurus baitaigouensis, a species of Choristodera, a diapsid group known from unequivocal fossil remains from the Middle Jurassic to the early Miocene (about 165 to 20 million years ago). This specimen provides the first evidence of viviparity in choristoderan reptiles and is also the sole record of viviparity in fossil reptiles which lived in freshwater ecosystems. This exquisitely preserved specimen contains up to 18 embryos arranged in pairs. Size comparison with small free-living individuals and the straight posture of the posterior-most pair suggest that those embryos were at term and had probably reached parturition. The posterior-most embryo on the left side has the head positioned toward the rear, contrary to normal position, suggesting a complication that may have contributed to the mother’s death. Viviparity would certainly have freed species of Hyphalosaurus from the need to return to land to deposit eggs; taking this advantage, they would have avoided intense competition with contemporaneous terrestrial carnivores such as dinosaurs.
23 citations
TL;DR: Two flexible-shelled eggs of the hyphalosaurid choristodere Hyphalosaurus baitaigouensis from the Early Cretaceous of China are reported, one containing an embryo and the second associated with a neonate.
Abstract: Flexible, or soft-shelled, eggs are almost unknown in the fossil record, leaving large gaps in our knowledge of the reproductive biology of many tetrapod clades. Here, we report two flexible-shelled eggs of the hyphalosaurid choristodere Hyphalosaurus baitaigouensis from the Early Cretaceous of China, one containing an embryo and the second associated with a neonate. Choristoderes are an enigmatic group of aquatic reptiles that survived the K–T extinction but died out in the Miocene. Hyphalosaurids, a specialized clade of Choristodera, resemble miniature plesiosaurs and are considered to be primarily aquatic in habit. Scanning electron microscopy of samples from the eggs reveals a thin, non-columnar external mineralized layer characterized by rounded nodes and tentatively identified poorly structured irregular pores, with an underlying amorphous layer presumably representing decomposed protein fibrils. While the relationships of Choristodera remain controversial, eggshell microstructure more closely resembles that of Lepidosauromorpha (the lineage including lizards) as opposed to that of Archosauromorpha (the lineage including birds and crocodiles).
17 citations
1 Jun 2006
TL;DR: Li et al. as mentioned in this paper reported a well-preserved specimen of Hyphalosaurus baitaigouensis with leathery embryonic eggs from the Jiufotang Formation in western Liaoning, China, which provides the first direct evidence to indicate that choristoderian reptiles are most likely viviparous like Late Triassic Keichousaurus hui from Guizhou, Southern China.
Abstract: The Choristodera is a poorly known clade, but very a distinctive group of aquatic reptiles, which has been found from the Late Triassic to the Late Oligocene in Asia, North America and Europe. Although thousands of choristoderian specimens have been collected from the Early Cretaceous non-marine beds in Liaoning, China, no direct evidences have been found to determine whether they were oviparous like sea turtles or viviparous like Keichousaurus hui of Pacbypleurosauria (marine reptiles). Here we report a well-preserved specimen of Hyphalosaurus baitaigouensis with leathery embryonic eggs from the Jiufotang Formation in western Liaoning, China. It provides the first direct evidence to indicate that choristoderian reptiles are most likely viviparous like Late Triassic Keichousaurus hui from Guizhou, Southern China.
11 citations
TL;DR: Li et al. as mentioned in this paper formally synonymized Hyphalosaurus and Sinohydrosaurus using Articles 67 and 72 of the Fourth Edition (1999) of the International Code of Zoological Nomenclature (ICZN).
Abstract: It has come to our attention, while examining the fossils and paleoecology (Smith et al., 1998) of the much publicized ‘‘feathered dinosaur biota’’ from the lower Yixian Formation of western Liaoning Province, China (Wang, 1998), that there is a taxonomic incongruity concerning the diapsid genera Hyphalosaurus lingyuanensis Gao et al., 1999 and Sinohydrosaurus lingyuanensis Li et al., 1999. These two taxa, described in 1999 by authors from two institutions in Beijing, the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) and the Beijing Natural History Museum (BVC), are based on the part and counterpart of the same skeleton (Fig. 1). As this makes Hyphalosaurus and Sinohydrosaurus objective synonyms according to Articles 67 and 72 of the Fourth Edition (1999) of the International Code of Zoological Nomenclature (ICZN), we hereby propose formally synonymizing these two names.
7 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2010 | 2 |
| 2008 | 1 |
| 2007 | 1 |
| 2006 | 1 |
| 2001 | 1 |