Incomplete Mandible Research Articles

Giant temnospondyl amphibians from the Early to Middle Triassic Narrabeen Group of the Sydney Basin, New South Wales, Australia

Material of giant temnospondyl amphibians is described from two localities in the Early to Middle Triassic Narrabeen Group of the Sydney Basin, Australia. The capitosaurid Bulgosuchus gargantua gen. et. sp. nov. from the Bulgo Sandstone (Scythian) at Longreef, represented by an incomplete mandible and a femur, is the largest known Early Triassic temnospondyl and the earliest occurrence of a temnospondyl in the Sydney Basin Triassic. B. gargantua is phenetically most similar to Paracyclotosaurus and to ‘P’. gunganj, but also shows affinities with Eryosuchus and Middle Triassic species of ‘Parotosuchus’. An anterior portion of a large mandible from the Terrigal Formation (late Scythian-early Anisian) at Bouddi is also described and tentatively referred to the Capitosauridae, but is generically indeterminate. The morphology of the post-glenoid area in members of the Capitosauridae is described, and derived characters of the capitosaurid mandible are provided.

Reassessment ofPlatyognathus hsuiYoung, 1944 (Archosauria: Crocodyliformes) from the Lower Lufeng Formation (Lower Jurassic) of Yunnan, China

ABSTRACT The holotype of Platyognathus hsui Young, 1944, an incomplete mandible from the Lower Jurassic Lower Lufeng Formation of Yunnan (China), was lost or destroyed during World War II. Material subsequently referred to this taxon actually represents a different taxon of basal Crocodyliformes, and some authors have recently questioned the validity of P. hsui. A partial skull collected in 1984 is referable to P. hsui and is designated as a neotype. It corroborates most of the features originally used by Young to diagnose P. hsui and provides additional diagnostic characters for that taxon. P. hsui can be distinguished from other basal crocodyliform taxa primarily by the fused mandibular symphysis, large caniniform teeth in positions 5 and 6 in the dentary, and the polygonal cross-section of (at least) the sixth dentary tooth. P. hsui is referred to the Protosuchia sensu Wu et al. (1994).

Late oligocene amphictids (Mammalia: Carnivora) from La Milloque, Aquitaine Basin, France

Abstract Two incomplete mandibles and several isolated upper and lower teeth of Amphictis milloquensis ( Helbing , 1928 ) and M2 of Amphictis ambigua ( Gervais , 1872 ) are described from the Late Oligocene (MP 29) of La Milloque (Lot-et-Garonne) in the Aquitaine Basin, south-western France. No significant differences in size of teeth or their form were detected between the fossil population of Amphictis milloquensis from La Milloque and that from Dieupentale (MP 29). Although the M2 of Amphictis ambigua from La Milloque is congruent in morphology with those of this species from Pech Desse and Pech du Fraysse (MP 28), it exceeds the corresponding teeth from both the localities in size, providing supporting evidence for a progressive trend towards size increase through time in Amphictis ambigua.

New specimens of Neosaimiri fieldsi from La Venta, Colombia: a middle Miocene ancestor of the living squirrel monkeys

Abstract During the 1989 and 1990 field seasons, more than 200 new specimens of Neosaimiri fieldsi were recovered from the middle Miocene Villavieja Formation in La Venta, Colombia, South America. The stratigraphic horizon for new materials is about 100 meters above that of the type locality. New radioisotopic dates obtained from tuffaceous beds just above the present materials horizon are 12-13 Ma. The holotype of Neosaimiri, which was recovered in 1949, is an incomplete mandible and dentition, while new materials include not only lower but also upper dentition and deciduous teeth. The present materials closely resemble Saimiri in the shape and size proportion of molar series and in the basic crown morphology of other teeth, suggesting a close relationship to extant Saimiri. However, these materials are differentiated from Saimiri in the proportions of tooth series, with smaller incisors and larger molars; in the structure of the P4 hypocone; and in the morphology of M1-2, which shows strong polymorphism. Therefore, the present materials are identified as an independent genus, Neosaimiri, which is a middle Miocene ancestor of Saimiri . Laventiana annectens, which was recovered at the same location as the present materials in 1988, is concluded to be a junior synonym of Neosaimiri. A close relationship between Saimiri and a late Oligocene form from Bolivia, Branisella, which has been suggested by several researchers, is refuted by the crown structure of P4 in Neosaimiri . The Neosaimiri-Saimiri lineage needs another Oligocene ancestor.

A new specimen of Utatsusaurus (Reptilia: Ichthyosauria) from the Lower Triassic Sulphur Mountain Formation of British Columbia

An incomplete skull and mandible of the primitive ichthyosaur Utatsusaurus is described from the Lower Triassic Vega Phroso Member of the Sulphur Mountain Formation of British Columbia. The specimen contributes to our knowledge of the cranial anatomy of the genus, which was previously known primarily from postcranial material, and extends its geographic range to Canada. The presence of an isodont dentition in this primitive genus suggests that isodonty rather than heterodonty may be the primitive character state for the Ichthyosauria.

A new shark-toothed dolphin (Cetacea Squalodontidae) from the upper Oligocene of New Zealand

Abstract A new genus and species of squalodont cetacean, based upon a pair of incomplete mandibles, are described from Duntroonian (Upper Oligocene) sediments from Fossil Point, N.W. Nelson. The mandibles indicate a genus allied to Squalodon Grateloup but differing in the presence of a small median third root on the molariform teeth.

An Additional Specimen of the Rodent Dikkomys from the Miocene of Nebraska

Dikkomys matthewi Wood Dikkomys matthewi Wood, Amer. Mus. Nat. Hist. Novitates no. 866, p. 26, fig. 32. July 2, 1936. Referred material:-C.N.H.M. no. P26284, an incomplete right mandible with p4-m3; Upper Rosebud, Shannon County, South Dakota. The writer is indebted to Mr. Bryan Patterson of the Chicago Natural History Museum for the loan of this specimen and permission to describe it. The ramus of the mandible is similar to, although smaller than, that of Pleurolicus sulcifrons Cope. Compared to the ramus of Gre-

Note on a Large Reptillian Skull from Brooke, Isle of Wight, probably Dinosaurian, and referable to the Genus Iguanodon

It is remarkable that so little is known of the skulls of the Wealden Dinosauria, the more so as their other remains have been procured in some abundance in the south-east of England and the Isle of Wight during the fifty years which have elapsed since Dr. Mantell’s discovery of an Iguanodon’s tooth in the quarry near Cuckfield. Hypsilophodon Foxii is, I believe, the only one the form and a great part of the structure of whose skull are known, and this only recently, from the Rev. W. Fox’s unique specimen, first exhibited at the Meeting of the British Association 1868, and described by Prof. Huxley in the 26th vol. of our Journal. Of the skulls of Iguanodon Mantelli and Megalosaurus Bucklandi , the only parts which have been determined are incomplete mandibles and fragments of maxillæ. The skull of Hylæosaurus is still, so far as I can learn, represented by the single small fragment of the base imbedded, at the end of the vertebral column, in the Tilgate-Forest slab, purchased by the British Museum of the late Dr. Mantell, and figured by him in his ‘Fossils of the British Museum,’ and by Prof. Owen in the ‘British Fossil Reptilia;’ and the skulls of Polacanthus Foxii, Pelorosaurus , the Cetiosauri , and Streptospondyli are altogether unknown. In August 1865 I saw in the Rev. W. Fox’s collection a fossil which he had recently found in Brixton Bay. I t was plainly a splendid fragment of what before its mutilation had been a very