First record of a turtle (Protochelydra, Chelydridae, Testudines) from the Cenozoic of Alaska (Chickaloon Formation, Paleocene–Eocene)

A chelydrid turtle from the late Paleocene (Clarkforkian NALMA) of the Chickaloon Formation, near Anchorage, is the first record of a turtle from the Cenozoic of Alaska and the most northerly record of the family known thus far. The specimen consists of a partial carapace from a plant-rich carbonaceous mudstone. It compares most closely with Protochelydra zangerli from the late Paleocene (Tiffanian NALMA) of North Dakota.

TOP OF PAGE

Postcranial material of Jachaleria candelariensis Araújo and Gonzaga 1980 (Therapsida, Dicynodontia), Upper Triassic of Rio Grande do Sul, Brazil

Additional postcranial material attributed to the Late Triassic dicynodont Jachaleria candelariensis Araújo and Gonzaga, found in Rio Grande do Sul State, Brazil, is described. All material came from the same outcrop and stratigraphic level as the holotype, and consists of disarticulated and sometimes fragmentary bone elements. The preserved axial skeleton consists of eight cervical, five middle dorsal, two posterior dorsal and two caudal vertebrae, two cervical ribs, six anterior dorsal ribs, thirteen posterior dorsal ribs and a sternum. We also identified three scapulae, two ulnae, five radii, two pelvic girdles, two ilia, two femora, a tibia and a calcaneum. Based on the studied material, a reconstruction of the specimen is presented. The lack of a complete scapular girdle and a humerus makes the posture of the forelimbs uncertain, but the morphology of the femur and pelvic girdle indicates that the hind limbs of Jachaleria should be should be upright, as in the other Triassic dicynodonts.

TOP OF PAGE

Early Eocene Microsyops (Mammalia, ?Primates) from the Washakie Basin, southern Wyoming, with a description of newly recovered specimens

Microsyops is a small-bodied mammalian genus that spans a biostratigraphic range from the early through late middle Eocene of North America, and is well-known from many areas of the interior Rocky Mountain region. Microsyops has previously been described in detail, largely based on material from the better-known early Tertiary basins of Wyoming (e.g., Bighorn and Wind River Basins). Here we present data on a stratigraphically controlled Microsyops sample from the early Eocene (Graybullian and Lysitean faunal zones) of the Washakie Basin, Wyoming. Although the sample described here consists primarily of isolated teeth, one specimen collected in 2001 from Lysitean strata (biochron Wa6) in the Bitter Creek area of the basin preserves the mandibular symphysis, alveoli for the incisor and P2, and complete teeth from P3 through M2. Measurements for this specimen fall within published size ranges for M. latidens. In addition, this specimen exhibits a P4 talonid morphology (distinct hypoconulid) consistent with that of M. latidens. Specimens from the older Graybullian strata of the Bitter Creek and Patrick Draw areas exhibit a morphology consistent with M. angustidens (e.g., variably present maxillary molar mesostyles). The apparent transition from M. angustidens to M. latidens across the Graybullian-Lysitean boundary in the Washakie Basin is consistent with the pattern of phyletic change seen in Microsyops in other areas of Wyoming (e.g., Bighorn Basin). This suggests a general pattern of early Tertiary biostratigraphic change and taxonomic diversity for microsyopids throughout the northern Rocky Mountain region.

TOP OF PAGE

New skull material of Osteodontornis orri (Aves: Pelagornithidae) from the Miocene of California

New material of the bony-toothed bird Osteodontornis orri from the middle Miocene Round Mountain Silt on Sharktooth Hill, Kern County, California clarifies the identification of some Asian Osteodontornis material and provides previously unreported morphological details of the rostrum of Osteodontornis and pelagornithids. This material is approximately the same age as the O. orri holotype and some of the referred Osteodontornis material from California, and is younger than the Osteodontornis material from Japan. The Sharktooth Hill specimens have some morphological characters in common with specimens from Japan (e.g., neurovascular groove on the medial surface of the dentary), and the new specimens differ somewhat morphometrically from the older and penecontemporaneous material. The new material supports the assignation of the Japanese material to O. orri, and suggests that O. orri either had greater variation in size among individuals than currently is recognized or possibly underwent size change over its geologic history.

TOP OF PAGE

First occurrence of Brachiosaurus (Dinosauria: Sauropoda) from the Upper Jurassic Morrison Formation of Oklahoma

The giant sauropod Brachiosaurus is one of the rarest sauropods from the Upper Jurassic of North America. The genus has previously been reported from Colorado, Utah, and Wyoming. OMNH 01138 is a sauropod metacarpal of unusual proportions from the Upper Jurassic Morrison Formation of Oklahoma. The bone is longer and more slender than the metacarpals of diplodocids and Camarasaurus, and is most similar in size and proportions to the elongate metacarpals of Brachiosaurus. This is the first report of Brachiosaurus from Oklahoma.

TOP OF PAGE

The first discovery of a rhynchosaur from the upper Moenkopi Formation (Middle Triassic) of northern Arizona

Ammorhynchus navajoi gen. et sp. nov. (Archosauromorpha: Rhynchosauria) is described from a nearly complete left maxilla and additional dental elements from lower Middle Triassic (Lower Anisian) deposits of the Moenkopi Formation of Arizona. The single maxillary groove present in Ammorhynchus navajoi gen. et sp. nov. occurs in some species of the Middle Triassic genus Rhynchosaurus, but is consistently present in Late Triassic forms of the genus Hyperodapedon, and is typical of all other North American rhynchosaurs. The presence of the single maxillary groove, in combination with well-developed maxillary lingual teeth and a low occlusal tooth row count, suggests that this is the plesiomorphic condition in all rhynchosaurs with blade and groove occlusion. Ammorhynchus navajoi gen. gen. et sp. nov. is the first rhynchosaur reported from the Moenkopi Formation (Holbrook Member), and is the earliest rhynchosaur known from the Americas.

TOP OF PAGE

First report of Megapnosaurus (Theropoda: Coelophysoidea) from China

The biota of the Lower Jurassic Lufeng Formation (Yunnan Province, China) is critical to understanding Early Jurassic tetrapod evolution and biogeography. Theropod dinosaur material from the Lufeng Formation remains enigmatic and poorly known. For this reason, any theropod material that can be unequivocally identified as a particular taxon is valuable in understanding the theropod fauna of the Lufeng Formation. Here, two specimens are reported as being the first record of the dinosaur Megapnosaurus from the Lufeng Formation, and the whole of Asia. The presence of Megapnosaurus is consistent with previous work suggesting an Early Jurassic age for the Lufeng Formation. It also greatly extends the geographic range of the genus, and confirms the pangeographic distribution of Early Jurassic terrestrial tetrapods.

TOP OF PAGE

Mammuthus jeffersonii (Proboscidea, Mammalia) from Northern Illinois

A lower second molar of a Jeffersonian mammoth (Mammuthus jeffersonii) from northern Illinois provides the first reliable record of this species from the state. A radiocarbon date of 11,170 ± 140 ¹⁴C yr B.P. on spruce (Picea) wood from the site suggests an age of late Pleistocene for the mammoth specimen. Although this is the first description of M. jeffersonii from Illinois, the locality is within the expected range of this taxon. The restricted geographical distribution of M. jeffersonii in the upper Midwest during the late Pleistocene may indicate a close association between this species and spruce-dominated open forests.

TOP OF PAGE