[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

I New Papers You, Man



Ksepka, D.T. 2009. Broken gears in the avian molecular clock: new
phylogenetic analyses support stem galliform status for Gallinuloides
wyomingensis and rallid affinities for Amitabha urbsinterdictensis.
Cladistics. doi: 10.1111/j.1096-0031.2009.00250.x.

ABSTRACT: Galliformes (landfowl) have been the focus of numerous divergence
dating studies that seek a refined understanding of the early radiation of
living birds. The Eocene fossil birds Amitabha urbsinterdictensis (Bridger
Formation) and Gallinuloides wyomingensis (Green River Formation) have been
used extensively in studies dealing with the timing of evolution in crown
Galliformes. Divergence estimates from studies incorporating these fossils
as calibration points suggest that multiple galliform lineages radiated in
the Cretaceous and survived the Cretaceous-Tertiary mass extinction.
However, the phylogenetic position of both fossils has been disputed,
particularly with regard to crown or stem status. In order to resolve this
debate, a new study of A. urbsinterdictensis and G. wyomingensis was
undertaken. Further preparation and re-examination of the A.
urbsinterdictensis holotype indicates this fossil falls outside both crown
and stem Galliformes, and reveals evidence for a relationship with Rallidae
(rails). In order to reassess the status of G. wyomingensis, a matrix of 120
morphological characters was constructed by revising and expanding on
previous studies. Phylogenetic analyses using this matrix place G.
wyomingensis basal to all crown Galliformes. Stem placement of G.
wyomingensis is retained and resolution is improved in combined analyses
incorporating sequence data from cytochrome b, NADH dehydrogenase subunit 2,
mitochondrial control region, 12S rDNA, and nuclear ovomucoid intron G. All
evidence indicates that A. urbsinterdictensis and G. wyomingensis are
inappropriate internal calibration points for Galliformes and may have
contributed to overestimation of divergence event ages. Though stem
galliforms existed in the Cretaceous, the divergence of crown lineages in
the Cretaceous remains inconclusively demonstrated. Because few galliform
fossils have been evaluated phylogenetically, further investigations into
the tempo of galliform evolution must await identification of proper fossil
calibration points.



Fillmore, D.L., Simpson, E.L., and Lucas, S.G. 2009. Isaac Lea's
Palaeosauropus (= "Sauropus") primaevus: a review of his discovery. Ichnos
16(3):220-229. doi: 10.1080/10420940802686152.

ABSTRACT: In 1849, Isaac Lea named Sauropus primaevus for footprints from
Mount Carbon, Pennsylvania, USA, then the oldest fossil vertebrate
footprints reported. In 1902, O. P. Hay constructed a new ichnogenus
Palaeosauropus for this ichnospecies. Palaeosauropus has been one of the
most frequently reported Mississippian footprint ichnogenera in North
America and remains a valid ichnotaxon. The holotype of Palaeosauropus (=
"Sauropus") primaevus (referred to as P. primaevus), consisting of a single
manus/pes pair, is described and illustrated in Lea (1853) and is housed at
the Academy of Natural Sciences in Philadelphia, Pennsylvania (ANS9752).
Lea's large specimen of P. primaevus (approximately 86 cm by 53 cm), that
included a trackway of six manus/pes pairs, described and illustrated in
1853 and 1855, was a combination of ANS9752 and a second specimen
represented by a plaster cast housed at the National Museum of Natural
History (USNM487148). Historical documents and examination of the Mauch
Chunk Formation at Mount Carbon, Pennsylvania, enabled the identification of
Lea's tracksite, originally reported to be a few hundred feet (about 75 m)
from the former Mount Carbon Hotel. Our forensic evidence indicates the type
locality for P. primaevus is approximately 90 m south from the southwest
corner of Centre and Main Streets in Mount Carbon, Pennsylvania, with
geographical coordinates of N 40° 40' 25.7", W 76° 11' 14.9". The type
locality is within the middle member of the Mauch Chunk Formation, a fluvial
sequence of late Mississippian (Visean) Age.



Upchurch, P., Martin, J., and Taylor, M.P. 2009. Cetiosaurus Owen, 1841
(Dinosauria, Sauropoda): proposed conservation of usage by designation of
Cetiosaurus oxoniensis Phillips, 1871 as the type species. Bulletin of
Zoological Nomenclature 66(1):51-55.

ABSTRACT: The purpose of this application, under Article 81.1 of the Code,
is to preserve stability in the taxonomy of sauropod dinosaurs by
designating Cetiosaurus oxoniensis as the type species of Cetiosaurus. The
genus Cetiosaurus (including the species C. medius and C. oxoniensis) was
established during the earliest period of research on sauropod dinosaurs,
and is historically significant. The name Cetiosaurus was fixed to the type
species Cetiosaurus medius, a sauropod of indeterminate affinities; however,
the fragmentary nature of the type material of C. medius, combined with the
subsequent description of much more complete Middle Jurassic sauropod
material as Cetiosaurus oxoniensis, has meant that subsequent literature has
overwhelmingly adopted C. oxoniensis over C. medius as the primary exemplar
of Cetiosaurus. Stability would be best served by designating Cetiosaurus
oxoniensis as the type species of the genus Cetiosaurus in place of the
current type species, C. medius.



Perea, D., Soto, M., Veroslavsky, G., Martínez, S., and Ubilla, M. 2009. A
Late Jurassic fossil assemblage in Gondwana: biostratigraphy and
correlations of the Tacuarembó Formation, Parana Basin, Uruguay. Journal of
South American Earth Sciences. doi: 10.1016/j.jsames.2009.03.009.

ABSTRACT: The Tacuarembó Formation has yielded a fossil assemblage which
includes the best known body fossils, consisting of isolated scales, teeth,
spines, and molds of bones, recovered from thin and patchy bonebeds, from
the Botucatu Desert, Parana Basin, South America. The remains are preserved
in the sandstones widespread around the city of Tacuarembó. We propose a new
formalized nomenclature for the Tacuarembó Formation, naming its "Lower" and
"Upper" members as the Batovı´ (new name) and Rivera (new rank) members,
respectively. An assemblage-zone is defined for the Batovı´ Member
(fluviolacustrine and aeolian deposits). In this unit, the freshwater
hybodontid shark Priohybodus arambourgi D'Erasmo is well represented. This
species was previously recorded in Late Jurassic-Early Cretaceous units of
the Sahara and the southern Arabian Peninsula. Globally considered, the
fossil assemblage of this member (P. arambourgi, dipnoan fishes,
Ceratosaurus-like theropods, and conchostracans) is indicative of a
Kimmeridgian-Tithonian age, which in combination with the stratigraphic
relationships of the Tacuarembó Formation with the overlying basalts of the
Arapey Formation (132 My average absolute age) imply that the latter was
deposited during the Kimmeridgian-Hauterivian interval.



Jackson, S.J., Whyte, M.A., and Romano, M. 2009. Laboratory-controlled
simulations of dinosaur footprints in sand: a key to understanding
vertebrate track formation and preservation. Palaios 24(4):222-238. doi:
10.2110/palo.2007.p07-070r.

ABSTRACT: Dinosaur tracks and trackways yield invaluable information as to
the identity, size, and gait of the trackmaker and the conditions of the
media (=substrate) it traversed. Correctly interpreting tracks requires
consideration of their three-dimensional morphology. Laboratory-controlled
simulations were conducted to investigate the subsurface track morphology
formed from differently shaped feet, as the shape of the footprint
deteriorates with depth. A circular, triangular, and a tridactyl dinosaur
foot-shaped template, or indenter, were indented vertically into two types
of sand, with four moisture contents-dry, 10%, 20%, and saturated. The
morphology of all three indenters was preserved most accurately in the moist
sand. Tracks in dry and saturated sand were distorted by a greater degree of
media deformation. Digit imprints of tridactyl tracks were only clearly
discernible in near-surface layers and were deformed by shear zones or
inward movement of sediment in dry and saturated sand. The long digits of
the template produced the greatest degree of outward displacement, and
tracks became wider with depth and deepest in the heel region. This was most
distinct in dry sand, where extensive shear zones in cross section
demonstrated the outward and upward movement of sediment. All tracks in
saturated sand were characterized by considerable downward displacement of
sediment and features related to the upward pull of sediment as the
templates were withdrawn. These diagnostic features allow vertebrate tracks
to be differentiated from nonbiogenic, soft-sediment deformation. Fossil
tracks studied from the Middle Jurassic succession of the Cleveland Basin,
Yorkshire, demonstrate affinities to the experimental tracks formed in
saturated sand.



Milàn, J., and Chiappe, L.M. 2009. First American record of the Jurassic
ichnospecies Deltapodus brodricki and a review of the fossil record of
stegosaurian footprints. Journal of Geology 117(3):343-348. doi:
10.1086/597363.

ABSTRACT: We describe the first American stegosaur track of the ichnospecies
Deltapodus brodricki, collected in the Upper Jurassic Morrison Formation of
San Juan County, southeastern Utah, United States. The track is preserved as
a natural cast on the underside of a slab of fluvial sandstone and consists
of a well-preserved pes track and the eroded remains of a manus track.
Previously, Deltapodus was known only from the Middle Jurassic Yorkshire
coast of England and the Upper Jurassic of Portugal and Spain. The new
discovery thus substantially extends the geographic record of this
ichnospecies and highlights the similarities between the Late Jurassic
dinosaur faunas of North America and those of Western Europe.




Jinah, Z.A., Roberts, E.M., Deino, A.L., Larsen, J.S., Link, P.K., and
Fanning, C.M. 2009. New 40Ar-39Ar and detrital zircon U-Pb ages for the
Upper Cretaceous Wahweap and Kaiparowits formations on the Kaiparowits
Plateau, Utah: implications for regional correlation, provenance, and
biostratigraphy. Cretaceous Research 30(2):287-299. doi:
10.1016/j.cretres.2008.07.012. 

ABSTRACT: In order to better constrain the age and provenance of the Upper
Cretaceous Wahweap and Kaiparowits formations in southern Utah, U-Pb SHRIMP
ages were obtained for detrital zircons from three sandstone samples, in
addition to the first 40Ar-39Ar age for the Wahweap Formation, obtained from
a devitrified volcanic ash horizon (bentonite). The ash horizon, located 40
m above the base of the Wahweap Formation, yields an age of 80.1 ± 0.3 Ma.
The new radiometric data improve upon previous biostratigraphic age
estimates for the Wahweap Formation and indicate that the formation was
deposited between approximately 81 and 76 Ma. The youngest population of
detrital zircons from the base of the Wahweap Formation clusters around
83-82 Ma, while the youngest population in the capping sandstone near the
top of the formation is between 77-81 Ma, consistent with the 40Ar-39Ar age.
Detrital zircons from the base of the overlying Kaiparowits Formation
include a younger population clustering around 77-76 Ma, but are otherwise
broadly similar to those in the lower Wahweap. Detrital zircon assemblages
suggest the lower Wahweap and Kaiparowits sandstones were primarily
deposited by longitudinal stream systems sourced in the Cordilleran magmatic
arc in southern California or western Nevada, along with Mesozoic volcanics
in southern Arizona. The capping sandstone contains detrital zircons that
suggest it was proximately sourced from transverse stream systems that
drained eastward out of uplifted Mesozoic quartzose sandstones in the Sevier
thrust belt to the west.
     Revised correlations between the Wahweap Formation and coeval strata
and faunas across the Western Interior Basin show that the Wahweap Formation
is coeval with Judithian age localities including the type-Judithian Judith
River Formation. This suggests that the Aquilan and Judithian North American
Land Mammal "ages" are in need of recalibration based on recent acquisition
of this and other new radiometric data, as well as new faunal data.
Moreover, this study provides critical temporal constraint for important
mammalian and dinosaurian faunas of the Wahweap Formation.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
 and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

"Life is the art of drawing
sufficient conclusions from
insufficient premises."
               -- Samuel Butler