New Mesozoic vertebrate articles

[bh480@scn.org]

From: Ben Creisler bh480@scn.org
New Mesozoic vertebrate articles

Here are some new and not so new articles (new to me at 
least) about Mesozoic vertebrates that I don't recall 
seeing mentioned on the list.
Note that the first one is only available online and has 
not appeared in print in official form. Some other papers 
erect new non-dinosaur taxa.

Paton, Haddrath and Baker (2002 online). Complete 
mitochondrial DNA genome sequences show that modern birds 
are not descended from transitional shorebirds.
Proceedings of the Royal Society: Biological Sciences 
(online)

Abstract: To test the hypothesis put forward by 
Feduccia of the origin of modern birds from transitional 
birds, we sequenced the first two complete mitochondrial 
genomes of shorebirds (ruddy turnstone and blackish 
oystercatcher) and compared their sequences with those of 
already published avian genomes. When corrected for rate 
heterogeneity across sites and non-homogeneous nucleotide 
compositions among lineages in maximum likelihood (ML), 
the optimal tree places palaeognath birds as sister to the 
neognaths including shorebirds. This optimal topology is a 
re-rooting of recently published ordinal-level avian trees 
derived from mitochondrial sequences. Using a penalized 
likelihood (PL) rate-smoothing process in conjunction with 
dates estimated from fossils, we show that the basal 
splits in the bird tree are much older than the Cretaceous-
Tertiary (K-T) boundary, reinforcing previous molecular 
studies that rejected the derivation of modern birds from 
transitional shorebirds. Our mean estimate for the origin 
of modern birds at about 123 million years ago (Myr ago) 
is quite close to recent estimates using both nuclear and 
mitochondrial genes, and supports theories of continental 
break-up as a driving force in avian diversification. Not 
only did many modern orders of birds originate well before 
the K-T boundary, but the radiation of major clades 
occurred over an extended period of at least 40Myr ago, 
thus also falsifying Feduccia's rapid radiation scenario 
following a K-T bottleneck.

van Dijk, D. Eduard, 2001. Jurassic bipeds that could hop? 
Perch? Pounce? Fly? South African Journal of Science. 
September-
October, 2001; 97 (9-10): 373-374.
AB: THE DESCRIPTION OF THE ICHNOGENUS Molapopentapodiscus 
(Ellenberger, 1970) includes the presumption that forward 
progression was by bounding with feet together. That this 
genus, and other genera based on footprints or trackways, 
were hoppers, has been disputed. Material from KwaZulu-
Natal, South Africa, suggests that more than one Lower 
Jurassic biped was a hopper, but with feet adapted also to 
other functions.


O'Keefe, Frank Robin,  2001. A cladistic analysis and 
taxonomic revision of the Plesiosauria (Reptilia: 
Sauropterygia). Acta Zoologica Fennica 213:1-63.
The Plesiosauria (Reptilia: Sauropterygia) is a group of 
Mesozoic marine reptiles known from abundant material, 
with specimens described from all continents. The group 
originated very near the Triassic-Jurassic boundary and 
persisted to the end-Cretaceous mass extinction. This 
study describes the results of a specimen-based cladistic 
study of the Plesiosauria, based on examination of 34 taxa 
scored for 166 morphological characters. The Pliosauroidea 
is found to by polyphyletic due to the inclusion of the 
Polycotylidae; this second clade is instead a member of 
the Plesiosauroidea, and thus more closely related to 
elasmosaurs than to other `pliosaurs'. Characters of body 
proportion such as neck length and head size are very 
labile, with the `pliosauromorph' body plan evolving three 
times, while extremely long necks evolved in two clades. 
Characters from the entire skeleton support these 
relationships, although characters of the skull roof and 
palate are especially useful. Lastly, a new genus and 
species, Hauffiosaurus zanoni, is named based on German 
material of Toarcian age. 

O'Keefe, Frank Robin. 2002. The evolution of plesiosaur 
and pliosaur morphotypes in the Plesiosauria (Reptilia: 
Sauropterygia). Paleobiology: Vol. 28, No. 1, pp. 101-112.
ABSTRACT
 The dichotomy between short-necked, large-
headed ?pliosaurs? and long-necked, small-
headed ?plesiosaurs? has formed the basis of plesiosaur 
taxonomy for over one hundred years. Recent work has cast 
doubt on the taxonomic validity of this dichotomy, 
suggesting that the pliosaur morphotype may have evolved 
independently in more than one clade. This paper 
quantifies the variation in body proportion in the clade 
Plesiosauria using principal component analysis and 
demonstrates that the traditional plesiosaur/pliosaur 
dichotomy is an oversimplified view of the range of 
morphologies present in the group. The topology of the 
clade is mapped into the morphospace, demonstrating that 
the pliosaur morphotype evolved three times from two 
different regions of morphospace. Both the range of body 
morphologies displayed by plesiosaurs and the evolutionary 
history of those morphologies, are more complex than 
previously supposed.


Wilson, Jeffrey A., Malkani, M. Sadiq, Gingerich, Philip 
D., 2001. New crocodyliform (Reptilia, Mesoeucrocodylia) 
from the upper Cretaceous Pab Formation of Vitakri, 
Balochistan (Pakistan).
Contributions from the Museum of Paleontology
University of Michigan. December 31, 2001; 30 (12): 321-
336.
AB: Fossil remains from the upper part of the Pab 
Formation in eastern Balochistan, Pakistan, provide the 
first diagnostic remains of a Cretaceous crocodyliform 
from the Indian subcontinent, and provide important 
information for assessing its biogeographic history. 
Specimens collected to date include the well preserved 
rostrum of a new genus and species, Pabwehshi 
pakistanensis. The rostrum has a foreshortened anterior 
snout, with serrated teeth that interlock to form a zig-
zag cutting edge. The anterolaterally directed external 
nares are bordered ventrally and laterally by a well-
marked narial fossa. Comparisons with crocodyliforms of 
equivalent age indicate that Pabwehshi is a baurusuchid 
mesoeucrocodylian related to Baurusuchus from Brazil and 
Cynodontosuchus from Argentina. Pabwehshi is the first 
baurusuchid known outside South America. It provides 
further evidence of a Cretaceous biogeographic link 
between South America and Indo-Pakistan.

Hungerbuehler, A., 2002. The Late Triassic Phytosaur 
Mystriosuchus Westphali, With A Revision of the Genus. 
Palaeontology 45 (2): 377-418. (March 2002).    
Abstract:  
Mystriosuchus westphali is based on a large, well-
preserved cranium and a snout fragment from the 
Stubensandstein (Norian) of south-west Germany. The 
hypodigm is redescribed and new or poorly known cranial 
structures in phytosaurs are discussed. For the first 
time, the presence of a premaxillary crest is 
substantiated in a phytosaur. The type specimen shows a 
supernumerary occipital element (=?tabular?) that is 
probably fused to the parietal in other phytosaurs, and an 
orbitosphenoid. A computerised parsimony analysis confirms 
the hypothesis that Mystriosuchus is nested within 
Pseudopalatinae, the most derived clade of phytosaurs, and 
thus does not fall within basal phytosaurs. Mystriosuchus 
is characterised by five unique features (slit-like 
interpremaxillary fossa, triangular cross-section of the 
postorbito-squamosal bar, strongly reduced posttemporal 
fenestra, and two features of the cranial sculpture), plus 
eight synapomorphies that also occur in some more 
distantly related taxa. Mystriosuchus westphali is 
diagnosed by, among other apomorphies, a distinct 
premaxillary crest, a squamosal-proo¨tic contact, absence 
of a posterior process of the squamosal, and a slit-like 
posttemporal fenestra. The type species Mystriosuchus 
planirostris shows, most significantly, the naris facing 
forward anteriorly and upward posteriorly, and the longest 
rostrum and the highest degree of depression of the 
supratemporal opening in any phytosaur. Mystriosuchus 
exemplifies a common pattern in phytosaurids in being a 
genus that includes a gracile, elongated, slender-snouted 
and a more robust species with a broader, often crested 
snout. This study demonstrates that a detailed analysis of 
the cranial anatomy and the rigorous application of 
cladistic principles to identified character states help 
to clarify current inconsistencies in the taxonomy and 
nomenclature of phytosaurs.  

Li Chun & O. Rieppel, 2002. A new cyamodontoid placodont 
from Triassic of Guizhou, China. Chinese Science Bulletin. 
47(5): 403-407.
Abstract A new cyamodontoid placodont is named 
(Psephochelys polyosteoderma gen. et. sp. nov.) and 
described based on a three-dimensionally preserved 
specimen. The material comes from the Wayao Member of the 
Falang Formation (Carnian, Late Triassic) in Guizhou 
Province, southwestern China. The skull of Psephochelys 
shows a unique combination of characteristics observed in 
Psephoderma and Placochelys, and the carapace is 
diagnostic of a new taxon as well. The ventral dermal 
armor of Psephochelys differs from all other known 
cyamodontoids in that it comprises irregular marginal 
osteoderms in loose contact with each other, and gastralia 
between them. The cranial suture pattern is in part 
difficult to analyze due to apparent co-ossification of 
elements, or poor delimitation of sutures. This affects 
primarily the demarcation of the nasal from the 
prefrontal, and the relation between the anterior part of 
the parietal, posterior ends of the frontals, and 
postfrontals. However, the postfrontal appears to enter 
the anteromedial margin of the upper temporal fenestra, a 
characteristic otherwise known from Placodus, but not from 
other cyamodontoids. However, given the difficulties of 
interpretation of this skull, additional material is 
required to unequivocally assess some details of the 
pattern of cranial sutures.

Maisch M.W., 2002. A New Basal Lystrosaurid Dicynodont 
from the Upper Permian of South Africa. Palaeontology 45 
(2):343-359
Abstract: 
A new genus and species of late Permian dicynodont, 
Kwazulusaurus shakai, is described on the basis of a 
complete skull from the late Permian Dicynodon Assemblage 
Zone of the South African Beaufort Group. It is an 
advanced form which shows characters, such as the shape of 
the snout and the loss of the ectopterygoid, that link it 
to the early Triassic genus Lystrosaurus. Kwazulusaurus 
represents the most basal member of the lystrosaurian 
lineage. The phylogeny of progressive pristerodontian 
dicynodonts is discussed. It appears possible that the 
Kannemeyeriiformes and Lystrosauridae do not form a 
monophylum, as previously assumed. Instead a sister-group 
relationship between lystrosaurids and dicynodontids plus 
kannemeyeriiforms is suggested.