Fwd: Paleofest Abstracts

[David Marjanovic <david.marjanovic@gmx.at>]

I'm told there is no embargo on these abstracts, so I'm forwarding them. 
Enjoy!

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Betreff: [DinosaurMailingList-KilledThreads] Paleofest Abstracts
Datum: Thu, 28 Mar 2013 17:18:43 -0000
Von: Nick <kk8thwonder@yahoo.com>
An: DinosaurMailingList-KilledThreads@yahoogroups.com

Paleofest was held at the Burpee Museum earlier this month, and there 
apparently were several presentations and forthcoming papers that could 
be rather significant for Spec. I wasn't able to attend, but I did 
manage to get a copy of the abstract list. Here are some of the more 
interesting ones:

THE HIDDEN DIVERSITY OF SMALL-BODIED ORNITHISCHIANS

Caleb M. Brown1 and Clint A. Boyd2
1Department of Ecology and Evolutionary Biology, University of Toronto, 
Toronto, Ontario, Canada
2South Dakota School of Mines and Technology, Rapid City, South Dakota, USA

Recent work quantifying taphonomy (processes of decay and preservation) 
in well-sampled Late Cretaceous North American dinosaur assemblages has 
illustrated strong preservational biases against the completeness, 
articulation, discovery, and familial diversity of small-bodied (less 
than approximately 60 kg) dinosaur taxa (Figure 1A). The discovery rates 
of large taxa are best described by logarithmic curves nearing, or at a 
plateau, while small taxa show either a steady or increasing rate of 
discovery (Figure 1B). This suggests that, in well-sampled formations, 
our current knowledge of the large bodied dinosaur assemblage is 
reasonably representative of the true biological fauna; however, small 
taxa are greatly underestimated in both their diversity and abundance, 
with many more discoveries expected to be made with greater sampling. 
This is particularly true for small bodied ornithischians, as they lack 
the diagnostic, and abundant, teeth possessed by small-bodied theropods, 
making them much more problematic to identify to species level. Full 
understanding of dinosaurian faunal assemblages requires work 
concentrating on small species, which tend to be both rare and fragmentary.
Here we present on research specifically focused on the remains of small 
bodied ornithischians, based mainly on isolated elements or partial 
skeletons, which has revealed a higher diversity of these small animals 
throughout the Late Cretaceous of North America. New small 
`hypsilophodontid' taxa have been found in the Campanian Kaiparowits, 
Oldman, and Dinosaur Park Formations, as well as the Maastrichtian 
Prince Creek and Frenchman formations. The morphological data provided 
by these recent discoveries facilitates the resolution of many of the 
basal relationships within Ornithischia, which have long remained 
problematic. This work has resulted in the division of North American 
`hypsilophodontids' into two clades: one consisting of small bodied taxa 
typified by the Campanian taxon Orodromeus, and a second clade of medium 
to large sized taxa typified by the Maastrichtian taxa Parksosaurus and 
Thescelosaurus. Similar recent discovery or description of other 
small-bodied ornithischians has included leptoceratopsids and 
pachycephalosaurs from multiple Late Cretaceous formations, also based 
on isolated elements.
The work described here has resulted in moving a step closer in our 
understanding of the diversity and relationships of these small taxa and 
their potential ecological significance in the diverse dinosaur 
dominated faunas.

PTEROSAUR DIVERSITY THROUGH THE CAMPANIAN AND MAASTRICHTIAN

Nathan Carroll
Department of Earth Sciences, Montana State University, Bozeman, 
Montana, USA

Pterosaur diversity in the latest Cretaceous is traditionally depicted 
as extremely low, represented only by the Pteranodontidae, 
Nyctosauridae, and Azhdarchidae in the Campanian. Aside from a single 
late occurrence of the Nyctosauridae, the Maastrichtian record appears 
to be dominated by the Azhdarchidae (Prentice et al., 2011; Butler et 
al.,2012). Azhdarchids are highly disparate in size (ranging from 2.5m 
to 10 m wingspans) and ecologically distinct from other pterosaur groups 
as stork-like generalists, but ecologically conservative within their 
group (Witton and Naish, 2008). However, a new azhdarchid from the 
"Jack's Birthday Site" suggests that there were at least three 
morphologically distinct azhdarchids in the Campanian Two Medicine 
Formation of Montana. This new azhdarchid possesses relatively mature 
bone histology despite numerous unfused elements, suggesting that 
azhdarchid growth may differ from the better known ontogenetic sequences 
of Pteranodon (Bennett, 1993). A controversial rostrum from the 
Maastrichtian Javelina Formation of Texas may also challenge the 
hypothesis of reduced Latest Cretaceous pterosaur diversity and 
disparity. The robust nature of the specimen has led some authors 
(Kellner 2004) to suggest that it is a late surviving member of the 
Tapejaridae and others (Lü et al. 2006) to suggest that it is a new 
robust member of the Azhdarchidae. If the former is true, then diversity 
is indeed higher than previously recognized in the Campanian and 
Maastrichtian. If the latter is true the ecologic disparity of 
azhdarchids is greater than previously known. Furthermore, the recent 
reassignment of the small (~1 m wingspan) Piksi barburulna, also of the 
Two Medicine Formation of Montana, from Aves to the Ornithocheiroidea 
(Agnolin and Varricchio, 2012) suggests a greater diversity and size 
disparity in pterosaurs. The fragmentary nature of the specimen prevents 
speculations about its ecology, but its size suggests that it at least 
occupies the same morphospace as birds of this time. These recent 
reports highlight the taphonomic problems associated with assessing 
pterosaur diversity. Studies of pterosaur biology, diversity and 
disparity have long suffered from the incomplete and fragmentary 
preservation of most specimens. Lagerstätten provide views into growth, 
ecology, biology and diversity with reasonable clarity, but such 
localities are missing from the Latest Cretaceous. Recent arguments for 
the decline in pterosaur diversity, especially between the Campanian and 
Maastrichtian, point to the relatively high number of pterosaur-bearing 
formations in the Latest Cretaceous yet very low diversity of pterosaur 
remains (Butler et al., 2012). Pterosaur specimens from Maastrichtian 
formations are scarce and typically assigned to the terrestrially 
adapted Azhdarchidae. However, of the 21 pterosaur-bearing formations 
recognized in the Maastrichtian, only 4 represent marine environments, 
one of which produced the latest occurrence of a nyctosaur. The 
terrestrial preservation of pterosaurs is inherently challenging and has 
produced a much more fragmentary record. Thus the apparent drops in 
diversity and disparity may reflect either a greater abundance of 
terrestrial versus marine units or the overall poorer quality of 
pterosaur remains within terrestrial versus marine units.

THE COMPLEXITY OF SAUROPOD DINOSAUR EVOLUTIONARY HISTORY DURING THE LATE 
CRETACEOUS

Michael D. D'Emic
Anatomical Sciences Department, Health Sciences Center, School of 
Medicine, Stony Brook University, Stony Brook, New York, USA

The abundance, global distribution, and immense size of sauropod 
dinosaurs makes them important for studies of Mesozoic paleoecology 
leading up to the end-Cretaceous mass extinction. Sauropods are 
currently being discovered at a rapid pace; in the last decade about 
fifty genera were named in the clade Titanosauriformes alone. 
Discoveries over the past two decades have overturned the traditional 
view of waning sauropod diversity giving way to ornithischian radiation 
through the Cretaceous; currently sauropods are known from all major 
landmasses up to the end of the Mesozoic. Most pre-Campanian sauropods 
belong to one of four morphologically disparate clades – 
rebbachisaurids, euhelopodids, brachiosaurids, and titanosaurs – but 
only the latter group persisted through the last 10–20 million years of 
the Mesozoic. Late Cretaceous sauropod evolution is characterized by a 
reduction in ecological breadth (inferred by tooth shape and skeletal 
morphology) and an unprecedented increase in body size range – both the 
largest and smallest known sauropods date from the Late Cretaceous. The 
last 5–10 million years of sauropod evolution gave rise to several 
dwarfed genera, the smallest being about the weight of a small 
rhinoceros. A large number of species have sister taxa on other 
landmasses, and few endemic clades existed.
Sauropod evolutionary history during the Cretaceous of North America is 
especially complex. Near the Early/Late Cretaceous boundary, sauropod 
body and ichnofossil records disappeared from North America and did not 
reappear for nearly 30 million years, a period of absence known as the 
`sauropod hiatus'. A variety of post-hiatus sauropod fossils from across 
the southwestern USA are referable to the derived titanosaur Alamosaurus 
sanjuanensis, whereas many fragmentary specimens from these horizons 
require detailed study and may represent other titanosaur taxa. No 
titanosaurs inhabited the Early Cretaceous of North America, and the 
closest relatives of Alamosaurus are likely South American taxa, 
indicating that the sauropod hiatus was ended by immigration, most 
likely from that landmass. This scenario is congruent with the 
penecontemporaneous appearance of titanosaur fossils across several 
basins, their sudden, abundant appearance within (rather than between) 
some formations, and the recognition of other inter-American immigrants 
at the same time (e.g., hadrosaurid dinosaurs). Sauropod geographic and 
paleoenvironmental distribution was largely a subset of hadrosaurid 
distribution, not partitioned from it. Sauropods persisted in abundance 
in the North American southwest up to the K/Pg boundary, as on most 
other landmasses.

THE END OF THE AGE OF DINOSAURS IN ANTARCTICA

Matthew C. Lamanna
Section of Vertebrate Paleontology, Carnegie Museum of Natural History, 
Pittsburgh, Pennsylvania, USA

The late Mesozoic terrestrial fossil record of Antarctica is 
insufficiently known, a circumstance that is due in large part to the 
continent's remote location and its extensive covering of ice sheets. 
Nevertheless, sedimentary sequences exposed on James Ross, Vega, 
Seymour, and Snow Hill islands in the James Ross Basin of the northern 
Antarctic Peninsula have provided a critical glimpse into the Late 
Cretaceous terrestrial biotas of this unique landmass. Among the most 
significant fossil discoveries are rare continental vertebrate remains, 
including those of birds and non-avian dinosaurs. Body fossils belonging 
to multiple non-avian dinosaur clades have been recovered, including the 
ankylosaur Antarctopelta oliveroi, non-hadrosaurid ornithopods 
(Trinisaura santamartaensis and perhaps one or two additional taxa), a 
hadrosaurid, a titanosaurian sauropod, and possible basal tetanuran and 
dromaeosaurid theropods. Putative non-avian dinosaur footprints have 
also recently been reported from Snow Hill Island. Several of these taxa 
(Antarctopelta, the non-hadrosaurid ornithopods, and the possible 
dromaeosaurid) are represented by associated partial skeletons, 
demonstrating the potential of the basin to yield informative non-avian 
dinosaur material. Rather than representing "relictual" lineages as has 
previously been proposed, most Antarctic Late Cretaceous dinosaurs 
appear closely related to coeval forms from other Gondwanan landmasses.
Bird remains are among the most abundant and best-preserved Late 
Cretaceous vertebrate fossils from the James Ross Basin. Consisting of 
multiple partial skeletons and dozens of isolated bones, this material 
is derived from Maastrichtian sites on Vega and Seymour islands. 
Interestingly, in contrast to penecontemporaneous avifaunas from most 
other Gondwanan regions, all described Antarctic Cretaceous birds have 
been proposed as members of the modern avian radiation (e.g., the 
anseriform Vegavis iaai, the purported gaviiform Polarornis gregorii).
Several collaborators and I are conducting field studies in the James 
Ross Basin in an effort to enhance Antarctica's Late Cretaceous 
terrestrial fossil record and our understanding of paleoenvironmental 
conditions on the continent during the final stages of the Mesozoic. 
Among our most important finds are numerous avian postcranial elements 
and a pedal phalanx and associated fragments of a medium-sized 
ornithopod or non-avian theropod. Additional discoveries include 
material of cartilaginous and bony fishes, plesiosaurs, and mosasaurs as 
well as a diverse macroflora from the Maastrichtian López de Bertodano 
Formation of Vega Island. Detailed studies of these fossils, currently 
underway, promise to yield further insight into Antarctic 
paleoecosystems at the end of the Age of Dinosaurs.

THE DINOSAURS OF ISLAND AFRICA: A NEW LATEST CRETACEOUS FAUNA FROM KENYA 
AND THE EVOLUTION OF GIGANTISM IN ABELISAURID THEROPODS

Joseph J. W. Sertich
Department of Earth Sciences, Denver Museum of Nature & Science, Denver, 
Colorado USA

The African fossil record of dinosaurs and their Cretaceous ecosystems 
has expanded significantly over the past two decades. Unfortunately, 
these discoveries have been limited to the Early and "middle" 
Cretaceous, with a conspicuous absence of fossils from the latest 
Cretaceous. In fact, much of the record of terrestrial evolution on the 
African continent following its isolation from the other Gondwanan 
landmasses approximately 100 million years ago remains a mystery. 
Dinosaur fossils, long known from the Lapurr Mountains of northwestern 
Turkana, Kenya, promise to provide the first glimpse at life during this 
prolonged period of African isolation during the end Cretaceous. A 
relatively diverse non-marine fauna from the Lapurr sandstone ("Turkana 
Grits") includes rocodyliforms, pterosaurs, and dinosaurs. Crocodyliform 
fossils are referable to at least two distinct taxa, an unusual, 
massively-built form likely mistaken for a spinosaurid theropod dinosaur 
in early reports, and a long-snouted dyrosaurid similar to taxa found in 
Maastrichtian nearshore deposits elsewhere in Africa. Though mostly 
fragmentary, the dinosaur record includes at least two taxa of 
iguanodontian ornithopods. Distinct vertebral morphologies indicate up 
to three sauropod taxa including two lithostrotian titanosaurians. Among 
the most common and complete dinosaur fossils are those of theropod 
dinosaurs, with both cranial and postcranial remains hinting at the 
presence of at least two distinct abelisaurid taxa. One taxon is known 
from multiple unassociated cranial and postcranial specimens that 
significantly expand the upper limits of body size in ceratosaurian 
theropods. A comprehensive phylogenetic analysis places this giant among 
derived abelisaurids, while comparisons with material from Madagascar 
and South America indicate that it likely exceeded 11-12m in length. 
Though efforts to establish solid chronostratigraphic dates for the 
deposits have long been met with little success, recently acquired data 
are suggestive of a latest Cretaceous age. If this age hypothesis is 
confirmed, these fossils will represent the first significant 
terrestrial vertebrate remains from Africa during this critical interval 
and provide important evidence for understanding the ecology and 
evolution of dinosaurs following African isolation.

DROMAEOSAURS AT THE END OF THE CRETACEOUS: THEIR EVOLUTION AND EXTINCTION

Alan H. Turner
Department of Anatomical Sciences, Stony Brook University, Health 
Science Center, Stony Brook, New York, USA

Dromaeosaurid theropods, such as Velociraptor and Deinonychus, are some 
of the most iconic of dinosaurs. Yet dromaeosaurid fossils are rare. In 
the past decade, however, we have seen a remarkable increase in the 
group's diversity, morphological disparity, and geographic extent. 
Numerous new species have been described, including several fragmentary 
forms that are ambiguously dromaeosaurids. Until recently the group was 
best known from the Upper Cretaceous of Asia and North America, but 
these new discoveries expanded their geographic and temporal range into 
the Lower and Upper Cretaceous of Asia, Europe, North America, and South 
America.
Dromaeosaurids are very closely related to troodontids and avialans 
(collectively known as paravians), and although their interrelationships 
have remained remarkably stable despite the rapid pace of discoveries, 
our estimate of what the ancestral paravian looked like has radically 
changed. Instead of a Velociraptor-like animal, it was much more 
bird-like than previously thought. Indeed, the morphological gap between 
the paravian clades has blurred to the point that basal dromaeosaurids, 
troodontids, and avialans are nearly indistinguishable from one another, 
and in life these animals would appear extremely similar. However, 
important morphological divisions exist that allow us to understand the 
evolutionary history of these three clades. This provides the 
evolutionary context to understand the origins of the dromaeosaurid 
fauna that existed up to the K/Pg extinction.
Heavily regionalized sampling and Lagerstätten effects bias attempts to 
quantify diversity and patterns of regional extinction. Nearly half of 
all named dromaeosaurids are from Campanian or Maastrichtian deposits. 
Yet this belies the fact that dromaeosaurid diversity likely peaked at 
the end of the Early Cretaceous and dromaeosaurids were nearing 
extinction by the beginning of the Maastrichtian, prior to the K/Pg 
event. What remained of dromaeosaurid diversity by the close of the Late 
Cretaceous looked quite different from that which preceded it in the 
Early Cretaceous, with the differences driven by multiple instances of 
body size increase, differential extinction, and/or long period of 
geographic isolation.