New paleo articles

[bh480@scn.org]

From: Ben Creisler bh480@scn.org

New paleo articles

Here are some new paleo vertebrate refs and a couple about 
dino trackways I don't recall seeing mentioned.

ZHU MIN AND YU XIAOBO, 2002. A primitive fish close to the 
common ancestor of tetrapods and lungfish. Nature 418: 
767 - 770.
The relationship of the three living groups of 
sarcopterygians or lobe-finned fish (tetrapods, lungfish 
and coelacanths) has been a matter of debate. Although 
opinions still differ, most recent phylogenies suggest 
that tetrapods are more closely related to lungfish than 
to coelacanths. However, no previously known fossil taxon 
exhibits a concrete character combination approximating 
the condition expected in the last common ancestor of 
tetrapods and lungfish-and it is still poorly understood 
how early sarcopterygians diverged into the tetrapod 
lineage (Tetrapodomorpha) and the lungfish lineage 
(Dipnomorpha). Here we describe a fossil sarcopterygian 
fish, Styloichthys changae gen. et sp. nov., that 
possesses an eyestalk and which exhibits the character 
combination expected in a stem group close to the last 
common ancestor of tetrapods and lungfish. Styloichthys 
from the Lower Devonian of China bridges the morphological 
gap between stem-group sarcopterygians (Psarolepis and 
Achoania) and basal tetrapodomorphs/basal dipnomorphs. It 
provides information that will help in the study of the 
relationship of early sarcopterygians, and which will also 
help to resolve the tetrapod-lungfish divergence into a 
documented sequence of character acquisition.


Geiser, Fritz, Nicola Goodship1,and Chris R. Pavey, 2002.
Was basking important in the evolution of mammalian 
endothermy? Naturwissenschaften online
Abstract. The first mammals were small, nocturnal, and 
presumably had low metabolic rates and were therefore 
probably unable to maintain a constant high body 
temperature throughout cool nights. How these animals, 
without sufficient heat production for endogenous 
rewarming, were able to become warm and active again 
before the next activity period remains unresolved. 
However, we discovered that, similar to reptiles, the 
carnivorous marsupial mammal Pseudantechinus 
macdonnellensis (body mass 30.8±5.0 g) uses the morning 
sun to rewarm from low (26.3±4.5°C) body temperatures 
during torpor. Our findings provide the first evidence of 
basking during rewarming from torpor in mammals and may 
provide an alternative explanation as to how ancestral 
mammals could have become nocturnal to avoid diurnal 
predators despite their small size and a low endogenous 
heat production.....
Thus, we propose, in agreement with previous hypotheses 
(Crompton et al. 1978; Ruben 1995), that small ancestral 
mammals used good insulation and modest heat production to 
be able to forage for part of the night. However, unlike 
previous hypotheses (Crompton et al. 1978; Ruben 1995), 
which assumed homeothermy in ancestral mammals, we propose 
that ancestral mammals were heterothermic and, when 
thermally challenged or when food supply was low, became 
torpid. While heterothermy in ancestral mammals seems 
likely it is, however, improbable that the pattern of 
torpor was identical to that in modern mammals with 
thermoregulatory control of Tb during torpor. It also 
seems unlikely that their low MR sufficed for endothermic 
arousal from low Tb and they therefore required external 
heat, not primarily to save energy as in modern mammals 
(Schmid 1996; Lovegrove et al. 1999), but to speed up the 
rewarming process or be able to rewarm at all.

http://www.paleo.pan.pl/acta/acta.htm
PDFS are still free on this site:

Kielan-Jaworowska, Zofia, Richard L. Cifelli, and Zhe-Xi 
Luo, 2002.  Dentition and relationships of the Jurassic 
mammal 
Shuotherium.  Acta Palaeontologica Polonica 47 (3), 
2002:479-486. 
The Middle Jurassic mammal Shuotherium has lower molars 
that possess a trigonid and talonid, but are unique in 
having the talonid situated in front of the trigonid, 
rather than behind it, as in molars of usual tribosphenic 
pattern. Shuotherium dongi Chow and Rich, 1982 was based 
on a dentary bearing seven teeth, originally interpreted 
as three premolars and four molars. Based on comparison 
with other groups of early mammals, we reinterpret the 
premolar-molar boundary in the holotype of S. dongi, and 
propose a dental formula of four (or more) premolars and 
three molars. The ultimate lower premolar (previously 
identified as the first molar) has a completely developed 
trigonid and no talonid or pseudo-talonid. We hypothesize 
that the mesial cingulid on molars of Australosphenida is 
a highly plausible structural antecedent to the pseudo-
talonid of Shuotherium. This and other shared, derived 
features support a relationship of Shuotherium and 
Australosphenida as sister-taxa. We hypothesize that the 
common ancestor of Shuotherium + Australosphenida had a 
global distribution no younger than early Middle Jurassic, 
and that the respective clades diverged prior to full 
separation of Gondwanan and Laurasian landmasses.       

Kielan-Jaworowska, Zofia,  J.H. Hurum, Philip J. Currie, 
and Rinchen Barsbold  New data on anatomy of the Late 
Cretaceous multituberculate mammal Catopsbaatar.        
 Acta Palaeontologica Polonica 47 (3), 2002:557-560. 
The Gobi Desert is famous for providing one of the worlds 
best preserved Cretaceous terrestrial faunas, including 
dinosaurs and mammals. Beginning with the Central Asiatic 
Expeditions in the 1920s, through the Polish-Mongolian 
Expeditions in the 1960s-1970s, Soviet-Mongolian 
Expeditions in 1970s, and finally the Mongolian Academy-
American Museum Expeditions in the 1990s-2000s, the number 
of complete skulls (see Kielan-Jaworowska et al. 2000 for 
review) of Cretaceous mammals often associated with 
postcranial skeletons, found in Mongolia increased to 
several hundred. In addition to these professional 
expeditions, there have been other types of trips to 
Mongolia, also aimed at collecting fossils. The Nomadic 
Expeditions Company in USA organizes one of these, and has 
made trips to Mongolia since 1996. During the 1999 Nomadic 
Expedition, a skull associated with parts of the 
postcranial skeleton of the multituberculate mammal 
Catopsbaatar catopsaloides was found. The specimen is more 
complete than others previously known of this species and 
brings new data on multituberculate anatomy and 
ontogenetic variation. In this note we discuss the new 
data on the structure of C. catopsaloides; the details of 
its anatomy will be described in subsequent papers by the 
two first authors       

Gierliñski, Gerard and Karol Sabath, 2002. A probable 
stegosaurian track from the Late Jurassic of Poland     
 Acta Palaeontologica Polonica 47 (3), 2002:561-564. 
Elusive tracks of stegosaurs have been long searched for 
by ichnologists, and various purported stegosaur imprints 
have recently been reported. A fragmentary trackway of a 
large, quadrupedal ornithischian dinosaur was found on an 
isolated slab of Oxfordian dolomite, on the northeastern 
slope of Holy Cross Mountains, Poland. The track is 
similar to large, blunt-toed Late Jurassic ichnites from 
North America. The footprints show a distinctive 
morphology, which fits the stegosaurian foot. The newly 
described ichnites from the Upper Jurassic of Poland 
provide the second ichnological evidence of the Late 
Jurassic dinosaurs in this country; numerous rich dinosaur 
footprint assemblages were previously known only from the 
Lower Jurassic outcrops. 

DIFLEY, ROSE L., and A. A. EKDALE, 2002. Footprints of 
Utah's Last Dinosaurs: Track Beds in the Upper Cretaceous 
(Maastrichtian) North Horn Formation of the Wasatch 
Plateau, Central Utah. PALAIOS: Vol. 17, No. 4, pp. 327-
346.
ABSTRACT
 Dinosaur track beds occur at several localities in the 
uppermost Cretaceous (Maastrichtian) North Horn Formation 
in the Wasatch Plateau, central Utah. The track bed 
localities, separated by up to 80 km, also contain 
dinosaur body fossils. At the type locality at North Horn 
Mountain in Emery County, more than 100 individual 
exposures and/or stratigraphic levels within a 1.2-km2 
study area exhibit tracks in vertical cross-sectional 
view. These biogenic structures are similar to others that 
have been interpreted elsewhere as deep dinosaur tracks. 
At the type section, track beds vertically span at least 
183 m from the base of the formation up to a few meters 
below the highest dinosaur eggshells, which are 
interpreted to occur immediately below the Cretaceous-
Tertiary (K-T) boundary interval. Track occurrence in the 
North Horn Formation demonstrates that large dinosaurs 
were present in central Utah until very shortly before the 
K-T boundary. 
 The track structures feature deformation, overprinting, 
and slip striae that are interpreted to exhibit individual 
dinosaur behavior. Some striae exhibit repeating patterns 
that suggest tubercle configuration or scale patterns on 
dinosaur feet. Track groupings at any individual level 
suggest that many animals repeatedly congregated in 
topographic lows of the floodplain or near shifting 
anastomosing river systems, and track-size distribution 
largely suggests the presence of different sizes or age 
groups of herbivores. The conditions produced by 
anastomosed fluvial environments provided the depositional 
setting responsible for formation and preservation of most 
of the North Horn tracks.

McGowen, M.R., K. Padian, M.A. de Sosa, and R.J. Harmon, 
2002. 
Description of Montanazhdarcho minor, an azhdarchid 
pterosaur from the Two Medicine Formation (Campanian) of 
Montana. Paleobios: 22(1), May 15, 2002 ($6.00) 20 pp.