scholarly journals Comparative digestive physiology of archosaurs with notes on bird origins

2018 ◽  
Author(s):  
Piotr Bajdek
Keyword(s):  
Gut Contents ◽  
Metabolic Rates ◽  
Digestive Physiology ◽  
Digestion Time ◽  
Theropod Dinosaurs ◽  
The Difference ◽  
Phylogenetic Hypotheses ◽  
Bird Origins

It is widely accepted that birds evolved from theropod dinosaurs, and few paleontologists disagree preferring a more ancient split of the avian and dinosaur lineages. The difference in digestive physiology between members of the theropod and crocodile lineages, documented by fossil feces and gut contents, offers an opportunity to test these phylogenetic hypotheses. Birds share with crocodiles the functional gizzard that contains swallowed stones and where gastric pellets are formed before regurgitation, as well as a mechanism that prevents the passage of indigestible residues into the intestine. Both these adaptations are missing in unquestionable theropod groups (compsognathids, tyrannosaurids, allosaurids, coelophysids). The theropod ancestry of birds implies reappearance and strong development of a specific stomach functionality that either had been already lost in the theropod dinosaurs or was never present in their lineage. Coprolites of early archosaurs contain undigested bones, which suggests a short digestion time and higher metabolic rates than in extant crocodiles. Early archosaurs were similar to birds, but not to dinosaurs, in all these aspects of physiology.

scholarly journals Comparative digestive physiology of archosaurs with notes on bird origins

2018 ◽  
Author(s):  
Piotr Bajdek
Keyword(s):  
Gut Contents ◽  
Metabolic Rates ◽  
Digestive Physiology ◽  
Digestion Time ◽  
Theropod Dinosaurs ◽  
The Difference ◽  
Phylogenetic Hypotheses ◽  
Bird Origins

It is widely accepted that birds evolved from theropod dinosaurs, and few paleontologists disagree preferring a more ancient split of the avian and dinosaur lineages. The difference in digestive physiology between members of the theropod and crocodile lineages, documented by fossil feces and gut contents, offers an opportunity to test these phylogenetic hypotheses. Birds share with crocodiles the functional gizzard that contains swallowed stones and where gastric pellets are formed before regurgitation, as well as a mechanism that prevents the passage of indigestible residues into the intestine. Both these adaptations are missing in unquestionable theropod groups (compsognathids, tyrannosaurids, allosaurids, coelophysids). The theropod ancestry of birds implies reappearance and strong development of a specific stomach functionality that either had been already lost in the theropod dinosaurs or was never present in their lineage. Coprolites of early archosaurs contain undigested bones, which suggests a short digestion time and higher metabolic rates than in extant crocodiles. Early archosaurs were similar to birds, but not to dinosaurs, in all these aspects of physiology.

scholarly journals Comparative digestive physiology of archosaurs with notes on bird origins

2018 ◽  
Author(s):  
Piotr Bajdek
Keyword(s):  
Gut Contents ◽  
Metabolic Rates ◽  
Digestive Physiology ◽  
Digestion Time ◽  
Theropod Dinosaurs ◽  
The Difference ◽  
Phylogenetic Hypotheses ◽  
Bird Origins

It is widely accepted that birds evolved from theropod dinosaurs, and few paleontologists disagree preferring a more ancient split of the avian and dinosaur lineages. The difference in digestive physiology between members of the theropod and crocodile lineages, documented by fossil feces and gut contents, offers an opportunity to test these phylogenetic hypotheses. Birds share with crocodiles the functional gizzard that contains swallowed stones and where gastric pellets are formed before regurgitation, as well as a mechanism that prevents the passage of indigestible residues into the intestine. Both these adaptations are missing in unquestionable theropod groups (compsognathids, tyrannosaurids, allosaurids, coelophysids). The theropod ancestry of birds implies reappearance and strong development of a specific stomach functionality that either had been already lost in the theropod dinosaurs or was never present in their lineage. Coprolites of early archosaurs contain undigested bones, which suggests a short digestion time and higher metabolic rates than in extant crocodiles. Early archosaurs were similar to birds, but not to dinosaurs, in all these aspects of physiology.

Ingestion and elemental budgets for Linuche unguiculata, a scyphomedusa with zooxanthellae

2005 ◽  
Vol 85 (3) ◽  
pp. 613-625 ◽  
Author(s):  
Patricia Kremer
Keyword(s):  
Egg Production ◽  
Tissue Growth ◽  
Gut Contents ◽  
Digestion Time ◽  
Dissolved Nutrients ◽  
Nitrogen And Phosphorus ◽  
Prey Concentration ◽  
Laboratory Results ◽  
Experimental Feeding ◽  
A Minor

Specific rations for the zooxanthellae-bearing medusa, Linuche unguiculata, were calculated using two approaches: (a) gut contents of field collected medusae combined with experimental measurements of digestion time; and (b) experimental feeding studies combined with estimates of ambient prey biomass. Estimates of specific daily ration from gut contents averaged 5% for carbon, 6% for nitrogen, and 4% for phosphorus for the dominant size of medusae. Of the 868 medusae examined, 86% contained recognizable prey with an average of 3.6 items per medusa. Copepods dominated the gut contents (51%) as well as the ambient zooplankton prey (82%), but there was an over-representation of shelled prey, larval molluscs and foraminifera, in the gut (33%) compared with their availability (4%). Digestion times for crustaceans ranged from 1—4 h with longer times for larger prey. Ambient prey concentrations in areas of abundant L. unguiculata ranged from 0.2—4.0 prey l-1, with an average of 1.7 and no measurable day—night differences. There were also no measurable day—night differences in ingestion rates for field or laboratory fed medusae. Feeding studies showed a linear relationship between ingestion and prey concentration up to 400 prey l-1. Rations determined from experimental feeding studies were higher but less than double the ration estimates based on field gut contents. Specific ration decreased with increased medusa size in both field and laboratory results. Heterotrophy was calculated to be a major source of both nitrogen and phosphorus, but only a minor source of carbon. Elemental budgets for carbon, nitrogen and phosphorus were calculated using measured inputs of photosynthesis, ingestion, and dissolved nutrients and measured outputs of respiration, excretion, reproduction and tissue growth. Total measured outputs balanced the inputs, within the uncertainty associated with egg production.

scholarly journals FACTORS INFLUENCING THE CORRELATION BETWEEN DIFFERENCES OF ELECTRIC POTENTIAL IN THE SKIN OF HUMAN SUBJECTS AND BASAL METABOLISM

1931 ◽  
Vol 54 (6) ◽  
pp. 789-800 ◽  
Author(s):  
Charlotte Purdy ◽  
Charles Sheard
Keyword(s):  
Metabolic Rate ◽  
Electric Potential ◽  
Human Subjects ◽  
Inverse Correlation ◽  
The Body ◽  
Metabolic Rates ◽  
Electric Potentials ◽  
Per Se ◽  
The Difference ◽  
Circulation Of The Blood

High metabolic rates are associated normally with small differences of electric potential, whereas low metabolic rates are associated with large differences of electric potential as measured on the extremities of the body. Within the normal range of metabolism there appears to be a definite correlation between the metabolic rates and the difference of electric potential over a specified area of the skin, provided the person under test has no abnormalities of the circulatory system or of the functions of the skin. If there are no dysfunctions of the circulation or of the skin, the metabolic rate may be calculated, within ±4 points, from the expression See PDF for Equation where x is the metabolic rate and y is the difference of electric potential across the specified areas of skin (electrodes 12 cm. apart). In general, there are abnormalities of the circulation of the blood or of the functions of the skin of persons for whom the metabolic rates determined by the two methods (difference of electric potentials and gasometric procedures) do not agree with ±4 points. Manifest retardation or return to normality in the rate of circulation of the blood, such as may be produced by the sphygmomanometric cuff under varying pressures, produces marked changes in the difference of electric potentials obtained across a specified intervening area of skin. Retardation of flow of blood produces increased differences of electric potential. Preliminary investigations indicate that there is an inverse correlation between cutaneous temperatures and differences of electric potential. Day by day variations, emotive effects and the partaking of food have less effect, in general, on the electric potentials across a specified area of skin than they have on the metabolic rates. These experimental results indicate that there may be a more direct correlation between electric potentials and the circulation of the blood per se than between electric potentials and the metabolism of the body per se. When normality of circulation of the blood and of the functions of the skin exists in the areas under test for differences of electric potential, there is apparently a correlation between metabolic rates and electric potentials.

Early Mesozoic Terrestrial Ecosystems: Faunal Changes Among Vertebrates

2000 ◽  
Vol 6 ◽  
pp. 115-140 ◽  
Author(s):  
Nicholas C. Fraser
Keyword(s):  
Morphological Characteristics ◽  
Terrestrial Ecosystems ◽  
The Past ◽  
Theropod Dinosaurs ◽  
Highly Active ◽  
The Face ◽  
Alternative Hypotheses ◽  
The Subject ◽  
Triassic Period ◽  
Bird Origins

The past decade has seen many advances in research on vertebrate faunas of the Triassic period. The end of the Triassic now is cited widely as the dawn of modern terrestrial ecosystems, and currently the earliest mammals, turtles, lissamphibians (frogs, toads and salamanders), lizards, and crocodiles are all documented from this period. Admittedly many of these early members of present day higher order taxa were very different from their modern counterparts. For instance, the earliest crocodiles were highly active cursorial forms (e.g., Crush, 1984), and the mammals were very different to the living placentals and marsupials. Nevertheless, they possessed many of the key morphological characteristics that diagnose the group and that may well have contributed to their ultimate success. However, the Triassic was also a time of bizarre and enigmatic tetrapods, some of whose relationships are the subject of considerable debate. Indeed, in the last year this debate has reached new heights with suggestions that certain rather unusual Triassic non-dinosaurian tetrapods may have more bearing on bird origins than theropod dinosaurs. This debate has been fueled by the discoveries of feathered dinosaurs from China which, on the face of it, one might expect to dampen the search for alternative hypotheses regarding bird origins.

Resource use of five sympatric turtle species: effects of competition, phylogeny, and morphology

2000 ◽  
Vol 78 (6) ◽  
pp. 992-1008 ◽  
Author(s):  
Peter V Lindeman
Keyword(s):  
Interspecific Competition ◽  
Resource Use ◽  
Nearest Neighbor ◽  
Morphological Characteristics ◽  
Niche Complementarity ◽  
Turtle Species ◽  
Kentucky Lake ◽  
The Difference ◽  
Phylogenetic Hypotheses ◽  
Significant Structure

I quantified resource use with respect to habitat, diet, and diel and seasonal use of basking time for five sympatric turtle species in a cove on Kentucky Lake, an impoundment of the lower Tennessee River in western Kentucky, U.S.A. I used pseudocommunity analyses to test for significant structure in resource use, compared resource-use matrices with matrices representing phylogenetic similarity, and measured morphological characteristics related to resource use. Three strictly riverine species (Graptemys pseudogeographica, Graptemys ouachitensis, and Apalone mutica) with relatively long limbs and digits used outer portions of the cove near deeper waters to a greater extent than did two shorter-limbed species (Trachemys scripta and Pseudemys concinna), which inhabit both lotic and lentic waters. Only the difference in habitat between A. mutica and the other four species was shown to be significant in pseudocommunity analysis, a result that can be better explained by differences in basking substrates than by competition. Dietary studies indicated two guilds, omnivore and algivore, in spite of the low pairwise overlap values that resulted from overall prey diversity. Analysis of use of diel and seasonal basking time revealed significant structure (partitioning) at only the rank of second-nearest neighbor for seasonal time. Clustering phenograms for resource similarity among the five species were overall highly similar to two phylogenetic hypotheses. Phylogeny was thus shown to be of greater importance in structuring resource use in Kentucky Lake than interspecific competition. In addition, the similarity in clustering phenograms was not consistent with the hypothesis of niche complementarity, suggesting that interspecific competition was of little importance.

scholarly journals FANTASY VS REALITY: A Critique of Smith et al.'s Bird Origins

2016 ◽  
Vol 9 (1) ◽  
pp. 14-38 ◽  
Author(s):  
Alan Feduccia
Keyword(s):  
Late Cretaceous ◽  
Theropod Dinosaurs ◽  
Terrestrial Predator ◽  
Bird Origins

Adherents of the current orthodoxy of a derivation of birds from theropod dinosaurs, criticize the commentary by Feduccia (2013, Auk, 130) [1 - 12] entitled “Bird Origins Anew” as well as numerous papers by Lingham-Soliar on theropod dermal fibers, using numerous mischaracterizations and misstatements of content, and illustrate their own misconceptions of the nature of the debate, which are here clarified. While there is general agreement with the affinity of birds and maniraptorans, the widely accepted phylogeny, advocating derived earth-bound maniraptorans giving rise to more primitive avians (i.e. Archaeopteryx), may be “topsy-turvy.” The current primary debate concerns whether maniraptorans are ancestral or derived within the phylogeny, and whether many maniraptorans and birds form a clade distinct from true theropods. Corollaries of the current scheme show largely terrestrial maniraptoran theropods similar to the Late CretaceousVelociraptorgiving rise to avians, and flight originatingviaa terrestrial (cursorial) “gravity-resisted,” as opposed to an arboreal “gravity-assisted” model. The current dogma posits pennaceous flight remiges in earth-bound theropods having evolved in terrestrial theropods that never flew. As part of the orthodoxy, fully feathered maniraptorans such as the tetrapteryx glidersMicroraptorand allies, are incorrectly reconstructed as terrestrial cursors, when in reality their anatomy and elongate hindlimb feathers would be a hindrance to terrestrial locomotion.The same is true of many early birds, exemplified by reconstruction of the arboreally adaptedConfuciusornisas a terrestrial predator, part of the overall theropodan scheme of birds evolving from terrestrial dinosaurs, and flight from the ground up. Both sides of this contentious debate must be constantly aware that new fossil or even molecular discoveries on birds may change current conclusions.

Loss of Water by Excretion and Defaecation in the Tsetse Fly

1960 ◽  
Vol 37 (4) ◽  
pp. 689-697 ◽  
Author(s):  
E. BURSELL
Keyword(s):  
Relative Humidity ◽  
Water Content ◽  
Blood Meal ◽  
Tsetse Fly ◽  
Gut Contents ◽  
Tsetse Flies ◽  
Total Water ◽  
Gut Content ◽  
Dry Air ◽  
The Difference

1. The water content of the blood meal of tsetse flies is reduced from 79 to about 55% within the first 3 hr. after feeding. 2. The water which is abstracted from the gut contents serves to bring the tissues of the fly to full hydration, and any excess is excreted. 3. The degree of dehydration of the gut content depends on the amount of blood taken, relatively more water being retained in partial feeds. 4. The water content of faecal matter is about 75% in flies maintained at high relative humidity throughout the hunger cycle, only 35% in flies maintained in dry air. The difference reflects a saving of more than 30% of the total water reserves of the fly under conditions of desiccation.

Comparative studies of beaches

1976 ◽  
Vol 274 (934) ◽  
pp. 401-415 ◽  
Keyword(s):  
Population Dynamics ◽  
Energy Flow ◽  
Winter Season ◽  
Fish Populations ◽  
Metabolic Rates ◽  
Invertebrate Fauna ◽  
Population Distributions ◽  
Poor Indicator ◽  
The Difference ◽  
Different Parts

Over a period of six years, scientists from Scottish marine laboratories and universities worked for the winter season with colleagues in India on the ecology of Indian beaches. The intention was to compare the population dynamics with similar studies on west coast Scottish beaches. Microbial, invertebrate and vertebrate fauna were studied, in terms of population distributions and especially, by experimental work, in relation to energy flow. The results show that, for the microbial and invertebrate fauna, the rates of energy flow are very much greater on the Indian than on the Scottish beaches. Thus population biomass, which is similar for the two areas, is a poor indicator of the dynamics. For the fish populations, metabolic rates are very similar, indicating almost complete compensation to the difference in temperatures. These differences between different parts of the ecosystem lead to speculations about the factors determining adaptation in the different environments.

The Fossil Record of Predation in Dinosaurs

2002 ◽  
Vol 8 ◽  
pp. 251-266 ◽  
Author(s):  
James O. Farlow ◽  
Thomas R. Holtz
Keyword(s):  
Taxonomic Composition ◽  
Gut Contents ◽  
Hunting Behavior ◽  
Remarkable Feature ◽  
Predator Prey ◽  
Theropod Dinosaurs ◽  
Large Size ◽  
Mammalian Faunas ◽  
Cenozoic Era ◽  
Prey Handling

Predatory theropod dinosaurs can usually be identified as such by features of their jaws, teeth, and postcrania, but different clades of these reptiles differed in their adaptations for prey handling. Inferences about theropod diets and hunting behavior based on functional morphology are sometimes supported by evidence from taphonomic associations with likely prey species, bite marks, gut contents, coprolites, and trackways. Very large theropods like Tyrannosaurus are unlikely to have been pure hunters or scavengers, and probably ate whatever meat they could easily obtain, dead or alive. Theropods were not the only dinosaur hunters, though; other kinds of large reptiles undoubtedly fed on dinosaurs as well The taxonomic composition of dinosaurian predator-prey complexes varies as a function of time and geography, but an ecologically remarkable feature of dinosaurian faunas, as compared with terrestrial mammalian faunas, is the very large size commonly attained by both herbivorous and carnivorous dinosaurs. The K/T extinction event(s) did not end dinosaurian predation, because carnivorous birds remained prominent predators throughout the Cenozoic Era.

Sign in / Sign up

Export Citation Format

Share Document