The Parisian comparative anatomist Claude Perrault, dissecting an Indian giant tortoise in 1676, was the first to observe that the urinary bladder is of an extraordinary size in terrestrial tortoises. In 1799, the English comparative physiologist Robert Townson suggested that the bladder functioned as a water reservoir, as he had shown previously for frogs and toads. However, these observations went unnoticed in subsequent reports on tortoise water economy that were made by travellers and naturalists visiting the Galapagos Archipelago and marvelling over the huge numbers of giant tortoises that inhabited these desert-like islands. The first such report was by an American naval officer, David Porter, who was a privateer in the 1812–15 war with England. In his journal he referred to the constant supply of water which the Galapagos tortoises carried with them. References to the location in the body, as well as the amounts and quality of the water stored, were, however, contradictory.

The confusion concerning the anatomical identity of the water reservoir in the Galapagos tortoise, Geochelone elephantopus, persisted throughout the nineteenth century, and continued when studies of tortoise water economy and drinking behaviour in arid environments were taken up independently in the desert tortoise, Gopherus agassizii, which inhabits the desert regions in the south-western United States. In 1881 Cox found large sacs filled with clear water under the carapace, but it was half a century later that these sacs were identified as the large bilobed bladder; references to specific water sacs continued to appear in the literature until the 1960s.

Since 1970, information on the water economy of desert tortoises has been obtained from extensive field studies. Rates of disappearance of tritiated water injected into the body have shown that during the drought periods of the summer, water turnover (intake) rates do not differ from the rates of metabolic water production. Under these conditions urine is not voided, but is stored in the large bladder. During a drought period the bladder urine increases from initially low osmolality finally to reach isosmolality with the blood plasma. Soluble K+ is the major cation of the urine, but large amounts of K+ are also present as precipitated urates. During a drought period the body is in negative water balance, but despite substantial losses of total body water, the plasma concentrations of Na+ and Cl− can remain constant for many months, indicating regulation of the extracellular fluid and water content of the body tissues by reabsorption of water from the urinary bladder. The bladder thus acts both as a store for nitrogenous waste and K+ and as a water reservoir during droughts. Following rain showers, there is a sharp decline in tritium activity correlated with copious drinking from temporary pools of rain water. The old bladder urine is voided and most of the water drunk is stored as a highly dilute urine.

In 1676 Perrault observed that in a freshwater turtle, Emys orbicularis, but not in the giant tortoise, two other bladders opened into the cloaca. By the mid-twentieth century it had been established that these cloacal bladders typically were restricted to species of chelonians that led a semi-terrestrial or semi-aquatic life. The function of the bladders has been debated since Townson observed in 1799 that dehydrated freshwater turtles took up water by anal drinking, suggesting that anal drinking served in the water economy of semi-terrestrial turtles. Since then, the bladders have been ascribed hydrostatic and respiratory functions, but the recent literature mostly argues for a respiratory function. The possible role of the cloacal bladders as a water reservoir in amphibious turtles is still open.

Terrestrial amphibians and tortoises are unique among vertebrates in possessing large urinary bladders that may function as water reservoirs in dry environments. This function depends upon copious water intake when water becomes available combined with discontinued voiding of urine in the absence of water. Adaptation to terrestrial habitats in ureotelic amphibians is correlated with tolerance of high urea concentrations in the body fluids. In arid-zone tortoises and uricotelic tree frogs, nitrogenous waste products are precipitated in the bladder, which functions as the main sink. Renewed contact with water releases drinking behaviour and voiding of the bladder urine until the accumulated excretory products are eliminated from the body and/or bladder, preparing the organism for re-exposure to arid conditions.

The Triassic reptile Euparkeria has been frequently given a pivotal position in interpretations of the evolution of archosaurs. Most recently, Welman (1995) has argued from braincase data that Euparkeria is more closely related to birds than are either theropod dinosaurs or crocodilians – a conclusion clearly at odds with the current orthodoxy. The braincase of a single specimen of Euparkeria is described in detail and compared with previous descriptions and with the braincases of other diapsids. Variations among the known specimens are documented. The homology of various braincase structures are reassessed in light of the study by Welman (1995). We argue that the braincase of Euparkeria has an undivided metotic fissure, an incompletely ossified medial wall of the otic capsule, a well-defined ‘semilunar depression’, and posteroventrally positioned foramina in the parabasisphenoid for the entrance of the cerebral branches of the internal carotid arteries. It lacks enclosure of the Eustachian system in bone, well-developed tympanic sinuses, or a well-defined recess for the lagena. A review of braincase morphology in extinct and extant diapsids suggests that braincase features of Euparkeria are largely plesiomorphic for Archosauria. The evolutionary relationships between Euparkeria and extant archosaurs (birds and crocodilians) are considered by reviewing braincase morphology in extant and extinct diapsids. No shared derived characters could be found that support the resolutions (crocodilians (Euparkeria+birds)) or (birds (Euparkeria+crocodilians)). Three derived characters shared by extant archosaurs support the resolution (Euparkeria (crocodilians+birds)), but only the presence of laterally positioned foramina in the parabasisphenoid for the entrance of the cerebral branches of the internal carotid arteries appears to represent strong evidence. The other two features are a degree of ossification (of the medial wall of the otic capsule) that exhibits some homoplasy among archosaurs, and an absence (of the ‘semilunar depression’), and therefore do not represent particularly robust hypotheses of homology. Our interpretation of the braincase of Euparkeria is fully congruent with the consensus among recent explicit phylogenetic analyses that this taxon is close to, but not a member of, the archosaur crown group. Birds and crocodilians share a number of other derived similarities (subdivided metotic fissure, elongated and tubular cochlear recess, enclosed Eustachian system, extensive tympanic sinuses, quadrate-prootic articulation) that are probably not homologous because of their absence in a number of non-avian dinosaurs and crocodilian-line crown-group archosaurs.

Current knowledge of frugivory and seed dispersal by vertebrates in the Oriental Region is summarized. Some degree of frugivory has been reported for many fish and reptile species, almost half the genera of non-marine mammals and more than 40% of bird genera in the region. Highly frugivorous species, for which fruit dominates the diet for at least part of the year, occur in at least two families of reptiles, 12 families of mammals and 17 families of birds. Predation on seeds in fleshy fruits is much less widespread taxonomically: the major seed predators are colobine monkeys and rodents among the mammals, and parrots, some pigeons, and finches among the birds. Most seeds in the Oriental Region, except near its northern margins, are dispersed by vertebrate families which are endemic to the region or to the Old World. Small fruits and large, soft fruits with many small seeds are consumed by a wide range of potential seed dispersal agents, including species which thrive in small forest fragments and degraded landscapes. Larger, bigger-seeded fruits are consumed by progressively fewer dispersers, and the largest depend on a few species of mammals and birds which are highly vulnerable to hunting, fragmentation and habitat loss.

A description of the relationship between mean food intake rate (MFIR) and group size is important in assessing the adaptiveness of group living in animals. Several hypotheses argue that foraging in groups can be beneficial in terms of MFIR but an overall assessment of the evidence available thus far was lacking. I examined this relationship in birds using studies that provided a measure of MFIR in groups of different sizes and evaluated the effect of study design and food type. In addition, I noted some of the mechanisms thought to be responsible for changes in MFIR with group size and quantified the impact of the addition of individual foragers. The most common pattern of change in MFIR with group size was a monotonic increase. The different patterns of change in MFIR with group size occurred with similar frequencies in experimental and observational studies despite the fact that observational studies often lacked control for confounding factors. Increases in MFIR were more likely to be associated with seeds as a food type than with fish or invertebrates, and were least likely with carcasses. This finding was related to the ease with which individuals can use aggression to increase their share of resources that are more concentrated in space. Adjustments in vigilance levels and aggression, as well as more subtle changes in speed of search and handling time, were correlated with changes in MFIR with group size. Finally, the addition of three to four individuals appeared to be needed to double the MFIR of a solitary bird. The results suggest that foraging in avian groups is often associated with increased MFIRs and that several ecological factors, including food dispersion, influence the pattern of change with group size.