The early Miocene charadriiform bird Becassius charadriioides De Pietri and Mayr, 2012, from the Saint-GÃrand-le-Puy area in France, was originally described as a member of uncertain affinities within the shorebird clade Scolopaci (jacanas, seedsnipe, painted-snipe, sandpipers, and allies). Following a re-assessment of the material attributed to this taxon and in the context of a larger comparative sample of extinct and extant charadriiform birds, we conclude that it is a member of the Glareolidae (pratincoles and coursers). We also demonstrate that certain elements, such as the coracoid, which were only tentatively referred to B. charadriioides, are very likely to belong to this taxon. We describe for the first time a tarsometatarsus that we tentatively attribute to this species. Based on the morphology of the humerus and other elements, it is not possible to associate Becassius charadriioides with any extant lineage within Glareolidae; it displays a combination of morphological features that can be presumed to be ancestral to Glareolidae based on outgroup comparisons and on the distinctiveness of B. charadriioides among other glareolids. The referral of Becassius charadriioides to Glareolidae bridges a gap in the evolutionary history of the clade, attesting to the presence of members of this clade in Europe during the earliest Miocene. Additionally, we provide a review of the fossil record of Glareolidae and re-assess some of the oldest fossils to have been attributed to this group.
Flapping flight is the most energetically demanding form of sustained forwards locomotion that vertebrates perform. Flock dynamics therefore have significant implications for energy expenditure. Despite this, no studies have quantified the biomechanical consequences of flying in a cluster flock or pair relative to flying solo. Here, we compared the flight characteristics of homing pigeons (Columba livia) flying solo and in pairs released from a site 7 km from home, using high-precision 5 Hz global positioning system (GPS) and 200 Hz tri-axial accelerometer bio-loggers. As expected, paired individuals benefitted from improved homing route accuracy, which reduced flight distance by 7% and time by 9%. However, realising these navigational gains involved substantial changes in flight kinematics and energetics. Both individuals in a pair increased their wingbeat frequency by 18% by decreasing the duration of their upstroke. This sharp increase in wingbeat frequency caused just a 3% increase in airspeed but reduced the oscillatory displacement of the body by 22%, which we hypothesise relates to an increased requirement for visual stability and manoeuvrability when flying in a flock or pair. The combination of the increase in airspeed and a higher wingbeat frequency would result in a minimum 2.2% increase in the total aerodynamic power requirements if the wingbeats were fully optimised. Overall, the enhanced navigational performance will offset any additional energetic costs as long as the metabolic power requirements are not increased above 9%. Our results demonstrate that the increases in wingbeat frequency when flying together have previously been underestimated by an order of magnitude and force reinterpretation of their mechanistic origin. We show that, for pigeons flying in pairs, two heads are better than one but keeping a steady head necessitates energetically costly kinematics.
Complete and perfect regeneration of appendages is a process that has fascinated and perplexed biologists for centuries. Some tetrapods possess amazing regenerative abilities, but the regenerative abilities of others are exceedingly limited. The reasons underlying these differences have largely remained mysterious. A great deal has been learned about the morphological events that accompany successful appendage regeneration, and a handful of experimental manipulations can be reliably applied to block the process. However, only in the last decade has the goal of attaining a thorough molecular and cellular biological understanding of appendage regeneration in tetrapods become within reach. Advances in molecular and genetic tools for interrogating these remarkable events are now allowing for unprecedented access to the fundamental biology at work in appendage regeneration in a variety of species. This information will be critical for integrating the large body of detailed observations from previous centuries with a modern understanding of how cells sense and respond to severe injury and loss of body parts. Understanding commonalities between regenerative modes across diverse species is likely to illuminate the most important aspects of complex tissue regeneration.