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Mammalian megafauna have been critical to the functioning of Earth's biosphere for millions of years. However, since the Plio-Pleistocene, their biodiversity has declined concurrently with dramatic environmental change and hominin evolution. While these biodiversity declines are well-documented, their implications for the ecological function of megafaunal communities remain uncertain. Here, we adapt ecometric methods to evaluate whether the functional link between communities of herbivorous, eastern African megafauna and their environments (i.e., functional trait-environment relationships) was disrupted as biodiversity losses occurred over the past 7.4 Ma. Herbivore taxonomic and functional diversity began to decline during the Pliocene as open grassland habitats emerged, persisted, and expanded. In the mid-Pleistocene, grassland expansion intensified, and climates became more variable and arid. It was then that phylogenetic diversity declined, and the trait-environment relationships of herbivore communities shifted significantly. Our results divulge the varying implications of different losses in megafaunal biodiversity. Only the losses that occurred since the mid-Pleistocene were coincident with a disturbance to community ecological function. Prior diversity losses, conversely, occurred as the megafaunal species and trait pool narrowed towards those adapted to grassland environments. Mammalian megafaunal biodiversity has declined since the Plio-Pleistocene. Here, the authors apply ecometric methods to evaluate the functional link between eastern African herbivorous megafauna and their environments, showing that some biodiversity loss coincided with community ecological function disturbance. [ABSTRACT FROM AUTHOR]

Hox genes regulate regionalization of the axial skeleton in vertebrates, and changes in their expression have been proposed to be a fundamental mechanism driving the evolution of new body forms. The origin of the snake-like body form, with its deregionalized pre-cloacal axial skeleton, has been explained as either homogenization of Hox gene expression domains, or retention of standard vertebrate Hox domains with alteration of downstream expression that suppresses development of distinct regions. Both models assume a highly regionalized ancestor, but the extent of deregionalization of the primaxial domain (vertebrae, dorsal ribs) of the skeleton in snake-like body forms has never been analysed. Here we combine geometric morphometrics and maximum-likelihood analysis to show that the pre-cloacal primaxial domain of elongate, limb-reduced lizards and snakes is not deregionalized compared with limbed taxa, and that the phylogenetic structure of primaxial morphology in reptiles does not support a loss of regionalization in the evolution of snakes. We demonstrate that morphometric regional boundaries correspond to mapped gene expression domains in snakes, suggesting that their primaxial domain is patterned by a normally functional Hox code. Comparison of primaxial osteology in fossil and modern amniotes with Hox gene distributions within Amniota indicates that a functional, sequentially expressed Hox code patterned a subtle morphological gradient along the anterior-posterior axis in stem members of amniote clades and extant lizards, including snakes. The highly regionalized skeletons of extant archosaurs and mammals result from independent evolution in the Hox code and do not represent ancestral conditions for clades with snake-like body forms. The developmental origin of snakes is best explained by decoupling of the primaxial and abaxial domains and by increases in somite number, not by changes in the function of primaxial Hox genes. [ABSTRACT FROM AUTHOR]

Amphisbaenia is a speciose clade of fossorial lizards characterized by a snake-like body and a strongly reinforced skull adapted for head-first burrowing. The evolutionary origins of amphisbaenians are controversial, with molecular data uniting them with lacertids, a clade of Old World terrestrial lizards, whereas morphology supports a grouping with snakes and other limbless squamates. Reports of fossil stem amphisbaenians have been falsified, and no fossils have previously tested these competing phylogenetic hypotheses or shed light on ancestral amphisbaenian ecology. Here we report the discovery of a new lacertid-like lizard from the Eocene Messel locality of Germany that provides the first morphological evidence for lacertid-amphisbaenian monophyly on the basis of a reinforced, akinetic skull roof and braincase, supporting the view that body elongation and limblessness in amphisbaenians and snakes evolved independently. Morphometric analysis of body shape and ecology in squamates indicates that the postcranial anatomy of the new taxon is most consistent with opportunistically burrowing habits, which in combination with cranial reinforcement indicates that head-first burrowing evolved before body elongation and may have been a crucial first step in the evolution of amphisbaenian fossoriality. [ABSTRACT FROM AUTHOR]

The largest extant snakes live in the tropics of South America and southeast Asia where high temperatures facilitate the evolution of large body sizes among air-breathing animals whose body temperatures are dependant on ambient environmental temperatures (poikilothermy). Very little is known about ancient tropical terrestrial ecosystems, limiting our understanding of the evolution of giant snakes and their relationship to climate in the past. Here we describe a boid snake from the oldest known neotropical rainforest fauna from the Cerrejón Formation (58–60 Myr ago) in northeastern Colombia. We estimate a body length of 13 m and a mass of 1,135 kg, making it the largest known snake. The maximum size of poikilothermic animals at a given temperature is limited by metabolic rate, and a snake of this size would require a minimum mean annual temperature of 30–34 °C to survive. This estimate is consistent with hypotheses of hot Palaeocene neotropics with high concentrations of atmospheric CO2 based on climate models. Comparison of palaeotemperature estimates from the equator to those from South American mid-latitudes indicates a relatively steep temperature gradient during the early Palaeogene greenhouse, similar to that of today. Depositional environments and faunal composition of the Cerrejón Formation indicate an anaconda-like ecology for the giant snake, and an earliest Cenozoic origin of neotropical vertebrate faunas. [ABSTRACT FROM AUTHOR]

The article discusses how the discovery of fossils belonging to a very early turtle named Odontochelys semitestacea may change ideas about the origins of turtles and their physiological evolution. Prior to this discovery, the bulk of fossil evidence for turtle origins was derived from Proganochelys quenstedti. While it was suggested that the earliest of these creatures lived in terrestrial environments, the osteology of O. semitestacea implies that they are closely related to the diapsid reptiles. The location of this turtle's fossils also suggest that it lived in a shallow marine environment.

A correction to the article "Giant boid snake from the Paleocene neotropics reveals hotter past equatorial temperatures" that was published in the 2009 issue is presented.

Replying to: J. M. K. Sniderman 460, 10.1038/nature08222 (2009); A. M. Makarieva, V. G. Gorshkov & B.-L. Li 460, 10.1038/nature08223 (2009); M. W. Denny, B. L. Lockwood & G. N. Somero 460, 10.1038/nature08224 (2009)Denny et al. and Sniderman question our use of body size in Titanoboa cerrejonensis as an equatorial temperature proxy during the Palaeocene, and Makarieva et al. suggest an adjustment to our temperature estimates. Denny et al. misinterpret the physiological model of our study and the implications of their body temperature (Tb) estimates relative to the thermal ecology of extant snakes. They assert that our model is inappropriate for large-bodied animals because the relationship between Tb and air temperature (mean annual temperature; MAT) is not constant across different body sizes in poikilotherms. In fact, the model does not assume constancy of Tb relative to MAT. Changes in Tb (and thus body size) relative to MAT resulting from increasing thermal inertia with size are inherent in the model, as evidenced by the scaling of body length and MAT (see Fig. 3 in ref. 3). The model is accurate for the longest extant snake, Python reticulatus, with a maximum body length ∼70% that of Titanoboa, indicating that it is appropriate to use with animals approximating the sizes of the largest known snakes. [ABSTRACT FROM AUTHOR]