Daniel A. Driscoll, Alexander M. Dunhill, Thomas L. StubbsÂ & Michael J. Benton (2018)
The mosasaur fossil record through the lens of fossil completeness.
Palaeontology (advance online publication)
The quality of the fossil record affects our understanding of macroevolutionary patterns. Palaeodiversity is filtered through geological and human processes; efforts to correct for these biases are part of a debate concerning the role of sampling proxies and standardization in biodiversity models. We analyse the fossil record of mosasaurs in terms of fossil completeness as a measure of fossil quality, using three novel, correlating metrics of fossil completeness and 4083 specimens. A new qualitative measure of character completeness (QCM) correlates with the phylogenetic character completeness metric. Mean completeness by species decreases with specimen count; average completeness by substage varies significantly. Mean specimen completeness is higher for speciesânamed fossils than those identified to genus and family. We consider the effect of toothâonly specimens. Importantly, we find that completeness of species does not correlate with completeness of specimens. Completeness varies by palaeogeography: North American specimens show higher completeness than those from Eurasia and Gondwana. These metrics can be used to identify exceptional preservation; specimen completeness varies significantly by both formation and lithology. The Belgian Ciply Formation displays the highest completeness; clay lithologies show higher completeness values. Neither species diversity nor sea level correlates significantly with fossil completeness. A generalized least squares (GLS) analysis using multiple variables agrees with this result, but reveals two variables with significant predictive value for modelling averaged diversity: sea level, and mosasaur and plesiosaurâbearing formations (the latter is redundant with diversity). Mosasaur completeness is not driven by sea level, nor does completeness limit the mosasaur diversity signal.
Bryan M. Gee, Steven J. Rosscoe, Diane Scott, Judie Ostlien and Robert R. Reisz (2018)
Faunal overview of the Mud Hill locality from the early Permian Vale Formation of Taylor County, Texas.
Journal of Paleontology (advance online publication)
The Texas red beds represent one of the richest series of early Permian deposits in the world. In particular, the Clear Fork Group has produced a diverse assemblage of temnospondyls, early reptiles, and synapsids. However, most of this material has been sourced from the oldest member, the Arroyo Formation, and the understanding of the paleoecosystem of the younger Vale and Choza formations is less well resolved. Here we present a previously undescribed Vale locality, the first vertebrate-bearing locality from the formation to be described in detail in several decades, from near Abilene, Texas with juvenile diplocaulids, captorhinids, abundant material of rare taxa such as Varanops and diadectids, and the first report of a recumbirostran 'microsaur' from the formation. This assemblage is atypical of early Permian deposits in the taxonomic and size distribution of the vertebrate fauna in comparison to other localities from the Vale Formation that preserve a greater abundance of aquatic taxa (e.g., fishes, Trimerorhachis) and synapsids (e.g., Dimetrodon). Minimal abrasion of the elements, relative articulation and association of the specimen of Varanops, and the paucity of aquatic taxa suggest an ephemeral pond deposit in which organisms were preserved essentially in situ. Our characterization of the locality also permits a revision and discussion of the vertebrate faunal assemblage of the Vale Formation.
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Scott Jarvie, Tim Jowett, Michael B. Thompson, Philip J. Seddon and Alison Cree (2018)
Effects of Warm Temperatures on Metabolic Rate and Evaporative Water Loss in Tuatara, a Cool-Climate Rhynchocephalian Survivor.
Physiological and Biochemical Zoology 91(4): 950-966
The thermal sensitivity of physiological rates is a key characteristic of organisms. For tuatara (Sphenodon punctatus), the last surviving member of the reptilian order Rhynchocephalia and an unusually cold-tolerant reptile, we aimed to clarify responses in indices of metabolic rate (oxygen consumption [VËO2] and carbon dioxide production [VËCO2]) as well as rates of total evaporative water loss (TEWL) to temperatures at the warmer end of the known tolerated range; currently, patterns for metabolic rate are unclear above 25ÂC, and TEWL has not been measured above 25ÂC. We first established that metabolic rate was lowest during the photophase and then measured VËO2, VËCO2, and TEWL at six temperatures (12Â, 20Â, 24Â, 27Â, 29Â, and 30ÂC) during this phase. Consistent with our predictions, we found that mass-adjusted VËO2, VËCO2, and TEWL increased at least 3.5-fold between 12Â and 30ÂC (at 30ÂC, rates were 2.509 mL gâ1 hâ1, 2.001 mL gâ1 hâ1, and 1.829 mgâ1 gâ1 hâ1, respectively). Temperature coefficients (Q10 values) for mass-adjusted VËO2 and TEWL showed thermal dependence between 12Â and 29ÂC but with a reduced increase or thermal independence between 29Â and 30ÂC. There was no observed effect of egg incubation temperature (inferred sex) on the subsequent metabolic rates of juveniles. The respiratory exchange ratio implied a switch from carbohydrate metabolism at <22ÂC to lipid metabolism at >27ÂC. The rigorous measurement of VËO2 and TEWL provides a basis for future studies to predict the thermal sensitivity of tuatara to human-mediated climate change.
Anwesha Saha Louise McRae, C. Kenneth Dodd, Jr., Hector Gadsden, Kelly M. Hare, Vimoksalehi Lukoschek and Monika BÃhm (2018)
Tracking Global Population Trends: Population Time-Series Data and a Living Planet Index for Reptiles.
Journal of Herpetology 52(3):259-268
Effective conservation action relies on access to the best-available species data. Reptiles have often been overlooked in conservation prioritization, especially because of a paucity of population data. Using data for 549 reptile populations representing 194 species from the Living Planet database, we provide the first detailed analysis of this database for a specific taxonomic group. We estimated an average global decline in reptile populations of 54â55% between 1970 and 2012. Disaggregated indices at taxonomic, system, and biogeographical levels showed trends of decline, often with wide confidence intervals because of a prevalence of short time series. We assessed gaps in our reptile time-series data and examined what types of publication they primarily originated from to provide an overview of the range of data sources captured in the Living Planet database. Data were biased toward crocodilians and chelonians, with only 1% and 2% of known lizard and snake species represented, respectively. Population time-series data stemmed primarily from published ecological research (squamates) and data collected for conservation management (chelonians and crocodilians). We recommend exploration of novel survey and analytical techniques to increase monitoring of reptiles, especially squamates, over time. Open access publication and sharing of data sets are vital to improve knowledge of reptile status and trends, aided by the provision of properly curated databases and data-sharing agreements. Such collaborative efforts are vital to effectively address global reptile declines.