ALBERT

Description: 〈span〉There are several paths to being a great paleontologist. You can be an intrepid discoverer of fossils and fossil deposits. You can influence the field through fresh hypotheses, innovative analyses, and novel syntheses. You can teach and popularize paleontology so that others can see how satisfying and important it is to know the history of life. Very few of us have ever been outstanding in all three of these ways, but Kay Behrensmeyer is, and that’s why she is so deserving of the Paleontological Society Medal.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉The phylogenetic relationships of Paleozoic blastozoan echinoderms are poorly understood and many of the traditionally ascribed groups are likely polyphyletic. Diploporitans, those blastozoans with double pore (diplopore) respiratory structures, have never been placed within a rigorous phylogenetic framework, and their highly variable morphologies suggest that they do not represent a natural clade. A maximum parsimony phylogenetic analysis, spanning a wide range of diploporitan and related taxa, indicates that diplopore-bearing blastozoans are a polyphyletic grouping and, consequently, that diplopore respiratory structures have evolved more than once within the echinoderms. Constraint analyses indicate that a single diplopore-bearing clade bearing the traditionally defined Glyptosphaeritida, Sphaeronitida, Asteroblastida is less parsimonious than multiple diplopore-bearing clades inferred by the unconstrained analysis.〈/span〉

Description: 〈span〉〈div〉Abstract〈/div〉Researchers often interpret the presence of tortoises in Pleistocene assemblages as evidence of an interglacial age, based on an assumption that these fossils indicate thermic climates, as modern giant tortoises require. Since the Paleocene, tortoises have been common components of terrestrial fossil assemblages and have repeatedly evolved species of giant size. Whereas extant giant tortoises are found only on islands off the coasts of South America and Africa, at least two species persisted in North America until the terminal Pleistocene. These tortoises, 〈span〉Hesperotestudo crassiscutata〈/span〉 and 〈span〉Gopherus〈/span〉 “〈span〉hexagonatus〈/span〉,” both of which reached carapace lengths of 〉1 m, were distributed across the southern United States. This study provides new metrics to derive quantitative weight estimates from measurements of the tortoise shell. The linear measurements of 69 anatomical features of the shells of 108 live tortoises indicate that the regression between straight carapace length and weight is most significant, with a maximum 〈span〉r〈/span〉〈sup〉2〈/sup〉 〉 0.99. This regression is useful for tortoises that weigh between 1.8 and 339 kg. This mass estimate, coupled with a heat dissipation rate derived from thermoregulation modeling, provides estimates of how long tortoises can maintain a viable body temperature at low ambient temperatures. Depending on size, a tortoise can survive a maximum of 2.3 to 33 hours of freezing temperatures, which corresponds to a mean annual temperature ≥22°C and a mean winter low temperature ≥7.5°C. This analysis infers warmer temperatures at Pleistocene sites with fossil tortoise occurrences than previous qualitative estimates.〈/span〉