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The Plio-Pleistocene turnover event in the western Atlantic following the closure of the Central American Seaway involved high rates of extinction for both gastropod and bivalve molluscs. This extinction was associated with declining nutrient conditions and has been presumed to be associated with a decrease in molluscan body size. Previous work which has been concordant with this expectation, however, has either focused on bivalves or not considered the effects of the recovery post extinction. In three phylogenetically diverse clades, we found that body-size evolution in gastropods across the turnover event is likely tied to ecology. One clade increased in size, one decreased, and another exhibited no substantial change. Individual species lineages exhibit a mixture of microevolutionary changes from the Pliocene to today. This study indicates that gastropod body-size evolution may be more complex than in bivalves, with ecology and other functional traits playing a significant role. Macroevolutionary processes, especially whether a clade re-radiated post extinction, were found to be important. Indeed, a low portion of extant diversity consists of survivors from clades that increased in size or have similar size distributions among their species relative to the Pliocene. [ABSTRACT FROM AUTHOR]

Today's students were born well after the dramatic scientific reinterpretations of theropod dinosaur stance and metabolism of the late 1960s and early 1970s. Yet, if asked to draw a picture of "Tyrannosaurus rex," most of these students will likely draw an animal with an upright, tail-dragging posture, remarkably like the original 1905 description of this famous dinosaur. We documented this phenomenon by asking college (n = 111) and elementary to middle school students (n = 143) to draw pictures of "T. rex." On each drawing, we measured the angle of the spine from a horizontal surface. An average angle of 50-608 was found in drawings from all ages, which is within about 58 of the 1905 posture at 578. This is in striking contrast to images created by modern dinosaur scientists, which average between 0 and 108. In an effort to explain this pattern, we measured "T. rex" images in a wide variety of popular books, most of them for children, published from the 1940s to today. Since 1970, a gradually increasing proportion has represented "T. rex" with a more horizontal back (lower tail angle). Thus, popular books, while slow to change, cannot entirely account for this pattern. The erect "T. rex" stance continues, however, to dominate other areas of popular experience, such as toys and cartoons, which most American children encounter early in life. We hypothesize that older-style images long embedded in pop culture could lead to cultural inertia, in which outdated scientific ideas are maintained in the public consciousness long after scientists have abandoned them.

This article examines the concept of holes in philosophy and their practical implications in zoological morphology, specifically in gastropod shells. The authors introduce different types of openings in gastropod shells, such as the true umbilicus, pseudoumbilicus, and a newly identified opening called the hollow newel. They propose that the axial openings in gastropod shells be designated as hollow newels, which lack complete inner shell walls forming the columella. The authors compare this concept to spiral staircases without a central supporting pillar. The text explores the presence of a hole, known as the "HN," in certain gastropod shells, discussing its attachment points for muscles and various character states associated with this feature. The authors conducted a survey and found that HNs are primarily found in turritellids. The text also delves into the potential functions and evolutionary significance of the HN. Overall, the article emphasizes the need for further research and examination of physical specimens to gain a better understanding of gastropod evolution and ecology. [Extracted from the article]

Turritellid gastropods are among the most widespread, abundant, and diverse mollusks in Plio-Pleistocene deposits of the Atlantic coastal plain and Florida, with at least 46 species and subspecies described over almost two centuries. Yet the systematic status of these common fossil species and their phylogenetic relationships--to each other and to turritellids living today in the western Atlantic--have never been investigated in detail. We make use of recent molecular phylogenetic work on living turritellids and new analyses of shell characters to review the group from this time interval to the present in a comprehensive phylogenetic analysis and assessment of their evolutionary history in the region. We conclude that 20 fossil and two Recent species are valid. Four of these species are placed in the genus Torcula Gray, 1847; five in Caviturritella new genus, and eleven in "Turritella" sensu lato. We identify Torcula perattenuata as the likely direct ancestor of one of the two turritellid species living today off the southeastern U.S. coast, Torcula exoleta, and we elucidate the fossil record of the other extant species, "Turritella" perexilis (senior synonym of Turritella acropora). We show that Caviturritella was extirpated from the United States Gulf and Atlantic coastal plains in the Early Pleistocene but is still represented in the western Atlantic by the living species C. variegata in the southern Caribbean. We also present the first detailed treatment of Plio-Pleistocene turritellid fossils from Georgia. Our analysis shows that the Plio-Pleistocene Pinecrest beds of Florida contain 18 co-occurring turritellid species, which is the highest turritellid species diversity in one formation known in the fossil record. [ABSTRACT FROM AUTHOR]