Just out @ Journal of Vertebrate Paleontology
Was Diplodocus (Diplodocoidea, Sauropoda) capable of propalinal jaw motion?
John A. Whitlock
As the largest land animals to ever walk the earth, sauropods have long been a source of interest and wonderment, both for lay society and for vocational paleobiologists. In particular, aspects of their biology related to feeding and ecology have served as fodder for dozens of researchers within the past decade alone (e.g., Rauhut et al., 2007; Sereno et al., 2007 Hummel et al., 2008; Chure et al., 2010; Hummel and Clauss, 2011; Whitlock, 2011a; Young et al., 2012; D’Emic et al., 2013; Barrett, 2014; Button et al., 2014, 2016; Schwarz et al., 2015; MacLaren et al., 2017). The longest-tenured mystery has been the function of the unusual feeding apparatus associated with Diplodocus (see literature review in Whitlock, 2011a). The peg-like teeth, elongate jaw, and short dental arcade of Diplodocus have commonly been considered unsuitable for the typical forms of biting and slicing associated with other herbivores, and so numerous alternative hypotheses have been advanced, including scraping algae from rocks (Holland, 1906) and carnivory (Tornier, 1911; Sternfeld in Holland, 1924). More recent hypotheses have generally coalesced around two basic concepts: ground-level browsing (e.g., Barrett and Upchurch, 1994; Stevens and Parrish, 1999; Sereno et al., 2007; Whitlock, 2011a; Young et al., 2012) and branch-stripping (e.g., Coombs, 1975; Bakker, 1986; Barrett and Upchurch, 1994, 2005; Christiansen, 2000; Upchurch and Barrett, 2000; Young et al., 2012; MacLaren et al., 2017). Although ground-level browsing does not require the invention of a de novo feeding mechanism, it remains to be demonstrated how some of the unusual, labially facing wear facets form on the upper dentition. Branch-stripping provides an explanation for the wear facets (see Upchurch and Barrett, 2000), but as stated, it requires the invention of a novel feeding behavior, and some evidence suggests that wear patterns are inconsistent with this feeding strategy (Whitlock, 2011a). Definitively testing either hypothesis has proven challenging, although one key aspect can be objectively examined: propalinal movement of the jaw. (…)
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