Recent non-dino papers with free pdfs:
Walter G. Joyce and Yann Rollot (2020)
An alternative interpretation of Peltochelys duchastelii as a paracryptodire.
Fossil Record 23: 83â93
doi:
https://doi.org/10.5194/fr-23-83-2020 https://www.foss-rec.net/23/83/2020/Free pdf:
https://www.foss-rec.net/23/83/2020/fr-23-83-2020.pdfPeltochelys duchastelii is an enigmatic turtle from Early Cretaceous (middle Barremianâearly Aptian) Sainte-Barbe Formation of Bernissart, Belgium. In more recent literature, there has been strong support for the trionychian affinities of this taxon, but this interpretation is less consistent with external data, in particular biogeography and temporal considerations. We provide a reinterpretation here of the lectotype of Peltochelys duchastelii that differs from more recent ones in key features. Although we agree that this turtle lacks mesoplastra, we conclude that it has 11 pairs of peripherals (not 10), likely had 12 pairs of marginals (not 11), lacks a contact between peripheral 1 and costal 1, and that a midline contact of peripherals 1 hinders the nuchal from contributing to the margin of the shell. This unusual set of characters is otherwise known from roughly coeval taxa from Europe and North America. Phylogenetic analysis yields a previously unrecognized clade of basal paracryptodiran turtles from the Late Jurassic to Paleogene of Euramerica united by a nuchal that is withdrawn from the anterior margin of the shell. The name Compsemydidae is referred to this clade. The novel hypothesis suggests that Peltochelys duchastelii did not immigrate from Asia but instead originated in Europe.
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Two main theories have been used to explain the origin of pectoral and pelvic appendages. The 'finâfold theory' proposes that they evolved from a trunk bilateral fin fold, while Gegenbaur's theory assumes they derived from the head branchial arches. However, none of these theories has been fully supported. The 'finâfold' theory is mainly often accepted due to some existing developmental data, but recent developmental studies have revived Gegenbaur's theory by revealing common mechanisms underlying the patterning of branchial arches and paired appendages. Here I review developmental data and many others lines of evidence, which lead to a crucial question: might the apparent contradictions between the two theories be explained by a dual origin of the pectoral appendage, i.e. the pectoral girdle and fin/limb being mainly related to the head and trunk, respectively? If this is so then a) the pectoral and pelvic girdles would not be serial homologues; b) the term 'developmental serial homologues' could only potentially be applied to the pectoral and pelvic fins/limbs. Fascinatingly, in a way this would be similar to what Owen had already suggested, more than 170âyears ago: that the pectoral and pelvic girdles are mainly related to the head and trunk, respectively.