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A nomenclature for vertebral fossae in sauropods and other saurischian dinosaurs.

Wilson JA, D'Emic MD, Ikejiri T, Moacdieh EM, Whitlock JA - PLoS ONE (2011)

Bottom Line: We standardize the naming process by creating tripartite names from "primary landmarks," which form the zygodiapophyseal table, "secondary landmarks," which orient with respect to that table, and "tertiary landmarks," which further delineate a given fossa.The proposed nomenclatural system for lamina-bounded fossae adds clarity to descriptions of complex vertebrae and allows these structures to be sourced as character data for phylogenetic analyses.These anatomical terms denote potentially homologous pneumatic structures within Saurischia, but they could be applied to any vertebrate with vertebral laminae that enclose spaces, regardless of their developmental origin or phylogenetic distribution.

View Article: PubMed Central - PubMed

Affiliation: Museum of Paleontology and Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States of America. wilsonja@umich.edu

ABSTRACT

Background: The axial skeleton of extinct saurischian dinosaurs (i.e., theropods, sauropodomorphs), like living birds, was pneumatized by epithelial outpocketings of the respiratory system. Pneumatic signatures in the vertebral column of fossil saurischians include complex branching chambers within the bone (internal pneumaticity) and large chambers visible externally that are bounded by neural arch laminae (external pneumaticity). Although general aspects of internal pneumaticity are synapomorphic for saurischian subgroups, the individual internal pneumatic spaces cannot be homologized across species or even along the vertebral column, due to their variability and absence of topographical landmarks. External pneumatic structures, in contrast, are defined by ready topological landmarks (vertebral laminae), but no consistent nomenclatural system exists. This deficiency has fostered confusion and limited their use as character data in phylogenetic analysis.

Methodology/principal findings: We present a simple system for naming external neural arch fossae that parallels the one developed for the vertebral laminae that bound them. The nomenclatural system identifies fossae by pointing to reference landmarks (e.g., neural spine, centrum, costal articulations, zygapophyses). We standardize the naming process by creating tripartite names from "primary landmarks," which form the zygodiapophyseal table, "secondary landmarks," which orient with respect to that table, and "tertiary landmarks," which further delineate a given fossa.

Conclusions/significance: The proposed nomenclatural system for lamina-bounded fossae adds clarity to descriptions of complex vertebrae and allows these structures to be sourced as character data for phylogenetic analyses. These anatomical terms denote potentially homologous pneumatic structures within Saurischia, but they could be applied to any vertebrate with vertebral laminae that enclose spaces, regardless of their developmental origin or phylogenetic distribution.

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Representative vertebrae of Camarasaurus supremus.Anterior (top), left lateral (middle), and posterior (bottom) views of anterior cervical (ca. cv 4), mid-cervical (ca. cv 8), anterior dorsal (ca. dv 3), posterior dorsal (ca. dv 10), and anterior caudal (ca. ca 2) vertebrae representing multiple individuals (AMNH 5761/X-3; AMNH 5761/X-7; AMNH 5761-a/D-X-106); AMNH 5760′/D-X-125; AMNH 5761/Cd-X-2) and are to scale. Positions of vertebrae were assigned based on comparisons with complete axial series. Important changes along the column include division of the spinodiapophyseal fossa (sdf) is divided into two smaller fossae (sdf1, sdf2) by the epipophyseal prezygapophyseal lamina (eprl) in anterior and middle cervical vertebrae. The eprl is more subtly developed or absent in more posterior cervical vertebrae (see text for discussion). Images are modified from [12] (pl. 67, figs. 4, 8; pl. 70, fig. 10; pl. 71, fig. 2). Abbreviations and color scheme as in Figure 7.
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pone-0017114-g009: Representative vertebrae of Camarasaurus supremus.Anterior (top), left lateral (middle), and posterior (bottom) views of anterior cervical (ca. cv 4), mid-cervical (ca. cv 8), anterior dorsal (ca. dv 3), posterior dorsal (ca. dv 10), and anterior caudal (ca. ca 2) vertebrae representing multiple individuals (AMNH 5761/X-3; AMNH 5761/X-7; AMNH 5761-a/D-X-106); AMNH 5760′/D-X-125; AMNH 5761/Cd-X-2) and are to scale. Positions of vertebrae were assigned based on comparisons with complete axial series. Important changes along the column include division of the spinodiapophyseal fossa (sdf) is divided into two smaller fossae (sdf1, sdf2) by the epipophyseal prezygapophyseal lamina (eprl) in anterior and middle cervical vertebrae. The eprl is more subtly developed or absent in more posterior cervical vertebrae (see text for discussion). Images are modified from [12] (pl. 67, figs. 4, 8; pl. 70, fig. 10; pl. 71, fig. 2). Abbreviations and color scheme as in Figure 7.

Mentions: The caudal vertebrae show some lamination that define a small rounded sdf, a very narrow cprf, an sprf, and a shallow prcdf. Laminae and fossae are reduced or absent in middle and posterior caudal vertebrae.


A nomenclature for vertebral fossae in sauropods and other saurischian dinosaurs.

Wilson JA, D'Emic MD, Ikejiri T, Moacdieh EM, Whitlock JA - PLoS ONE (2011)

Representative vertebrae of Camarasaurus supremus.Anterior (top), left lateral (middle), and posterior (bottom) views of anterior cervical (ca. cv 4), mid-cervical (ca. cv 8), anterior dorsal (ca. dv 3), posterior dorsal (ca. dv 10), and anterior caudal (ca. ca 2) vertebrae representing multiple individuals (AMNH 5761/X-3; AMNH 5761/X-7; AMNH 5761-a/D-X-106); AMNH 5760′/D-X-125; AMNH 5761/Cd-X-2) and are to scale. Positions of vertebrae were assigned based on comparisons with complete axial series. Important changes along the column include division of the spinodiapophyseal fossa (sdf) is divided into two smaller fossae (sdf1, sdf2) by the epipophyseal prezygapophyseal lamina (eprl) in anterior and middle cervical vertebrae. The eprl is more subtly developed or absent in more posterior cervical vertebrae (see text for discussion). Images are modified from [12] (pl. 67, figs. 4, 8; pl. 70, fig. 10; pl. 71, fig. 2). Abbreviations and color scheme as in Figure 7.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3046170&req=5

pone-0017114-g009: Representative vertebrae of Camarasaurus supremus.Anterior (top), left lateral (middle), and posterior (bottom) views of anterior cervical (ca. cv 4), mid-cervical (ca. cv 8), anterior dorsal (ca. dv 3), posterior dorsal (ca. dv 10), and anterior caudal (ca. ca 2) vertebrae representing multiple individuals (AMNH 5761/X-3; AMNH 5761/X-7; AMNH 5761-a/D-X-106); AMNH 5760′/D-X-125; AMNH 5761/Cd-X-2) and are to scale. Positions of vertebrae were assigned based on comparisons with complete axial series. Important changes along the column include division of the spinodiapophyseal fossa (sdf) is divided into two smaller fossae (sdf1, sdf2) by the epipophyseal prezygapophyseal lamina (eprl) in anterior and middle cervical vertebrae. The eprl is more subtly developed or absent in more posterior cervical vertebrae (see text for discussion). Images are modified from [12] (pl. 67, figs. 4, 8; pl. 70, fig. 10; pl. 71, fig. 2). Abbreviations and color scheme as in Figure 7.
Mentions: The caudal vertebrae show some lamination that define a small rounded sdf, a very narrow cprf, an sprf, and a shallow prcdf. Laminae and fossae are reduced or absent in middle and posterior caudal vertebrae.

Bottom Line: We standardize the naming process by creating tripartite names from "primary landmarks," which form the zygodiapophyseal table, "secondary landmarks," which orient with respect to that table, and "tertiary landmarks," which further delineate a given fossa.The proposed nomenclatural system for lamina-bounded fossae adds clarity to descriptions of complex vertebrae and allows these structures to be sourced as character data for phylogenetic analyses.These anatomical terms denote potentially homologous pneumatic structures within Saurischia, but they could be applied to any vertebrate with vertebral laminae that enclose spaces, regardless of their developmental origin or phylogenetic distribution.

View Article: PubMed Central - PubMed

Affiliation: Museum of Paleontology and Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, United States of America. wilsonja@umich.edu

ABSTRACT

Background: The axial skeleton of extinct saurischian dinosaurs (i.e., theropods, sauropodomorphs), like living birds, was pneumatized by epithelial outpocketings of the respiratory system. Pneumatic signatures in the vertebral column of fossil saurischians include complex branching chambers within the bone (internal pneumaticity) and large chambers visible externally that are bounded by neural arch laminae (external pneumaticity). Although general aspects of internal pneumaticity are synapomorphic for saurischian subgroups, the individual internal pneumatic spaces cannot be homologized across species or even along the vertebral column, due to their variability and absence of topographical landmarks. External pneumatic structures, in contrast, are defined by ready topological landmarks (vertebral laminae), but no consistent nomenclatural system exists. This deficiency has fostered confusion and limited their use as character data in phylogenetic analysis.

Methodology/principal findings: We present a simple system for naming external neural arch fossae that parallels the one developed for the vertebral laminae that bound them. The nomenclatural system identifies fossae by pointing to reference landmarks (e.g., neural spine, centrum, costal articulations, zygapophyses). We standardize the naming process by creating tripartite names from "primary landmarks," which form the zygodiapophyseal table, "secondary landmarks," which orient with respect to that table, and "tertiary landmarks," which further delineate a given fossa.

Conclusions/significance: The proposed nomenclatural system for lamina-bounded fossae adds clarity to descriptions of complex vertebrae and allows these structures to be sourced as character data for phylogenetic analyses. These anatomical terms denote potentially homologous pneumatic structures within Saurischia, but they could be applied to any vertebrate with vertebral laminae that enclose spaces, regardless of their developmental origin or phylogenetic distribution.

Show MeSH
Related in: MedlinePlus