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Sauropod haemal arches classification

From: Ben Creisler

New online paper:

Alejandro Otero, Pablo Ariel Gallina, Juan Ignacio Canale & Alejandro
Haluza (2011)
Sauropod haemal arches: morphotypes, new classification and phylogenetic
Historical Biology (advance online publication)

Sauropod haemal arches are caudal bony structures that have been
traditionally incorporated into two different types observed in different
anatomical views: Y-shaped (anterior view) and forked (lateral view). This
research proposes a classification combining information observed in
anterior and lateral views. Four types of ?Y-shaped? and six types of
?V-shaped? chevrons were recognised. Complete chevron series in some
eusauropods allows the comparison of topological equivalent structures
along the tail and also among taxa. A basal titanosaur from Argentina
exhibits mid-caudal chevron morphology in which more than one cranial and
caudal process is present, arising from the distal blades as well as from
the proximal rami, a condition not seen before in a sauropod dinosaur. The
morphological variability seen in sauropod chevrons along the tail is in
close relationship with the development and distribution of muscle.
caudofemoralis longus, as seen in extant crocodiles and as previously
proposed for non-avian theropods and for caudal centra and transverse
processes of sauropod dinosaurs. Two new characters related to middle
chevrons are proposed here, in which the transitional morphology is

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