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Re: Willinaqake salitralensis, South American hadrosaurid



Sorry, Tim, forgot to response your question. I do not much know what
the mean saurolophid size is, so as to evaluate if 9 m (maximal size)
is low, nor are we aware of correlations between size and number of
sacrals, even when it seems logically possible (as both size and
sacral count increase with age, even if the correlation is not always
perfect, and mechanically as greater size implies greater weight,
which may require further support via a greater sacral attachment
area, which in turn can be provided by more sacrals).

Our first idea was that the low number of sacrals was just a primitive
feature, and that the South American hadrosaurs were basal to the
hadrosaurine-lambeosaurine dichotomy. This was supported by a
preliminary phylogenetic analysis mainly based on the 127 characters
data matrix of Prieto-Márquez et al. (2006), with some modifications,
especially those dealing with recognizing additive (=ordered)
characters as such. However, later Prieto-Márquez and his
collaborators published much larger data matrices, of which
Prieto-Márquez and Wagner (2009) was the first, which did not
supported this hypothesis. As they also considered Willinakaqe (their
"Salitral Moreno OTU") in that large data matrix (299 characters), and
some even larger that came afterwards, and as we did not find mistakes
in their codfications, we just surrendered our hypothesis.

References:

Prieto-Márquez, A., Gaete, R., Rivas, G., Galobart, A., & Boada, M.
2006. Hadrosauroid dinosaurs from the Late Cretaceous of Spain:
Pararhabdodon isonensis revisited and Koutalisaurus kohlerorum, gen.
et. sp. nov. Journal of Vertebrate Paleontology, 26: 929-943.

Prieto-Márquez, A., & Wagner, J. R. 2009. Pararhabdodon isonensis and
Tsintaosaurus spinorhinus: a new clade of lambeosaurine hadrosaurids
from Eurasia. Cretaceous Research, 30: 1238-1246.