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Megaraptor adult humerus described

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Ben Creisler

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Jan 19, 2025, 11:19:21 AMJan 19
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Ben Creisler

Not yet mentioned....

Jorge O. Calvo, Juan D. Porfiri, Alexis M. Aranciaga Rolando, Fernando E. Novas, Domenica D. Dos Santos, Derek E. Wessel & Matthew C. Lamanna (2025)
Morphological and Phylogenetic Significance of the First Adult Humerus of the Patagonian Cretaceous Theropod Megaraptor namunhuaiquii Novas, 1998
Annals of Carnegie Museum 90(3): 161-181
doi: https://doi.org/10.2992/007.090.0301
https://bioone.org/journals/annals-of-carnegie-museum/volume-90/issue-3/007.090.0301/Morphological-and-Phylogenetic-Significance-of-the-First-Adult-Humerus-of/10.2992/007.090.0301.short


Megaraptorans are medium- to large-bodied tetanuran theropod dinosaurs known from Cretaceous deposits in Asia, Australia, and especially South America. The megaraptoran skeleton is far from well known, and the humerus is one of the least-frequently preserved elements. Here we describe the first-documented adult humerus of a South American megaraptoran, recovered from the Upper Cretaceous (Turonian–Coniacian) Portezuelo Formation of the Neuquén Basin on the southeast coast of Lago Barreales in Neuquén Province, northern Patagonia, Argentina. The humerus is referred to the namesake megaraptoran Megaraptor namunhuaiquii Novas, 1998, based on its geographic and stratigraphic provenance as well as its morphological similarity to the corresponding element of a juvenile skeleton of the same taxon. Nevertheless, the new adult humerus exhibits osteological distinctions from that of the juvenile that we interpret as reflective of their differing ontogenetic stages. We also highlight anatomical differences between the humerus of M. namunhuaiquii and that of the enigmatic Patagonian theropod Gualicho shinyae Apesteguía et al., 2016, that show that these taxa are not closely related.

Mickey Mortimer

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Jan 20, 2025, 3:18:54 AMJan 20
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Is it just me, or is the section "We also highlight anatomical differences between the humerus of M. namunhuaiquii and that of the enigmatic Patagonian theropod Gualicho shinyae Apesteguía et al., 2016, that show that these taxa are not closely related" an example of Makovicky and Dyke's (2001) famous Naive Falsification fallacy? As a reminder, it's point is that when e.g. Feduccia or Martin would claim a structure differs between dinosaurs and birds, those authors believed it meant the two groups couldn't be closely related. The classic case was Velociraptor's furcula, which "has a round cross-section, while that of the primitive Mesozoic birds — Archaeopteryx, Confuciusornis and the enantiornithines — is dissimilar, being grooved postero-dorsally along almost its entire length" (Feduccia and Martin, 1998). So yeah, we all agree Gualicho has a dissimilar humerus from Megaraptor, Australovenator and Fukuiraptor, but that's meaningless without suggesting a greater similarity to another taxon which you feel is phylogenetic in nature. But Calvo et al. explicitly say "like Gual. shinyae, alvarezsaurids and tyrannosaurids have short forelimbs, which strongly suggests that these similarities represent convergences rather than shared apomorphies" and "the humeral similarities between Gual. shinyae and ornithomimosaurs are probably best interpreted as functional convergences rather than apomorphic traits." So if all these characters are convergent, it tells us nothing about the affinities of Gualicho. Considering humeral characters alone, Gualicho might as well be a megaraptoran that converged with ornithomimosaurs instead of e.g. a ceratosaur that converged with ornithomimosaurs. To make any headway in the direction Calvo et al. want to, you would have to show the characters joining Gualicho to megaraptorans in analyses where it falls out as one are flawed, AND show a better result for placing it in another clade.

References- Feduccia and Martin, 1998. Theropod-bird link reconsidered. Nature. 391, 754.

Makovicky and Dyke, 2001. Naive falsification and the origin of birds: A commentary. In Gauthier and Gall (eds.). New Perspectives on the Origin and Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. Yale University. 501-509.

Ben Creisler

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Jan 25, 2025, 4:30:50 PMJan 25
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Now with free pdf link:

Free pdf:

Jorge O. Calvo, Juan D. Porfiri, Alexis M. Aranciaga Rolando, Fernando E. Novas, Domenica D. Dos Santos, Derek E. Wessel & Matthew C. Lamanna (2025)
Morphological and Phylogenetic Significance of the First Adult Humerus of the Patagonian Cretaceous Theropod Megaraptor namunhuaiquii Novas, 1998
Annals of Carnegie Museum 90(3): 161-181
doi: https://doi.org/10.2992/007.090.0301
https://bioone.org/journals/annals-of-carnegie-museum/volume-90/issue-3/007.090.0301/Morphological-and-Phylogenetic-Significance-of-the-First-Adult-Humerus-of/10.2992/007.090.0301.short

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