Evidence for a Giant Nyctosaurus or Two
Nyctosaurus is not just a genus. It is a clade with a wider variety of shapes and sizes than previously thought.
Bennett (1991, 1992, 1994, 2000, 2001) pretty much established the traditional concepts of Nyctosaurus by declaring that non-fusion of certain skeletal elements meant immaturity. He did this using “logic” and patterns found in archosaurs, not phylogenetic analysis. As it turns out, phylogenetically, no Nyctosaurus has fused skeletal elements or a crest — not until you get to the highly derived crested specimens.
What’s interesting is now, with this information, we can reclassify a large pterosaur knuckle, YPM 2501 (Fig. 1), as a giant basal Nyctosaurus, based on the nonfusion of its extensor tendon process, rather than as a Pteranodon, based on size alone. This giant element goes along with the giant Nyctosaurus pelvis, KUVP 993 (Fig. 1), previously misidentified as a “female” Pteranodon pelvis based on size alone by Bennett (1991, 1992, 1994, 2001). It is morphologically closer to Nyctosaurus.
Figure 1. The clade of Nyctosaurus and kin. Click to enlarge.
Nyctosaurus nanus (known from a humerus and pectoral girdle) is the only Nyctosaurus that is genuinely and markedly smaller than the others pictured here. Earlier we looked at other aspects of sexual maturity and growth in Nyctosaurus, which is worth checking out.
This subject came up because I noticed an online pdf of the partial Nyctosaurus, LACM 51130, described as “immature,” despite being roughly the same size as other Nyctosaurus specimens. The author made reference to Bennett’s work regarding the non-fusion of certain elements, and this has to be nipped in the bud since it has been demonstrated to be invalid, unless you think that all known specimens of Nyctosaurus and that someday we’ll find adults. But that goes against the odds.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
References
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2000. New information on the skeletons of Nyctosaurus. Journal of Vertebrate Paleontology 20 (Supplement to Number 3):29A.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153.
Bennett SC 2003. New crested specimens of the Late Cretaceous pterosaur Nyctosaurus.Paläontologische Zeitschrift 77: 61-75.
Chinsamy A, Codorniú L and Chiappe LM 2008. Developmental growth patterns of the filter-feeder pterosaur, Pterodaustro guinazui. Biology Letters, 4: 282-285.
Kaplan M 2007. Iguana Age and Expected Size. iguana/agesize online
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrae Paleontology 22: 268–275.
Pianka E 1971. Notes on the Biology of Varanus tristis. West. Aust, Natur, 11(8):80-183.
2012-12-04 22:22:29
Source: http://pterosaurheresies.wordpress.com/2012/12/05/evidence-for-a-giant-nyctosaurus-or-two/
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